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

Abstract

The present invention relates to a solid electrolyte comprising: a sulfide-based solid electrolyte particle; and a coating layer encompassing, in a thin-film form, the entire surface of the sulfide-based solid electrolyte particle, and containing fluoride, wherein the fluoride contains at least one from among Al, Zn, Si and Sn.

Description

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

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

[0002]

[0003] Research on the safety issues and energy density of high-capacity batteries is attracting attention, and all-solid-state batteries are gaining attention as next-generation batteries.

[0004] The above all-solid-state battery is a battery that ensures battery safety because it replaces the liquid electrolyte that causes explosion with a solid electrolyte, does not use a flammable solvent in the battery, and thus does not cause ignition or explosion at all due to a reaction such as the decomposition reaction of a conventional electrolyte.

[0005] Additionally, since lithium metal or a lithium alloy can be used as the negative electrode material, the energy density for the mass and volume of the battery can be improved.

[0006] The solid electrolyte used in the above-mentioned all-solid-state battery is generally an inorganic solid electrolyte, and various studies are being conducted on a sulfide-based solid electrolyte having a composition such as Li6PS5Cl, which has an argyrodite structure among the above-mentioned all-solid-state batteries.

[0007] Although argyrodite-based sulfide solid electrolytes have high lithium ion conductivity, they have a problem with poor moisture stability, such as the S element among the constituent elements reacting sensitively with moisture in the air, causing a sharp decrease in ion conductivity.

[0008]

[0009] Accordingly, one object of the present invention is to provide a solid electrolyte with improved moisture stability, a method for producing the same, and an all-solid-state battery including the same.

[0010]

[0011] One embodiment of the present invention provides a solid electrolyte comprising: sulfide-based solid electrolyte particles; and a coating layer containing fluoride, which covers the entire surface of the sulfide-based solid electrolyte particles in a thin film form, wherein the fluoride contains at least one metal element selected from the group consisting of Al, Zn, Si, and Sn.

[0012] The above fluoride can be represented by the following chemical formula 1.

[0013] [Chemical Formula 1]

[0014] M x F y

[0015] In the above chemical formula 1, M is at least one of Al, Zn, Si, and Sn, 0.1≤x≤5, and 1≤y≤20.

[0016] The average thickness of the above coating layer may be 0.01 to 1.2 nm.

[0017] The average difference between the maximum thickness and the minimum thickness of the above coating layer may be 0.1 nm or less.

[0018] The content of the above metal element may be 0.001 to 0.5 wt% based on the total weight of the solid electrolyte.

[0019] The average particle diameter (D50) of the above sulfide-based solid electrolyte particles may be 0.7 to 10 μm.

[0020] The sphericity of the above sulfide-based solid electrolyte particles may be 0.1 or more.

[0021] The above sulfide-based solid electrolyte particles may be argyrodite-based solid electrolyte particles.

[0022] The above argyrodite-based solid electrolyte particles may contain Cl and Br as halogen elements.

[0023] At this time, the molar ratio of Br to Cl ([Br] / [Cl]) may be 0.7 to 1.3.

[0024]

[0025] Another embodiment of the present invention provides a method for manufacturing a solid electrolyte, comprising the steps of: preparing sulfide-based solid electrolyte particles; and forming a coating layer containing fluoride by covering the entire surface of the sulfide-based solid electrolyte particles in a thin film form by an atomic layer deposition (ALD) method using a fluorine precursor and a metal precursor, wherein the fluoride contains at least one metal element selected from the group consisting of Al, Zn, Si, and Sn.

[0026] The above atomic layer deposition can be performed for 2 to 100 cycles.

[0027] The above fluorine precursor may be HF, NH3 or a combination thereof.

[0028] The metal precursor may be aluminum alkoxide, zinc alkoxide, silicon alkoxide, tin alkoxide, or a combination thereof.

[0029] The above atomic layer deposition can be performed at a temperature of 20 to 100°C.

[0030] The above atomic layer deposition can be performed in an argon or nitrogen atmosphere.

[0031]

[0032] Another embodiment of the present invention provides an all-solid-state battery comprising the above-described solid electrolyte.

[0033]

[0034] A solid electrolyte according to one embodiment of the present invention can improve moisture stability by including a fluoride coating layer that covers the entire surface of the solid electrolyte particles in a thin film form.

[0035]

[0036] Figure 1 is a conceptual diagram of a solid electrolyte according to one embodiment of the present invention.

[0037] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0038] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0039] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0040] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0041] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0042] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0043] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0044]

[0045] 1. Solid electrolyte

[0046] Figure 1 is a conceptual diagram of a solid electrolyte according to one embodiment of the present invention.

[0047] Referring to FIG. 1, a solid electrolyte according to one embodiment of the present invention includes sulfide-based solid electrolyte particles.

[0048] The above sulfide-based solid electrolyte particles may be, more specifically, argyrodite-based solid electrolyte particles. Accordingly, excellent ionic conductivity can be achieved.

[0049] The above argyrodite-based solid electrolyte is not particularly limited as long as it has an argyrodite-based crystal structure.

[0050] The above argyrodite-based solid electrolyte may include basic elements Li, P, S, and halogen elements, and may optionally further include other doping elements as needed.

[0051] Specifically, the above-mentioned argyrodite-based solid electrolyte may include Cl as a base among halogen elements. When Cl is included among halogen elements, there is an advantage of stability.

[0052] In addition, the argyrodite-based solid electrolyte may simultaneously contain Cl and Br as halogen elements. When the argyrodite-based solid electrolyte simultaneously contains Cl and Br as halogen elements, ionic conductivity can be more preferably implemented.

[0053] At this time, the molar ratio of Br to Cl ([Br] / [Cl]) may be 0.7 to 1.3. If the molar ratio of Br to Cl ([Br] / [Cl]) is too small, the additional improvement effect of ionic conductivity may be minimal. If the molar ratio of Br to Cl ([Br] / [Cl]) is too large, there may be a problem of reduced ionic conductivity.

[0054] Meanwhile, the other doping elements may be, for example, Si, Al, In, Zr, B, Na, Mg, Ca, Ge, Ga, Zn, Sn, or a combination thereof. The amount of the other doping elements introduced may be appropriately controlled and introduced within a range that does not deteriorate the electrochemical properties of the solid electrolyte.

[0055] However, although sulfide-based solid electrolyte particles have excellent ionic conductivity immediately after synthesis, there is a problem in that the ionic conductivity rapidly deteriorates as the S among the constituent elements reacts with moisture in the air, causing deterioration of the crystal structure.

[0056] Accordingly, a solid electrolyte according to one embodiment of the present invention includes a coating layer containing fluoride on the surface of sulfide-based solid electrolyte particles. In this case, the fluoride may be a fluorine compound containing at least one metal element selected from the group consisting of Al, Zn, Si, and Sn. Such a fluorine compound has hydrophobic properties, and thus can block contact with moisture in the air, thereby improving the moisture stability of the solid electrolyte, and thus reducing deterioration of ionic conductivity over time when the solid electrolyte is exposed to the air.

[0057] Meanwhile, the coating layer can conformally cover the entire surface of the sulfide-based solid electrolyte particles in a thin film form. Accordingly, the effect of blocking contact between the solid electrolyte and moisture in the air can be maximized, and the effect of improving moisture stability can be more preferably implemented. Meanwhile, the implementation of the conformal coating layer in the form of a thin film can be implemented through the atomic layer deposition (ALD) method, as described in the manufacturing method described below. This will be described in more detail in the manufacturing method described below.

[0058] At this time, the fluoride can be represented by the following chemical formula 1.

[0059] [Chemical Formula 1]

[0060] M x F y

[0061] In the above chemical formula 1, M is at least one of Al, Zn, Si, and Sn, 0.1≤x≤5, and 1≤y≤20.

[0062] The above fluoride may be more specifically AlF3, ZnF2, SiF4, SnF4 or a combination thereof.

[0063] In addition, the average thickness of the coating layer may be 0.01 to 1.2 nm, and more specifically, 0.03 to 0.2 nm. If the average thickness of the coating layer is too thin, the effect of improving the moisture stability of the solid electrolyte by covering the coating layer may be minimal. If the average thickness of the coating layer is too thick, the moisture stability may be improved, but the ionic conductivity of the solid electrolyte may deteriorate. Therefore, in order to simultaneously excellently implement the moisture stability and ionic conductivity of the solid electrolyte, it is preferable that the average thickness of the coating layer satisfies the above range. The average thickness of the coating layer can be measured by the following method. First, the thickness of the coating layer for one solid electrolyte particle can be obtained by observing the solid electrolyte particle with a TEM (Transmission Electron Microscope) image and deriving the average value of the thickness for 10 measurement areas around the entire circumference of the outer part of the solid electrolyte particle. Next, the average thickness of the coating layer can be obtained by deriving the average value of the coating layer thickness obtained in the same manner as above for 20 random solid electrolyte particles among the solid electrolyte powders.

[0064] In addition, the average of the difference between the maximum thickness and the minimum thickness of the coating layer may be 0.1 nm or less. That is, the coating layer according to the present invention may have very good thickness uniformity of the coating layer, and thus may implement a moisture stabilization effect. The average of the difference between the maximum thickness and the minimum thickness of the coating layer may be measured by the following method. First, the difference between the maximum thickness and the minimum thickness of the coating layer for one solid electrolyte particle may be derived by calculating the thickness of each of 10 measurement areas in the circumferential direction of the outer part of the solid electrolyte particle, and then calculating the difference between the maximum and minimum values ​​among them. Next, the average of the difference between the maximum thickness and the minimum thickness of the coating layer may be derived by deriving the average value of the difference between the maximum thickness and the minimum thickness of the coating layer for any 20 solid electrolyte particles among the solid electrolyte powders by the same method.

[0065] In addition, the content of the metal element may be 0.001 to 0.5 wt% based on the total weight of the solid electrolyte, and more specifically, 0.008 to 0.03 wt%. If the content of the metal element is too low, a sufficient coating layer may not be formed, and thus the effect of improving moisture stability may be minimal. If the content of the metal element is too high, an excessive coating layer may be formed, and the ionic conductivity of the solid electrolyte may deteriorate. Therefore, in order to simultaneously excellently implement moisture stability and ionic conductivity of the solid electrolyte, it is preferable that the content of the metal element satisfies the above range.

[0066] The average particle diameter (D50) of the above sulfide-based solid electrolyte particles may be 0.7 to 10 μm. If the average particle diameter of the sulfide-based solid electrolyte particles is too small, there may be a problem of reduced production efficiency. If the average particle diameter of the sulfide-based solid electrolyte particles is too large, there may be a problem of increased resistance due to difficulty in forming an ion conduction path. In the present specification, the average particle diameter (D50) may be defined as a particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) may be measured using, for example, a laser diffraction method.

[0067] In addition, the sphericity of the sulfide-based solid electrolyte particles may be 0.1 or more, and more specifically, 0.5 or 0.6 or more. As the sphericity of the sulfide-based solid electrolyte particles improves, the effect of increasing the density of the electrode can be realized through appropriate packing. In the present specification, the sphericity is a numerical expression of the degree to which a particle is close to a sphere, and refers to a value obtained by dividing the perimeter of a circle having the same area as a particle projection shape by the actual perimeter of the particle projection shape through a flow-type particle analysis device. This sphericity can be measured using an analyzer for obtaining an optical image (Fluid Imaging Technologies, Flowcam 8100) and analysis S / W (visual spreadsheet).

[0068]

[0069] 2. Solid electrolyte manufacturing method

[0070] Another embodiment of the present invention provides a method for manufacturing a solid electrolyte, comprising the steps of: preparing sulfide-based solid electrolyte particles; and forming a coating layer containing fluoride by covering the entire surface of the sulfide-based solid electrolyte particles in a thin film form by an atomic layer deposition (ALD) method using a fluorine precursor and a metal precursor, wherein the fluoride contains at least one metal selected from the group consisting of Al, Zn, Si, and Sn.

[0071] Hereinafter, a method for manufacturing a solid electrolyte according to another embodiment of the present invention will be described step by step.

[0072]

[0073] First, prepare sulfide-based solid electrolyte particles.

[0074] The above sulfide-based solid electrolyte can be prepared by purchasing a commercially available sulfide-based solid electrolyte, or can be manufactured according to a manufacturing method of a sulfide-based solid electrolyte common in the art.

[0075] The above sulfide-based solid electrolyte may be, more specifically, an argyrodite-based solid electrolyte.

[0076] The above argyrodite-based solid electrolyte can be manufactured, for example, by a step of forming a mixture by mixing a lithium raw material, a phosphorus raw material, and a halogen element raw material; and a step of heat-treating the mixture to form a sulfide-based solid electrolyte having an argyrodite-based crystal structure.

[0077] The above lithium raw material may be, for example, Li2S, Li2S2, or a combination thereof, but is not necessarily limited thereto.

[0078] The above raw material may be, for example, P2S5, P2O5 or a combination thereof, but is not necessarily limited thereto.

[0079] The above halogen element raw material may be, for example, LiF, LiCl, LiBr, LiI, or a combination thereof, but is not necessarily limited thereto. More specifically, the above halogen element raw material may be LiCl.

[0080] The above mixing can be performed by mechanical mixing or chemical mixing.

[0081] The above mechanical mixing can be performed by, for example, a planetary mill, a paint shaker, a ball mill, a bead mill, a homogenizer, a hammer mill, a turbo mill, a disc mill, a planetary mill, a mechanofusion mill, etc.

[0082] The above chemical mixing can be performed, for example, by melt quenching.

[0083] The above mixing can be performed for 4 to 12 hours, specifically 6 to 10 hours, and more specifically 7 to 9 hours. If the mixing time is too short, the mixing will not be sufficient, and thus the synthesis of the solid electrolyte may not proceed well in the heat treatment process described later. If the mixing time is too long, the mixing will be completed after a certain period of time, and even if the mixing is performed further, the mixing state will remain the same, which may cause problems in terms of process efficiency.

[0084] The above mixing can be performed at a rotation speed of 100 to 500 rpm, specifically 150 to 450 rpm, and more specifically 200 to 400 rpm. If the rotation speed is too slow, the balls may not be able to enter the inside of the powder particles, which may result in a problem of less overall mixing of the powder particles or less atomization of the powder particles due to low energy. On the other hand, if the rotation speed is too fast, the powder particles may be concentrated in one area, which may result in a problem of less even mixing.

[0085] Of course, if a doping element is to be introduced into the argyrodite-based solid electrolyte, the doping raw material can be further mixed in when forming the mixture.

[0086] Next, optionally, after the step of forming the mixture, a step of compressing the mixture to form pellets may be further included.

[0087] At this time, the compression can be performed at a pressure of 100 to 500 Mpa, specifically 150 to 450 Mpa, more specifically 200 to 400 Mpa. If the pressure is too low, a problem may arise in that the interfacial resistance may increase due to insufficient bonding between the powder particles. On the other hand, if the pressure is too high, the bonding between the powder particles may already occur, and the bonding state may not change even if further pressure is applied, which may cause a problem in terms of process efficiency. Therefore, it is desirable in terms of productivity to form pellets at an appropriate pressure.

[0088] Next, the mixture is heat-treated to form a sulfide-based solid electrolyte having an argyrodite-based crystal structure.

[0089] At this time, the heat treatment can be performed at a temperature of 400 to 700°C, and more specifically, can be performed at 500 to 600°C. If the heat treatment temperature is too low, the synthesis of a solid electrolyte having an argyrodite crystal structure may not occur sufficiently, or the solid electrolyte may be synthesized in an amorphous crystal structure, which may reduce the ionic conductivity of the solid electrolyte. If the heat treatment temperature is too high, the elements forming the solid electrolyte may vaporize, resulting in the loss of the solid electrolyte, or an impurity phase may be generated, which may reduce the ionic conductivity of the solid electrolyte.

[0090] In addition, the heat treatment may be performed for 2 to 8 hours, and more specifically, for 3 to 5 hours. If the heat treatment time is too short, the synthesis of the solid electrolyte having an argyrodite crystal structure may not occur sufficiently, or the solid electrolyte may be synthesized in an amorphous crystal structure, which may reduce the ionic conductivity of the solid electrolyte. If the heat treatment time is too long, the elements constituting the solid electrolyte may vaporize, resulting in the loss of the solid electrolyte, or an impurity phase may be generated, which may reduce the ionic conductivity of the solid electrolyte.

[0091] Additionally, the heat treatment may be performed in an inert gas atmosphere. Since the heat treatment is performed in an inert gas atmosphere, there may be an advantage in that contact with atmospheric moisture can be prevented. The inert gas atmosphere may be, for example, an Ar, N2, H2, or He atmosphere, and more specifically, an Ar atmosphere.

[0092] A sulfide-based solid electrolyte can be manufactured through the above series of steps.

[0093] At this time, the average particle diameter (D50) of the sulfide-based solid electrolyte particles may be 0.7 to 10 μm. In addition, the sphericity of the sulfide-based solid electrolyte particles may be 0.1 or more, and more specifically, 0.5 or 0.6 or more. The technical significance of controlling the average particle diameter and sphericity of the sulfide-based solid electrolyte particles is as described above, and therefore is omitted.

[0094]

[0095] Next, a fluoride precursor and a metal precursor are used to cover the entire surface of the sulfide-based solid electrolyte particles in a thin film form using an atomic layer deposition (ALD) method, thereby forming a coating layer containing fluoride. At this time, the fluoride may be a fluorine compound containing at least one metal selected from the group consisting of Al, Zn, Si, and Sn.

[0096] Atomic Layer Deposition (ALD) is a process technology that utilizes a vapor-phase chemical vapor deposition reaction, but suppresses the vapor-phase reaction by injecting precursors and reactants at different times, and precisely controls the thickness of a thin film by utilizing a self-limiting reaction in which the reaction occurs on the surface of the substrate. Due to the self-limiting reaction characteristics, the thickness of the thin film can be precisely controlled to sub-atomic layers through the ALD process, and precise composition control can be achieved through thickness control.

[0097] More specifically, the atomic layer deposition can be performed for 2 to 100 cycles, and more specifically, for 5 to 60 cycles. If the number of atomic layer deposition cycles is too small, there may be a problem in which the coating layer is not properly formed. If the number of atomic layer deposition cycles is too large, there may be a problem in which the surface resistance increases, reducing the ionic conductivity.

[0098] When performing the above atomic layer deposition, one cycle can more specifically form a fluoride-containing coating layer by supplying and reacting a fluorine precursor and a metal precursor on a sulfide-based solid electrolyte particle.

[0099] At this time, the fluorine precursor and the metal precursor can be supplied at different times according to the atomic layer deposition method, and the metal precursor can be first adsorbed on the sulfide-based solid electrolyte particles, and then the fluorine precursor can be supplied to induce a reaction with the metal precursor.

[0100] At this time, the fluorine precursor may be HF, NH3 or a combination thereof, and may be in a gaseous state.

[0101] In addition, the metal precursor may be aluminum alkoxide, zinc alkoxide, silicon alkoxide, tin alkoxide, or a combination thereof, and may be in a gaseous state. At this time, the amount of the metal precursor input may be adjusted to be implemented with the content of the metal element according to the present invention mentioned above.

[0102] Additionally, the atomic layer deposition can be performed at a temperature of 20 to 100°C. If the temperature is too low during atomic layer deposition, there may be a problem of reduced deposition efficiency. If the temperature is too high during atomic layer deposition, there may be a problem of excessive deposition.

[0103] The above atomic layer deposition can be performed at a pressure of 2 to 10 torr. If the pressure is too low during atomic layer deposition, excessive deposition may occur. If the pressure is too high during atomic layer deposition, the deposition efficiency may be reduced.

[0104] The above atomic layer deposition can be performed in an argon or nitrogen atmosphere. Accordingly, a uniform deposition effect can be advantageous.

[0105]

[0106] 3. All-solid-state battery

[0107] Another embodiment of the present invention provides an all-solid-state battery comprising the above-described solid electrolyte.

[0108] The above-mentioned all-solid-state battery more specifically includes a positive electrode layer; a negative electrode layer, and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, and at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer may include the above-mentioned solid electrolyte.

[0109] (bipolar layer)

[0110] More specifically, the above positive electrode layer may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

[0111] The above-described positive electrode active material layer may further include, for example, a positive electrode active material and optionally a solid electrolyte as needed. The solid electrolyte included in the positive electrode active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0112] A cathode active material is a material that can reversibly absorb and desorb lithium ions. Examples of cathode active materials include, but are not limited to, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate; nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide; and the like. Any material used as a cathode active material in the relevant technical field may be used. The cathode active materials may be singly or in a mixture of two or more.

[0113] The above lithium transition metal oxide is, for example, Li a A 1-b B b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α F α(In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoGb O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); A compound represented by any one of the chemical formulas of LiFePO4. In this 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; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of this compound, and it is also possible to use a mixture of the above-mentioned compound and the compound having a coating layer added. The coating layer added to the surface of these compounds includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0114] The positive electrode active material layer may include, for example, a binder. The binder may include, but is not limited to, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and the like, and any binder used in the art may be used.

[0115] The positive electrode active material layer may include, for example, a conductive material. The conductive material may include, but is not limited to, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc., and any conductive material used in the relevant technical field may be used.

[0116] The positive electrode active material layer may further include, for example, additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the above-described positive electrode active material, solid electrolyte, binder, and conductive agent.

[0117] As fillers, coating agents, dispersants, ion conductive aids, etc. that the positive electrode active material layer may include, known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[0118] The positive electrode collector may be, for example, 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 electrode collector may be, for example, 1 um to 100 um, 1 um to 50 um, 5 um to 25 um, or 10 um to 20 um.

[0119]

[0120] (cathode layer)

[0121] The above negative electrode layer may more specifically include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0122] The above negative electrode active material layer may include, for example, a negative electrode active material and a binder, and may optionally further include a solid electrolyte as needed.

[0123] The above negative electrode active material may include, for example, a carbon-based negative electrode active material, a metal / metalloid negative electrode active material, or a combination thereof.

[0124] The above carbon-based negative electrode active material may be amorphous carbon, crystalline carbon, or a mixture or composite thereof. The amorphous carbon may be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., but is not necessarily limited thereto, and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon. The crystalline carbon may be, for example, natural graphite, artificial graphite, or a combination thereof.

[0125] The metal / metalloid negative electrode active material includes at least one selected from the group consisting of lithium (Li), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited thereto, and any metal negative electrode active material or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used.

[0126] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0127] By including a binder in the negative electrode active material layer, the negative electrode active material layer is stabilized on the negative electrode current collector. Furthermore, cracking of the negative electrode active material layer is suppressed despite changes in volume and / or relative position of the negative electrode active material layer during the charge / discharge process.

[0128] The negative active material layer may further include additives used in conventional all-solid-state batteries, such as fillers, coating agents, dispersants, and ion conductive aids.

[0129] The all-solid-state battery may further include a second negative electrode active material layer disposed between the negative electrode current collector and the negative electrode active material layer during charging. The second negative electrode active material layer may be deposited between the negative electrode current collector and the negative electrode current collector during the charging process, or may be further disposed on the negative electrode active material layer during electrode assembly. The second negative electrode active material layer may be a metal layer containing lithium or a lithium alloy. The lithium alloy includes, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, and the like, and any lithium alloy used in the art may be used. The second negative electrode active material layer may be made of one of these alloys and / or lithium, or may be made of multiple types of alloys and / or lithium.

[0130] The negative electrode current collector may be composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or compound. The negative electrode current collector may include, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that is used as an electrode current collector in the art may be used. The negative electrode current collector may be composed of one of the above-described metals, or may be composed of an alloy or a coating material of two or more metals. The negative electrode current collector may be, for example, in the form of a plate or foil.

[0131] When the negative electrode active material layer includes a solid electrolyte, the solid electrolyte included in the negative electrode active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0132]

[0133] (solid electrolyte layer)

[0134] The above solid electrolyte layer can be manufactured by mixing and drying the above-described solid electrolyte and binder, or by rolling the above-described solid electrolyte powder into a certain shape under a pressure of 1 ton to 10 tons.

[0135] At this time, the solid electrolyte may be in the form of a powder or a molded product. The solid electrolyte in the form of a molded product may be in the form of, for example, pellets, sheets, thin films, etc., but is not necessarily limited to these and may have various forms depending on the intended use.

[0136] The above solid electrolyte layer may further include a solid electrolyte such as a conventional sulfide-based solid electrolyte and / or an oxide-based solid electrolyte in addition to the above-described solid electrolyte, if necessary.

[0137] The above binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, etc., but is not limited thereto, and any binder used in the relevant technical field may be used. The binder of the solid electrolyte layer may be the same as or different from the binders of the positive and negative electrode layers.

[0138]

[0139] Another embodiment of the present invention provides an electric vehicle including the all-solid-state battery.

[0140]

[0141] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0142]

[0143] Example 1

[0144] (Preparation of solid electrolyte powder) The raw materials Li2S, P2S5 and LiCl were mixed at a stoichiometric ratio so that the final solid electrolyte composition was Li6PS5Cl, and a mixture was formed by mixing them at 300 rpm for about 8 hours using a planetary mill.

[0145] Afterwards, a pressure of 300 MPa was applied to the mixture to form pellets.

[0146] Thereafter, the pellets were heat-treated at 550°C for 8 hours in an argon (Ar) atmosphere to produce a Li6PS5Cl solid electrolyte.

[0147] (After coating), the solid electrolyte was introduced into the reaction chamber of an atomic layer deposition (ALD) device. At this time, the reaction chamber was controlled to an Ar or N2 atmosphere, a temperature of 20 to 100°C, and a pressure of 2 to 10 torr. Thereafter, NH3 or HF as a fluorine precursor and aluminum alkoxide as a metal precursor were introduced onto the surface of the solid electrolyte in the reaction chamber and deposited using the atomic layer deposition method. At this time, the number of atomic layer deposition cycles was set to 3.

[0148] Thus, a solid electrolyte was manufactured in which a coating layer containing AlF3 fluoride was formed on the surface of argyrodite solid electrolyte particles.

[0149]

[0150] Example 2

[0151] A solid electrolyte was manufactured in the same manner as in Example 1, except that the number of cycles of atomic layer deposition was 10.

[0152]

[0153] Example 3

[0154] A solid electrolyte was manufactured in the same manner as in Example 1, except that the number of cycles of atomic layer deposition was 50.

[0155]

[0156] Example 4

[0157] A solid electrolyte was manufactured in the same manner as in Example 1, except that the number of cycles of atomic layer deposition was 70.

[0158]

[0159] Example 5

[0160] A solid electrolyte was manufactured in the same manner as in Example 1, except that the number of cycles of atomic layer deposition was set to 100.

[0161]

[0162] Table 1 below summarizes the process conditions of examples and comparative examples.

[0163] ALD cycle Suarrodite solid electrolyte composition [Li][P][S][Cl][Br] Example 1361510 Example 21061510 Example 35061510 Example 47061510 Example 510061510 Comparative examples 1-61510

[0164] (In Table 1 above, [Li], [P], [S], [Cl], and [Br] in the column of the argyrodite solid electrolyte composition represent the molar ratio of Li, P, S, Cl, and Br per 1 mol of the argyrodite solid electrolyte, respectively.)

[0165] Experimental Example 1: Evaluation of Solid Electrolyte Properties

[0166] (1) Evaluation of average particle diameter (D50) of solid electrolyte particles

[0167] The particle size corresponding to 50% of the volume accumulation was measured using the laser diffraction method.

[0168] (2) Evaluation of sphericity of solid electrolyte particles

[0169] The sphericity was evaluated by dividing the perimeter of a circle with the same area as the particle projection shape by the actual perimeter of the particle projection shape using a flow particle analysis device. At this time, the measurement was performed using an analyzer for optical image acquisition (Fluid Imaging Technologies, Flowcam 8100) and analysis S / W (visual spreadsheet).

[0170] (3) Evaluation of metal element content

[0171] Considering the weight of the final solid electrolyte and the amount of metal precursor introduced during the atomic layer deposition coating process, the content of metal elements based on the total weight of the solid electrolyte was evaluated.

[0172] (4) Evaluation of fluorine compounds in the coating layer

[0173] Fluorine compounds were evaluated through ICP analysis.

[0174] (5) Evaluation of average thickness of coating layer

[0175] First, the coating layer thickness for a single solid electrolyte particle was obtained by observing the solid electrolyte particle using a transmission electron microscope (TEM) image and deriving the average value of the thickness for 10 measurement areas around the entire circumference of the outer surface of the solid electrolyte particle. Next, the average thickness of the coating layer was obtained by deriving the average value of the coating layer thickness obtained in the same manner as above for 20 random solid electrolyte particles among the solid electrolyte powders.

[0176] Metal element typeMetal element content (wt%)Solid electrolyte particle average particle size (D50, μm)Solid electrolyte particle sphericityCoating layerFluorine compoundCoating layer average thickness (nm)Example 1Al0.00130.65AlF30.01Example 2Al0.0130.65AlF30.05Example 3Al0.0230.65AlF30.1Example 4Al0.0530.65AlF30.3Example 5Al0.230.65AlF30.6Comparative example 1-030.65AlF30

[0177] Referring to Table 2, it was confirmed that as the number of ALD cycles increased and the content of metal elements increased, the average thickness of the coating layer also increased.

[0178] Experimental Example 2: Evaluation of Solid Electrolyte Ionic Conductivity and Moisture Stability

[0179] (1) Evaluation of ionic conductivity before exposure to air (25℃, 0.1C)

[0180] We conducted experiments to evaluate the ionic conductivity of solid electrolytes using a pressure powder cell. Specifically, the synthesized solid electrolyte was pulverized and then manufactured into pellets under a pressure of 300 MPa. The cell was then fabricated using SUS as the working electrode at a pressure of 70 MPa. Impedance was then measured at 25°C with a voltage of 10 mV applied.

[0181] (2) Evaluation of ionic conductivity after exposure to air (25℃, 0.1C)

[0182] In a dry room with a dew point of approximately -45°C, 0.5 g of a solid electrolyte in powder form was left for approximately 8 hours, then recovered and the impedance was re-measured using the same method as above.

[0183] (3) Moisture stability evaluation

[0184] Moisture stability was derived by converting the value of ionic conductivity after atmospheric exposure to the value of ionic conductivity before atmospheric exposure derived above into a percentage (%).

[0185] Ionic Conductivity Before Atmospheric Exposure (mS / cm) Ionic Conductivity After Atmospheric Exposure (mS / cm) Moisture Stability (%) Example 11.5 1.17 4.3 Example 21.10 7.79 Example 30.6 0.584 Example 40.4 0.33 83 Example 50.2 0.17 85 Comparative Example 12.3 1.774

[0186] Referring to Table 3, it was confirmed that the solid electrolyte of the example to which the AlF3 coating layer was applied had improved moisture stability compared to the solid electrolyte of Comparative Example 1 to which the AlF3 coating layer was not applied. Comparing Examples 1 to 5, it was confirmed that as the content of the Al element or the average thickness of the coating layer increased, the moisture stability improved, but the ionic conductivity deteriorated. Therefore, it was confirmed that when the content of the Al element or the average thickness of the coating layer was more appropriately controlled, the moisture stability was improved while at the same time preventing the deterioration of the ionic conductivity.

[0187]

[0188] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0189] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Sulfide-based solid electrolyte particles; and a coating layer containing fluoride, which covers the entire surface of the sulfide-based solid electrolyte particles in a thin film form, The above fluoride is a solid electrolyte which is a fluorine compound containing at least one metal element selected from the group consisting of Al, Zn, Si, and Sn.

2. In paragraph 1, The above fluoride is a solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] M x F y In the chemical formula 1 above, M is at least one of Al, Zn, Si, and Sn, and 0.1≤x≤5 and 1≤y≤20.

3. In paragraph 1, A solid electrolyte having an average thickness of the coating layer of 0.01 to 1.2 nm.

4. In paragraph 1, A solid electrolyte wherein the average difference between the maximum thickness and the minimum thickness of the coating layer is 0.1 nm or less.

5. In paragraph 1, A solid electrolyte having a content of the metal element of 0.001 to 0.5 wt% based on the total weight of the solid electrolyte.

6. In paragraph 1, A solid electrolyte having an average particle diameter (D50) of the above sulfide-based solid electrolyte particles of 0.7 to 10 μm.

7. In paragraph 1, A solid electrolyte having a sphericity of the above sulfide-based solid electrolyte particles of 0.1 or more.

8. In paragraph 1, The above sulfide-based solid electrolyte particles are solid electrolyte particles of the argyrodite-based solid electrolyte.

9. In paragraph 8, The above argyrodite-based solid electrolyte particles are solid electrolytes containing Cl and Br as halogen elements.

10. In paragraph 9, A solid electrolyte having a molar ratio of Br to Cl ([Br] / [Cl]) of 0.7 to 1.

3.

11. Step of preparing sulfide-based solid electrolyte particles; and It includes a step of forming a coating layer containing fluoride by covering the entire surface of the sulfide-based solid electrolyte particle in a thin film form by an atomic layer deposition (ALD) method using a fluorine precursor and a metal precursor. The above fluoride is a fluorine compound containing at least one metal element among Al, Zn, Si, and Sn. Method for manufacturing a solid electrolyte.

12. In paragraph 11, A method for manufacturing a solid electrolyte, wherein the above atomic layer deposition is performed for 2 to 100 cycles.

13. In paragraph 11, A method for producing a solid electrolyte wherein the fluorine precursor is HF, NH3 or a combination thereof.

14. In paragraph 11, A method for producing a solid electrolyte, wherein the metal precursor is aluminum alkoxide, zinc alkoxide, silicon alkoxide, tin alkoxide or a combination thereof.

15. In paragraph 11, A method for manufacturing a solid electrolyte, wherein the above atomic layer deposition is performed at a temperature of 20 to 100°C.

16. In paragraph 11, The above atomic layer deposition is a method for manufacturing a solid electrolyte performed in an argon or nitrogen atmosphere.

17. An all-solid-state battery comprising a solid electrolyte according to paragraph 1.

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