Solid electrolyte and all-solid-state battery comprising same

Abstract

The present invention relates to a sulfide-based solid electrolyte comprising a sulfide-based compound which contains lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D) and has an argyrodite-based crystal structure, wherein the compound further includes a basic functional group (E), the molar ratio ([D] / [P]) of the halogen element (D) to phosphorus (P) in the compound is 1-2, and the moisture stability of the compound is 75% or more.

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, and more specifically, to provide a sulfide-based 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] To improve this, there were attempts to improve moisture stability by doping various metal elements into the argyrodite sulfide-based solid electrolyte. However, in this case, although moisture stability was improved, the ionic conductivity of the solid electrolyte was rather deteriorated, and there was a problem that the electrochemical characteristics such as the capacity characteristics of the battery were deteriorated.

[0009]

[0010] Accordingly, one object of the present invention is to provide a sulfide-based solid electrolyte and an all-solid-state battery including the same, which can not only improve moisture stability but also enhance electrochemical properties such as ionic conductivity or capacity characteristics of the battery.

[0011]

[0012] One embodiment of the present invention provides a sulfide-based solid electrolyte comprising a sulfide-based compound containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D), and having an argyrodite-based crystal structure, wherein the compound further comprises a basic functional group (E), and the compound has a molar ratio of the halogen element (D) to phosphorus (P) ([D] / [P]) of 1 to 2 and a moisture stability of 75% or more.

[0013] The above basic functional group (E) may be OH, NH3, NO3, HCO3 or a combination thereof.

[0014] The molar ratio of the basic functional group (E) to the above compound may be 0.005 to 0.45.

[0015] The above compound may have a molar ratio of basic functional group (E) to phosphorus (P) ([E] / [P]) of 0.005 to 0.8.

[0016] The molar ratio of phosphorus (P) to the above compound may be 0.55 to 0.995.

[0017] The above compound may have a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4 to 5.

[0018] The compound can be more specifically represented by the following chemical formula 1.

[0019] [Chemical Formula 1]

[0020] Li 7-6a-x+ax P 1-a S 6-6a-x+ax D x-ax (E) a

[0021] In the above chemical formula 1, 0.005≤a≤0.45, 1≤x≤2, D is a halogen element such as F, Cl, Br, I or a combination thereof, and E is a basic functional group such as OH, NH3, NO3, HCO3 or a combination thereof.

[0022] In the above chemical formula 1, 0.03≤a≤0.25 may be satisfied.

[0023] The above compound may have an ionic conductivity of 2.2 mS / cm or more at 30°C.

[0024]

[0025] 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.

[0026]

[0027] A sulfide-based solid electrolyte according to one embodiment of the present invention comprises a sulfide-based compound having an argyrodite-based crystal structure, and since the compound further comprises a basic functional group (E), not only is moisture stability improved, but electrochemical properties such as ionic conductivity or capacity characteristics of a battery can also be improved.

[0028]

[0029] 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 solely 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0034] 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.

[0035] 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.

[0036]

[0037] 1. Solid electrolyte

[0038] A sulfide-based solid electrolyte according to one embodiment of the present invention comprises a sulfide-based compound containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element (D), and having an argyrodite-based crystal structure. Since the sulfide-based compound has an argyrodite-based crystal structure, excellent ionic conductivity can be achieved.

[0039] 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.

[0040] Accordingly, the sulfide compound according to the present invention further includes a basic functional group (E). Accordingly, the basic functional group can neutralize the acidic sulfide solid electrolyte or the sulfide solid electrolyte decomposition product, thereby improving moisture stability.

[0041] In addition, there have been attempts to dope metal elements to improve the moisture stability of argyrodite-based sulfide-based solid electrolytes in the past. In this case, although moisture stability is improved, there was a problem that ionic conductivity was rather deteriorated compared to the basic argyrodite-based sulfide-based solid electrolyte, or electrochemical characteristics such as capacity characteristics of the battery were deteriorated when applied to the battery. On the other hand, the sulfide-based compound according to the present invention can not only improve moisture stability but also improve ionic conductivity. The inventors of the present invention believe that this is because a stabilized material is synthesized through a neutralization reaction between a basic additive and an acidic sulfide-based solid electrolyte material. In addition, the sulfide-based compound according to the present invention can improve the capacity characteristics of the battery. The inventors of the present invention believe that this is because the interface is stabilized by the introduction of an oxide.

[0042] The basic functional group (E) may be more specifically OH, NH3, NO3, HCO3, or a combination thereof. However, from the perspective of more desirable implementation of the aforementioned solid electrolyte's moisture stability, ionic conductivity, or improved battery electrochemical properties, the basic functional group (E) may be more appropriately OH.

[0043] At this time, the molar ratio of the basic functional group (E) to the compound may be 0.005 to 0.45, more specifically 0.03 to 0.25. Alternatively, the compound may have a molar ratio of the basic functional group (E) to phosphorus (P) ([E] / [P]) of 0.005 to 0.8, more specifically 0.03 to 0.3. When the content of the basic functional group satisfies the above range, the aforementioned effects of improving the moisture stability, ionic conductivity, or battery electrochemical characteristics of the solid electrolyte can be more preferably implemented.

[0044] In addition, the sulfide compound according to the present invention has a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 1 to 2. If the molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) is too small, the content of halogen element that facilitates lithium ion movement may become too small, thereby deteriorating the ionic conductivity of the solid electrolyte. If the molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) is too large, the ionic conductivity of the solid electrolyte may be improved, but the electrochemical characteristics such as the capacity characteristics of the battery may deteriorate.

[0045] In addition, the molar ratio of phosphorus (P) to the compound may be 0.55 to 0.995, and more specifically, 0.75 to 0.97. The molar ratio of phosphorus (P) to the compound may vary depending on the amount of the basic functional group (E) introduced, and when the molar ratio of phosphorus (P) to the compound satisfies the above range, the aforementioned effects of improving the moisture stability, ionic conductivity, or battery electrochemical characteristics of the solid electrolyte may be more preferably implemented.

[0046] In addition, the compound may have a molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) of 4 to 5. If the molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) is too small, the content of halogen elements may increase too much, thereby improving the ionic conductivity of the solid electrolyte, but may deteriorate the electrochemical characteristics such as the capacity characteristics of the battery. If the molar ratio of sulfur (S) to phosphorus (P) ([S] / [P]) is too large, the content of halogen elements that facilitate lithium ion movement may decrease too much, thereby deteriorating the ionic conductivity of the solid electrolyte.

[0047] The sulfide compound according to the present invention can be more specifically represented by the following chemical formula 1.

[0048] [Chemical Formula 1]

[0049] Li 7-6a-x+ax P 1-a S 6-6a-x+ax D x-ax (E)a

[0050] In the above chemical formula 1, 0.005≤a≤0.45, 1≤x≤2, D is a halogen element such as F, Cl, Br, I or a combination thereof, and E is a basic functional group such as OH, NH3, NO3, HCO3 or a combination thereof.

[0051] In the above chemical formula 1, a may represent the amount of basic functional group introduced, and may be 0.005≤a≤0.45 or 0.03≤a≤0.25. When the range of a representing the amount of basic functional group introduced satisfies the above range, the aforementioned effects of improving the moisture stability, ionic conductivity, or battery electrochemical characteristics of the solid electrolyte may be more preferably implemented.

[0052] In the above chemical formula 1, x may represent the basic doping amount of the halogen element, and may be 1≤x≤2, 1≤x≤1.7, or 1≤x≤1.4. If x is too small, the content of the halogen element that facilitates lithium ion movement may become too small, which may deteriorate the ionic conductivity of the solid electrolyte. If x is too large, the content of the halogen element may become too large, which may improve the ionic conductivity of the solid electrolyte, but may deteriorate the electrochemical characteristics, such as the capacity characteristics, of the battery.

[0053] At this time, 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.

[0054] 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.

[0055] In addition, from the viewpoint of more preferable implementation of ionic conductivity, the halogen element (D) may further include at least one element selected from Br and I in addition to Cl. At this time, the molar ratio of Cl and at least one element selected from Br and I (Cl:Br and / or I) may be 3:7 to 7:3, and more specifically, may be 4:6 to 6:4. When the molar ratio of Cl and at least one element selected from Br and I (Cl:Br and / or I) satisfies the above range, ionic conductivity can be more preferable.

[0056]

[0057] The sulfide compound according to the present invention may have an ionic conductivity of 2.2 mS / cm or more, and more specifically, 2.3 or 2.33 mS / cm or more, at 30°C, as the aforementioned configurations are applied.

[0058] In addition, the sulfide compound according to the present invention may have a moisture stability of 75% or more, and more specifically, 80% or more, as the aforementioned components are applied. In the present specification, the moisture stability of the sulfide compound can be obtained by calculating the percentage value of the ionic conductivity of the compound after exposure to the air to the ionic conductivity of the compound before exposure to the air. The ionic conductivity of the compound before exposure to the air is the ionic conductivity measured at 30°C immediately after synthesizing the solid electrolyte. The ionic conductivity of the compound after exposure to the air is the ionic conductivity measured at 30°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.

[0059]

[0060]

[0061] 2. Solid electrolyte manufacturing method

[0062] Another embodiment of the present invention provides a method for producing a sulfide-based solid electrolyte, comprising: forming a mixture by mixing a lithium raw material, a phosphorus raw material, a halogen element raw material, and a basic functional group raw material; and heat-treating the mixture to form a sulfide-based compound having an argyrodite-based crystal structure.

[0063] Hereinafter, a method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention will be described in detail step by step.

[0064]

[0065] First, a mixture is formed by mixing lithium raw material, phosphorus raw material, halogen element raw material, and basic functional group raw material.

[0066] The above lithium raw material may be, for example, Li2S, Li2S2, or a combination thereof, but is not necessarily limited thereto.

[0067] The above raw material may be, for example, P2S5, P2O5 or a combination thereof, but is not necessarily limited thereto.

[0068] The 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 halogen element raw material may be LiCl, and may also be a mixture of LiCl, LiBr, and / or LiI to further maximize ionic conductivity.

[0069] The above basic functional group raw material may be, for example, LiOH, LiNH4, LiNO3, LiHCO3, or a combination thereof.

[0070] The input amounts of the above lithium raw material, phosphorus raw material, halogen element raw material, and basic functional group raw material can be stoichiometrically adjusted and input in accordance with the composition of the target sulfide-based solid electrolyte.

[0071] The above mixing can be performed by mechanical mixing or chemical mixing.

[0072] 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.

[0073] The above chemical mixing can be performed, for example, by melt quenching.

[0074] 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.

[0075] 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.

[0076]

[0077] Next, optionally, after the step of forming the mixture, a step of compressing the mixture to form pellets may be further included.

[0078] 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.

[0079]

[0080] Next, the mixture is heat-treated to form a sulfide compound having an argyrodite crystal structure.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] The sulfide compound formed above can be more specifically represented by the following chemical formula 1.

[0085] [Chemical Formula 1]

[0086] Li 7-6a-x+ax P 1-a S 6-6a-x+ax D x-ax (E) a

[0087] In the above chemical formula 1, 0.005≤a≤0.45, 1≤x≤2, D is a halogen element such as F, Cl, Br, I or a combination thereof, and E is a basic functional group such as OH, NH3, NO3, HCO3 or a combination thereof.

[0088] A detailed description of the compound of the above chemical formula 1 is omitted as it is the same as described above.

[0089]

[0090] 3. All-solid-state battery

[0091] 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.

[0092]

[0093] (bipolar layer)

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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 Bc 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 dGeO2 (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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103]

[0104] (cathode layer)

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116]

[0117] (solid electrolyte layer)

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122]

[0123] Another embodiment of the present invention provides an electric vehicle including the all-solid-state battery.

[0124]

[0125] 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.

[0126]

[0127] Example 1: Li 5.95 P 0.99 S 4.95 Cl 0.99 (OH) 0.01 compound manufacturing

[0128] (1) Manufacturing of solid electrolyte

[0129] (Mixed) Final product Li 7-6a-x+ax P 1-a S 6-6a-x+ax Cl x-ax (OH) a In the compound, reactants Li2S, P2S5, LiCl, and LiOH were added in a stoichiometric ratio so that x=1 and a=0.01, and a mixture was formed by mixing at 300 rpm for about 8 hours using a planetary mill.

[0130] (Pellet manufacturing) Next, a pressure of 300 MPa was applied to the mixture to form pellets.

[0131] (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.

[0132] (2) All-solid-state battery manufacturing

[0133] 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.

[0134]

[0135] Comparative Example 1: Preparation of Li6PS5Cl solid electrolyte

[0136] The reactants Li2S, P2S5, and LiCl were mixed using a planetary mill at 300 rpm for about 8 hours to form a mixture.

[0137] Next, a pressure of 300 MPa was applied to the mixture to form pellets.

[0138] Next, the pellets were heat-treated at 550°C for about 4 hours in an argon (Ar) atmosphere to produce a Li6PS5Cl solid electrolyte.

[0139]

[0140] Other Examples and Comparative Examples

[0141] In the mixing stage, the final product, Li 7-6a-x+ax P 1-a S 6-6a-x+ax Cl x-ax (OH) aA 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 LiOH were added in a stoichiometric ratio so that x and a in the compound were as described in Table 1 below.

[0142]

[0143] Table 1 below shows the x and a values ​​of examples and comparative examples and the composition of the solid electrolyte manufactured accordingly.

[0144] Composition xa [Li] [P] [S] [Cl] [OH] Comparative Example 1 10 6 1 5 10 Example 1 10.0 1 5.9 5 0.9 4.9 5 0.9 9 0.01 Example 2 10.0 5 5.7 5 0.9 5 4.7 5 0.9 5 0.05 Example 3 10.1 5 0.9 4.5 0.9 0.1 Example 4 10.2 5 0.8 4 0.8 0.2 Example 5 10.3 4.5 0.7 3.5 0.7 0.3 Example 6 10.4 4 0.6 3 0.6 0.4 Comparative Example 2 10.5 3.5 0.5 2.5 0.5 0.5 Example 7 1.6 0.1 4.9 6 0.9 3.9 6 1.4 4 0.1

[0145] (In Table 1 above, [Li], [P], [S], [Cl], and [OH] represent the molar ratios for 1 mol of the manufactured solid electrolyte compound, respectively.)

[0146] Molar ratio between elements xa[Li] / [P][S] / [P][Cl] / [P][OH] / [P] Comparative example 1106.0005.001.000.000 Example 110.016.0105.001.000.010 Example 210.056.0535.001.000.053 Example 310.16.1115.001.000.111 Example 410.26.2505.001.000.250 Example 510.36.4295.001.000.429 Example 610.46.6675.001.000.667 Comparative example 210.57.0005.001.001.000Example 71.60.15.5114.401.600.111

[0147] Table 3 below summarizes the results of evaluating the ionic conductivity, moisture stability, and battery electrochemical characteristics of the solid electrolyte according to Experimental Examples 1 and 2 described below.

[0148] Ionic Conductivity (mS / cm) Moisture Stability (%) Discharge Capacity (mAh / g) Comparative Example 12.3174203 Example 12.378204 Example 22.3583205 Example 32.3382206 Example 42.4281203 Example 52.3179199 Example 62.2476194 Comparative Example 22.1573192 Example 77.4383201

[0149]

[0150] Experimental Example 1: Evaluation of Solid Electrolyte Properties

[0151] (1) Evaluation of ionic conductivity (before exposure to air) (30℃, 0.1C)

[0152] 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.

[0153] (2) Moisture stability evaluation

[0154] 1) Evaluation of ionic conductivity after exposure to air

[0155] 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.

[0156] 2) Moisture stability evaluation

[0157] 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 (%).

[0158]

[0159] Experimental Example 2: Evaluation of the electrochemical properties of an all-solid-state battery.

[0160] (1) Initial discharge capacity evaluation

[0161] 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.

[0162]

[0163] Referring to Tables 1 to 4, in the case of Examples 1 to 6, in which an OH basic functional group was introduced into an argyrodite sulfide compound, but the content of the introduced functional group was appropriately controlled so that the a value, [OH] value, [OH] / [P] value, or [P] value was appropriately controlled within the range according to the present invention, it was confirmed that the moisture stability was improved and the basic ionic conductivity was at a level almost equivalent to, or rather improved, compared to Comparative Example 1, which is a basic argyrodite composition. In addition, it was confirmed that the initial discharge capacity of the battery was at a level almost equivalent to, or rather improved, compared to Comparative Example 1.

[0164] Meanwhile, in the case of Example 7, which has the same content of functional groups introduced as Example 3 but a larger basic doping amount of Cl (which can be represented by the x value), the ionic conductivity was significantly improved compared to Example 3, and the moisture stability was also excellent. However, it was confirmed that the capacity characteristics of the battery were somewhat lower than in Example 3.

[0165] Meanwhile, when examining Examples 1 to 6 in more detail, it was confirmed that in Examples 2 to 4, where the content of the introduced functional group was more appropriately controlled, and the a value, [OH] value, [OH] / [P] value, or [P] value, etc. were more controlled, the ionic conductivity, moisture stability, and battery capacity characteristics were comprehensively implemented very well.

[0166]

[0167] 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.

[0168] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Contains a sulfide compound containing lithium (Li), phosphorus (P), sulfur (S) and a halogen element (D) and having an argyrodite crystal structure. The above compound further contains a basic functional group (E), The above compound is a sulfide-based solid electrolyte having a molar ratio of halogen element (D) to phosphorus (P) ([D] / [P]) of 1 to 2 and a moisture stability of 75% or more.

2. In paragraph 1, The above basic functional group (E) is OH, NH 3 , NO 3 , HCO 3 Or a sulfide-based solid electrolyte which is a combination of these.

3. In paragraph 1, A sulfide-based solid electrolyte having a molar ratio of basic functional groups (E) to the above compound of 0.005 to 0.

45.

4. In paragraph 1, The above compound is a sulfide-based solid electrolyte having a molar ratio of basic functional groups (E) to phosphorus (P) ([E] / [P]) of 0.005 to 0.

8.

5. In paragraph 1, A sulfide-based solid electrolyte having a molar ratio of phosphorus (P) to the above compound of 0.55 to 0.

995.

6. 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 to 5.

7. In paragraph 1, The above compound is a sulfide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] Li 7-6a-x+ax P 1-a S 6-6a-x+ax D x-ax (E) a In the chemical formula 1 above, 0.005≤a≤0.45, 1≤x≤2, D is a halogen element such as F, Cl, Br, I or a combination thereof, and E is a basic functional group such as OH or NH. 3 , NO 3 , HCO 3 Or a combination of these.

8. In paragraph 7, Sulfide-based solid electrolyte with 0.03≤a≤0.

25.

9. In paragraph 1, The above compound is a sulfide-based solid electrolyte having an ionic conductivity of 2.2 mS / cm or more at 30°C.

10. 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.