Preparation method for solid electrolyte, solid electrolyte prepared thereby, and all-solid-state battery comprising same

Abstract

The present invention provides an alkali metal ion-conductive chalcogenide-based solid electrolyte, wherein in order to mass-produce the solid electrolyte at a level that can be applied to all-solid-state batteries, Li2S is not used even when going through a complete dissolution method by which homogeneous synthesis can be performed, and a reaction is completed in one pot in a single solvent, thereby facilitating precursor recovery and solvent reuse and enabling high ionic conductivity.

Description

Method for producing a solid electrolyte, a solid electrolyte produced thereby, and an all-solid-state battery comprising the same

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

[0002]

[0003] With the recent expansion of the market for battery-powered electric vehicles (BEVs), demand for improved battery safety is increasing. Lithium secondary batteries, in particular, have become the primary secondary batteries for electric vehicles due to their higher energy density than conventional lead-acid, Ni-MH, and Ni-Cd batteries. However, concerns about leakage and the high risk of fire from the organic electrolytes used in lithium secondary batteries have led to growing interest in all-solid-state batteries using solid electrolytes.

[0004] Among the inorganic solid electrolytes with high thermal stability, sulfide-based solid electrolytes exhibit high lithium-ion conductivity comparable to that of liquid electrolytes and have unique ductility, so they are being actively studied as electrolytes for all-solid-state batteries.

[0005] Sulfide-based solid electrolytes can be manufactured by dry synthesis or wet synthesis. Dry synthesis can be manufactured through processes such as raw material mixing, heat treatment, and crushing. However, since some of the synthesis is mechanically performed after the raw material is mixed using high-energy rotational force and then heat treated, it has the disadvantage of being difficult to synthesize in large quantities.

[0006] Wet synthesis methods for solid electrolytes include a suspension method in which a solid electrolyte precursor powder is formed in a polar aprotic solvent through dispersion and reaction, the powder is recovered, and then heat-treated to produce the solid electrolyte; a dissolution method in which raw materials are completely dissolved as precursors in a polar protic solvent, a polar aprotic solvent, or a mixed solution thereof, and then dried and heat-treated; and a hybrid method in which a precursor is partially dissolved and then dried and heat-treated.

[0007] The suspension method has the advantage of being able to recover particulate solid electrolyte precursors, but it has the disadvantages of low compositional uniformity of the solid electrolyte precursors formed through particle-particle reactions of raw material powders, slow production rate, limited types of solid electrolytes that can be manufactured by this method, and relatively low ionic conductivity (less than 1 mS / cm for Li3PS4).

[0008] As a representative example of the dissolution method, Li2S and P2S5 are reacted in THF to produce a Li3PS4·3THF precursor, and then this precursor or solution is mixed with Li2S, LiX (X=F, Cl, Br, I) in ethanol to produce Li in a completely dissolved state. 7-a PS 6-a X a (0≤a≤2) precursor is prepared, the solvent is evaporated to recover the powder, and it is dried and heat treated to obtain Li 7-a PS 6-a X a A solid electrolyte powder of (0≤a≤2) can be obtained. Li 7-a PS 6-a X aIn the case of the Li-argyrodite structure represented by (0≤a≤2), it has been reported that a solid electrolyte having an ionic conductivity of 1 mS / cm or more can be synthesized through composition control. However, this method has a disadvantage in that it requires an additional process of evaporating the solvent or precipitating the powder by placing it in a non-polar solvent to recover the precursor powder from the completely dissolved solution.

[0009] Meanwhile, most solid electrolyte synthesis methods to date use Li2S as a raw material, and the core reaction in most wet synthesis methods, 3Li2S + P2S5 → 2Li3PS4, proceeds internally with Li2S as the core and Li3PS4 forming a shell. Therefore, not only is the reaction rate slow, but it is also greatly affected by the purity, particle size, and oxidation of Li2S. In addition, there are safety issues due to the use of a large amount of H2S, a hazardous gas, for Li2S synthesis, and additional costs are required for high purity, making the manufacturing process difficult. In addition, there is the difficulty of storing it in an inert gas, and commercially sold high-purity Li2S powder for batteries is sold at a high price of more than $1,000 per kg, which is a factor in securing the price competitiveness of solid electrolyte materials using Li2S as a raw material.

[0010] Recently, a one-pot wet synthesis method utilizing lithium metal, which can secure price competitiveness, has been reported. This method has the advantage of allowing easy mass synthesis of solid electrolytes by introducing all raw materials for solid electrolyte production, reacting them, and then proceeding with precipitation, filtration, drying, and heat treatment. However, the method has the disadvantage of producing a heterogeneous solid electrolyte due to the combined use of suspension and dissolution methods, resulting in a low ionic conductivity of 1.2 mS / cm.

[0011] In particular, even if a solid electrolyte is synthesized, particle size control requiring a grinding process is required for application to an all-solid-state battery, and there is a phenomenon in which ionic conductivity decreases during the particle size control process, and in order to apply to an all-solid-state battery, a high ionic conductivity of at least 3 mS / cm before grinding is required.

[0012] [Prior Art Literature]

[0013] (Patent Document 1) Korean Patent No. 1236059 (February 15, 2013)

[0014]

[0015] In order to solve the above-mentioned problems, the inventors of the present invention have conducted research and have developed a new method for synthesizing a solid electrolyte that exhibits high ionic conductivity, by completing the reaction in a single solvent in one pot without using Li2S, while undergoing a complete dissolution method that enables homogeneous synthesis in order to mass-produce a solid electrolyte applicable to all-solid-state batteries, thereby facilitating recovery of the precursor and reuse of the solvent.

[0016] Accordingly, the object of the present invention is to provide a wet manufacturing method for an alkali metal ion conductive chalcogenide-based solid electrolyte that enables mass production of an alkali metal ion conductive chalcogenide-based solid electrolyte at low cost, a solid electrolyte having high ionic conductivity manufactured thereby, and an all-solid-state battery including the same.

[0017]

[0018] In order to solve the above problem, the present invention provides a method for preparing an alkali metal ion conducting chalcogenide-based solid electrolyte, comprising the steps of: (1) preparing a first precursor solution in which a precursor of an alkali metal ion conducting chalcogenide-based solid electrolyte is completely dissolved in a polar aprotic solvent; (2) adding an alkali metal or an alkali metal-containing material to the first precursor solution to prepare a slurry in which a second precursor is dispersed; (3) recovering the second precursor in a powder form from the slurry; and (4) heat-treating the second precursor powder.

[0019] In addition, the present invention provides an alkali metal ion conductive chalcogenide-based solid electrolyte manufactured according to the above method and represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] (A + ) a (B n+ ) b (X 2- ) x (Y - ) y

[0022] Here, A is one or more elements selected from Li, Na, and K, B is one or more elements belonging to groups 2 to 15 of the periodic table, X is one or more elements selected from S, Se, and Te or a combination of these and O, Y is one or more elements or compounds selected from F, Cl, Br, I, CN, OCN, SCN, and N3, a + (n*b) - (2*x) - y = 0, a > 0, x > 0, and at least one of b and y is greater than 0.

[0023] In addition, the present invention provides an all-solid-state battery including the alkali metal ion conductive chalcogenide-based solid electrolyte.

[0024]

[0025] According to the method of the present invention, in order to mass-produce a solid electrolyte applicable to an all-solid-state battery, a complete dissolution method is used to achieve homogeneous synthesis, and the reaction is completed in a single pot in a single solvent without using Li2S, thereby facilitating recovery of the precursor and reuse of the solvent, and an alkali metal ion-conducting chalcogenide-based solid electrolyte exhibiting a high ionic conductivity of 3 mS / cm or more can be provided.

[0026] Accordingly, the present invention can provide a wet manufacturing method for an alkali metal ion conductive chalcogenide-based solid electrolyte that enables mass production of an alkali metal ion conductive chalcogenide-based solid electrolyte at low cost, a solid electrolyte having high ionic conductivity manufactured thereby, and an all-solid-state battery including the same.

[0027]

[0028] Figure 1 shows a method for manufacturing an alkali metal ion conductive chalcogenide-based solid electrolyte according to one embodiment of the present invention.

[0029] Figure 2 shows a method for manufacturing a solid electrolyte (Li6PS5Cl) according to one embodiment.

[0030] Figure 3 shows a photograph of a solution in which the first precursor of Example 1 is completely dissolved.

[0031] Figure 4 shows a photograph of a slurry in which the second precursor is dispersed in Example 1.

[0032] Figure 5 shows an XRD pattern obtained from the solid electrolyte (Li6PS5Cl) of Example 1.

[0033] Figure 6 shows the results of measuring the ionic conductivity of the solid electrolyte in Test Example 3.

[0034] Figure 7 shows a graph analyzing the particle size of the solid electrolyte in Test Example 3.

[0035] Figure 8 shows the ionic conductivity of the solid electrolyte before and after exposure to the atmosphere in Test Example 3.

[0036] Figure 9 shows a charge / discharge curve measured from an all-solid-state battery in Test Example 4.

[0037] Figure 10 shows the results of analyzing a solution in which the first precursor is completely dissolved using an electrospray ionization mass spectrometer.

[0038]

[0039] The terms used to refer to each component in this specification are used to distinguish it from other components and are not intended to limit the implementation examples. Furthermore, the singular expressions used in this specification include the plural expressions unless the context clearly dictates otherwise.

[0040] In this specification, the terms "first," "second," etc. are used to describe various components, and the components should not be limited by the terms. The terms are used for the purpose of distinguishing one component from another.

[0041] The word "comprising" or "including" in this specification is intended to specify particular features, regions, steps, processes, elements and / or components, and does not exclude the presence or addition of other features, regions, steps, processes, elements and / or components, unless specifically stated to the contrary.

[0042] In the numerical ranges that limit the size, physical properties, etc. of the components described in this specification, if a numerical range limited only to the upper limit and a numerical range limited only to the lower limit are separately exemplified, it should be understood that a numerical range in which these upper and lower limits are combined is also included in the exemplary range of the present invention.

[0043] According to one aspect of the present invention, a method for producing an alkali metal ion conducting chalcogenide-based solid electrolyte is provided, comprising: (1) preparing a first precursor solution in which a precursor of an alkali metal ion conducting chalcogenide-based solid electrolyte is completely dissolved in a polar aprotic solvent; (2) adding an alkali metal or an alkali metal-containing material to the first precursor solution to prepare a slurry in which a second precursor is dispersed; (3) recovering the second precursor in a powder form from the slurry; and (4) heat-treating the second precursor powder.

[0044] Figure 1 illustrates a method for manufacturing an alkali metal ion conductive chalcogenide-based solid electrolyte according to one embodiment of the present invention. Figure 2 illustrates a method for manufacturing a solid electrolyte (Li6PS5Cl) according to one embodiment of the present invention.

[0045] Referring to FIGS. 1 and 2, a method for manufacturing an alkali metal ion-conducting chalcogenide-based solid electrolyte according to one embodiment includes a step of reacting an alkali metal ion-conducting chalcogenide-based solid electrolyte raw material including an alkali metal-containing material, a transfer catalyst that ionizes an alkali metal to transfer ions and electrons, a chalcogen element, and a compound of at least one element from Groups 2 to 15 and Group 17 of the periodic table in a polar aprotic solvent. Accordingly, a first precursor solution is prepared in which an alkali metal ion-conducting chalcogenide-based solid electrolyte precursor is completely dissolved via an alkali metal polychalcogenide generated when ions and electrons are transferred from the alkali metal-containing material to the chalcogen element (S10). Thereafter, a step (S20) of adding an alkali metal and an alkali metal ion to the first precursor solution to prepare a slurry in which a second precursor is dispersed, a step (S30) of recovering an alkali metal ion conductive chalcogenide-based solid electrolyte precursor in powder form from the slurry in which the second precursor is dispersed, and a step (S40) of heat-treating the alkali metal ion conductive chalcogenide-based solid electrolyte precursor powder are performed.

[0046] Below, each step of the above manufacturing method is described in detail.

[0047]

[0048] Preparation of the first precursor solution

[0049] In step (1), a first precursor solution in which a precursor of an alkali metal ion conducting chalcogenide-based solid electrolyte is completely dissolved in a polar aprotic solvent is prepared.

[0050] For example, the first precursor solution can be prepared by reacting an alkali metal ion conductive chalcogenide-based solid electrolyte raw material in a polar aprotic solvent.

[0051] According to one embodiment, the first precursor solution can be prepared by reacting an alkali metal ion-conducting chalcogenide-based solid electrolyte raw material including (i) an alkali metal or an alkali metal-containing material, (ii) a transfer catalyst that ionizes the alkali metal to transfer ions and electrons, (iii) a chalcogen element, and (iv) a compound of one or more elements from groups 2 to 15 and 17 of the periodic table, in a polar aprotic solvent.

[0052] The above alkali metal-containing material may be, for example, an alkali metal-transfer catalyst radical solution formed by reacting an alkali metal with the transfer catalyst in the polar aprotic solvent.

[0053] As an example, an alkali metal may be used alone in the preparation of the first precursor solution. The alkali metal may be a component belonging to Group 1 of the periodic table. Specifically, the alkali metal may be at least one selected from the group consisting of lithium (Li), sodium (Na), and potassium (K).

[0054] As another example, an alkali metal-containing material may be used in the preparation of the first precursor solution. The alkali metal-containing material may be an alkali metal-transfer catalyst radical solution formed by reacting an alkali metal with a transfer catalyst in a polar aprotic solvent. By preparing the alkali metal-transfer catalyst radical solution in advance and then reacting it, the time required to dissolve and react the alkali metal is reduced.

[0055] As another example, a mixture of an alkali metal and an alkali metal-containing material may be used to prepare the first precursor solution.

[0056] The transfer catalyst that ionizes the alkali metal and transfers ions and electrons may be, for example, one or more polycyclic aromatic hydrocarbons (PAHs). Specifically, the transfer catalyst is selected from the group consisting of naphthalene, acenaphthylene, acenaphthene, biphenyl, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[k]fluoranthene, benzo[b]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene, and It can be selected from the group consisting of benzo[ghi]perylene.

[0057] In addition, the chalcogen element may be at least one element selected from the group consisting of, for example, sulfur (S), selenium (Se), tellurium (Te), and oxygen (O). Specifically, the chalcogen element may be at least one element selected from the group consisting of sulfur (S), selenium (Se), and tellurium (Te), or a combination of these elements and oxygen (O).

[0058] The first precursor solution can be prepared by reacting the alkali metal ion conductive chalcogenide solid electrolyte raw material exemplified above in a polar aprotic solvent.

[0059] The polar aprotic solvent may be, for example, an ether solvent, a vinyl solvent, an amide solvent, an acetate solvent, a carbonate solvent, an ester solvent, or a mixed solvent of at least one of these. Specifically, the polar aprotic solvent may be at least one selected from the group consisting of an aliphatic monoether, an aliphatic diether, a cyclic ether, a polyether, acrylonitrile (ACN), dimethylformamide (DMF), ethyl acetate (EA), dimethyl carbonate (DMC), and ethyl propionate (EP).

[0060] When reacting the above alkali metal ion conductive chalcogenide-based solid electrolyte raw material in a polar aprotic solvent, ultrasonic irradiation, stirring, a high-speed homogenizer, a high-pressure sprayer, mechanical grinding, or a combination thereof can be used.

[0061] The temperature during the reaction for preparing the first precursor solution may be, for example, -78°C or higher, -60°C or higher, -45°C or higher, -30°C or higher, or -15°C or higher, and may also be 70°C or lower, 55°C or lower, 40°C or lower, or 20°C or lower. Specifically, the temperature during the reaction for preparing the first precursor solution may be -78°C to 70°C, and more specifically, -78°C to 20°C.

[0062] In addition, the reaction for preparing the first precursor solution may be carried out with stirring, and the stirring time may be, for example, 5 minutes or more, 10 minutes or more, 15 minutes or more, or 20 minutes or more, and may also be 120 minutes or less, 90 minutes or less, 60 minutes or less, or 45 minutes or less. Specifically, the stirring time during the reaction for preparing the first precursor solution may be 5 to 120 minutes, and more specifically, 10 to 60 minutes.

[0063] As a result, a first precursor solution in which the precursor of an alkali metal ion-conducting chalcogenide-based solid electrolyte is completely dissolved in a polar aprotic solvent can be obtained.

[0064] According to one embodiment, the precursor of the alkali metal ion conductive chalcogenide-based solid electrolyte may be represented by the following chemical formula 1a.

[0065] [Chemical Formula 1a]

[0066] (A + ) a (B n+ ) b (X 2- ) x (Y - ) y

[0067] Here, A is one or more elements selected from Li, Na, and K, B is one or more elements belonging to groups 2 to 15 of the periodic table, X is one or more elements selected from S, Se, and Te or a combination of these and O, Y is one or more elements or compounds selected from F, Cl, Br, I, CN, OCN, SCN, and N3, and satisfies the values ​​0≤a≤3, 4≤x≤6, and 0≤y≤2 under the criterion of b = 1.

[0068] The first precursor solution is dissolved in the solution by alkali metal-transfer catalyst radicals generated by a reaction between the alkali metal-containing material and the transfer catalyst transferring alkali metal ions and electrons to the chalcogen element to form an alkali metal polychalcogenide, and the polychalcogenide reacts or mixes with the B element, Y element, or a compound thereof, so that the alkali metal ion conductive chalcogenide-based solid electrolyte first precursor can be completely dissolved in the solution.

[0069] The color of the first precursor solution may be, for example, yellow, red, or a mixture thereof.

[0070]

[0071] Preparation, recovery and heat treatment of the second precursor slurry

[0072] In step (2), an alkali metal or an alkali metal-containing material is added to the first precursor solution to prepare a slurry in which the second precursor is dispersed.

[0073] According to one embodiment, in step (2), the alkali metal or alkali metal-containing material may be lithium metal; a mixture of lithium metal and a transfer catalyst; or a mixture of lithium metal, a transfer catalyst, and a polar aprotic solvent.

[0074] In the above step (2), the first precursor and the alkali metal or alkali metal-containing material react to cause a second precursor having a different composition from the first precursor to be precipitated and dispersed in the solution, thereby producing a slurry.

[0075] After adding an alkali metal or an alkali metal-containing material to the first precursor solution, the particle size of the slurry precursor can be controlled by treating it with one or more of ultrasonic irradiation, passage through a high-pressure homogenizer, mechanical grinding, reaction rate with the alkali metal, and addition of a non-solvent, or the particle size of the second precursor can be controlled by inducing nucleation and growth of the suspended precursor by adjusting the concentration of the alkali metal-transfer catalyst radical.

[0076] The temperature during the reaction for preparing the second precursor solution may be, for example, -78°C or higher, -60°C or higher, -45°C or higher, -30°C or higher, or -15°C or higher, and may also be 70°C or lower, 55°C or lower, 40°C or lower, or 20°C or lower. Specifically, the temperature during the reaction for preparing the second precursor solution may be -78°C to 70°C, and more specifically, -78°C to 20°C.

[0077] Additionally, the reaction time for preparing the second precursor solution may be, for example, 1 hour or more, 4 hours or more, 10 hours or more, or 18 hours or more, and may also be 72 hours or less, 60 hours or less, 45 hours or less, or 24 hours or less. Specifically, the reaction time for preparing the second precursor solution may be 1 hour to 72 hours, and more specifically, 4 hours to 24 hours.

[0078] The alkali metal introduced for the production of the second precursor in the above step (2) may be the same component as the alkali metal introduced for the production of the first precursor in the previous step (1).

[0079] The amount of alkali metal (or the amount of alkali metal in the alkali metal-containing material) injected in each of the above steps (1) and (2) can be controlled within a specific range.

[0080] First, the amount of the alkali metal introduced in the step (1) (or the amount of the alkali metal in the alkali metal-containing material) may be, for example, 25 g or more, 35 g or more, 43 g or more, or 48 g or more, based on 1,000 g of sulfur (S), and may also be 195 g or less, 170 g or less, 145 g or less, or 130 g or less. Specifically, the amount of the alkali metal introduced in the step (1) may be 43 g to 145 g, and more specifically, 48 g to 130 g, based on 1,000 g of sulfur (S). It may be more advantageous to produce a homogeneous solid electrolyte having high ionic conductivity by creating a solution that is completely dissolved within the above preferred range.

[0081] Next, the amount of the alkali metal introduced in the step (2) (or the amount of the alkali metal in the alkali metal-containing material) may be, for example, 230 g or more, 260 g or more, 289 g or more, or 303 g or more, and may also be 470 g or less, 430 g or less, 390 g or less, or 385 g or less, based on 1,000 g of sulfur (s). Specifically, the amount of the alkali metal introduced in the step (2) may be 289 g to 390 g, and more specifically, 303 g to 385 g, based on 1,000 g of sulfur (s). Within the above preferred range, lithium is completely reacted so that there is no residual lithium metal and organic lithium, which may be more advantageous in reducing impurities.

[0082] In addition, the ratio of the amount of alkali metal (or the amount of alkali metal in the alkali metal-containing material) introduced in the above steps (1) and (2) may be, for example, 1:10 to 1:1.5, specifically 1:9 to 1:2, and more specifically 1:8 to 3:7. It may be more advantageous to manufacture a homogeneous solid electrolyte with high ionic conductivity through a complete dissolution process within the above preferred range.

[0083] In step (3), the second precursor is recovered in powder form from the slurry.

[0084] In the above step (3), recovery of the second precursor can be performed using co-precipitation, filtration, centrifugation, natural sedimentation, spray, hydrocyclone, or a combination thereof.

[0085] As a specific example, the second precursor can be recovered in powder form by filtering the slurry under reduced pressure.

[0086] In addition, in the above step (3), one or more processes of heat drying, solvent substitution, and spray drying may be further performed on the slurry to improve the precursor synthesis yield.

[0087] In step (4), the recovered second precursor powder is heat treated.

[0088] The above second precursor powder may first be heated or vacuum dried to remove any residue of the polar aprotic solvent or the transfer catalyst.

[0089] The temperature during the heating or vacuum drying may be, for example, room temperature or higher, 25°C or higher, 40°C or higher, 60°C or higher, 120°C or higher, or 150°C or higher, and may also be 300°C or lower, 250°C or lower, or 200°C or lower. Specifically, the temperature during the heating or vacuum drying may be room temperature to 300°C, room temperature to 200°C, 25°C to 200°C, or 120°C to 200°C.

[0090] Thereafter, the second precursor powder can be crystallized by heat treatment at a specific temperature.

[0091] The heat treatment for the above crystallization can be performed in one or more atmospheres of vacuum, inert gas, and hydrogen sulfide (H2S) gas.

[0092] The temperature of the heat treatment for the crystallization may be, for example, 140°C or higher, 200°C or higher, 300°C or higher, 400°C or higher, or 500°C or higher, and may also be 800°C or lower, 700°C or lower, or 600°C or lower. Specifically, the temperature of the heat treatment for the crystallization may be 140°C to 800°C, 140°C to 600, 200°C to 600°C, 300°C to 600°C, or 400°C to 600°C.

[0093] According to one embodiment, the heat treatment of the second precursor powder in the step (4) may include a process of removing residue by heating or vacuum drying at room temperature to 200°C, and then crystallizing at 200°C to 600°C under an inert gas atmosphere.

[0094] When performed under the above preferred heat treatment conditions, the crystal structure of a solid electrolyte with high ionic conductivity can be obtained, and there is an advantage in that the loss of sulfur and phosphorus due to volatilization can be suppressed. Specifically, the above preferred heat treatment conditions are advantageous in that sufficient diffusion between the constituent atoms of the solid electrolyte is achieved, while preventing excessive reduction in ionic conductivity due to deformation of the crystal structure caused by volatilization of the elements that make up the solid electrolyte.

[0095] According to the method of the present invention, by synthesizing an alkali metal ion conductive chalcogenide-based solid electrolyte precursor and only recovering powder and heat treating it, an alkali metal ion (Li) having a crystalline or glass-ceramic structure with high ionic conductivity is produced. + , Na + , K + ) It has the effect of being able to easily synthesize a conductive chalcogenide-based solid electrolyte without using expensive and difficult-to-store raw materials such as Li2S, Na2S, and K2S.

[0096] In addition, in the alkali metal-containing material reacting with a chalcogen element, a compound of one or more elements from groups 2 to 15 and 17 of the periodic table under a polar aprotic solvent, the alkali metal alone can be used, and in particular, when an alkali metal-transfer catalyst radical solution formed by reacting the alkali metal with a transfer catalyst in a polar aprotic solvent is prepared in advance and then reacted, there is an effect of reducing the time required to dissolve and react the alkali metal.

[0097] In addition, the particle size of the precursor in a suspended state can be controlled by physical powder grinding methods such as ultrasonic irradiation, passage through a high-pressure homogenizer, and mechanical grinding during the reaction for preparing the precursor solution, and there is an effect of controlling the particle size of the precursor by inducing chemical nucleation and growth of the precursor in a suspended state by adjusting the concentration of the alkali metal ion-transfer catalyst radical.

[0098] In addition, after recovering the alkali metal ion conducting chalcogenide-based solid electrolyte precursor powder, the remaining solvent can be recovered and recycled in a batch or continuous manner for the first step of synthesizing the alkali metal ion conducting chalcogenide-based solid electrolyte, which not only reduces costs but also has an advantageous effect in mass production.

[0099]

[0100] Alkali metal ion-conducting chalcogenide-based solid electrolyte and all-solid-state battery

[0101] According to another aspect of the present invention, an alkali metal ion conductive chalcogenide solid electrolyte manufactured according to the method described above is provided.

[0102] An alkali metal ion conductive chalcogenide solid electrolyte according to one embodiment is represented by the following chemical formula 1.

[0103] [Chemical Formula 1]

[0104] (A + ) a (B n+ ) b (X 2- ) x (Y - ) y

[0105] Here, A is one or more elements selected from Li, Na, and K, B is one or more elements belonging to groups 2 to 15 of the periodic table, X is one or more elements selected from S, Se, and Te or a combination of these and O, Y is one or more elements or compounds selected from F, Cl, Br, I, CN, OCN, SCN, and N3, a + (n*b) - (2*x) - y = 0, a > 0, x > 0, and at least one of b and y is greater than 0.

[0106] In the above chemical formula 1, A is one or more elements selected from Li, Na, and K, and for example, A may be Li, or a combination thereof with at least one element from among Na and K.

[0107] In the above chemical formula 1, B is one or more elements belonging to groups 2 to 15 of the periodic table, for example, B is one or more elements belonging to groups 13 to 15, and more specifically, may include elements of group 15.

[0108] In the above chemical formula 1, X is one or more elements selected from S, Se, and Te, or a combination of these and O, and for example, X may be S, or a combination of at least one element selected from Se and Te.

[0109] In the above chemical formula 1, Y is one or more elements or compounds selected from F, Cl, Br, I, CN, OCN, SCN, and N3, and for example, Y may be at least one halogen element selected from F, Cl, Br, and I.

[0110] In the above chemical formula 1, a + (n*b) - (2*x) - y = 0, a > 0, x > 0, and at least one of b and y is greater than 0, for example, a = 7-y, b = 1, x = 6-y, 0.1 ≤ y ≤ 2.

[0111] The alkali metal ion conductive chalcogenide solid electrolyte represented by the above chemical formula 1 may include a crystal structure of space group F-43m, and specifically, may include an argyrodite crystal structure.

[0112] A solid electrolyte according to one embodiment may comprise 10 wt% or more, 30 wt% or more, 50 wt% or more, or 70 wt% or more of an argyrodite crystal structure, and may also comprise 100 wt% or less, 90 wt% or less, or 80 wt% or less. Specifically, the solid electrolyte may comprise 50 wt% to 100 wt% of an argyrodite crystal structure.

[0113] According to a specific example, A is Li, B is P, X is S, Y is at least one halogen element selected from F, Cl, Br and I, a = 7-y, b = 1, x = 6-y, 0.1 ≤ y ≤ 2, and comprises 50 wt% to 100 wt% of an argyrodite crystal structure of space group F-43m.

[0114] The alkali metal ion conductive chalcogenide-based solid electrolyte according to the present invention has an ionic conductivity of a specific level or higher. The ionic conductivity of the solid electrolyte according to one embodiment may be 1.5 mS / cm or higher, 2 mS / cm or higher, 2.5 mS / cm or higher, 3 mS / cm or higher, or 3.5 mS / cm or higher immediately after production. For example, the ionic conductivity of the alkali metal ion conductive chalcogenide-based solid electrolyte may be 3 mS / cm or higher immediately after production. Meanwhile, the upper limit of the ionic conductivity is not particularly limited, but may be, for example, 10 mS / cm or lower, 8 mS / cm or lower, 6 mS / cm or lower, or 5 mS / cm or lower. As a specific example, the ionic conductivity of the solid electrolyte may be 1.5 mS / cm to 10 mS / cm, 2 mS / cm to 8 mS / cm, 2.5 mS / cm to 6 mS / cm, or 3 mS / cm to 5 mS / cm immediately after manufacture.

[0115] In addition, the alkali metal ion conductive chalcogenide-based solid electrolyte according to the present invention has a carbon content below a specific level. For example, the carbon content of the solid electrolyte according to one embodiment may be 10% or less, 7% or less, or 5% or less. Specifically, the carbon content of the alkali metal ion conductive chalcogenide-based solid electrolyte may be 3% or less. More specifically, the carbon content of the alkali metal ion conductive chalcogenide-based solid electrolyte may be 1% or less.

[0116] According to another aspect of the present invention, an all-solid-state battery comprising the alkali metal ion conductive chalcogenide-based solid electrolyte described above is provided.

[0117] The above all-solid-state battery may include a positive electrode, a negative electrode, and a solid electrolyte inserted between them.

[0118] The above-mentioned positive electrode may include a positive electrode active material, a solid electrolyte, a conductive material, a binder, etc., and any known material that can be used in an all-solid-state battery may be used. The above-mentioned positive electrode active material may include stainless steel, aluminum, nickel, titanium, sintered carbon, etc., and any material that has high conductivity without causing chemical changes may also be used. In addition, the above-mentioned positive electrode active material may be surface-treated with carbon, nickel, titanium, silver, etc.

[0119] The above-mentioned negative electrode may include a negative electrode active material, a solid electrolyte, a conductive material, a binder, etc., and any known material that can be used in an all-solid-state battery may be used. The above-mentioned negative electrode active material may include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper, etc., and any material that has high conductivity without causing chemical change may also be used. In addition, the above-mentioned negative electrode active material may be surface-treated with carbon, nickel, titanium, silver, etc.

[0120] An all-solid-state battery according to one embodiment includes an alkali metal ion-conducting chalcogenide-based solid electrolyte represented by the following chemical formula 1.

[0121] [Chemical Formula 1]

[0122] (A + ) a (B n+ ) b (X 2- ) x (Y - ) y

[0123] Here, A is one or more elements selected from Li, Na, and K, B is one or more elements belonging to groups 2 to 15 of the periodic table, X is one or more elements selected from S, Se, and Te or a combination of these and O, Y is one or more elements or compounds selected from F, Cl, Br, I, CN, OCN, SCN, and N3, a + (n*b) - (2*x) - y = 0, a > 0, x > 0, and at least one of b and y is greater than 0.

[0124] The description of the solid electrolyte of the above chemical formula 1 is as described above.

[0125] According to a specific example, A is Li, B is P, X is S, Y is at least one halogen element among F, Cl, Br and I, a = 7-y, b = 1, x = 6-y, 0.1 ≤ y ≤ 2, and comprises 50 wt% to 100 wt% of an argyrodite crystal structure of space group F-43m.

[0126]

[0127] Hereinafter, preferred examples are presented to aid in understanding the present invention. However, the scope of the present invention is not limited to the following examples.

[0128]

[0129] Examples 1 to 16

[0130] The solid electrolyte manufacturing process described below was carried out in a cooling bath at 0℃ before filtration. After dissolving naphthalene (NAP) in tetrahydrofuran (THF), lithium polysulfide (Li2S) was added. x , 1 <x≤10) 및 황화리튬(lithium sulfide, Li2S)을 형성하기 위한 리튬 금속(litium metal; 표 1의 1 st Li) was added and dissolved for 30 minutes, and then sulfur (S) was added and reacted for 30 minutes. Lithium chloride (LiCl) and phosphorus pentasulfide (P2S5) were added to the reaction solution and completely dissolved for 1 hour to prepare the first precursor solution. A photograph of the solution in which the first precursor was completely dissolved is shown in Fig. 3, and it was confirmed that it was a transparent complete solution with a yellow color.

[0131] Afterwards, lithium metal (Table 1, 2) was added to the first precursor solution. nd Li) was added to complete the addition of all raw materials. The solution containing all raw materials changed from black to green and then beige, and a synthetic reaction occurred in which powder was formed. The reaction was completed in 24 hours by becoming a slurry in which the second precursor was dispersed. A photograph of the slurry in which the second precursor was dispersed is shown in Fig. 4, and it can be confirmed that the supernatant and the powder-dense portion are observed because the slurry in which the second precursor was dispersed is in a powder-dispersed state.

[0132] The slurry, after the reaction was completed, was filtered under reduced pressure to obtain a powder. The powder was dried at 200°C for 14 hours in a vacuum atmosphere and heat-treated at 550°C for 4 hours in an Ar atmosphere to obtain the final solid electrolyte powder.

[0133] The input amounts for each component in Examples 1 to 16 are shown in the table below.

[0134] (Unit: g)THFNAP1 st LiSLiClP2S52 ndLiExample 130021.4910.3888.9604.73912.3233.491Example 23000.4313.448Example 33000.4853.394Example 43000.5543.325Example 53000.6473.233Example 63000.7763.103Example 73000.9702.909Example 83001.2932.586Example 91800.3883.491Example 101800.4313.448Example 111800.4853.394Example 121800.5543.325 Example 131800.6473.233 Example 141800.7763.103 Example 151800.9702.909 Example 161801.2932.586

[0135]

[0136] Comparative Example 1

[0137] After dissolving 21.491 g of naphthalene in 300 mL of tetrahydrofuran, 1.940 g of lithium metal was added first and reacted for 1 hour, and 8.960 g of sulfur was added. 4.739 g of lithium chloride and 12.323 g of phosphorus pentasulfide were added and dissolved in the solution. The solution was not completely dissolved, and a slurry containing powder was produced. 1.939 g of lithium metal was added to the slurry to complete the addition of all raw materials. The reaction was completed when the slurry in which the second precursor was dispersed was formed. The slurry in which the reaction was completed was filtered under reduced pressure to obtain a powder. The powder was dried at a temperature of 200°C for 14 hours in a vacuum atmosphere and heat-treated at a temperature of 550°C for 4 hours in an Ar atmosphere to obtain the final solid electrolyte powder.

[0138]

[0139] Comparative Example 2

[0140] After dissolving 21.491 g of naphthalene (NAP) in 300 mL of tetrahydrofuran, 3.879 g of lithium metal was added and reacted for 1 hour, and 8.960 g of sulfur was added. The addition of all raw materials was completed by adding 4.739 g of lithium chloride and 12.323 g of phosphorus pentasulfide to the reaction solution. After completion of the reaction, the obtained slurry was filtered under reduced pressure to obtain a powder. The powder was dried at 200°C for 14 hours in a vacuum atmosphere and heat-treated at 550°C for 4 hours in an Ar atmosphere to obtain the final solid electrolyte powder.

[0141]

[0142] Comparative Example 3

[0143] 21.491 g of naphthalene, 3.879 g of lithium metal, 8.960 g of sulfur, 4.739 g of lithium chloride, and 12.323 g of phosphorus pentasulfide were added to 300 mL of tetrahydrofuran and reacted for 24 hours to obtain a slurry. The slurry was filtered under reduced pressure to obtain a powder. The powder was dried at 200°C for 14 hours in a vacuum atmosphere and heat-treated at 550°C for 4 hours in an Ar atmosphere to obtain the final solid electrolyte powder.

[0144]

[0145] Test Example 1: Evaluation of the ionic conductivity of a solid electrolyte

[0146] Each 0.2 g of the solid electrolytes manufactured in the Examples and Comparative Examples was compression molded at 300 MPa in a 13 mm diameter circular mold, and AC impedance analysis was performed. The frequency range was 3 MHz to 1 Hz, and the amplitude was 10 mV. The results of the ionic conductivity evaluation are shown in the table below.

[0147] Classification Average ionic conductivity (mS / cm) Deviation (maximum value - minimum value) (mS / cm) Example 13.5 0.2 Example 23.4 0.2 Example 33.2 0.2 Example 43.2 0.3 Example 53.1 0.2 Example 63.0 0.2 Example 73.0 0.3 Example 83.0 0.3 Example 94.0 0.2 Example 103.9 0.2 Example 113.8 0.2 Example 123.5 0.3 Example 133.5 0.2 Example 143.5 0.2 Example 153.5 0.3 Example 163.5 0.3 Comparative Example 11.2 1.0 Comparative Example 21.2 1.1 Comparative Example 31.21.0

[0148]

[0149] Test Example 2: X-ray diffraction analysis of solid electrolyte

[0150] X-ray diffraction analysis (XRD) was performed on the solid electrolyte manufactured in Example 1, and the results are shown in Fig. 5.

[0151] Referring to FIG. 5, the alkali metal ion conductive chalcogenide-based solid electrolyte manufactured in Example 1 exhibited diffraction angles (2θ) in the regions of 15.5±0.5°, 18.0±0.5°, 25.5±0.5°, 30.0±0.5°, 31.5±0.5°, 40.0±0.5°, 45.5±0.5°, 48.0±0.5°, 53.0±0.5°, 55.0±0.5°, 56.5±0.5°, and 59.5±0.5° as major peaks. These peaks are the same peaks as Li6PS5Cl, which has an argyrodite-type crystal structure of space group F-43m, and peaks due to impurities were detected at a relatively very low level. Therefore, it can be confirmed that the alkali metal ion conductive chalcogenide-based solid electrolyte manufactured in Example 1 is an alkali metal ion conductive chalcogenide-based solid electrolyte having an argyrodite-type crystal structure.

[0152]

[0153] Test Example 3: Ionic conductivity and particle size after solid electrolyte pulverization

[0154] In this test example, the solid electrolyte corresponding to Example 1 was pulverized and the ionic conductivity and particle size were confirmed.

[0155] For grinding, 1124 g of 10 mm diameter zirconia balls, 376 g of 1 mm diameter zirconia balls, 60 g of solid electrolyte, 192 mL of normal heptane, and 48 mL of dibutyl ether were placed in a polypropylene container with a volume of 1 L and ball milled at a speed of 200 rpm for 20 hours. Afterwards, the powder was collected by filtration and dried in a vacuum at 90°C for 20 hours.

[0156] The ionic conductivity of the above-mentioned pulverized powder was measured using the same method as in Test Example 1, and the result was 1.8 mS / cm (see Fig. 6).

[0157] In addition, the particle size of the above-mentioned pulverized powder was analyzed using a particle size analyzer (Microtrac S3500), and the result was 0.93 ㎛ based on D50 (see Fig. 7). Xylene was used as the dispersion solvent during the particle size analysis.

[0158] Additionally, to assess the atmospheric stability of the above-mentioned pulverized powder, the ionic conductivity was measured before and after exposure to air. To this end, 0.15 g of each was extracted from two random portions of the pulverized powder. The ionic conductivity of one portion was measured without exposure to air, and the ionic conductivity of the other portion was measured after 24 hours of exposure to dry air with a dew point of -60°C, and the results were compared.

[0159] Ionic conductivity measurements were performed using an AC impedance analysis method using a 10 mm diameter circular mold under compression molding at 400 MPa. The frequency range was 1 MHz to 0.1 Hz, and the amplitude was 10 mV. The results, which showed an ionic conductivity retention rate of 87%, are shown in Fig. 8. The solid electrolytes of all examples showed an ionic conductivity retention rate of 80%±10% of the pulverized powder.

[0160]

[0161] Test Example 4: Performance Evaluation of All-Solid-State Battery

[0162] The performance of an all-solid-state battery using a powder of crushed solid electrolyte was evaluated.

[0163] 0.7 g of LiNbO3-coated NCM811, 0.3 g of the solid electrolyte powder of Example 1 pulverized in the above Test Example 3, and 0.03 g of VGCF (vapor grown carbon nanotubes) were mixed three times for 30 seconds using a Thinky mixer to prepare a cathode layer composite powder. 0.1 g of the pulverized solid electrolyte powder was placed in a 10 mm diameter mold and compression molded at 300 MPa to form a pellet. 0.1 g of the cathode layer composite powder was placed on one side of the pellet and compression molded again at 300 MPa. Thereafter, lithium metal foil and indium metal foil were sequentially laminated on the opposite side, and finally compression molded at 50 MPa to form an all-solid-state battery. The charge / discharge test of the manufactured all-solid-state battery was set to a terminal voltage of 3.7 V to 2.4 V at 0.1 C-rate.

[0164] The results are shown in Figure 9, and a very stable charge-discharge curve can be seen.

[0165]

[0166] Test Example 5: Anion Analysis of the First Precursor

[0167] The anions contained in the first precursor were analyzed using an electron spray ionization mass spectrometer. The solution in which the first precursor was completely dissolved in Example 3 was analyzed using an electron spray ionization mass spectrometer, and the results are shown in Figure 10.

[0168] As shown in Fig. 10, signals corresponding to 126.9, 222.8, 254.8, 286.7, 318.7, 452.6, 516.6, 548.5, 580.5, 612.6, and 644.5 m / z were confirmed, and each was PS3 - , PS6 - , PS7 - , PS8 - , PS9 - , LiP2S 12- , LiP2S 14 - , LiP2S 15 - , LiP2S 16 - , LiP2S 17 - , LiP2S 18 - It was confirmed that a completely soluble chalcogenide ion corresponding to .

Claims

1. (1) A step of preparing a first precursor solution in which a precursor of an alkali metal ion conductive chalcogenide-based solid electrolyte is completely dissolved in a polar aprotic solvent; (2) A step of preparing a slurry in which a second precursor is dispersed by adding an alkali metal or an alkali metal-containing material to the first precursor solution; (3) a step of recovering the second precursor in powder form from the slurry; and (4) A method for producing an alkali metal ion conductive chalcogenide-based solid electrolyte, comprising a step of heat-treating the second precursor powder.

2. In paragraph 1, In the above step (1), the first precursor solution A method for producing an alkali metal ion-conducting chalcogenide-based solid electrolyte, comprising reacting alkali metal ion-conducting chalcogenide-based solid electrolyte raw materials including (i) an alkali metal or an alkali metal-containing material, (ii) a transfer catalyst that ionizes the alkali metal to transfer ions and electrons, (iii) a chalcogen element, and (iv) a compound of at least one element from groups 2 to 15 and 17 of the periodic table in a polar aprotic solvent.

3. In paragraph 2, The above transfer catalyst is Naphthalene, acenaphthylene, acenaphthene, biphenyl, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[k]fluoranthene, benzo[b]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene, and A method for producing an alkali metal ion conductive chalcogenide-based solid electrolyte selected from the group consisting of benzo[ghi]perylene.

4. In paragraph 2, The above polar aprotic solvent is A method for producing an alkali metal ion conductive chalcogenide-based solid electrolyte, the solid electrolyte comprising at least one selected from the group consisting of aliphatic monoether, aliphatic diether, cyclic ether, polyether, acrylonitrile (ACN), dimethylformamide (DMF), ethyl acetate (EA), dimethyl carbonate (DMC), and ethyl propionate (EP).

5. In paragraph 2, When the above alkali metal ion conductive chalcogenide solid electrolyte raw material is reacted in a polar aprotic solvent, A method for producing an alkali metal ion conductive chalcogenide solid electrolyte using ultrasonic irradiation, stirring, a high-speed homogenizer, a high-pressure sprayer, mechanical grinding, or a combination thereof.

6. In paragraph 1, In the above step (1), the precursor is represented by the following chemical formula 1a, a method for producing an alkali metal ion conductive chalcogenide-based solid electrolyte: [Chemical Formula 1a] (A + ) a (B n+ ) b (X 2- ) x (Y - ) y Here A is one or more elements selected from Li, Na, and K, B is one or more elements belonging to groups 2 to 15 of the periodic table, X is one or more elements selected from S, Se and Te or a combination of these and O, Y is one or more elements or compounds selected from F, Cl, Br, I, CN, OCN, SCN and N3, Under the criterion b = 1, it satisfies the values ​​0≤a≤3, 4≤x≤6, and 0≤y≤2.

7. In paragraph 1, In the above step (2), the alkali metal or alkali metal-containing material lithium metal; A mixture of lithium metal and a transfer catalyst; or A method for producing an alkali metal ion-conducting chalcogenide-based solid electrolyte, which is a mixture of lithium metal, a transfer catalyst, and a polar aprotic solvent.

8. In paragraph 1, In the above step (3), the recovery of the second precursor A method for producing an alkali metal ion conductive chalcogenide-based solid electrolyte, the method comprising: using co-precipitation, filtration, centrifugation, natural sedimentation, spraying, hydrocyclone, or a combination thereof.

9. In paragraph 1, In the above step (4), the heat treatment of the second precursor powder After removing residue by heating or vacuum drying at room temperature to 200℃, A method for producing an alkali metal ion conductive chalcogenide-based solid electrolyte, comprising a crystallization process at 200°C to 600°C under an inert gas atmosphere.

10. Manufactured according to the method of paragraph 1, An alkali metal ion-conducting chalcogenide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] (A + ) a (B n+ ) b (X 2- ) x (Y - ) y Here A is one or more elements selected from Li, Na, and K, B is one or more elements belonging to groups 2 to 15 of the periodic table, X is one or more elements selected from S, Se and Te or a combination of these and O, Y is one or more elements or compounds selected from F, Cl, Br, I, CN, OCN, SCN and N3, a + (n*b) - (2*x) - y = 0, a > 0, x > 0, and at least one of b and y is greater than 0.

11. In paragraph 10, A is Li, B is P, X is S, Y is at least one halogen element selected from F, Cl, Br and I, a = 7-y, b = 1, x = 6-y, 0.1 ≤ y ≤ 2, An alkali metal ion-conducting chalcogenide-based solid electrolyte comprising 50 to 100 wt% of an argyrodite crystal structure of space group F-43m.

12. In paragraph 10, An alkali metal ion conductive chalcogenide-based solid electrolyte having an ionic conductivity of 3 mS / cm or more immediately after manufacture.

13. In paragraph 10, An alkali metal ion conductive chalcogenide-based solid electrolyte having a carbon content of 3% or less.

14. An all-solid-state battery comprising the alkali metal ion-conducting chalcogenide-based solid electrolyte of Article 10.

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