Solid electrolyte and all solid state battery comprising same

Abstract

The present invention relates to a sulfide-based solid electrolyte comprising a compound containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D) and having an argyrodite-based crystal structure, wherein at least a part of the crystal structure is doped with oxygen (O) and a transition metal element (M) composed of Nb, Ta, V, or a combination thereof.

Description

Solid electrolyte and all-solid-state battery containing the same

[0001] The present invention relates to a solid electrolyte 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 any ignition or explosion due to a reaction such as the decomposition reaction of a conventional electrolyte.

[0005] The solid electrolyte used in the above-mentioned all-solid-state battery is generally an inorganic solid electrolyte, and among these, a sulfide-based solid electrolyte having an argyrodite-based crystal structure has high ionic conductivity, and various studies are being conducted on it.

[0006] Meanwhile, in the case of all-solid-state batteries, since lithium metal or lithium alloy can be used as the negative electrode material, the energy density for the mass and volume of the battery can be improved.

[0007] However, when lithium metal or lithium alloy is used as the negative electrode material, there is a problem in that lithium dendrites are formed on the surface of the negative electrode as charging and discharging are repeated, causing a short circuit in the battery.

[0008]

[0009] Accordingly, one object of the present invention is to provide a solid electrolyte having an argyrodite crystal structure and a sulfide-based solid electrolyte capable of suppressing lithium dendrite formation, and an all-solid-state battery including the same.

[0010]

[0011] One embodiment of the present invention provides a sulfide-based solid electrolyte comprising a compound containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D), having an argyrodite-based crystal structure, and wherein at least a portion of the crystal structure is doped with oxygen (O) and a transition metal element (M) composed of Nb, Ta, V, or a combination thereof.

[0012] The above compound may have a molar ratio of transition metal element (M) to phosphorus (P) ([M] / [P]) of 0.01 to 1.1.

[0013] The above compound may have a molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) of 0.03 to 2.5.

[0014] The above compound may have a molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) of 5.5 to 6.5.

[0015] The above compound may have a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4.5 to 5.5.

[0016] The above compound may have a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 0.5 to 1.5.

[0017] The above compound can exhibit a first peak in the range of 15.4˚≤2θ≤15.8˚ when analyzing an X-ray diffraction (XRD) pattern.

[0018] The above compound may exhibit a second peak in the range of 25.4˚≤2θ≤25.7˚ when analyzing an X-ray diffraction (XRD) pattern.

[0019] The above compound can exhibit a third peak in the range of 34.7˚≤2θ≤34.9˚ when analyzing an X-ray diffraction (XRD) pattern.

[0020] The compound may have a ratio of the second peak intensity to the first peak intensity of 2.4 to 2.9.

[0021] The compound may have a ratio of the third peak intensity to the first peak intensity of 0.03 to 0.8.

[0022] The above compound can be represented by the following chemical formula 1.

[0023] [Chemical Formula 1]

[0024] Li 7a-ax P a M 2-2a S 6a-ax O 5-5a D ax

[0025] In the above chemical formula 1, 1≤x≤2, 0.65≤a≤0.995, M is a transition metal element composed of Nb, Ta, V or a combination thereof, and D is a halogen element composed of F, Cl, Br, I or a combination thereof.

[0026] In the above chemical formula 1, 0.8≤a≤0.96 may be satisfied.

[0027]

[0028] Another embodiment of the present invention provides an all-solid-state battery comprising a positive electrode layer; a negative electrode layer, and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises the above-described solid electrolyte.

[0029]

[0030] According to one embodiment of the present invention, a solid electrolyte has an argyrodite crystal structure, wherein at least a portion of the crystal structure is doped with oxygen (O) and a transition metal element (M) composed of Nb, Ta, V, or a combination thereof. Accordingly, when applied to an all-solid-state battery using a lithium metal or lithium alloy negative electrode, the formation of lithium dendrites can be suppressed, thereby preventing a battery short circuit due to excessive production of lithium dendrites.

[0031]

[0032] Figure 1 is a graph showing the results of X-ray diffraction pattern analysis of solid electrolytes manufactured according to Examples 1 to 4.

[0033]

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0039] 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.

[0040] 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.

[0041]

[0042] 1. Solid electrolyte

[0043] A solid electrolyte according to one embodiment of the present invention comprises a compound containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D), and having an argyrodite crystal structure. Accordingly, excellent ionic conductivity can be achieved.

[0044] At this time, the compound is doped with a transition metal element (M) consisting of oxygen (O) and Nb, Ta, V, or a combination thereof, at least part of the argyrodite crystal structure. In the present specification, “doping” may mean not only replacing some elements of the compound with new elements, but also the doped element becoming a component of the crystal phase of the compound.

[0045] Accordingly, when applied to all-solid-state batteries using lithium metal or lithium alloy anodes, the formation of lithium dendrites during charge / discharge can be suppressed. This prevents battery short-circuiting due to excessive lithium dendrite formation. Furthermore, the capacity characteristics of the battery can be improved.

[0046] More specifically, the compound may have a molar ratio of transition metal element (M) to phosphorus (P) ([M] / [P]) of 0.01 to 1.1, and more specifically, 0.08 to 0.4. If the molar ratio of transition metal element (M) to phosphorus (P) ([M] / [P]) is too small, the dendrite formation suppression effect or the capacity characteristic improvement effect of the battery due to the transition metal element doping mentioned above may be minimal. If the molar ratio of transition metal element (M) to phosphorus (P) ([M] / [P]) is too large, M acts as an impurity, so that the lithium dendrite formation suppression effect and the battery capacity characteristic improvement effect may be reduced, and the argyrodite crystal structure may be significantly deformed, which may deteriorate the ionic conductivity.

[0047] The above compound may have a molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) of 0.03 to 2.5, more specifically, 0.2 to 0.8. If the molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) is too small, the dendrite formation inhibition effect or the capacity characteristic improvement effect of the battery due to the oxygen doping mentioned above may be small. If the molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) is too large, the lithium dendrite formation inhibition effect and the battery capacity characteristic improvement effect may rather be reduced, and the argyrodite crystal structure may be significantly deformed, which may deteriorate the ionic conductivity.

[0048] The above compound may have a molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) of 5.5 to 6.5, more specifically, 5.8 to 6.2. When the molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) satisfies the above range, the argyrodite crystal structure is fully maintained, so that the ionic conductivity of the solid electrolyte or the electrochemical characteristics of the battery can be more preferably implemented.

[0049] The above compound may have a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4.5 to 5.5, more specifically, 4.8 to 5.2. When the molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) satisfies the above range, the argyrodite crystal structure is fully maintained, so that the ionic conductivity of the solid electrolyte or the electrochemical characteristics of the battery can be more preferably implemented.

[0050] The above compound may have a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 0.5 to 1.5, more specifically, 0.8 to 1.2. When the molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) satisfies the above range, the argyrodite crystal structure is fully maintained, so that the ionic conductivity of the solid electrolyte or the electrochemical characteristics of the battery can be more preferably implemented.

[0051] In addition, the halogen element (D) is not particularly limited as long as it is a halogen element, and may be, for example, F, Cl, Br, I, or a combination thereof.

[0052] However, from the viewpoint of structural stabilization of the solid electrolyte, ease of synthesis, and reduction of process cost, the halogen element (D) may be Cl.

[0053] In addition, from the viewpoint of more desirable implementation of ionic conductivity, the halogen element (D) may further include one or more elements selected from Br and I in addition to Cl, and more specifically, the halogen element (D) may include Cl and Br.

[0054]

[0055] Meanwhile, the compound may exhibit a first peak in the range of 15.4˚≤2θ≤15.8˚ when analyzing an X-ray diffraction (XRD) pattern. The first peak appearing in the above range may be a peak appearing in an argyrodite crystal structure.

[0056] The above compound may exhibit a second peak in the range of 25.4˚≤2θ≤25.7˚ when analyzing an X-ray diffraction (XRD) pattern. The second peak appearing in the above range may be a unique peak that appears as a result of additional doping of a transition metal element (M) consisting of oxygen (O) and Nb, Ta, V, or a combination thereof into the solid electrolyte compound according to the present invention.

[0057] The above compound may exhibit a third peak in the range of 34.7˚≤2θ≤34.9˚ when analyzing an X-ray diffraction (XRD) pattern. The third peak appearing in the above range may also be a unique peak that appears as a result of additional doping of a transition metal element (M) consisting of oxygen (O) and Nb, Ta, V, or a combination thereof into the solid electrolyte compound according to the present invention.

[0058] At this time, the compound may have a ratio of the second peak intensity to the first peak intensity of 2.4 to 2.9, more specifically, 2.55 to 2.73. When the ratio of the second peak intensity to the first peak intensity satisfies the above range, a transition metal element (M) composed of oxygen (O) and Nb, Ta, V, or a combination thereof may be doped in an appropriate amount, so that the aforementioned dendrite formation suppression effect, battery capacity characteristic improvement effect, and good ion conductivity implementation effect can be preferably implemented.

[0059] The compound may have a ratio of the third peak intensity to the first peak intensity of 0.03 to 0.8, more specifically, 0.3 to 0.65. When the ratio of the third peak intensity to the first peak intensity satisfies the above range, a transition metal element (M) composed of oxygen (O) and Nb, Ta, V, or a combination thereof may be doped in an appropriate amount, so that the aforementioned dendrite formation suppression effect, battery capacity characteristic improvement effect, and good ion conductivity implementation effect can be preferably implemented.

[0060]

[0061] The above compound can be more specifically represented by the following chemical formula 1.

[0062] [Chemical Formula 1]

[0063] Li 7a-ax P a M 2-2a S 6a-ax O5-5a D ax

[0064] In the above chemical formula 1, 1≤x≤2, 0.65≤a≤0.995, M is a transition metal element composed of Nb, Ta, V or a combination thereof, and D is a halogen element composed of F, Cl, Br, I or a combination thereof.

[0065] In the above chemical formula 1, x satisfies 1 ≤ x ≤ 2. If x is too small, the ionic conductivity of the solid electrolyte may deteriorate. If x is too large, the ionic conductivity of the solid electrolyte may improve, but the electrochemical properties such as moisture stability and capacity characteristics of the battery may deteriorate.

[0066] In the above chemical formula 1, a may be 0.65≤a≤0.995, and more specifically, 0.8≤a≤0.96. a is inversely proportional to the doping amount of the transition metal element or oxygen. If a is too small, the effect of suppressing dendrite formation and improving battery capacity characteristics may be reduced due to excessive doping of the transition metal element or oxygen, and the ionic conductivity of the solid electrolyte may deteriorate. If a is too large, the effect of suppressing dendrite formation or improving battery capacity characteristics due to doping of the transition metal element or oxygen may be minimal.

[0067]

[0068] 2. Solid electrolyte manufacturing method

[0069] Another embodiment of the present invention provides a method for producing a sulfide-based solid electrolyte, comprising the steps of: forming a mixture by mixing a lithium raw material, a phosphorus raw material, a halogen element raw material, and a doping raw material; and heat-treating the mixture to form a sulfide-based solid electrolyte having an argyrodite-based crystal structure, wherein the doping raw material includes a transition metal (M) raw material. Here, the transition metal (M) is a transition metal element composed of Nb, Ta, V, or a combination thereof.

[0070] Hereinafter, a method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention will be described step by step.

[0071]

[0072] First, a mixture is formed by mixing lithium raw materials, phosphorus raw materials, halogen element raw materials, and doping raw materials. At this time, the doping raw materials include a transition metal (M) raw material. Here, the transition metal (M) is a transition metal element composed of Nb, Ta, V, or a combination thereof.

[0073] The above lithium raw material may be, for example, Li2S, Li2S2, or a combination thereof, but is not necessarily limited thereto.

[0074] The above raw material may be, for example, P2S5, P2O5 or a combination thereof, but is not necessarily limited thereto.

[0075] 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.

[0076] The above transition metal (M) raw material is not particularly limited as long as it is a compound containing a transition metal (M), but more specifically, it may be a transition metal (M) oxide. Accordingly, oxygen (O) can be doped into the argyrodite compound simultaneously with the transition metal (M).

[0077] The above transition metal (M) oxide may be, for example, Nb2O5, Ta2O5, V2O5, or a combination thereof.

[0078] The input amounts of the above lithium raw material, phosphorus raw material, halogen element raw material, and doping raw material can be stoichiometrically adjusted and input to suit the composition of the target sulfide-based solid electrolyte.

[0079] The above mixing can be performed by mechanical mixing or chemical mixing.

[0080] 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.

[0081] The above chemical mixing can be performed, for example, by melt quenching.

[0082] 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 problem of insufficient mixing may occur. If the mixing time is too long, the mixing is completely completed within a certain amount of time, and even if further mixing is performed, the mixing state remains the same, which may cause problems in terms of process efficiency.

[0083] 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.

[0084]

[0085] Next, optionally, after the step of forming the mixture, a step of compressing the mixture to form pellets may be further included.

[0086] 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.

[0087]

[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]

[0093] 3. All-solid-state battery

[0094] Another embodiment of the present invention provides an all-solid-state battery comprising a positive electrode layer; a negative electrode layer, and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises the above-described solid electrolyte.

[0095]

[0096] (bipolar layer)

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106]

[0107] (cathode layer)

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] The metal / metalloid negative electrode active material includes at least one selected from the group consisting of lithium (Li), gold (Au), platinum (Pt), indium (In), 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119]

[0120] (solid electrolyte layer)

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125]

[0126] Another embodiment of the present invention provides an electric vehicle including the all-solid-state battery.

[0127]

[0128] 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.

[0129]

[0130] Example 1: Li 5.94 P 0.99 Nb 0.02 S 4.95 O 0.05 Cl 0.99 Solid electrolyte manufacturing

[0131] (1) Manufacturing of solid electrolyte

[0132] (Mixed) Final product Li 7a-ax P a M 2-2a S 6a-ax O 5-5a D ax In the solid electrolyte, reactants Li2S, P2S5, LiCl, and Nb2O5 were added in a stoichiometric ratio so that x=1 and a=0.99, and a mixture was formed by mixing at 300 rpm for about 8 hours using a planetary mill.

[0133] (Pellet manufacturing) Next, a pressure of 300 MPa was applied to the mixture to form pellets.

[0134] (Heat treatment) Next, the pellets were heat treated at 550°C for about 4 hours in an argon (Ar) atmosphere to obtain Li 5.94 P 0.99 Nb 0.02 S 4.95 O 0.05 Cl 0.99 A solid electrolyte was prepared.

[0135] (2) All-solid-state battery manufacturing

[0136] The above-mentioned manufactured solid electrolyte is used as an electrolyte, and Li1Ni is used as a cathode active material. 0.8 Co 0.1 Mn 0.1 An all-solid-state battery was manufactured using O2 and an In-Li alloy as a negative electrode active material.

[0137]

[0138] Comparative Example 1: Preparation of Li6PS5Cl solid electrolyte

[0139] The reactants Li2S, P2S5, and LiCl were mixed using a planetary mill at 300 rpm for about 8 hours to form a mixture.

[0140] Next, a pressure of 300 MPa was applied to the mixture to form pellets.

[0141] Next, the pellets were heat-treated at 550°C for about 4 hours in an argon (Ar) atmosphere to produce a Li6PS5Cl solid electrolyte.

[0142]

[0143] Other Examples and Reference Examples

[0144] In the mixing stage, the final product, Li 7a-ax P a M 2-2a S 6a-ax O 5-5a D axA solid electrolyte and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the reactants Li2S, P2S5, LiCl, and Nb2O5 were added in a stoichiometric ratio so that x and a in the solid electrolyte were as described in Table 1 below.

[0145]

[0146] Table 1 below shows the x and a values ​​of examples, comparative examples, and reference examples, and the composition of solid electrolytes manufactured accordingly.

[0147] xaComposition[Li][P][Nb][S][O][Cl]Comparative Example 111610501Example 110.995.940.990.024.950.050.99Example 210.975.820.970.064.850.150.97Example 310.955.70.950.14.750.250.95Example 410.95.40.90.24.50.50.9Example 510.74.20.70.63.51.50.7Reference Example 110.63.60.60.8320.6Reference Example 210.530.512.52.50.5

[0148] (In Table 1 above, [Li], [P], [Nb], [S], [O], and [Cl] represent the molar ratios for 1 mol of the manufactured solid electrolyte, respectively.)

[0149] Molar ratio of xa elements [Li] / [P][P] / [P][Nb] / [P][O] / [P][S] / [P][Cl] / [P]Comparative example 111610.0000.00051Example 110.99610.0200.05151Example 210.97610.0620.15551Example 310.95610.1050.26351Example 410.9610.2220.55651Example 510.7610.8572.14351Reference example 110.6611.3333.33351Reference example 210.5612.0005.00051

[0150]

[0151] Table 3 below is a table that summarizes the results of X-ray diffraction analysis of solid electrolytes according to Experimental Examples 1 and 2 described below, and the results of evaluating the ionic conductivity, short-circuit c-rate, initial discharge capacity, and life characteristics of all-solid-state batteries.

[0152] Solid electrolyteAll-solid-state batteryXRDIon conductivityShort circuitC-rateDischarge capacityLifetimeWhether the first peak appearsWhether the second peak appearsWhether the third peak appearsWhether the second peak / first peak intensity ratioThird peak / first peak intensity ratiomS cm-1%mAh g-1%Comparative example 1OXX002.660.5191.291Example 1OOO2.820.052.542191.893Example 2OOO2.750.212.222193.794Example 3OOO2.710.341.875192.695Example 4OOO2.690.621.495192.393Example 5OOO2.510.70.922180.672Reference example 1OOO1.921.30.720.5171.670 Reference example 2OOO1.411.60.160.5164.277

[0153]

[0154] Experimental Example 1: XRD Analysis of Solid Electrolyte and Evaluation of Ionic Conductivity

[0155] (1) Solid electrolyte XRD analysis

[0156] X-ray diffraction pattern analysis was performed on the solid electrolyte to evaluate whether peaks were expressed in the range of 15.4˚≤2θ≤15.8˚ (first peak), the range of 25.4˚≤2θ≤25.7˚ (second peak), and the range of 34.7˚≤2θ≤34.9˚ (third peak). At this time, the intensity ratio of the second peak to the intensity of the first peak and the intensity ratio of the third peak to the intensity of the first peak were evaluated. At this time, the XRD analysis graphs of Examples 1 to 4 are shown in Fig. 1.

[0157] (2) Ionic conductivity evaluation (30℃, 0.1C)

[0158] The manufactured solid electrolyte was pulverized and then formed into pellets under a pressure of 300 MPa. Subsequently, a cell was fabricated using SUS as the working electrode at a pressure of 70 MPa. Impedance was then measured by applying a voltage of 10 mV at 30°C.

[0159]

[0160] Referring to Table 3, it was confirmed that in the examples and reference examples doped with Nb and O, a second peak and a third peak appeared in addition to the first peak. In addition, it was confirmed that as the doping amount of Nb and O increased, the intensity ratio of the second peak to the intensity of the first peak decreased, and the intensity ratio of the third peak to the intensity of the first peak increased.

[0161] On the other hand, in the case of Comparative Example 1 of the basic argyrodite composition without Nb and O doping, it was confirmed that only the first peak appeared, and the second and third peaks did not appear.

[0162] Looking at the ionic conductivity, it was confirmed that as the doping amount of Nb and O in the solid electrolyte increased, it decreased compared to Comparative Example 1 of the basic argyrodite composition. If this is interpreted as in the experimental example described below, it was confirmed that rather than indiscriminately increasing the doping amount of Nb and O, when doping in an appropriate amount, it is possible to implement good ionic conductivity of the solid electrolyte along with the effects of preventing short circuits, improving discharge capacity, and improving lifespan.

[0163]

[0164] Experimental Example 2: Evaluation of the electrochemical properties of an all-solid-state battery

[0165] (1) Initial discharge capacity evaluation

[0166] At room temperature (25℃), the battery was charged to 4.25 V (vs. Li+ / Li) at 0.1 C, and the charging current was set to 0.02 C at that voltage to terminate the charging. After discharging to 2.50 V (vs. Li+ / Li) at 0.1 C under the same conditions, the initial discharge capacity was evaluated.

[0167] (2) Life characteristics evaluation

[0168] After performing the formation cycle at 0.1C, the percentage of the discharge capacity at the 50th cycle was calculated with respect to the discharge capacity at the 1st cycle at a current density of 0.5C.

[0169] (3) Paragraph C-rate evaluation

[0170] All-solid-state batteries were fabricated and their short-circuit C-rates were evaluated.

[0171]

[0172] When evaluating the short-circuit C-rate, it was confirmed that the short-circuit prevention effect was improved in the examples and reference examples doped with Nb and O compared to Comparative Example 1 of the basic argyrodite composition. In particular, it was confirmed that the short-circuit prevention effect was more preferably implemented when Nb and O were doped in appropriate amounts, that is, when the molar ratio of niobium (Nb) to phosphorus (P) ([Nb] / [P]), the molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]), or the a value was adjusted to an appropriate range.

[0173] When evaluating the initial discharge capacity, it was confirmed that the initial discharge capacity improved as the doping amounts of Nb and O increased compared to Comparative Example 1 of the basic argyrodite composition, but then showed a tendency to deteriorate again. Therefore, it was confirmed that the capacity characteristics were more desirably implemented when Nb and O were doped in appropriate amounts, that is, when the molar ratio of niobium (Nb) to phosphorus (P) ([Nb] / [P]), the molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]), or the a value was adjusted to an appropriate range.

[0174] When evaluating the life characteristics, it was confirmed that the life characteristics improved as the doping amounts of Nb and O increased compared to Comparative Example 1 of the basic argyrodite composition, but then showed a tendency to deteriorate again. Therefore, it was confirmed that the life characteristics were more desirably implemented when Nb and O were doped in appropriate amounts, that is, when the molar ratio of niobium (Nb) to phosphorus (P) ([Nb] / [P]), the molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]), or the a value was adjusted to an appropriate range.

[0175]

[0176] 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.

[0177] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A compound containing lithium (Li), phosphorus (P), sulfur (S) and a halogen element (D) and having an argyrodite crystal structure. A sulfide-based solid electrolyte doped with a transition metal element (M) comprising at least a portion of the crystal structure of oxygen (O) and Nb, Ta, V or a combination thereof.

2. In paragraph 1, The above compound is a sulfide-based solid electrolyte having a molar ratio of transition metal element (M) to phosphorus (P) ([M] / [P]) of 0.01 to 1.

1.

3. In paragraph 1, The above compound is a sulfide-based solid electrolyte having a molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) of 0.03 to 2.

5.

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

5.

5. In paragraph 1, The above compound is a sulfide-based solid electrolyte having a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4.5 to 5.

5.

6. In paragraph 1, The above compound is a sulfide-based solid electrolyte having a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 0.5 to 1.

5.

7. In paragraph 1, The above compound is a sulfide-based solid electrolyte that exhibits a first peak in the range of 15.4˚≤2θ≤15.8˚ when analyzing an X-ray diffraction (XRD) pattern.

8. In paragraph 7, The above compound is a sulfide-based solid electrolyte that exhibits a second peak in the range of 25.4˚≤2θ≤25.7˚ when analyzing an X-ray diffraction (XRD) pattern.

9. In paragraph 7, The above compound is a sulfide-based solid electrolyte that exhibits a third peak in the range of 34.7˚≤2θ≤34.9˚ when analyzing an X-ray diffraction (XRD) pattern.

10. In paragraph 8, The compound is a sulfide-based solid electrolyte having a ratio of the second peak intensity to the first peak intensity of 2.4 to 2.

9.

11. In paragraph 9, The compound is a sulfide-based solid electrolyte having a ratio of the third peak intensity to the first peak intensity of 0.03 to 0.

8.

12. In paragraph 1, The above compound is a sulfide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] Li 7a-ax P a M 2-2a S 6a-ax Oh 5-5a D ax In the chemical formula 1 above, 1≤x≤2, 0.65≤a≤0.995, M is a transition metal element composed of Nb, Ta, V or a combination thereof, and D is a halogen element composed of F, Cl, Br, I or a combination thereof.

13. In paragraph 12, Sulfide-based solid electrolyte with 0.8≤a≤0.

96.

14. Comprising a positive electrode layer; a negative electrode layer and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, An all-solid-state battery, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises a solid electrolyte according to claim 1.

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