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

Abstract

This method for manufacturing a solid electrolyte comprises the steps of: preparing a lithium source material, a phosphorus source material, and a halogen source material; mixing the lithium source material, the phosphorus source material, and the halogen source material by using a dry bead mill to form a mixture; and heat-treating the mixture to form a sulfide-based compound having an argyrodite crystal structure. By performing a mixing process using a dry bead mill, a simple process without solvent treatment is applied, and continuous production up to pulverization and classification processes is possible, thereby reducing process costs while improving the quality of a sulfide-based solid electrolyte.

Description

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

[0001] The present invention provides a solid electrolyte, an all-solid-state battery comprising the same, and a method for manufacturing the same. More specifically, a sulfide-based solid electrolyte, an all-solid-state battery comprising the same, and a method for manufacturing the same are provided.

[0002] The present invention claims priority based on Korean Patent Application No. 10-2024-0190813 filed on December 19, 2024, the entire contents of said application incorporated herein by reference.

[0003] Recently, the demand for batteries has increased significantly due to the growing demand for electric vehicles and small power drive systems, such as electric bicycles and compact electric cars, in addition to mobile devices. However, conventional lithium-ion batteries using liquid electrolytes can experience increases in internal temperature and pressure due to external impacts or malfunctions of the Battery Management System (BMS). In such cases, there is a risk of explosion caused by ignition resulting from the decomposition of the flammable liquid electrolyte or leakage of the electrolyte. In particular, since lithium-ion batteries used in electric vehicles have high capacities, the damage caused by an explosion is even greater. Furthermore, when these lithium-ion batteries are manufactured with high capacities, there is a problem of increased volume and weight.

[0004] Due to the problems associated with lithium-ion batteries using liquid electrolytes, active research is being conducted on batteries using solid electrolytes, namely all-solid-state batteries. Since all-solid-state batteries utilize non-flammable solid electrolytes, they have a low risk of ignition due to electrolyte decomposition reactions or leakage, and offer high energy density. However, due to the physical limitations of solid electrolytes, their ionic conductivity is lower than that of liquid electrolytes. Furthermore, solid electrolytes may fail to make proper contact with the electrode surface, forming unstable interfaces that can degrade battery performance.

[0005] Solid electrolytes used in all-solid-state batteries include sulfide-based, oxide-based, and polymer-based solid electrolytes. Among these, research on the mass production of sulfide-based solid electrolytes, which exhibit high ionic conductivity and such as Li6PS5Cl with an argyrodite structure, is actively underway. However, sulfide-based solid electrolytes are difficult to handle in normal atmospheric conditions due to adverse reactions with moisture. Consequently, when a wet mixing process is applied to the manufacturing process of sulfide-based solid electrolytes, additional steps such as solvent treatment are required, increasing process costs. Furthermore, the material cost of lithium sulfide, which is used as a raw material for the manufacture of sulfide-based solid electrolytes, is also high.

[0006] One embodiment of the present invention is intended to improve the quality of a sulfide-based solid electrolyte while reducing the process cost of the sulfide-based solid electrolyte.

[0007] In addition to the above-mentioned tasks, embodiments according to the present invention may be used to achieve other tasks not specifically mentioned.

[0008] A method for manufacturing a solid electrolyte according to one embodiment of the present invention comprises the steps of: preparing a lithium raw material, a phosphorus raw material, and a halogen element raw material; mixing the lithium raw material, the phosphorus raw material, and the halogen element raw material using a dry bead mill to form a mixture; and heat-treating the mixture to form a sulfide-based compound having an azirodite crystal structure.

[0009] In one embodiment, the mixture may include lithium phosphate (Li3PO4).

[0010] In one embodiment, mixing using a dry bead mill can be performed for about 20 minutes to about 150 minutes.

[0011] In one embodiment, mixing using a dry bead mill can be performed at about 150 rpm to about 450 rpm.

[0012] In one embodiment, the heat treatment may be performed at about 300°C to about 600°C.

[0013] A solid electrolyte according to one embodiment of the present invention has an azirodite crystal structure and comprises a sulfide-based compound represented by the following chemical formula 1, and

[0014] [Chemical Formula 1]

[0015] Li 7-x PS 6-x D 2-x

[0016] In the above Chemical Formula 1, 0 <x≤1이고, D는 F, Cl, Br, I 또는 이들의 조합으로 이루어진 할로겐 원소이고, 인산리튬(Li3PO4)을 포함하면서, 인산리튬(Li3PO4)의 이차상이 형성되지 않은 것이다.

[0017] In one embodiment, the sulfide-based compound may be formed from a lithium raw material, a phosphorus raw material, and a halogen element raw material, and the lithium raw material, the phosphorus raw material, and the halogen element raw material may be mixed using a dry bead mill.

[0018] A solid-state battery according to one embodiment of the present invention comprises a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer and including a solid electrolyte. The solid electrolyte comprises a sulfide-based compound having an azirodite crystal structure derived from a lithium source material, a phosphorus source material, and a halogen element source material, and comprises lithium phosphate (Li3PO4), wherein a secondary phase of lithium phosphate (Li3PO4) is not formed.

[0019] In one embodiment, the anode layer may include an anode current collector and an anode active material layer disposed on the anode current collector.

[0020] In one embodiment, the cathode layer may include a cathode current collector and a cathode active material layer disposed on the cathode current collector.

[0021] According to one embodiment of the present invention, by performing a mixing process using a dry bead mill, a simple process with the solvent treatment omitted is applied, and continuous production is possible up to the process after mixing and heat treatment, thereby reducing process costs while improving the quality of the sulfide-based solid electrolyte.

[0022] FIG. 1 is a schematic flowchart of a method for manufacturing a solid electrolyte according to one embodiment of the present invention.

[0023] FIG. 2 is a schematic cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0024] Embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts unrelated to the explanation have been omitted to clearly explain the invention, and the same reference numerals are used for identical or similar components throughout the specification. Furthermore, specific descriptions of widely known prior art are omitted.

[0025] Throughout the specification, technical terms used are intended merely to refer to specific embodiments and are not intended to limit the invention. Throughout the specification, singular forms used include plural forms unless phrases clearly indicate otherwise.

[0026] Throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0027] Then, a solid electrolyte according to an embodiment of the present invention, an all-solid-state battery including the same, and a method for manufacturing the same will be described in detail.

[0028] The solid electrolyte contains lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D), and includes a sulfide-based compound having an argyrodite crystal structure. Accordingly, high ionic conductivity can be achieved.

[0029] The halogen element (D) may be F, Cl, Br, I, or a combination thereof. When the halogen element (D) is Cl, the solid electrolyte can be structurally stabilized, the synthesis of the solid electrolyte can be easy, and process costs can be reduced. Furthermore, when the halogen element (D) includes Br or I in addition to Cl, the ionic conductivity of the solid electrolyte can be increased, and when the halogen element (D) includes Cl and Br, the ionic conductivity of the solid electrolyte can be further increased.

[0030] Sulfide compounds can be represented by the following chemical formula 1.

[0031] [Chemical Formula 1]

[0032] Li 7-x PS 6-x D 2-x

[0033] In Chemical Formula 1, 0 <x≤1이고, D는 F, Cl, Br, I 또는 이들의 조합으로 이루어진 할로겐 원소이다.

[0034] In Chemical Formula 1, if x is too small, the ionic conductivity of the solid electrolyte may deteriorate, and if x is greater than 1, the ionic conductivity of the solid electrolyte improves, but electrochemical properties such as moisture stability and battery capacity characteristics may deteriorate.

[0035] The solid electrolyte may contain lithium phosphate (Li3PO4). Lithium phosphate may be used in an amount greater than about 0.01 mol% and less than or equal to about 20 mol%; when used in an amount greater than about 1 mol%, the solid electrolyte may be structurally and electrochemically stabilized, and when used in an amount less than or equal to about 20 mol%, the degradation of conductivity may be small.

[0036] Sulfide compounds can be formed from lithium, phosphorus, and halogen source materials, and these source materials can be mixed using a dry bead mill. Consequently, the quality of the solid electrolyte can be improved. Furthermore, since mixing by a dry bead mill does not use solvents, a simple process can be applied that eliminates solvent treatment, thereby reducing solvent treatment costs.

[0037] FIG. 1 is a schematic flowchart of a method for manufacturing a solid electrolyte according to one embodiment of the present invention.

[0038] Referring to FIG. 1, a method for manufacturing a solid electrolyte comprises the steps of preparing a lithium raw material, a phosphorus raw material, and a halogen element raw material (S10), mixing the lithium raw material, the phosphorus raw material, and the halogen element raw material to form a mixture (S20), and heat-treating the mixture to form a sulfide-based compound having an azirodite crystal structure (S30). Additionally, after forming the mixture and before heat treatment, a step of compressing the mixture to form a pellet may be additionally performed optionally.

[0039] First, a step of preparing lithium raw material, phosphorus raw material, and halogen element raw material is performed (S10).

[0040] For example, the lithium source material may be Li2S, Li2S2, or a combination thereof, but is not necessarily limited thereto. The phosphorus source material may be P2S5, P2O5, or a combination thereof, but is not necessarily limited thereto. The halogen element source material may be LiF, LiCl, LiBr, LiI, or a combination thereof, but is not necessarily limited thereto.

[0041] Next, a step is performed to form a mixture by mixing a lithium raw material, a phosphorus raw material, and a halogen element raw material (S20).

[0042] The input amounts of lithium raw materials, phosphorus raw materials, and halogen element raw materials can be appropriately adjusted stoichiometrically to match the composition of the target sulfide-based compound.

[0043] In addition, lithium phosphate (Li3PO4) may be added to the raw material. Lithium phosphate may be used in an amount greater than about 0.01 mol% and less than or equal to about 20 mol%; when used in an amount greater than about 1 mol%, the solid electrolyte may be structurally and electrochemically stabilized, and when used in an amount less than or equal to about 20 mol%, the degradation of conductivity may be small.

[0044] The mixing of raw materials is performed using a dry bead mill, and since no residual carbon is generated, the quality of the solid electrolyte can be improved. In addition, because the method using a dry bead mill does not use solvents, a simple process can be applied without solvent treatment, and solvent treatment costs can be reduced. Furthermore, by using the dry bead mill even for processes following mixing and heat treatment, continuous production is possible, which can reduce process costs. In contrast, the method using a wet bead mill increases costs and complicates the process due to the use of solvents, and the quality of the solid electrolyte may deteriorate due to the generation of residual carbon.

[0045] Mixing using a dry bead mill can be performed for about 20 minutes to about 150 minutes; if performed for more than about 20 minutes, the raw materials can be mixed uniformly, and if performed for less than about 150 minutes, the raw materials can be mixed uniformly while increasing process efficiency. Furthermore, mixing using a dry bead mill can be performed for about 30 minutes to about 120 minutes; if performed for more than about 30 minutes, the raw materials can be mixed more uniformly, and if performed for less than about 120 minutes, the raw materials can be mixed more uniformly while increasing process efficiency.

[0046] Mixing using a dry bead mill can be performed at approximately 150 rpm to approximately 450 rpm. When performed at approximately 150 rpm or higher, the beads can penetrate into the interior of the powder particles to mix the powder particles uniformly, and when performed at approximately 450 rpm or lower, the powder particles can be mixed evenly without leaning to one side. Furthermore, mixing using a dry bead mill can be performed for approximately 250 rpm to approximately 350 rpm. When performed at approximately 250 rpm or higher, the beads can penetrate into the interior of the powder particles to mix the powder particles even more uniformly, and when performed at approximately 350 rpm or lower, the powder particles can be mixed evenly without leaning to one side.

[0047] The diameter of the beads used may be approximately 0.5 mm to approximately 8 mm. If the diameter of the beads is approximately 0.5 mm or larger, it is advantageous for producing powder with small particle size, and if the diameter of the beads is approximately 8 mm or smaller, the proportion of coarse powder can be reduced. Furthermore, the diameter of the beads may be approximately 1 mm to approximately 5 mm. If the diameter of the beads is approximately 1 mm or larger, it is more advantageous for producing particles of 1 μm or smaller, and if the diameter of the beads is approximately 5 mm or smaller, the amount of coarse powder can be minimized.

[0048] In addition, beads having two or more diameters may be used in a mixture. To satisfy the performance requirements of an all-solid-state battery, it is required to control the particle size distribution of the solid electrolyte, and to easily control this particle size distribution, beads having two or more diameters may be used in a mixture. For example, among the indicators representing the particle size distribution, D50 can be maintained at approximately 2.5 μm to approximately 3.5 μm while D99 is made as small as possible, thereby maintaining the particle size of the solid electrolyte uniformly and improving the performance of the all-solid-state battery. However, if milling is performed using beads having only one diameter to reduce D99, D50 also decreases, which may lower the ionic conductivity value of the solid electrolyte. Accordingly, by using a mixture of beads having two or more diameters, the particle size distribution of the solid electrolyte can be easily controlled so that D50 is maintained at the required value while minimizing D99. For example, D99 can be minimized to about 6 µm or less, while D50 can be maintained at about 2.5 µm to about 3.5 µm, and more specifically, D50 can be maintained at about 2.8 µm to about 3.5 µm. In addition, when using beads having two or more types of diameters, when using a larger diameter bead in a greater weight than a smaller diameter bead, D99 can be minimized to about 6 µm or less, while D50 can be maintained at about 2.8 µm to about 3.5 µm.

[0049] Next, a step is performed to heat-treat the mixture to form a sulfide-based compound having an azirodite crystal structure (S30).

[0050] The heat treatment temperature of the mixture can be performed at approximately 300°C to approximately 600°C. If performed at approximately 300°C or higher, sufficient synthesis of a solid electrolyte with an azirodite crystal structure can occur, and synthesis into an amorphous crystal structure can be reduced, thereby increasing the ionic conductivity of the solid electrolyte. If performed at approximately 600°C or lower, vaporization of the solid electrolyte can be prevented, thereby reducing the loss of the solid electrolyte and preventing the formation of impurity phases, thereby increasing the ionic conductivity of the solid electrolyte. Furthermore, the heat treatment temperature of the mixture can be performed at approximately 400°C to approximately 500°C. If performed at approximately 400°C or higher, the synthesis of a solid electrolyte with an azirodite crystal structure can occur more sufficiently, and the synthesis into an amorphous crystal structure can be reduced, thereby further increasing the ionic conductivity of the solid electrolyte. If performed at approximately 500°C or lower, the vaporization of the solid electrolyte can be prevented, thereby further reducing the loss of the solid electrolyte and preventing the formation of impurity phases, thereby further increasing the ionic conductivity of the solid electrolyte. Accordingly, even at a relatively low temperature of approximately 400°C to approximately 450°C, a sulfide-based solid electrolyte containing lithium phosphate can be produced by reacting the mixture with lithium phosphate without forming a secondary phase (impurity phase) of lithium phosphate.

[0051] The heat treatment of the mixture can be performed in an inert gas atmosphere. Since the heat treatment is performed in an inert gas atmosphere, contact with moisture in the atmosphere is blocked, which can increase the synthesis efficiency of the solid electrolyte. For example, the inert gas can be Ar, N2, H2, or He.

[0052] FIG. 2 is a schematic cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0053] Referring to FIG. 2, an all-solid-state battery (1) using a solid electrolyte includes a positive electrode layer (10), a negative electrode layer (20), and a solid electrolyte layer (30) located between the positive electrode layer (10) and the negative electrode layer (20). Furthermore, an electric vehicle including such an all-solid-state battery may be provided.

[0054] The positive layer (10) may include a positive current collector and a positive active material layer disposed on the positive current collector.

[0055] For example, the positive current collector may include a plate or foil made of 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. The thickness of the positive current collector may be about 1 μm to about 100 μm, about 1 μm to about 50 μm, about 5 μm to about 25 μm, or about 10 μm to about 20 μm.

[0056] The positive active material layer comprises a positive active material and may optionally further comprise a solid electrolyte. The type of solid electrolyte included in the positive active material layer is not particularly limited.

[0057] The positive electrode active material is a material capable of reversibly absorbing and desorbing lithium ions. For example, the positive electrode active material may be lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, as well as nickel sulfide, copper sulfide, lithium sulfide, iron oxide, vanadium oxide, etc. Each positive electrode active material may be a single material or a mixture of two or more materials.

[0058] Lithium transition metal oxide is 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 Co b Bc O 2-α F2(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 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 1-b-c Mn b B c O 2-α F2(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(0.90 ≤ 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 Mn2G bO4(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) It is a compound represented by any one of the chemical formulas Fe2(PO4)3 (0 ≤ f ≤ 2) or 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. It is also possible to use a compound with a coating layer added to the surface of such a compound, and it is also possible to use a mixture of the aforementioned compound and the compound with the coating layer added. For example, a coating layer added to the surface of a compound may include a compound containing functional groups such as oxide, hydroxide, oxyhydroxide, oxycarbonate, hydroxycarbonate, etc. The compound forming the coating layer is amorphous or crystalline. The functional groups included in the coating layer may be combined with Li, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, Ta, B, As, Zr, Nb, or two or more of these metals. Methods for forming the coating layer include spray coating, immersion, etc.

[0059] The positive active material layer may include a binder. For example, the binder is styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc.

[0060] The positive active material layer may include a conductive material. For example, the conductive material is graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc.

[0061] The positive active material layer may further include additives such as fillers, coating agents, dispersants, and ion conductivity aids. As for the fillers, coating agents, dispersants, and ion conductivity aids that the positive active material layer may include, known materials generally used in electrodes of all-solid-state secondary batteries may be used.

[0062] The negative electrode layer (20) may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0063] For example, the negative current collector may include copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The negative current collector may be composed of one of the aforementioned metals, or may be composed of an alloy of two or more metals or a coating material. Additionally, the negative current collector may be in the form of a plate or a foil.

[0064] The negative electrode active material layer comprises a negative electrode active material. The negative electrode active material layer may optionally further comprise a solid electrolyte, and the type of solid electrolyte included in the negative electrode active material layer is not particularly limited.

[0065] For example, the negative electrode active material may include a carbon-based negative electrode active material, a metal / metallic negative electrode active material, or a combination thereof.

[0066] Carbon-based cathode active materials may be amorphous carbon, crystalline carbon, or mixtures or composites thereof. For example, amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. Crystalline carbon may be natural graphite, synthetic graphite, or a combination thereof.

[0067] The metal / metallic negative electrode active material may be lithium (Li), gold (Au), platinum (Pt), indium (In), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn) and zinc (Zn), or an alloy containing two or more of these.

[0068] The negative electrode active material layer may further include a binder. For example, the binder may be styrene-butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc. When the negative electrode active material layer includes a binder, the negative electrode active material layer can be stabilized on the negative electrode current collector. In addition, cracking of the negative electrode active material layer can be suppressed despite volume changes and / or relative positional changes of the negative electrode active material layer during the charge / discharge process.

[0069] The cathode active material layer may further include additives such as fillers, coating agents, dispersants, and ion-conducting aids.

[0070] The all-solid-state battery (1) may further include a second negative active material layer disposed between the negative current collector and the negative active material layer by charging. The second negative active material layer may be deposited between the negative current collector and the negative current collector during the charging process, or may be further disposed on the negative active material layer during electrode assembly. For example, the second negative active material layer may be lithium, one or more lithium alloys, or a metal layer containing two or more of these. One or more lithium alloys may be 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, or an alloy containing two or more of these.

[0071] The solid electrolyte layer (30) 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.

[0072] In this case, 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 in the form of pellets, sheets, thin films, etc.

[0073] The solid electrolyte layer (30) may further include a solid electrolyte such as a conventional sulfide-based solid electrolyte and / or a conventional oxide-based solid electrolyte in addition to the aforementioned solid electrolyte.

[0074] The binder used with the solid electrolyte may be styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, etc. The binder of the solid electrolyte layer may be of the same type as or different from the binder of the anode layer and the cathode layer.

[0075] The present invention will be explained in more detail below with reference to examples, but the following examples are merely embodiments of the present invention and the present invention is not limited to the following examples.

[0076] Comparative Example 1

[0077] The reactants Li2S, P2S5, and LiCl are introduced into a device using a wet bead mill containing a solvent in stoichiometric ratios to form Li6PS5Cl, and then mixed at 300 rpm for about 30 minutes. The diameter of the bead A used is 3 mm, and the total weight of the A beads is 600 g.

[0078] Next, the mixture is heat-treated at approximately 500°C in an Ar atmosphere to synthesize a Li6PS5Cl solid electrolyte.

[0079] The manufactured solid electrolyte is used as the electrolyte, and Li1Ni is used as the positive active material. 0.8 Co 0.1 Mn 0.1 An all-solid-state battery is manufactured using O2 and an In-Li alloy as the negative electrode active material.

[0080] Comparative Example 2

[0081] In a device using a wet bead mill containing a solvent, the reactants Li2S, P2S5, and LiCl are added in stoichiometric ratios to form Li6PS5Cl, and about 3 mol% of Li3PO4 is added, and then mixed at 300 rpm for about 30 minutes. The diameter of the bead A used is 3 mm, and the total weight of the A beads is 600 g.

[0082] Next, the mixture is heat-treated at approximately 500°C in an Ar atmosphere to synthesize a Li6PS5Cl solid electrolyte.

[0083] The manufactured solid electrolyte is used as the electrolyte, and Li1Ni is used as the positive active material. 0.8 Co 0.1 Mn 0.1 An all-solid-state battery is manufactured using O2 and an In-Li alloy as the negative electrode active material.

[0084] Example 1

[0085] In a device using a dry bead mill, the reactants Li2S, P2S5, and LiCl are added in stoichiometric ratios to form Li6PS5Cl, and about 3 mol% of Li3PO4 is added, and then mixed at 300 rpm for about 30 minutes. Beads A and B are used in combination, the diameter of Bead A is 5 mm, and the total weight of the A beads is 300 g, and the diameter of Bead B is 5 mm, and the total weight of the B beads is 300 g.

[0086] Next, the mixture is heat-treated at about 500°C in an Ar atmosphere to synthesize a Li6PS5Cl solid electrolyte containing 3 mol% Li3PO4.

[0087] The manufactured solid electrolyte is used as the electrolyte, and Li1Ni is used as the positive active material. 0.8 Co 0.1 Mn 0.1 An all-solid-state battery is manufactured using O2 and an In-Li alloy as the negative electrode active material.

[0088] Other Examples

[0089] In a device utilizing a dry bead mill, the reactants Li2S, P2S5, and LiCl are added in stoichiometric ratios to form Li6PS5Cl, and after adding approximately 3 mol% of Li3PO4, the mixture is mixed at 300 rpm for the time specified in Table 1. Beads A and B specified in Table 1 are used in combination.

[0090] Next, the mixture is heat-treated in an Ar atmosphere at the temperature listed in Table 1 to synthesize a Li6PS5Cl solid electrolyte containing 3 mol% Li3PO4.

[0091] The manufactured solid electrolyte is used as the electrolyte, and Li1Ni is used as the positive active material. 0.8 Co 0.1 Mn 0.1 An all-solid-state battery is manufactured using O2 and an In-Li alloy as the negative electrode active material.

[0092] Experimental Example 1: Evaluation of Ionic Conductivity (30℃, 0.1C)

[0093] For the aforementioned comparative examples and embodiments, the manufactured solid electrolyte is crushed and then formed into pellets under a pressure of 300 MPa. Then, a cell is fabricated using SUS as the working electrode under a pressure of 70 MPa. After that, the impedance is measured by applying a voltage of 10 mV at 30°C and is listed in Table 1.

[0094] Experimental Example 2: Evaluation of Initial Discharge Capacity

[0095] For the aforementioned comparative examples and embodiments, charging is performed at 30°C at 0.1C to 4.25V (vs. Li+ / Li), and the application of the charging current is terminated by setting the current amount to 0.02C at the corresponding voltage. After discharging to 2.50V (vs. Li+ / Li) at a current amount of 0.1C under the same conditions, the initial discharge capacity is evaluated and listed in Table 1.

[0096] Experimental Example 3: Evaluation of Life Characteristics

[0097] For the aforementioned comparative examples and embodiments, after performing a formation cycle at 0.1C, the percentage of the discharge capacity at the 50th cycle relative to the discharge capacity at the 1st cycle at a current density of 0.5C is calculated and listed in Table 1.

[0098] Experimental Example 4: Particle Size Measurement

[0099] For the aforementioned comparative examples and examples, the particles were dispersed by applying ultrasound for 60 seconds using a toluene or xylene solvent with a Microtrac-S3500 particle size analyzer, and the particle size distribution was measured and D50 and D99 were listed in Table 1.

[0100] Experimental Example 5: XRD Measurement

[0101] For the aforementioned comparative examples and embodiments, XRD is measured to determine whether Li3PO4 peaks were detected, and this is recorded in Table 1.

[0102]

[0103] Classification A Bead Diameter (mm) B Bead Diameter (mm) A Beads Weight (g) B Beads Weight (g) Mixing Time (min) Temperature (°C) Li3PO4 Phase Detection D50 (㎛) D99 (㎛) Ion Conductivity (mS / cm) Initial Discharge Capacity (mAh / g) Efficiency (%) Comparative Example 13-600-30500X2.85.62.119689.7 Comparative Example 23-600-30500O35.71.619889.8 Example 15530030030500X2.96.12.219990.4 Example 23530030030500X2.76.22.319790.3 Example 31530030030500X2.36219990.3 Example 43330030030500X3.16.82.219690.0 Example 51330030030500X2.17.42.319890.2 Example 63530030060500X2.97. 22.219389.5 Example 73530030090500X2.76.72.219489.8 Example 835300300120500X2.56.92.119890.1 Example 93510050030500X2.85.91.920191.5 Example 103550010030500X2.18.12.520091.1 Example 113510050030450X2.66.1219590.9 Example 123510050030400X2.75.92.119489.1

[0104] Referring to Table 1, it can be seen that the ion conductivity, initial discharge capacity, and efficiency of Examples 1 to 12 using a dry bead mill are similar to those of Comparative Examples 1 and 2 using a wet bead mill.

[0105] In addition, when a wet bead mill is used in Comparative Example 2, the Li3PO4 phase is detected when 3 mol% of Li3PO4 is used, but when a dry bead mill is used in Examples 1 to 12, the Li3PO4 phase is not detected even when 3 mol% of Li3PO4 is used. Also, as can be seen in Examples 11 and 12, a Li3PO4-containing sulfide-based solid electrolyte can be produced that does not form a Li3PO4 secondary phase even when the mixture is reacted with 3 mol% of Li3PO4 at a relatively low temperature of about 400°C to about 450°C.

[0106] Referring to Examples 1 and 4, it can be seen that when using beads of one type of diameter, as the diameter of the bead increases, D99 decreases and D50 also decreases. Additionally, referring to Examples 1 to 3, it can be seen that when using beads of two types of diameters, as one of the diameters decreases, D99 remains similar but D50 decreases, resulting in a decrease in ionic conductivity. Accordingly, referring to Examples 9 and 10, it can be seen that when using beads of two types of diameters, if the larger diameter bead is used in a greater weight than the smaller diameter bead, D99 is minimized while D50 is maintained.

[0107] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

1. Step of preparing lithium raw materials, phosphorus raw materials, and halogen element raw materials, A step of forming a mixture by mixing the lithium raw material, the phosphorus raw material, and the halogen element raw material using a dry bead mill, and A step of heat-treating the above mixture to form a sulfide-based compound having an azirodite crystal structure. A method for manufacturing a solid electrolyte comprising 2. In Paragraph 1, A method for manufacturing a solid electrolyte, wherein the above mixture comprises lithium phosphate (Li3PO4).

3. In Paragraph 1, A method for manufacturing a solid electrolyte, wherein mixing using the above dry bead mill is performed for 20 to 150 minutes.

4. In Paragraph 3, A method for manufacturing a solid electrolyte, wherein mixing using the above dry bead mill is performed at 150 rpm to 450 rpm.

5. In Paragraph 1, A method for manufacturing a solid electrolyte, wherein the above heat treatment is performed at 300°C to 600°C.

6. A sulfide compound having an azirodite crystal structure and represented by the following chemical formula 1, and [Chemical Formula 1] Li 7-x P.S. 6-x D 2-x In the above Chemical Formula 1, 0 <x≤1이고, D는 F, Cl, Br, I 또는 이들의 조합으로 이루어진 할로겐 원소이고, A solid electrolyte containing lithium phosphate (Li3PO4) in which a secondary phase of lithium phosphate (Li3PO4) is not formed.

7. In Paragraph 6, The above sulfide-based compound is formed from a lithium raw material, a phosphorus raw material, and a halogen element raw material, and the lithium raw material, the phosphorus raw material, and the halogen element raw material are mixed using a dry bead mill, forming a solid electrolyte.

8. Bipolar layer, cathode layer, and A solid electrolyte layer located between the anode layer and the cathode layer and comprising a solid electrolyte Includes, The above solid electrolyte is, Derived from lithium raw materials, phosphorus raw materials, and halogen element raw materials, It includes sulfide compounds having an azirodite crystal structure, and All-solid-state battery containing lithium phosphate (Li3PO4) in which a secondary phase of lithium phosphate (Li3PO4) is not formed.

9. In Paragraph 8, The above-described positive layer comprises a positive current collector and a positive active material layer disposed on the positive current collector, in an all-solid-state battery.

10. In Paragraph 8, The above-described negative electrode layer comprises a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, in an all-solid-state battery.

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