Solid electrolyte, all-solid-state battery comprising same, and method for manufacturing same

Abstract

The present invention relates to a solid electrolyte, an all-solid-state battery comprising same, and a method for manufacturing same and more specifically comprises: an argyrodite-type compound; and impurities in an amount of more than 0 ppm and at most 500 ppm, wherein the lightness (L*) value is 90 or more.

Description

Solid electrolyte, all-solid-state battery including the same, and method for manufacturing the same

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

[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] All-solid-state batteries do not use flammable organic dispersion media, significantly reducing the risk of fire or explosion even if a short circuit occurs. Consequently, these all-solid-state batteries can boast excellent safety.

[0004] One embodiment provides a solid electrolyte capable of achieving a lightness (L*) value of 90 or higher and excellent cell performance.

[0005] Another embodiment provides an all-solid-state battery comprising the solid electrolyte.

[0006] Another embodiment provides a method for producing the solid electrolyte.

[0007] According to one embodiment, a solid electrolyte may include an argyrodite-type compound; and impurities in an amount of more than 0 ppm and less than or equal to 500 ppm. The solid electrolyte may have a lightness (L*) value of 90 or greater.

[0008] According to another embodiment, an all-solid-state battery includes a cathode layer; a cathode layer; and a solid electrolyte layer disposed between the cathode layer and the cathode layer, wherein the solid electrolyte layer includes a solid electrolyte and a binder, and the solid electrolyte includes an argyrodite-type compound; and impurities in an amount of more than 0 ppm and less than or equal to 500 ppm; and may have a lightness (L*) value of 90 or more.

[0009] According to another embodiment, a method for manufacturing a solid electrolyte includes: mixing powder-state starting materials, wherein the powder-state starting materials include a sulfur (S) precursor, a phosphorus (P) precursor, a halogen precursor, and a metal precursor; calcining the mixed mixture; and pulverizing the calcined mixture; wherein the powder-state starting materials may further include impurities.

[0010] A solid electrolyte according to one embodiment can have a lightness (L*) value of 90 or more, thereby providing excellent cell performance to an all-solid-state battery including the same.

[0011] FIG. 1 is a cross-sectional view illustrating an all-solid-state battery according to embodiments of the present invention.

[0012] Figure 2 is an image showing the color of a solid electrolyte according to an example and a comparative example.

[0013] Figure 3 is a graph showing the cell performance of an all-solid-state battery including a solid electrolyte according to an example and a comparative example.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0018] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0019]

[0020] According to one embodiment of the present invention, a solid electrolyte including an argyrodite-type compound; and an impurity; can be provided.

[0021] Argyrodite-type compounds may include a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be manufactured by treating starting materials such as Li2S and P2S5 by a melting quenching method or a mechanical milling method. In addition, a heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may include, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material including Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form a solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0022] 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 (0≤x≤2) may be an argyrodite-type compound including at least one selected from. In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. 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 solid electrolyte is, for example, 15 GPa to 35 GPa.

[0023] Sulfide-based solid electrolytes include, for example, Li a M1 x M2 w PS y M3 zM1 may be one or more elements selected from Groups 2 and 11 of the periodic table. M2 may be one or more metal elements other than Li selected from Group 1 of the periodic table. M3 may be one or more elements selected from Group 17 of the periodic table. For example, M1 may include copper (Cu), silver (Ag), magnesium (Mg), or a combination thereof. For example, M2 may include sodium (Na), potassium (K), or a combination thereof. For example, M3 may include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or a combination thereof. 4≤a≤8, 0 <x<0.5, 0≤w<0.5, 3≤y≤7, 및 0≤z≤2일 수 있다. 예를 들어, 5≤a≤8, 0<x<0.5, 0≤w<0.5, 4≤y≤7, 및 0≤z≤2일 수 있다. 예를 들어, 5≤a≤7, 0<x<0.5, 0≤w<0.5, 4≤y≤6, 및 0≤z≤2일 수 있다. 예를 들어, 5.5≤a≤7, 0<x<0.5, 0≤w<0.5, 4.5≤y≤6, 및 0.2≤z≤1.8일 수 있다.

[0024] The content of the impurity may be greater than 0 ppm and less than or equal to 500 ppm. For example, the content of the impurity may be from 50 ppm to 500 ppm, from 50 ppm to 300 ppm, or from 200 ppm to 300 ppm. When the content of the impurity satisfies the range described above, the brightness (L*) value of the solid electrolyte may be 90 or more, and excellent cell characteristics may be achieved. When the content of the impurity is outside the range described above, the brightness of the solid electrolyte may be lowered, and the quality of the solid electrolyte may be deteriorated.

[0025] The impurity may include iron (Fe). The iron (Fe) content may be from 10 ppm to 220 ppm. For example, the iron (Fe) content may be from 10 ppm to 200 ppm, or from 180 ppm to 220 ppm. When the iron (Fe) content satisfies the above-described range, the lightness (L*) value of the solid electrolyte may be 90 or higher, and excellent cell characteristics may be achieved.

[0026] In addition to iron (Fe), the impurity may further include at least one selected from the group consisting of manganese (Mn), chromium (Cr), and zirconium (Zr). For example, the impurity may further include manganese (Mn) in an amount of 10 ppm to 20 ppm. For example, the impurity may further include chromium (Cr) in an amount of 40 ppm to 100 ppm. For example, the impurity may further include zirconium (Zr) in an amount of 10 ppm to 20 ppm. When the contents of each of manganese (Mn), chromium (Cr), and zirconium (Zr) satisfy the above-described ranges, the lightness (L*) value of the solid electrolyte may be 90 or more, and excellent cell characteristics may be achieved.

[0027] A method for measuring the components and contents of a solid electrolyte can be performed by scanning electron microscope-energy-dispersive X-ray spectroscopy (SEM-EDS) on the surface of the solid electrolyte. In addition to SEM-EDS, other methods for measuring the components and contents of a solid electrolyte include inductively coupled plasma-mass spectrometry (ICP-MS) or inductively coupled plasma-optical emission spectroscopy (ICP-OES). A colorimetric system can be used as a faster and simpler method for measuring the components and contents of a solid electrolyte.

[0028] The color of a solid electrolyte can be expressed by the L*a*b* colorimetric system. L* can represent lightness. The lightness (L*) value can be expressed as 0 to 100. For example, if the lightness (L*) value is 0, it can be black, and if the lightness (L*) value is 100, it can be white. a* can be an indicator of whether the color is leaning toward red or green. For example, if the a* value is negative, the color can be leaning toward green, and if the a* value is positive, the color can be leaning toward red. b* can be an indicator of whether the color is leaning toward yellow or blue. For example, if the b* value is negative, the color can be leaning toward blue, and if the b* value is positive, the color can be leaning toward yellow.

[0029] The lightness (L*) value of the L*a*b* colorimetric system of the solid electrolyte may vary depending on the content of impurities. The lightness (L*) value of the L*a*b* colorimetric system of the solid electrolyte according to one embodiment of the present invention may be 90 or higher. For example, the lightness (L*) value of the solid electrolyte may be 90 to 100, preferably 94 to 97. When the lightness (L*) value of the solid electrolyte satisfies the above-described range, excellent cell characteristics may be exhibited.

[0030] The a* value of the L*a*b* colorimetric system of the solid electrolyte may be from -1 to 0, preferably from -0.5. The b* value of the L*a*b* colorimetric system of the solid electrolyte may be from 4 to 6, preferably from 4 to 5.

[0031]

[0032] FIG. 1 is a cross-sectional view illustrating an all-solid-state battery according to embodiments of the present invention. Referring to FIG. 1, the all-solid-state battery (10) 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).

[0033] The positive electrode layer (100) may include 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.

[0034] 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 have a plate or foil shape. For example, the positive electrode current collector (110) can include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0035] 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).

[0036] The cathode active material may be a material that can reversibly absorb and desorb lithium ions. For example, the cathode active material may include, but is not 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 thereof.

[0037] 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-fIt may be 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.

[0038] 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 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 Mnz 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.

[0039] 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 for forming the coating layer may be selected within a range that does not adversely affect the physical properties of the positive electrode active material. The method for forming the coating layer may include, for example, a spray coating method or an immersion method.

[0040] When the positive electrode active material includes 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 in a charged state. As a result, the cycle characteristics of the all-solid-state battery (10) in a charged state can be 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 can 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 can have a large degree of deterioration of the all-solid-state battery (10) due to charge / discharge.

[0041] The shape of the positive electrode active material may include particle shapes such as a sphere or an ellipsoid, for example. The particle size and content of the positive electrode active material are not particularly limited.

[0042] 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).

[0043] 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 (0≤x≤2) may be an argyrodite-type compound including at least one selected from. In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. 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 solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0044] Sulfide-based solid electrolytes include, for example, Li a M1 x M2 w PS y M3 zM1 may be one or more elements selected from Groups 2 and 11 of the periodic table. M2 may be one or more metal elements other than Li selected from Group 1 of the periodic table. M3 may be one or more elements selected from Group 17 of the periodic table. For example, M1 may include copper (Cu), silver (Ag), magnesium (Mg), or a combination thereof. For example, M2 may include sodium (Na), potassium (K), or a combination thereof. For example, M3 may include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or a combination thereof. 4≤a≤8, 0 <x<0.5, 0≤w<0.5, 3≤y≤7, 및 0≤z≤2일 수 있다. 예를 들어, 5≤a≤8, 0<x<0.5, 0≤w<0.5, 4≤y≤7, 및 0≤z≤2일 수 있다. 예를 들어, 5≤a≤7, 0<x<0.5, 0≤w<0.5, 4≤y≤6, 및 0≤z≤2일 수 있다. 예를 들어, 5.5≤a≤7, 0<x<0.5, 0≤w<0.5, 4.5≤y≤6, 및 0.2≤z≤1.8일 수 있다.

[0045] The solid electrolyte may further include impurities. The content of the impurities may be greater than 0 ppm and less than or equal to 500 ppm. For example, the content of the impurities may be 50 ppm to 500 ppm, 50 ppm to 300 ppm, or 200 ppm to 300 ppm. When the content of the impurities satisfies the above-described range, the lightness (L*) value of the solid electrolyte may be 90 or more, and excellent cell characteristics may be achieved. When the content of the impurities is outside the above-described range, the lightness of the solid electrolyte may be reduced, and the quality of the solid electrolyte may be degraded.

[0046] The impurity may include iron (Fe). The iron (Fe) content may be from 10 ppm to 220 ppm. For example, the iron (Fe) content may be from 10 ppm to 200 ppm, or from 180 ppm to 220 ppm. When the iron (Fe) content satisfies the above-described range, the lightness (L*) value of the solid electrolyte may be 90 or higher, and excellent cell characteristics may be achieved.

[0047] In addition to iron (Fe), the impurity may further include at least one selected from the group consisting of manganese (Mn), chromium (Cr), and zirconium (Zr). For example, the impurity may further include manganese (Mn) in an amount of 10 ppm to 20 ppm. For example, the impurity may further include chromium (Cr) in an amount of 40 ppm to 100 ppm. For example, the impurity may further include zirconium (Zr) in an amount of 10 ppm to 20 ppm. When the contents of each of manganese (Mn), chromium (Cr), and zirconium (Zr) satisfy the above-described ranges, the lightness (L*) value of the solid electrolyte may be 90 or more, and excellent cell characteristics may be achieved.

[0048] 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.

[0049] 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 and the solid electrolyte. The conductive material may include a carbon-based material. The conductive material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0050] 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). For example, the binder may include polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, or polymethyl methacrylate.

[0051] When the total amount of the positive electrode active material, the solid electrolyte, the conductive material, and the binder is 100 parts by weight, the positive electrode active material layer (120) may include 85 parts by weight to 92 parts by weight of the positive electrode active material. The positive electrode active material layer (120) may include 0.5 parts by weight to 1.5 parts by weight of the binder.

[0052] Within the positive electrode active material layer (120), the conductive material may be present in an amount of 1 to 50 parts by weight relative to 100 parts by weight of the solid electrolyte. If the conductive material is present in an amount less than 1 part by weight relative to 100 parts by weight of the solid electrolyte, the electrical conductivity of the positive electrode active material layer (120) may be reduced. If the conductive material is present in an amount greater than 50 parts by weight relative to 100 parts by weight of the solid electrolyte, the conductive material ratio may be excessively high, and thus a covering layer covering the surface of the solid electrolyte may not be properly formed.

[0053] According to embodiments, the positive electrode active material layer (120) may further include at least one additive selected from the group consisting of a filler, a coating agent, a dispersant, and an ion conductive auxiliary agent in addition to the above-described positive electrode active material, solid electrolyte, conductive agent, and binder.

[0054] The solid electrolyte layer (300) is disposed between the positive electrode layer (100) and the negative electrode layer (200) and may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics. The solid electrolyte layer (300) may include a solid electrolyte, a binder, etc. The solid electrolyte may include an argyrodite-type compound and impurities. The solid electrolyte included in the solid electrolyte layer (300) may be the same as or different from any one of the materials that may be included in the solid electrolyte included in the positive electrode active material layer (120) described above.

[0055] The solid electrolyte may include, for example, the solid electrolyte described above. For convenience of explanation, the same details as those described above will be omitted below, and differences will be described in detail.

[0056] The binder 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 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 negative electrode coating layer (220).

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] 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, thereby deteriorating the cycle characteristics of the all-solid-state battery (10).

[0063] 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).

[0064]

[0065] According to one embodiment of the present invention, a method for producing a solid electrolyte can be provided, including mixing powder-state starting materials; calcining the mixed mixture; and pulverizing the calcined mixture.

[0066] Starting materials in powder form can be mixed. For example, the starting materials can be processed by melt quenching or mechanical milling.

[0067] In the melt-quenching method, starting materials can be mixed and formed into pellets. The pellets can be reacted at a predetermined reaction temperature and under vacuum conditions. For example, the reaction temperature can be 400°C to 1000°C, preferably 800°C to 900°C. For example, the reaction time can be 0.1 hour to 12 hours, preferably 1 hour to 12 hours. Thereafter, the pellets can be quenched. For example, the quenching temperature can be 10°C or lower, preferably 0°C or lower. For example, the quenching rate can be 1°C / sec to 10,000°C / sec, preferably 1°C / sec to 1000°C / sec.

[0068] In the mechanical milling method, the starting materials can be stirred using a ball mill or the like. For example, the stirring speed can be 0 rpm to 1000 rpm. For example, the stirring time can be 1 hour to 48 hours. The stirring speed and stirring time are not particularly limited, but a fast stirring speed can accelerate the production rate of the solid electrolyte, and a long stirring time can increase the production rate of the solid electrolyte.

[0069] To obtain the desired solid electrolyte, the stoichiometric molar ratio of the powder-state starting materials can be changed, and the content of each of the powder-state starting materials can be changed.

[0070] The powder-state starting materials may include sulfur (S) precursors, phosphorus (P) precursors, etc. For example, the powder-state starting materials may include Li2S, P2S5, etc. The powder-state starting materials may further include halogen precursors, metal precursors, etc. For example, the halogen precursors may be fluorine (F) precursors, chlorine (Cl) precursors, bromine (Br) precursors, iodine (I) precursors, etc. For example, the metal precursors may include magnesium (Mg) precursors, silver (Ag) precursors, copper (Cu) precursors, etc.

[0071] The starting materials in powder form may further contain impurities. The impurities may include at least one selected from the group consisting of iron (Fe), manganese (Mn), chromium (Cr), and zirconium (Zr). For example, the impurities may include iron (Fe) and further include at least one selected from the group consisting of manganese (Mn), chromium (Cr), and zirconium (Zr).

[0072] The mixed mixture can be calcined under an inert gas. For example, the inert gas can be nitrogen (N2), argon (Ar), helium (He), etc. The calcination can be performed at a predetermined temperature. For example, the calcination temperature can be from 0°C to 1000°C. For example, the calcination time can be from 1 hour to 48 hours.

[0073] The calcined mixture can be pulverized. Through pulverization, a solid electrolyte in particle form can be produced. The pulverization can be performed using a jet mill, for example. The desired particle size can be controlled using a jet mill. For example, the rotation speed can be between 0 and 1,000 rpm. For example, the pulverization time can be between 1 and 48 hours.

[0074]

[0075] 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.

[0076]

[0077] Example 1

[0078] Manufacturing Example 1-1: Preparation of solid electrolyte

[0079] A solid electrolyte having a lightness (L*) value of 94.5 in the L*a*b* colorimetric system was prepared. The solid electrolyte contained an argyrodite-type compound (Li6PS5Cl) and impurities. The impurities included 200 ppm of iron (Fe), 15 ppm of manganese (Mn), 50 ppm of chromium (Cr), and 10 ppm of zirconium (Zr). To ensure that the solid electrolyte had the contents of the impurities described above, the raw materials were adjusted to prepare the solid electrolyte. The color of the solid electrolyte was analyzed by placing the solid electrolyte powder in a transparent vinyl pouch, flattening it, and then placing the colorimetric system vertically to measure five times, and taking the average value. The results of the colorimetric analysis are shown in Table 1.

[0080]

[0081] Manufacturing Example 1-2: Manufacturing of an All-Solid-State Battery

[0082] (1) Manufacturing of solid electrolyte layer

[0083] An acrylic binder (SX-A334, Zeon Co., Ltd.) was added to octyl acetate to prepare a 4 wt% acrylic binder solution. The acrylic binder solution was added to the solid electrolyte of Manufacturing Example 1-1 prepared above, and mixed with a thinky mixer to prepare a slurry. The slurry contained 1.5 parts by weight of the acrylic binder relative to 98.5 parts by weight of the solid electrolyte. The prepared slurry was applied onto a nonwoven fabric using a bar coater and dried in a convection oven at 50°C for 5 minutes to obtain a laminate. The obtained laminate was vacuum-dried at 40°C for more than 10 hours. A solid electrolyte layer was manufactured through the above process.

[0084] (2) Manufacturing of cathode layer

[0085] A 10 μm thick Ni foil was prepared as a negative electrode current collector. In addition, 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. 0.25 g of a mixed powder of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 2 g of an NMP solution containing 7 wt% PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. Next, NMP was gradually added to the mixed solution while stirring the mixed solution to prepare a slurry. The prepared slurry was applied to a Ni foil using a bar coater and dried in a convection oven at 80°C for 10 minutes to obtain a laminate. The obtained laminate was vacuum dried at 100°C for more than 8 hours, i.e., for 10 hours. A cathode layer was manufactured by forming a cathode coating layer on a cathode current collector through the above process.

[0086] (3) Manufacturing of the anode layer

[0087] LiNi as a cathode active material 0.8 Co 0.15 Mn 0.05 O2(NCM) was prepared. Li6PS5Cl solid electrolyte (D50=1 um or less, crystalline) in the form of argyrodite was used as a solid electrolyte. Polytetrafluoroethylene (PTFE) binder (Teflon binder from DuPont) was prepared as a binder. Carbon black (CB) and carbon nanofibers (CNF) were prepared as conductive agents. These materials were mixed with a xylene solvent in a weight ratio of positive electrode active material: solid electrolyte: carbon black: carbon nanofiber: binder = 85.5:10:1.5:1.5:1.5, and the positive electrode active material composition was molded into a sheet shape, and then vacuum dried at 40°C for 8 hours to manufacture a positive electrode sheet.

[0088] (4) Manufacturing of all-solid-state batteries

[0089] A laminate was prepared by placing a solid electrolyte layer between the positive and negative electrode layers. The prepared laminate was hot-plate pressed at 80°C and a pressure of 500 MPa for 10 minutes to produce an all-solid-state battery. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the pressed positive active material layer was approximately 80 μm, the thickness of the negative active material layer was 7 μm, and the thickness of the solid electrolyte layer was 60 μm.

[0090]

[0091] Example 2

[0092] Manufacturing Example 2-1: Preparation of solid electrolyte

[0093] A solid electrolyte having a lightness (L*) value of 96.2 in the L*a*b* colorimetric system was prepared. The solid electrolyte contained an argyrodite-type compound (Li6PS5Cl) and impurities. It was prepared in the same manner as Example 1, except that the impurities included 10 ppm of iron (Fe), 15 ppm of manganese (Mn), 52 ppm of chromium (Cr), and 12 ppm of zirconium (Zr).

[0094]

[0095] Manufacturing Example 2-2: Manufacturing of an All-Solid-State Battery

[0096] It was manufactured in the same manner as the example, except that the solid electrolyte layer was manufactured using the solid electrolyte of Manufacturing Example 2-1.

[0097]

[0098] Example 3

[0099] Manufacturing Example 3-1: Preparation of solid electrolyte

[0100] A solid electrolyte having a lightness (L*) value of 96.2 in the L*a*b* colorimetric system was prepared. The solid electrolyte contained an argyrodite-type compound (Li6PS5Cl) and impurities. It was prepared in the same manner as Example 1, except that the impurities included 58 ppm of iron (Fe), 20 ppm of manganese (Mn), 100 ppm of chromium (Cr), and 20 ppm of zirconium (Zr).

[0101]

[0102] Manufacturing Example 3-2: Manufacturing of an All-Solid-State Battery

[0103] It was manufactured in the same manner as the example, except that the solid electrolyte layer was manufactured using the solid electrolyte of Manufacturing Example 3-1.

[0104]

[0105] Comparative Example 1

[0106] Manufacturing Example 1-3: Preparation of solid electrolyte

[0107] A solid electrolyte having a lightness (L*) value of 87.4 in the L*a*b* colorimetric system was prepared. The solid electrolyte contained an argyrodite-type compound (Li6PS5Cl) and impurities. It was prepared in the same manner as Example 1, except that the impurities included 550 ppm of iron (Fe), 50 ppm of manganese (Mn), 50 ppm of chromium (Cr), and 10 ppm of zirconium (Zr).

[0108]

[0109] Manufacturing Example 1-4: Manufacturing of an all-solid-state battery

[0110] It was manufactured in the same manner as in the example, except that the solid electrolyte layer was manufactured using the solid electrolyte of Manufacturing Example 1-3.

[0111]

[0112] Comparative Example 2

[0113] Manufacturing Example 2-3: Preparation of solid electrolyte

[0114] A solid electrolyte having a lightness (L*) value of 75.5 in the L*a*b* colorimetric system was prepared. The solid electrolyte contained an argyrodite-type compound (Li6PS5Cl) and impurities. It was prepared in the same manner as Example 1, except that the impurities included 30 ppm of iron (Fe), 572 ppm of manganese (Mn), 54 ppm of chromium (Cr), and 22 ppm of zirconium (Zr).

[0115]

[0116] Manufacturing Example 2-4: Manufacturing of an All-Solid-State Battery

[0117] It was manufactured in the same manner as the example, except that the solid electrolyte layer was manufactured using the solid electrolyte of Manufacturing Example 2-3.

[0118]

[0119] Comparative Example 3

[0120] Manufacturing Example 3-3: Preparation of solid electrolyte

[0121] A solid electrolyte having a lightness (L*) value of 78.8 in the L*a*b* colorimetric system was prepared. The solid electrolyte contained an argyrodite-type compound (Li6PS5Cl) and impurities. It was prepared in the same manner as Example 1, except that the impurities included 74 ppm of iron (Fe), 24 ppm of manganese (Mn), 663 ppm of chromium (Cr), and 30 ppm of zirconium (Zr).

[0122]

[0123] Manufacturing Example 3-4: Manufacturing of an All-Solid-State Battery

[0124] It was manufactured in the same manner as the example, except that the solid electrolyte layer was manufactured using the solid electrolyte of Manufacturing Example 3-3.

[0125]

[0126] Comparative Example 4

[0127] Manufacturing Example 4-3: Preparation of solid electrolyte

[0128] A solid electrolyte having a lightness (L*) value of 82 in the L*a*b* colorimetric system was prepared. The solid electrolyte contained an argyrodite-type compound (Li6PS5Cl) and impurities. It was prepared in the same manner as Example 1, except that the impurities included 250 ppm of iron (Fe), 22 ppm of manganese (Mn), 50 ppm of chromium (Cr), and 641 ppm of zirconium (Zr).

[0129]

[0130] Manufacturing Example 4-4: Manufacturing of an All-Solid-State Battery

[0131] It was manufactured in the same manner as the example, except that the solid electrolyte layer was manufactured using the solid electrolyte of Manufacturing Example 4-3.

[0132]

[0133] Classification L*a*b*FeMnCrZrExample 194.5-0.54.3200155010Example 296.2-0.54.810155212Example 396.2-0.54.8582010020Comparative Example 187.4-0.56.6550505010Comparative Example 275.5-0.67305725422Comparative Example 378.8-0.56.2742466330Comparative Example 482-0.58.12502250641

[0134]

[0135] Experimental Example 1: Measurement of ionic conductivity of solid electrolyte

[0136] The ionic conductivity of the solid electrolytes of the examples and comparative examples was investigated by the following method. 200 mg of solid electrolyte powder was dissolved in 4 ton / cm 2A pellet specimen with a thickness of approximately 100 ㎛ and a diameter of approximately 13 mm was prepared by pressing at a pressure of 100 ㎛ for 2 minutes. Indium (In) electrodes with a thickness of 50 ㎛ and a diameter of 13 mm were placed on both sides of the prepared specimen to prepare a symmetry cell. The symmetry cell was prepared in an argon (Ar) atmosphere. The impedance of the pellet was measured by the 2-probe method using an impedance analyzer (Material Mates 7260 impedance analyzer). The frequency range was 0.1 Hz to 1 MHz. The amplitude voltage was 10 mV. The measurement was performed at 25℃ in an Ar atmosphere. The resistance value was obtained from the arc of the Nyquist plot for the impedance measurement results, and the ionic conductivity was calculated by considering the area and thickness of the specimen. The results are shown in Table 2.

[0137]

[0138] Classification Example 1 Comparative Example 1 Ionic Conductivity (mS / cm) 3.632.12

[0139] According to Table 2, the ionic conductivity of Example 1 was higher than that of Comparative Example 1.

[0140]

[0141] Experimental Example 2: Investigation of Cell Performance of All-Solid-State Battery

[0142] To verify cell performance, the discharge capacity and capacity retention rate of each of the all-solid-state batteries of the examples and comparative examples were investigated. Charge and discharge tests were performed by placing the all-solid-state batteries in a thermostatic chamber at 60°C. The batteries were charged at a constant current of 0.1 C for 10 hours until the battery voltage reached 4.25 V, and then discharged at a constant current of 0.05 C for 20 hours until the battery voltage reached 2.5 V (the first cycle). Subsequently, the batteries were charged at a constant current of 0.1 C for 10 hours until the battery voltage reached 4.25 V, and then discharged at a constant current of 0.33 C for 3 hours until the battery voltage reached 2.5 V (the second cycle). After that, the batteries were charged at a constant current of 0.1 C for 10 hours until the battery voltage reached 4.25 V. Next, the battery was discharged for 2 hours at a constant current of 0.5 C until the battery voltage became 2.5 V (3rd cycle). Then, it was charged for 10 hours at a constant current of 0.1 C until the battery voltage became 4.25 V. Then, it was discharged for 1 hour at a constant current of 1 C until the battery voltage became 2.5 V (4th cycle). Then, it was charged for 3 hours at a constant current of 0.33 C until the battery voltage became 4.25 V. Then, it was discharged for 3 hours at a constant current of 0.33 C until the battery voltage became 2.5 V (5th cycle). The above cycles were repeated a total of 50 times, and the capacity change and capacity retention rate according to the number of cycles were evaluated. The results are shown in Fig. 3.

[0143] According to Fig. 3, Example 1 had better discharge capacity and capacity retention rate than Comparative Example 1.

[0144]

[0145] 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. Argyrodite-type compounds; and Contains impurities exceeding 0 ppm and not exceeding 500 ppm; The brightness (L*) value is 90 or higher, Solid electrolyte.

2. In paragraph 1, The above impurities include iron (Fe). Solid electrolyte.

3. In paragraph 2, The content of the above iron (Fe) is 10 ppm to 220 ppm, Solid electrolyte.

4. In paragraph 2, The above impurities further include at least one selected from the group consisting of manganese (Mn), chromium (Cr), and zirconium (Zr). Solid electrolyte.

5. In paragraph 2, The above impurities further include manganese (Mn) of 10 ppm to 20 ppm. Solid electrolyte.

6. In paragraph 2, The above impurities further include 40 ppm to 100 ppm of chromium (Cr). Solid electrolyte.

7. In paragraph 2, The above impurities further include 10 ppm to 20 ppm of zirconium (Zr). Solid electrolyte.

8. In paragraph 1, The lightness (L*) value of the L*a*b* colorimetric system of the above solid electrolyte is 90 or more. Solid electrolyte.

9. In paragraph 1, The a* value of the L*a*b* colorimetric system of the above solid electrolyte is -1 to 0, b* value is between 4 and 6, Solid electrolyte.

10. In paragraph 1, The above azirodite-type compound is Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x (0≤x≤2), and Li a M1 x M2 w PS y M3 z Including one or more selected from: The above M1 is one or more elements selected from groups 2 and 11 of the periodic table, The above M2 is one or more metal elements other than Li selected from group 1 of the periodic table, The above M3 is one or more elements selected from group 17 of the periodic table, 4≤a≤8, 0 <x<0.5, 0≤w<0.5, 3≤y≤7, 및 0≤z≤2인, Solid electrolyte.

11. Bipolar layer; cathode layer; and A solid electrolyte layer is included between the positive electrode layer and the negative electrode layer, The above solid electrolyte layer comprises a solid electrolyte and a binder, The above solid electrolyte is, Argyrodite-type compounds; and Contains impurities exceeding 0 ppm and not exceeding 500 ppm; The brightness (L*) value is 90 or higher, All-solid-state battery.

12. In paragraph 11, The above impurities include iron (Fe). All-solid-state battery.

13. In paragraph 12, The content of the above iron (Fe) is 10 ppm to 220 ppm, All-solid-state battery.

14. In paragraph 12, The above impurities further include at least one selected from the group consisting of manganese (Mn), chromium (Cr), and zirconium (Zr). All-solid-state battery.

15. In paragraph 12, The above impurities further include manganese (Mn) of 10 ppm to 20 ppm. All-solid-state battery.

16. In paragraph 12, The above impurities further include 40 ppm to 100 ppm of chromium (Cr). All-solid-state battery.

17. In paragraph 12, The above impurities further include 10 ppm to 20 ppm of zirconium (Zr). Solid electrolyte.

18. In paragraph 11, The above azirodite-type compound is Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x (0≤x≤2), and Li a M1 x M2 w PS y M3 z Including one or more selected from: The above M1 is one or more elements selected from groups 2 and 11 of the periodic table, The above M2 is one or more metal elements other than Li selected from group 1 of the periodic table, The above M3 is one or more elements selected from group 17 of the periodic table, 4≤a≤8, 0 <x<0.5, 0≤w<0.5, 3≤y≤7, 및 0≤z≤2인,All-solid-state battery.

19. Mixing powder-state starting materials, wherein the powder-state starting materials include a sulfur (S) precursor, a phosphorus (P) precursor, a halogen precursor, and a metal precursor; Calcining the above mixed mixture; and Comprising: crushing the above-mentioned calcined mixture; The above powder-state starting material further contains impurities. Method for manufacturing a solid electrolyte.

20. In paragraph 19, The above impurities include at least one selected from the group consisting of iron (Fe), manganese (Mn), chromium (Cr), and zirconium (Zr). Method for manufacturing a solid electrolyte.

Images