Solid electrolyte and all solid state battery comprising same

Abstract

The present invention relates to a sulfide-based solid electrolyte which comprises lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D), and has an argyrodite-based crystal structure, wherein at least a portion of the crystal structure is doped with at least one element among boron (B) and aluminium (Al), and the moisture stability is at least 75%.

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] 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 sulfide-based solid electrolyte having an argyrodite-based crystal structure with improved moisture stability and an all-solid-state battery including the same.

[0010]

[0011] One embodiment of the present invention provides a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D), having an argyrodite-based crystal structure, wherein at least a portion of the crystal structure is doped with at least one element selected from the group consisting of boron (B) and aluminum (Al), and having a moisture stability of 75% or more.

[0012] The above solid electrolyte may further have at least a portion of the crystal structure doped with oxygen (O).

[0013] The above solid electrolyte may have a molar ratio of aluminum (Al) to phosphorus (P) ([Al] / [P]) of 0.01 to 0.3.

[0014] The above solid electrolyte may have a molar ratio of boron (B) to phosphorus (P) ([B] / [P]) of 0.01 to 0.2.

[0015] The above solid electrolyte may have a molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) of 0.05 to 0.6.

[0016] The above solid electrolyte may have a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4 to 5.

[0017] The above solid electrolyte may have a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 1 to 2.

[0018] The above solid electrolyte may have a molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) of 5 to 6.

[0019] The above halogen element (D) may be any two or more selected from Cl, Br, and I.

[0020] The above solid electrolyte can be represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li7-x-7a+ax-7b+bxP 1-a-b Al 2a B 2b S6-6a-6b-x+ax+bx O 3a+3b D x-ax-bx

[0023] In the above chemical formula 1, 1≤x≤2, 0≤a≤0.15, 0≤b≤0.09, and D is a halogen element such as F, Cl, Br, I, or a combination thereof.

[0024] In the above chemical formula 1, 0.005≤a≤0.06 may be satisfied.

[0025] In the above chemical formula 1, 0.005≤b≤0.055 may be satisfied.

[0026]

[0027] 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.

[0028]

[0029] A sulfide-based solid electrolyte according to one embodiment of the present invention has an argyrodite-based crystal structure, so that not only does it have excellent ionic conductivity, but at least a portion of the crystal structure is doped with at least one element selected from boron (B) and aluminum (Al), so that moisture stability can be improved.

[0030] In addition, in one embodiment of the present invention, the sulfide-based solid electrolyte can improve the capacity characteristics of the battery by doping at least a portion of the crystal structure with at least one element selected from boron (B) and aluminum (Al).

[0031]

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0037] 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.

[0038] 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.

[0039]

[0040] 1. Solid electrolyte

[0041] A sulfide-based solid electrolyte according to one embodiment of the present invention has an argyrodite-based crystal structure containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D). Accordingly, excellent ionic conductivity can be achieved.

[0042] However, although the argyrodite-based sulfide solid electrolyte has high lithium ion conductivity, it has a problem of weak 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.

[0043] Accordingly, in accordance with one embodiment of the present invention, a sulfide-based solid electrolyte has at least a portion of its argyrodite-based crystal structure doped with at least one element selected from the group consisting of boron (B) and aluminum (Al). Accordingly, not only can moisture stability be improved, but also electrochemical properties such as battery capacity characteristics can be enhanced.

[0044] In this specification, “doping” may mean not only replacing some elements of a compound with new elements, but also making the doped element a component of the crystalline phase of the compound.

[0045] From the perspective of more desirable implementation of the aforementioned effects of improving the moisture stability and electrochemical properties of the solid electrolyte, it may be more appropriate for at least a portion of the argyrodite crystal structure to be co-doped with boron (B) and aluminum (Al).

[0046] In addition, the solid electrolyte may further have at least a portion of the argyrodite-based crystal structure doped with oxygen (O). As at least a portion of the argyrodite-based crystal structure is further doped with oxygen (O) in addition to boron (B) and / or aluminum (Al), the aforementioned effects of improving the moisture stability and battery electrochemical characteristics of the solid electrolyte may be more preferably implemented. Meanwhile, the doping of oxygen (O) may be implemented by using boron oxide and aluminum oxide as boron source materials and aluminum source materials, as described in the manufacturing method described below.

[0047] At this time, the boron (B) and aluminum (Al) can be doped independently of each other. In other words, the doping amounts of boron and aluminum do not have a fixed correlation with each other, but can be randomly and independently adjusted. Accordingly, by independently adjusting the doping amounts of boron and aluminum to an optimized range, the aforementioned effects of improving the water stability of the solid electrolyte and the electrochemical characteristics of the battery can be maximized.

[0048]

[0049] The above solid electrolyte may have a molar ratio of aluminum (Al) to phosphorus (P) ([Al] / [P]) of 0.01 to 0.3, more specifically, 0.01 to 0.15. If the molar ratio of aluminum (Al) to phosphorus (P) ([Al] / [P]) is too low, the aluminum doping effect may be minimal, and the aforementioned effects of improving the moisture stability and battery electrochemical properties of the solid electrolyte may be minimal. If the molar ratio of aluminum (Al) to phosphorus (P) ([Al] / [P]) is too high, the basic argyrodite crystal structure may be significantly deformed, which may deteriorate the ionic conductivity, and the moisture stability and battery electrochemical properties of the solid electrolyte may rather deteriorate.

[0050] The above solid electrolyte may have a molar ratio of boron (B) to phosphorus (P) ([B] / [P]) of 0.01 to 0.2, more specifically, 0.01 to 0.12. If the molar ratio of boron (B) to phosphorus (P) ([B] / [P]) is too low, the boron doping effect may be minimal, and the aforementioned effects of improving the moisture stability and battery electrochemical properties of the solid electrolyte may be minimal. If the molar ratio of boron (B) to phosphorus (P) ([B] / [P]) is too high, the basic argyrodite crystal structure may be significantly deformed, which may deteriorate the ionic conductivity, and the moisture stability and battery electrochemical properties of the solid electrolyte may rather deteriorate.

[0051] The above solid electrolyte may have a molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) of 0.05 to 0.6. If the molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) is too low, the additional doping effect of oxygen may be minimal, and the aforementioned effects of improving the moisture stability and battery electrochemical properties of the solid electrolyte may be minimal. If the molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) is too high, the basic argyrodite crystal structure may be significantly deformed, which may deteriorate the ionic conductivity, and the moisture stability and battery electrochemical properties of the solid electrolyte may rather deteriorate.

[0052] The above solid electrolyte may have a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4 to 5. 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.

[0053] The above solid electrolyte may have a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 1 to 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.

[0054] The above solid electrolyte may have a molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) of 5 to 6. 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058]

[0059] The above solid electrolyte can be more specifically represented by the following chemical formula 1.

[0060] [Chemical Formula 1]

[0061] Li7-x-7a+ax-7b+bxP 1-a-b Al 2a B 2b S 6-6a-6b-x+ax+bx O 3a+3b D x-ax-bx

[0062] In the above chemical formula 1, 1≤x≤2, 0≤a≤0.15, 0≤b≤0.09, and D is a halogen element such as F, Cl, Br, I, or a combination thereof.

[0063] 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.

[0064] In the above chemical formula 1, a may be more specifically 0≤a≤0.15 or 0.005≤a≤0.06. a is proportional to the doping amount of aluminum (Al). If a is too small, the aluminum doping effect may be minimal, and the aforementioned effects of improving the moisture stability of the solid electrolyte and the electrochemical properties of the battery may be minimal. If a is too large, the basic argyrodite crystal structure may be significantly deformed, which may deteriorate the ionic conductivity, and the moisture stability of the solid electrolyte and the electrochemical properties of the battery may actually deteriorate.

[0065] In the above chemical formula 1, b may be more specifically 0≤b≤0.09 or 0.005≤b≤0.055. B is proportional to the doping amount of boron (B). If b is too small, the boron doping effect may be minimal, and the aforementioned effects of improving the moisture stability and battery electrochemical properties of the solid electrolyte may be minimal. If b is too large, the basic argyrodite crystal structure may be significantly deformed, which may deteriorate the ionic conductivity, and the moisture stability and battery electrochemical properties of the solid electrolyte may actually deteriorate.

[0066]

[0067] As mentioned above, a sulfide-based solid electrolyte according to one embodiment of the present invention is doped with at least one element of boron (B) and aluminum (Al), and when the doping amount is appropriately controlled, the ionic conductivity at 25°C may be 1.7 mS / cm or more, and more specifically, 1.9 mS / cm or 2.0 mS / cm or more.

[0068] In addition, a sulfide-based solid electrolyte according to one embodiment of the present invention is doped with at least one element selected from the group consisting of boron (B) and aluminum (Al), and when the doping amount is appropriately controlled, the moisture stability may be 75% or more, and more specifically, 80% or more. In the present specification, the moisture stability of the solid electrolyte can be obtained by calculating the percentage value of the ionic conductivity of the solid electrolyte after exposure to the air to the ionic conductivity of the solid electrolyte before exposure to the air. The ionic conductivity of the solid electrolyte before exposure to the air is the ionic conductivity measured at 25°C immediately after synthesizing the solid electrolyte. The ionic conductivity of the solid electrolyte after exposure to the air is the ionic conductivity measured at 25°C after applying 0.5 g of the solid electrolyte in powder form to a watch face in a dry room having a dew point of about -45°C and leaving it for about 8 hours, and then recovering the solid electrolyte.

[0069]

[0070] 2. Solid electrolyte manufacturing method

[0071] 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 boron (B) raw material and an aluminum (Al) raw material.

[0072] Hereinafter, a method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention will be described step by step.

[0073]

[0074] 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 boron (B) raw materials and aluminum (Al) raw materials.

[0075] The above lithium raw material may be, for example, Li2S, Li2S2, or a combination thereof, but is not necessarily limited thereto.

[0076] The above raw material may be, for example, P2S5, P2O5 or a combination thereof, but is not necessarily limited thereto.

[0077] 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.

[0078] The above boron (B) raw material is not particularly limited as long as it is a boron-containing compound. However, for oxygen doping, the boron (B) raw material may be a boron oxide, for example, B2O3.

[0079] The above aluminum (Al) raw material is not particularly limited as long as it is an aluminum-containing compound. However, for oxygen doping, the aluminum (Al) raw material may be aluminum oxide, for example, Al2O3.

[0080] 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.

[0081] The above mixing can be performed by mechanical mixing or chemical mixing.

[0082] 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.

[0083] The above chemical mixing can be performed, for example, by melt quenching.

[0084] 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.

[0085] 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.

[0086]

[0087] Next, optionally, after the step of forming the mixture, a step of compressing the mixture to form pellets may be further included.

[0088] 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.

[0089]

[0090] Next, the mixture is heat-treated to form a sulfide-based solid electrolyte having an argyrodite-based crystal structure.

[0091] 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.

[0092] 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.

[0093] 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.

[0094]

[0095] 3. All-solid-state battery

[0096] 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.

[0097]

[0098] (bipolar layer)

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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-bB 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 dO2 (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 CoG b 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108]

[0109] (cathode layer)

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121]

[0122] (solid electrolyte layer)

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127]

[0128] Another embodiment of the present invention provides an electric vehicle including the all-solid-state battery.

[0129]

[0130] 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.

[0131]

[0132] Example 1: Li 5.82 P 0.97 B 0.06 S 4.85 O 0.09 Cl 0.97 Solid electrolyte manufacturing

[0133] (1) Manufacturing of solid electrolyte

[0134] The final product is Li7-x-7a+ax-7b+bxP 1-a-b Al 2a B 2b S 6-6a-6b-x+ax+bx O 3a+3b D x-ax-bx In the solid electrolyte, reactants Li2S, P2S5, LiCl, and B2O3 were added in a stoichiometric ratio so that x=1, a=0, and b=0.03, and a mixture was formed by mixing at 300 rpm for about 8 hours using a planetary mill.

[0135] Next, a pressure of 300 MPa was applied to the mixture to form pellets.

[0136] Next, the pellets were heat-treated at 550°C for about 4 hours in an argon (Ar) atmosphere to obtain Li 5.82 P 0.97 B 0.06 S 4.85 O 0.09 Cl 0.97 A solid electrolyte was prepared.

[0137] (2) All-solid-state battery manufacturing

[0138] 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.

[0139]

[0140] Example 2: Li 5.76 P 0.96 Al 0.02 B 0.06 S 4.8 O 0.12 Cl 0.96 manufacturing

[0141] The final product is Li7-x-7a+ax-7b+bxP 1-a-b Al 2a B 2b S 6-6a-6b-x+ax+bx O 3a+3b D x-ax-bx A 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, B2O3, and Al2O3 were added in a stoichiometric ratio so that x=1, a=0.01, and b=0.03 in the solid electrolyte.

[0142]

[0143] Comparative Example 1: Preparation of Li6PS5Cl solid electrolyte

[0144] The reactants Li2S, P2S5, and LiCl were mixed using a planetary mill at 300 rpm for about 8 hours to form a mixture.

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

[0146] Next, the pellets were heat-treated at 550°C for about 4 hours in an argon (Ar) atmosphere to produce a Li6PS5Cl solid electrolyte.

[0147]

[0148] Other Examples and Comparative Examples

[0149] The final product is Li7-x-7a+ax-7b+bxP 1-a-b Al 2a B 2b S 6-6a-6b-x+ax+bx O 3a+3b D x-ax-bx A 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, B2O3, and Al2O3 were added in a stoichiometric ratio so that x, a, and b in the solid electrolyte were as described in Table 1 below.

[0150]

[0151] Table 1 below shows the x, a, and b values ​​of examples and comparative examples and the composition of solid electrolytes manufactured accordingly.

[0152] xab Solid electrolyte composition [Li][P][Al][B][S][O][Cl] Comparative example 11006100501 Example 1100.035.820.9700.064.850.090.97 Example 210.010.035.760.960.020.064.80.120.96 Example 310.020.035.70.950.040.064.750.150.95 Example 410.050.035.520.920.10.064.60.240.92 Example 510.080.035.340.890.160.064.450.330.89Example 610.10.035.220.870.20.064.350.390.87Comparative Example 210.20.034.620.770.40.063.850.690.77Comparative Example 310.50.032.820.4710.062.351.590.47Example 710.0205.880.980.0404.90.060.98Example 810.020.015.820.970.040.024.850.090.97Example 910.020.025.760.960.040.044.80.120.96Example 1010.020.045.640.940.040.084.70.180.94Example 1110.020.055.580.930.040.14.650.210.93Example 1210.020.065.520.920.040.124.60.240.92Example 1310.020.085.40.90.040.164.50.30.9Comparative Example 410.020.15.280.880.040.24.40.360.88

[0153] (In Table 1 above, [Li], [P], [Al], [B], [S], [O], and [Cl] represent the molar ratios for 1 mol of the manufactured solid electrolyte, respectively.)

[0154] Molar ratio of elements in solid electrolyte [Al] / [P][B] / [P][O] / [P][S] / [P][Cl] / [P][Li] / [P] Comparative example 10.0000.0000.0005.0001.0006.000 Example 10.0000.0620.0935.0001.0006.000 Example 20.0210.0630.1255.0001.0006.000 Example 30.0420.0630.1585.0001.0006.000 Example 40.1090.0650.2615.0001.0006.000 Example 50.1800.0670.3715.0001.0006.000Example 60.2300.0690.4485.0001.0006.000Comparative Example 20.5190.0780.8965.0001.0006.000Comparative Example 32.1280.1283.3835.0001.0006.000Example 70.0410.0000.0615.0001.0006.000Example 80.0410.0210.0935.0001.0006.000Example 90.0420.0420.1255.0001.0006.000Example 100.0430.0850.1915.0001.0006.000Example 110.0430.1080.2265.0001.0006.000Example 120.0430.1300.2615.0001.0006.000Example 130.0440.1780.3335.0001.0006.000Comparative Example 40.0450.2270.4095.001.0006.000

[0155]

[0156] Table 3 below summarizes the results of evaluating the ionic conductivity, atmospheric stability, and initial discharge capacity characteristics of the solid electrolyte and the all-solid-state battery according to Experimental Examples 1 and 2 described below.

[0157] Ionic ConductivityMoisture StabilityDischarge CapacitymS cm-1%mAh g-1Comparative Example 12.373202Example 12.2577203Example 22.1584205Example 32.0283206Example 41.981205Example 51.8381203Example 61.8080203Comparative Example 21.0469191Comparative Example 30.3955190Example 72.2376203Example 82.2080204Example 92.2182205Example 102.1582203Example 112.1281204Example 122.1079204Example 132.0576203Comparative Example 41.9371203

[0158]

[0159] Experimental Example 1: Evaluation of Solid Electrolyte Ionic Conductivity and Moisture Stability

[0160] An experiment was conducted to evaluate the ionic conductivity and atmospheric stability of the solid electrolyte manufactured according to the examples and comparative examples, and the results are shown in Table 3 above. The specific experimental method is as follows.

[0161] (1) Evaluation of ionic conductivity before exposure to air (25℃, 0.1C)

[0162] 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 25°C.

[0163] (2) Moisture stability evaluation

[0164] 1) Evaluation of ionic conductivity after exposure to air

[0165] In a dry room with a dew point of approximately -45°C, 0.5 g of a solid electrolyte in powder form was applied to the watch face and left for approximately 8 hours. After this, it was recovered and the impedance was re-measured using the same method as above.

[0166] 2) Moisture stability evaluation

[0167] The moisture stability was evaluated by converting the value of ionic conductivity after atmospheric exposure to the ionic conductivity before atmospheric exposure derived above into a percentage (%).

[0168]

[0169] Experimental Example 2: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0170] An experiment was conducted to evaluate the electrochemical characteristics of lithium secondary batteries manufactured according to the examples and comparative examples, and the results are shown in Table 3 above. The specific experimental method is as follows.

[0171] (1) Initial discharge capacity evaluation

[0172] 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 charging capacity, discharge capacity, and initial efficiency were evaluated.

[0173]

[0174] Referring to Table 3, in the case of an example in which boron (B) and / or aluminum (Al) was doped into an argyrodite-based solid electrolyte, and the a and b values ​​or [B] / [P] and [Al] / [P] values ​​were appropriately controlled, it was confirmed that moisture stability was improved, ionic conductivity was excellent, and the initial discharge capacity of the battery was improved.

[0175] On the other hand, in the case of Comparative Example 1, which is a basic argyrodite-based solid electrolyte in which boron (B) and aluminum (Al) are not doped at all in the argyrodite-based solid electrolyte, it was confirmed that the ionic conductivity was good, but the moisture stability and the initial discharge capacity of the battery were poor.

[0176] In addition, in the case of Comparative Examples 2 and 3, where the a value or [Al] / [P] value was too large and the aluminum doping amount was too large, not only was the ionic conductivity significantly deteriorated, but it was also confirmed that the moisture stability and the initial discharge capacity of the battery were also deteriorated compared to Comparative Example 1, which is a basic argyrodite composition.

[0177] In addition, in the case of Comparative Example 4, where the b value or [B] / [P] value was too large and the boron doping amount was too large, it was confirmed that not only was the ionic conductivity deteriorated, but the moisture stability was also deteriorated compared to Comparative Example 1, which is a basic argyrodite composition.

[0178] Meanwhile, when comparing the examples, it was confirmed that when the a value or the [Al] / [P] value, the b value or the [B] / [P] value were more appropriately controlled, moisture stability was maximized, and ionic conductivity and initial discharge capacity of the battery were preferably implemented.

[0179]

[0180] 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.

[0181] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Contains lithium (Li), phosphorus (P), sulfur (S) and halogen elements (D), and has an argyrodite crystal structure. At least a portion of the above crystal structure is doped with at least one element of boron (B) and aluminum (Al), A sulfide-based solid electrolyte with a moisture stability of 75% or more.

2. In paragraph 1, A sulfide-based solid electrolyte wherein at least a portion of the above crystal structure is further doped with oxygen (O).

3. In paragraph 1, The above solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of aluminum (Al) to phosphorus (P) ([Al] / [P]) of 0.01 to 0.

3.

4. In paragraph 1, The above solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of boron (B) to phosphorus (P) ([B] / [P]) of 0.01 to 0.

2.

5. In paragraph 2, The above solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of oxygen (O) to phosphorus (P) ([O] / [P]) of 0.05 to 0.

6.

6. In paragraph 1, The above solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4 to 5.

7. In paragraph 1, The above solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 1 to 2.

8. In paragraph 1, The above solid electrolyte is a sulfide-based solid electrolyte having a molar ratio of lithium (Li) to phosphorus (P) ([Li] / [P]) of 5 to 6.

9. In paragraph 1, A sulfide-based solid electrolyte wherein the above halogen element (D) is at least two selected from Cl, Br, and I.

10. In paragraph 1, The above solid electrolyte is a sulfide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] Li7-x-7a+ax-7b+bxP 1-a-b Al 2a B 2b S 6-6a-6b-x+ax+bx O 3a+3b D x-ax-bx In the chemical formula 1 above, 1≤x≤2, 0≤a≤0.15, 0≤b≤0.09, and D is a halogen element such as F, Cl, Br, I, or a combination thereof.

11. In paragraph 10, Sulfide-based solid electrolyte with 0.005≤a≤0.

06.

12. In paragraph 10, A sulfide-based solid electrolyte with 0.005≤b≤0.

055.

13. Including 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.