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

Abstract

The present invention relates to a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), oxygen (O), and a plurality of halogen elements, wherein the sulfide-based solid electrolyte has an argyrodite-based crystal structure, and exhibits a single phase in the region of 400 to 450 cm-1 in Raman analysis of the sulfide-based solid electrolyte.

Description

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

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

[0002] This application claims priority to Korean Patent Application No. 10-2024-0191923 filed on December 19, 2024, the entire contents of which are incorporated herein by reference.

[0003] With the recent increase in demand for electric vehicles, the demand for high-energy, high-output lithium-ion batteries is also rising. Lithium-ion batteries have the advantage of higher energy density and greater capacity per unit area compared to nickel-manganese or nickel-cadmium batteries.

[0004] However, conventional lithium-ion batteries mainly used flammable organic liquid electrolytes as electrolytes, which caused safety issues such as overheating. Recently, all-solid-state batteries using non-flammable solid electrolytes have been gaining attention.

[0005] All-solid-state batteries are batteries that ensure safety by replacing the liquid electrolyte, which causes explosions, with a solid electrolyte and eliminating the use of flammable solvents within the battery, thereby preventing any ignition or explosion caused by the decomposition reaction of conventional electrolytes.

[0006] Inorganic solid electrolytes are generally used in all-solid-state batteries. Among solid electrolytes, sulfides are characterized by high ionic conductivity and relative flexibility, making it easy to form solid-solid interfaces. Additionally, they are stable with respect to active materials, leading to various ongoing studies on sulfide-based solid electrolytes.

[0007] However, sulfide-based solid electrolytes generate hydrogen sulfide (H2S) gas upon contact with humid air, which causes a degradation in conductivity and can lead to a problem of reduced performance in cell characteristics compared to lithium secondary batteries using liquid electrolytes.

[0008] Therefore, there is a need to develop technology capable of stabilizing sulfide-based solid electrolytes that are unstable in moisture.

[0009] One objective of the present invention is to provide a sulfide-based solid electrolyte that includes heterogeneous halogen elements, has improved ionic conductivity, and is stable in moisture.

[0010] Another objective of the present invention is to provide a method for manufacturing a sulfide-based solid electrolyte having the aforementioned advantages by introducing oxygen during heat treatment to oxidize the sulfide-based solid electrolyte during the manufacture of the sulfide-based solid electrolyte.

[0011] Another objective of the present invention is to provide an all-solid-state battery with improved electrochemical properties without degradation of cell performance by including a sulfide-based solid electrolyte having the aforementioned advantages.

[0012] A sulfide-based solid electrolyte according to one embodiment of the present invention is a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), oxygen (O), and a plurality of halogen elements, wherein the sulfide-based solid electrolyte has an azirodite-based crystal structure and satisfies the following Equation 1 during Raman analysis of the sulfide-based solid electrolyte.

[0013] [Equation 1]

[0014] 0.1 ≤ B / A ≤ 9.5

[0015] In Equation 1 above, A is the Raman shift of 400 to 430 cm⁻¹ measured by Raman analysis. -1 It is the peak area in the range, and B is the Raman shift of 405 to 445 cm⁻¹ -1 It refers to the peak area within the range.

[0016] The above sulfide-based solid electrolyte may exhibit a peak in the range of 133±0.5 to 135±0.5 eV in X-ray photoelectron spectroscopy (XPS).

[0017] The above halogen elements may be at least two selected from F, Cl, Br, and I.

[0018] The above sulfide-based solid electrolyte may have a molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) of 5.5 to 6.5.

[0019] The above sulfide-based solid electrolyte may have a molar ratio of sulfur (S) to phosphorus (P) ([P] / [S]) of 4.0 to 5.5.

[0020] The above sulfide-based solid electrolyte may have a molar ratio ([P] / [D]) of a plurality of halogen elements (D) to phosphorus (P) of 0.5 to 1.5.

[0021] A method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention comprises: a step of mixing a lithium mixture, a phosphorus mixture, and a halogen mixture to form a mixture; and a step of heat-treating the mixture in an atmosphere of inert gas and oxygen while simultaneously oxidizing it to form a sulfide-based solid electrolyte having an agyrodite-based crystal structure.

[0022] The above heat treatment can be performed at a temperature of 400 to 700°C.

[0023] The above heat treatment time may be 5 to 10 hours.

[0024] The above oxygen input amount may be 100 to 20,000 ppm.

[0025] The above halogen mixture may include at least two of LiCl, LiF, LiBr, and LiI.

[0026] The amount of LiCl added above may be 0.95 to 1.45 mol% based on the total molar amount of the mixture.

[0027] The amount of LiF added above may be 0.01 to 0.1 mol% based on the total moles of the mixture.

[0028] The amount of LiBr added may be 0.01 to 0.1 mol% based on the total moles of the mixture.

[0029] A solid-state battery according to another embodiment of the present invention comprises a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises the aforementioned sulfide-based solid electrolyte.

[0030] A sulfide-based solid electrolyte according to one embodiment of the present invention may have improved ionic conductivity and be stable in moisture by including a different type of halogen element.

[0031] An all-solid-state battery according to another embodiment of the present invention can improve the discharge capacity of the all-solid-state battery by including a sulfide-based solid electrolyte whose surface is oxidized by mixing oxygen during heat treatment.

[0032] Figure 1 is a graph of the Raman spectroscopy results of a sulfide-based solid electrolyte according to one embodiment and a comparative example of the present invention.

[0033] Figure 2 is a graph of the Raman spectroscopic results of a sulfide-based solid electrolyte according to one embodiment and a comparative example of the present invention, separated into peaks A and B.

[0034] Figure 3 is a graph of the X-ray photoelectron spectroscopy results of a sulfide-based solid electrolyte according to one embodiment and a comparative example of the present invention.

[0035] In this specification, terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the invention.

[0036] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0037] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0038] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0039] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0040] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0041] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0042] Sulfide-based solid electrolytes

[0043] A sulfide-based solid electrolyte according to one embodiment of the present invention is a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), oxygen (O), and a plurality of halogen elements, wherein the sulfide-based solid electrolyte has an azirodite-based crystal structure and satisfies the following Equation 1 during Raman analysis of the sulfide-based solid electrolyte.

[0044] [Equation 1]

[0045] 0.1 ≤ B / A ≤ 9.5

[0046] In Equation 1 above, A is the Raman shift of 400 to 430 cm⁻¹ measured by Raman analysis. -1 It is the peak area in the range, and B is the Raman shift of 405 to 445 cm⁻¹ -1 It refers to the peak area within the range. If the above range is satisfied, there may be an advantage in maintaining the azirodite crystal structure without any change in the bulk structure of the sulfide-based solid electrolyte. Specifically, this may mean that oxygen is not doped into the sulfide-based solid electrolyte, and only the surface of the solid electrolyte exists in an oxidized form.

[0047] In one embodiment, the sulfide-based solid electrolyte may exhibit a peak in the range of 132±0.5 to 135±0.5 eV in X-ray photoelectron spectroscopy (XPS), specifically in the range of 133±0.5 to 134±0.5 eV. If the peak satisfies the above range, the PS4 corresponding to the 132.85 eV position is PO x S 4-x This may mean that the peak has shifted due to oxidation.

[0048] In one embodiment, the halogen element may be at least two selected from F, Cl, Br, and I, but is not limited thereto, and any material that can be included in a sulfide-based solid electrolyte to improve ionic conductivity may be used.

[0049] In one embodiment, the molar ratio of lithium (Li) to phosphorus (P) in the sulfide-based solid electrolyte ([Li] / [P]) may be 5.5 to 6.5, specifically 5.8 to 6.2. When the molar ratio of lithium (Li) to phosphorus (P) satisfies the above range, the ionic conductivity of the sulfide-based solid electrolyte is improved, which may lead to improved electrochemical stability and increased charge / discharge efficiency during the manufacture of an all-solid-state battery. On the other hand, if the molar ratio of lithium (Li) to phosphorus (P) is too low, problems may arise such as a decrease in the ionic conductivity of the sulfide-based solid electrolyte and a reduction in the mobility of lithium ions. Additionally, if the molar ratio of lithium (Li) to phosphorus (P) is too high, problems may arise such as reduced safety due to structural instability caused by excessive lithium and an increased possibility of electrolyte decomposition.

[0050] In one embodiment, the molar ratio of sulfur (S) to phosphorus (P) in the sulfide-based solid electrolyte ([P] / [S]) may be 4.0 to 5.5, specifically 4.5 to 5.0. When the molar ratio of sulfur (S) to phosphorus (P) satisfies the above range, a stable crystal structure is formed, which may have the advantage of improving the stability of the sulfide-based solid electrolyte. On the other hand, if the molar ratio of sulfur (S) to phosphorus (P) is too low, the ionic conductivity of the sulfide-based solid electrolyte may decrease, and problems such as an unstable crystal structure may occur. In addition, if the molar ratio of sulfur (S) to phosphorus (P) is too high, problems such as a decrease in the characteristics of the sulfide-based solid electrolyte and the performance of the all-solid-state battery may occur due to excessive sulfur content.

[0051] In one embodiment, the molar ratio ([P] / [D]) of a plurality of halogen elements (D) to phosphorus (P) in the sulfide-based solid electrolyte may be 0.5 to 1.5, specifically 0.9 to 1.2. When the molar ratio of a plurality of halogen elements (D) to phosphorus (P) satisfies the above range, the thermal stability of the solid electrolyte is improved and the interfacial resistance is reduced, thereby improving the performance of the all-solid-state battery. On the other hand, if the molar ratio of a plurality of halogen elements (D) to phosphorus (P) is too low, the distribution of halogen elements within the sulfide-based solid electrolyte becomes non-uniform due to insufficient halogen doping, which may result in local performance differences. Additionally, if the molar ratio of a plurality of halogen elements (D) to phosphorus (P) is too high, the halogen elements may be excessively doped, which may lower the structural stability of the solid electrolyte and cause a decrease in battery performance due to side reactions with the electrode material.

[0052] Method for manufacturing sulfide-based solid electrolytes

[0053] A method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention comprises: a step of mixing a lithium mixture, a phosphorus mixture, and a halogen mixture to form a mixture; and a step of heat-treating the mixture in an atmosphere of inert gas and oxygen while simultaneously oxidizing it to form a sulfide-based solid electrolyte having an agyrodite-based crystal structure. When oxygen is mixed while heat-treating the mixture, there may be an advantage in that the surface or bulk of the sulfide-based solid electrolyte is oxidized, thereby stabilizing the sulfide-based solid electrolyte.

[0054] In another embodiment, the heat treatment may be performed at a temperature of 400 to 700°C, specifically 450 to 650°C, and more specifically 500 to 600°C. When the heat treatment temperature satisfies the above range, the azirodite crystal structure of the sulfide-based solid electrolyte is properly formed, which improves structural stability and removes unnecessary components, which may have the advantage of improving purity. On the other hand, if the heat treatment temperature is too low, incomplete crystallization may occur during the manufacture of the sulfide-based solid electrolyte, and a problem of reduced ionic conductivity may occur. In addition, if the heat treatment temperature is too high, problems such as structural instability or the formation of other crystal phases may occur.

[0055] The above heat treatment time may be 5 to 10 hours, specifically 7 to 8 hours. If the above heat treatment time satisfies the above range, the surface of the sulfide-based solid electrolyte can be oxidized to stabilize the solid electrolyte. On the other hand, if the above heat treatment time is too short, the oxidation of the sulfide-based solid electrolyte is insufficient, which may cause the crystal structure of the solid electrolyte to become unstable and lead to a decrease in ion conductivity. In addition, if the above heat treatment time is too long, the sulfide-based solid electrolyte may become structurally unstable due to excessive heat treatment, and a problem may arise in which other crystal phases are formed.

[0056] In another embodiment, the amount of oxygen input may be 100 to 20,000 ppm, specifically 300 to 10,000 ppm, and more specifically 500 to 5,000 ppm. When the amount of oxygen input satisfies the above range, the PS4 unit of the sulfide-based solid electrolyte is oxidized, and PO on the surface of the sulfide-based solid electrolyte x S 4-xA unit can be formed to stabilize the solid electrolyte. On the other hand, if the amount of oxygen introduced is too small, the oxidation of the solid electrolyte may be insufficient, leading to a problem where the stability of the sulfide-based solid electrolyte is reduced. Furthermore, if the amount of oxygen introduced is excessive, the structure of the sulfide-based solid electrolyte may be deformed, potentially causing a self-discharge problem due to increased electron conductivity.

[0057] In another embodiment, the halogen compound may include at least two of LiCl, LiF, LiBr, and LiI, but is not limited thereto, and any material capable of improving the moisture stability and ionic conductivity of the sulfide-based solid electrolyte may be used.

[0058] In another embodiment, the amount of LiCl added may be 0.95 to 1.45 mol% based on the total molar amount of the mixture, specifically 0.99 to 1.2 mol%. When the amount of LiCl added satisfies the above range, the crystal structure of the solid electrolyte may be improved, the ion transport pathway may be made more efficient, interfacial resistance may be reduced, and electrochemical stability may be improved. On the other hand, if the amount of LiCl added is too small, the content in the sulfide-based solid electrolyte may be too low, so the improvement in ion conductivity may not be sufficient. In addition, if the amount of LiCl added is too large, structural instability of the solid electrolyte may occur due to excessive LiCl, and problems such as deterioration of the mechanical properties of the electrolyte may occur.

[0059] In another embodiment, the amount of LiF added may be 0.01 to 0.1 mol% based on the total molar amount of the mixture, specifically 0.05 to 0.08 mol%. When the amount of LiF added satisfies the above range, the movement of lithium ions within the sulfide-based solid electrolyte is promoted, thereby improving ion conductivity and increasing the charge-discharge cycle life of the all-solid-state battery. On the other hand, if the amount of LiF added is too small, the amount of LiF in the sulfide-based solid electrolyte is too small, so the effect of improving ion conductivity may be insufficient. In addition, if the amount of LiF added is too large, the structural stability of the solid electrolyte may be reduced due to the excessive LiF, and unnecessary side reactions may occur.

[0060] In another embodiment, the amount of LiBr added may be 0.01 to 0.1 mol% based on the total molar amount of the mixture, specifically 0.05 to 0.08 mol%. If the LiBr satisfies the above range, there may be an advantage in maintaining the structural stability of the sulfide-based solid electrolyte. On the other hand, if the amount of LiBr added is too small, the effect of improving the ion conductivity of the sulfide-based solid electrolyte may be negligible. In addition, if the amount of LiBr added is excessive, the instability of the crystal structure of the sulfide-based solid electrolyte increases, which may lead to a decrease in ion conductivity and a reduction in battery performance.

[0061] All-solid-state battery

[0062] Another embodiment of the present invention provides an all-solid-state battery comprising: an anode layer; a cathode layer; and a solid electrolyte layer located between the anode layer and the cathode layer, wherein at least one of the anode layer, the cathode layer, and the solid electrolyte layer comprises the aforementioned sulfide-based solid electrolyte.

[0063] (Bipolar layer)

[0064] More specifically, the anode layer may include an anode current collector and an anode active material layer disposed on the anode current collector.

[0065] The above-mentioned positive active material layer may further include, for example, a positive active material and, optionally, a solid electrolyte. The solid electrolyte included in the positive active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0066] The cathode active material is a material capable of reversibly absorbing and desorbing lithium ions. The cathode active material may be, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not necessarily limited to these; any material used as a cathode active material in the relevant technical field is acceptable. The cathode active material may be a single material or a mixture of two or more materials.

[0067] The above lithium transition metal oxide is, for example, Li a A 1-b B b D2(wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c(In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 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 (In the above equation, 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 F2(wherein 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 (In the above equation, 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 O 2-α F α (In the above equation, 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 O 2-α F2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G dO2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2(wherein the above formula, 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(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 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)Fe2(PO4)3(0 ≤ f ≤ 2); a compound represented by any one of the chemical formulas of LiFePO4. In such a compound, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. A compound having a coating layer added to the surface of such a compound may also be used, and a mixture of the compound described above and a compound having a coating layer added may also be used. The coating layer applied to the surface of such compounds comprises, for example, a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element. The compounds forming this coating layer are amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the cathode active material. The coating method is, for example, spray coating or immersion. Since specific coating methods are well understood by those skilled in the art, a detailed explanation will be omitted.

[0068] The positive active material layer may include, for example, a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these, and any binder used in the relevant technical field is acceptable.

[0069] The positive active material layer may include, for example, a conductive material. The conductive material may include, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc., but is not limited to these, and any material used as a conductive material in the relevant technical field is acceptable.

[0070] The positive active material layer may further include additives such as fillers, coating agents, dispersants, and ion conductivity aids in addition to the positive active material, solid electrolyte, binder, and conductive material described above, for example.

[0071] As fillers, coating agents, dispersants, ion conductivity aids, etc. that may be included in the positive electrode active material layer, known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[0072] The positive current collector may be a plate or foil made of, 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 alloys thereof. The thickness of the positive current collector may be, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0073] (Cathode layer)

[0074] More specifically, the above cathode layer may include a cathode current collector and a cathode active material layer disposed on the cathode current collector.

[0075] The above-mentioned cathode active material layer may include, for example, a cathode active material and a binder, and may optionally further include a solid electrolyte as needed.

[0076] The above-mentioned negative electrode active material may include, for example, a carbon-based negative electrode active material, a metal / metallic negative electrode active material, or a combination thereof.

[0077] The carbon-based cathode active material may be amorphous carbon, crystalline carbon, or a mixture or composite thereof. The amorphous carbon may be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Kettjen black (KB), graphene, etc., but is not necessarily limited to these, and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. The crystalline carbon may be, for example, natural graphite, artificial graphite, or a combination thereof.

[0078] The metal / metallic anode active material comprises one or more selected from the group consisting of lithium (Li), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited to these, and any metal anode active material or metallic anode active material that forms an alloy or compound with lithium in the relevant technical field is acceptable.

[0079] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these, and any binder used in the relevant technical field is acceptable. The binder may be composed of a single binder or a plurality of different binders.

[0080] The cathode active material layer is stabilized on the cathode current collector by including a binder. In addition, cracking of the cathode active material layer is suppressed despite volume changes and / or relative positional changes of the cathode active material layer during the charging and discharging process.

[0081] The negative electrode active material layer may further include additives used in conventional all-solid-state batteries, such as fillers, coating agents, dispersants, ion conductivity aids, etc.

[0082] The all-solid-state battery may further include a second negative electrode active material layer disposed between the negative electrode current collector and the negative electrode active material layer upon charging. The second negative electrode active material layer may be deposited between the negative electrode current collector and the negative electrode current collector during the charging process, or may be further disposed on the negative electrode active material layer during electrode assembly. This second negative electrode active material layer may be a metal layer comprising lithium or a lithium alloy. The lithium alloy may be, for example, 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, but is not limited thereto; any alloy used as a lithium alloy in the relevant technical field is acceptable. The second negative electrode active material layer may be composed of one of these alloys and / or lithium, or may be composed of various types of alloys and / or lithium.

[0083] The negative electrode current collector may be composed of, for example, a material that does not react with lithium, that is, does not form either an alloy or a compound. The negative electrode current collector may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited to these; any material used as an electrode current collector in the relevant technical field is acceptable. The negative electrode current collector may be composed of one of the metals described above, or may be composed of an alloy or coating material of two or more metals. The negative electrode current collector may be, for example, in the form of a plate or a foil.

[0084] When the above-mentioned cathode active material layer includes a solid electrolyte, the solid electrolyte included in the above-mentioned cathode active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0085] (Solid electrolyte layer)

[0086] The above solid electrolyte layer can be manufactured by mixing and drying the aforementioned solid electrolyte and binder, or by rolling the aforementioned solid electrolyte powder into a certain shape under a pressure of 1 ton to 10 ton.

[0087] At this time, the solid electrolyte may be in the form of a powder or a molded article. The solid electrolyte in the form of a molded article may be, for example, in the form of pellets, sheets, thin films, etc., but is not necessarily limited to these and may have various forms depending on the application.

[0088] The above solid electrolyte layer may, if necessary, further include a solid electrolyte such as a conventional sulfide-based solid electrolyte and / or an oxide-based solid electrolyte in addition to the aforementioned solid electrolyte.

[0089] The above binder is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, etc., but is not limited to these, and any binder used in the relevant technical field is acceptable. The binder of the solid electrolyte layer may be of the same type as or different from the binders of the anode layer and the cathode layer.

[0090] Another embodiment of the present invention provides an electric vehicle comprising the all-solid-state battery.

[0091] The embodiments of the present invention will be described in more detail below through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited by the following examples.

[0092]

[0093] Example 1

[0094] The composition of the sulfide-based solid electrolyte is Li6PS5Cl 0.95 F 0.05 The amounts of Li2S, P2S5, LiCl, and LiF were adjusted as much as possible and fed into a planetary mill, mixed at 400 rpm for about 8 hours, and pellets were produced at 300 MPa. Subsequently, 500 ppm of O2 gas and Ar gas were introduced and heat-treated at 550°C to oxidize the surface or bulk of the sulfide-based solid electrolyte, thereby producing a stabilized sulfide-based solid electrolyte.

[0095] Example 2

[0096] The composition of the sulfide-based solid electrolyte is Li6PS5Cl 0.95 Br 0.05 After adjusting the amounts of Li2S, P2S5, LiCl, and LiBr to achieve this, the product was manufactured under the same conditions as Example 1.

[0097] Example 3

[0098] The composition of the sulfide-based solid electrolyte is Li 5.5 PS 4.5 Cl 1.45 F 0.05 It was prepared under the same conditions as Example 1, except that the amounts of Li2S, P2S5, LiCl, and LiF were adjusted as much as possible and introduced into a planetary mill.

[0099] Example 4

[0100] The composition of the sulfide-based solid electrolyte is Li 5.5 PS 4.5 Cl 1.45 Br 0.05 After adjusting the amounts of Li2S, P2S5, LiCl, and LiBr to achieve this, the product was manufactured under the same conditions as Example 1.

[0101] Comparative Example 1

[0102] Li2S, P2S5, and LiCl were introduced into a planetary mill and mixed at 400 rpm for about 8 hours, then pellets were produced at 300 MPa, Ar gas was introduced, and heat treatment was performed at 550°C to produce a sulfide-based solid electrolyte.

[0103] Comparative Examples 2 to 7

[0104] Li2S, P2S5, and LiCl were introduced into a planetary mill and mixed at 400 rpm for about 8 hours, after which pellets were produced at 300 MPa. Subsequently, O2 gas and Ar gas were introduced according to the oxygen introduction amounts listed in Table 1, and heat treatment was performed at 550°C to produce a sulfide-based solid electrolyte in which the surface or bulk of the sulfide-based solid electrolyte was oxidized.

[0105] Experimental Example 1: Raman Spectroscopy

[0106] Raman spectroscopy was performed on the sulfide-based solid electrolytes prepared according to the examples and comparative examples. The specific experimental methods are as follows.

[0107] When irradiating the solid electrolyte with an excitation light wavelength of 532 nm using Raman spectroscopy (equipment name: LabRAM HR Evolution, manufactured by Horiba Co., Ltd.), the sulfide-based solid electrolyte was measured by integrating 10 times in 2 seconds with a power of 1 to 3 mW, and the results are shown in Fig. 1.

[0108] Referring to Fig. 1, 400 to 450 cm -1 Since there is no change in the nearby Raman peak, it can be confirmed that there is no change in the bulk structure even if a step of simultaneous oxidation by introducing oxygen during heat treatment is included when manufacturing sulfide-based solid electrolytes.

[0109] Figure 2 is a graph of the Raman spectroscopy results of a sulfide-based solid electrolyte according to an embodiment and a comparative example of the present invention, separated into peaks A and B. Referring to Figure 2 and Table 1, it can be seen that when manufacturing a sulfide-based solid electrolyte in which the surface of the sulfide-based solid electrolyte is oxidized, the value of the area of ​​peak B relative to the area of ​​peak A decreases as the amount of oxygen input increases.

[0110] Experimental Example 2: X-ray photoelectron spectroscopy

[0111] X-ray photoelectron spectroscopy was performed on the sulfide-based solid electrolytes prepared according to the examples and comparative examples. The specific experimental method is as follows.

[0112] X-ray photoelectron spectroscopy (Instrument name: K-Alpha of ThermoFiher Scientific Inc.) + The solid electrolyte was measured in CAE (Constant Analyzer Energy) operating mode using a monochromatic Al Kα X-ray source of 1486.6 eV. At this time, the X-ray spot size was 400 μm, the pass energy was 50 eV, and Avantage software was used, and the results are shown in Fig. 3.

[0113] Referring to Fig. 3, when oxidation is performed simultaneously with heat treatment during the manufacture of sulfide-based solid electrolytes, the PS4 unit corresponding to the 132.85 eV position is PO x S 4-x It can be confirmed that the peak shifted to the 134 eV region due to oxidation by the unit.

[0114] Experimental Example 3: Evaluation of Ionic Conductivity (30℃, 0.1C)

[0115] An experiment to evaluate the ionic conductivity of a solid electrolyte was conducted using a pressure powder cell. Specifically, the synthesized solid electrolyte was ground and then formed into pellets under a pressure of 300 MPa. Subsequently, a cell was fabricated using SUS as the working electrode under a pressure of 70 MPa. Afterward, the impedance was measured by applying a voltage of 10 mV at 30°C, and the results are shown in Table 2.

[0116] Experimental Example 4: Evaluation of Electrochemical Properties

[0117] (1) Discharge capacity evaluation

[0118] An initial discharge capacity evaluation experiment was conducted when the sulfide-based solid electrolytes prepared according to the examples and comparative examples were applied to batteries. The specific experimental method is as follows.

[0119] Electrochemical evaluations of the solid electrolytes prepared in the Comparative and Examples were conducted using a pressure powder cell. The composite anode electrode had an anode : solid electrolyte : conductive material (Denka Black) ratio of 70 : 29 : 1 wt% and a diameter of 0.785 cm 2Electrodes were fabricated with a loading of 20.0 mg over an area and densified to 300 MPa. Subsequently, bonding was performed at 50 MPa using an Indium-Lithium counter electrode, and the cells were assembled under the same pressure. After fabrication, charge and discharge tests were conducted after aging at room temperature for 2 hours. Capacity evaluation was performed using 180 mAh / g as the reference capacity, and charge / discharge conditions were applied at CC / CV 1.9 to 3.60 V and a 1 / 20C cut-off. Initial capacity was evaluated under 0.1C charge / 0.1C discharge conditions, and the results are shown in Table 2.

[0120] (2) Life characteristic evaluation (30℃, 100 cycles)

[0121] Lifetime characteristics were evaluated when the sulfide-based solid electrolytes prepared according to the examples and comparative examples were applied to batteries. The specific experimental methods are as follows.

[0122] After fabricating the battery half cell, it was charged to 3.63V at 30°C with a constant current of 0.5C, then switched to a constant voltage and charged until the terminal current reached 0.1C. After a rest time of 10 minutes following charging, it was discharged with a constant current of 0.5C until it reached 1.9V. 100 charge-discharge cycles were performed under these conditions, and the capacity retention rate of the 100th cycle compared to the first cycle was calculated, and the results are shown in Table 2.

[0123] Area ratio (B / A)Ar10.1O2, 500ppm6.7O2, 1500ppm2.6

[0124] Referring to Table 1, it can be seen that when manufacturing a sulfide-based solid electrolyte in which the surface of the sulfide-based solid electrolyte is oxidized with O2, the value of the B peak area relative to the A peak area decreases as the amount of oxygen input increases.

[0125] Composition Oxygen Intake Amount (ppm) Ion Conductivity (mS / cm) Discharge Capacity (mAh / g) Comparative Example 1 Li6PS5Cl 0 1.6208 Comparative Example 2 Li6PS5Cl 100 1.7209 Comparative Example 3 Li6PS5Cl 200 1.9209 Comparative Example 4 Li6PS5Cl 500 2.1211 Comparative Example 5 Li6PS5Cl 1000 2210 Comparative Example 6 Li6PS5Cl 5000 1.9207 Comparative Example 7 Li6PS5Cl 20000 1.3205 Example 1 Li6PS5Cl 0.95 F 0.05 5002.1210 Example 2 Li6PS5Cl 0.95 Br 0.05 5002.3211 Example 3 Li 5.5 PS 4.5 Cl 1.45 F 0.05 5007.4209 Example 4Li 5.5 PS 4.5 Cl 1.45 Br 0.05 5007.5209

[0126] Referring to Table 2, it can be confirmed that Examples 1 to 4, in which a sulfide-based solid electrolyte containing multiple halogen elements was oxidized by introducing oxygen simultaneously with heat treatment, exhibit superior ionic conductivity and no decrease in discharge capacity compared to Comparative Examples 1 to 7. Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

[0127] Therefore, the substantive scope of the present invention shall be defined by the appended claims and their equivalents.

Claims

1. A sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), oxygen (O), and a plurality of halogen elements, The above sulfide-based solid electrolyte has an azirodite-based crystal structure, and A sulfide-based solid electrolyte satisfying the following Equation 1 during Raman analysis of the above sulfide-based solid electrolyte: [Equation 1] 0.1 ≤ B / A ≤ 9.5 In Equation 1 above, A is the Raman shift of 400 to 430 cm⁻¹ measured by Raman analysis. -1 It is the peak area in the range, and B is the Raman shift of 405 to 445 cm⁻¹ -1 It refers to the peak area within the range.

2. In Paragraph 1, A sulfide-based solid electrolyte that exhibits a peak in the range of 133±0.5 to 135±0.5 eV in X-ray photoelectron spectroscopy (XPS) of the above sulfide-based solid electrolyte.

3. In Paragraph 1, A sulfide-based solid electrolyte in which the above halogen elements are at least two selected from F, Cl, Br, and I.

4. In Paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) of 5.5 to 6.

5.

5. In Paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of sulfur (S) to phosphorus (P) ([P] / [S]) of 4.0 to 5.

5.

6. In Paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte in which the molar ratio ([P] / [D]) of a plurality of halogen elements (D) to phosphorus (P) is 0.5 to 1.

5.

7. A step of mixing a lithium mixture, a phosphorus mixture, and a halogen mixture to form a mixture; and A method for manufacturing a sulfide-based solid electrolyte, comprising the step of heat-treating the above mixture in an atmosphere of inert gas and oxygen while simultaneously oxidizing it to form a sulfide-based solid electrolyte with an agyrodite-based crystal structure.

8. In Paragraph 7, A method for manufacturing a sulfide-based solid electrolyte, wherein the above heat treatment is performed at a temperature of 400 to 700°C.

9. In Paragraph 7, A method for manufacturing a sulfide-based solid electrolyte, wherein the heat treatment time is 5 to 10 hours.

10. In Paragraph 7, A method for manufacturing a sulfide-based solid electrolyte, wherein the oxygen input amount is 100 to 20,000 ppm.

11. In Paragraph 7, A method for preparing a sulfide-based solid electrolyte, wherein the above halogen mixture comprises at least two of LiCl, LiF, LiBr, and LiI.

12. In Paragraph 11, A method for manufacturing a sulfide-based solid electrolyte, wherein the amount of LiCl added is 0.95 to 1.45 mol% based on the total molar amount of the mixture.

13. In Paragraph 11, A method for manufacturing a sulfide-based solid electrolyte, wherein the amount of LiF added is 0.01 to 0.1 mol% based on the total molar amount of the mixture.

14. In Paragraph 11, A method for manufacturing a sulfide-based solid electrolyte, wherein the amount of LiBr added is 0.01 to 0.1 mol% based on the total molar amount of the mixture.

15. Bipolar layer; cathode layer; and It includes a solid electrolyte layer disposed between the anode layer and the cathode layer, and An all-solid-state battery in which at least one of the anode layer, the cathode layer, and the solid electrolyte layer comprises a sulfide-based solid electrolyte according to any one of claims 1 to 6.

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