Solid electrolyte sheet and all solid state battery comprising the same

Abstract

The present invention relates to a solid electrolyte sheet comprising a first solid electrolyte and a second solid electrolyte, wherein the average particle diameter D50 of the first solid electrolyte is greater than the average particle diameter D50 of the second solid electrolyte, the content of the second solid electrolyte is 20-40 wt% based on the total weight of the first solid electrolyte and the second solid electrolyte, and the average particle diameter D50 of the second solid electrolyte is 0.5-3.5 μm.

Description

Solid electrolyte sheet and all-solid-state battery comprising the same

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

[0002]

[0003] Research on the safety and energy density of high-capacity batteries is gaining attention, and all-solid-state batteries are gaining attention as next-generation batteries. These all-solid-state batteries replace liquid electrolytes, which can be prone to explosion, with solid electrolytes. This eliminates the use of flammable solvents within the battery, eliminating the risk of ignition or explosion caused by reactions like the decomposition of conventional electrolytes. This ensures battery safety.

[0004] In addition, since lithium metal or a lithium alloy can be used as the negative electrode material, the energy density in relation to the mass and volume of the battery can be improved. 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.

[0005] The practical application of all-solid-state batteries requires the production of large-area batteries. This necessitates the sheet-forming of the cathode, separator, and anode, as in conventional lithium-ion batteries. In particular, the separator in all-solid-state batteries consists of a solid electrolyte and a binder, and its properties (ionic conductivity, electrochemical stability, and chemical stability) vary depending on the manufacturing method and the selected solid electrolyte material.

[0006] In particular, the solid electrolyte layer used as a separator in all-solid-state batteries must prevent short-circuiting of the cell by suppressing lithium dendrites during charge and discharge.

[0007] However, there is a problem that a large number of pores that generally exist between a plurality of solid electrolyte particles in a solid electrolyte layer may reduce the ionic conductivity of the solid electrolyte layer or cause lithium dendrite growth in the battery, resulting in a battery short circuit or deterioration of rate characteristics.

[0008]

[0009] Accordingly, one object of the present invention is to provide a solid electrolyte sheet that has improved ionic conductivity by reducing internal voids, can suppress internal short circuits when applied to an all-solid-state battery, and can improve rate characteristics.

[0010] Another object of the present invention is to provide an all-solid-state battery comprising the solid electrolyte sheet.

[0011]

[0012] This application claims priority to Republic of Korea Patent Application No. 10-2024-0045342, filed April 3, 2024, the entire contents of which are incorporated herein by reference.

[0013] One embodiment of the present invention comprises a first solid electrolyte and a second solid electrolyte,

[0014] A solid electrolyte sheet is provided, wherein the average particle diameter (D50) of the first solid electrolyte is larger than the average particle diameter (D50) of the second solid electrolyte, the content of the second solid electrolyte is 17 to 43 wt% based on the total weight of the first solid electrolyte and the second solid electrolyte, and the average particle diameter (D50) of the second solid electrolyte is 0.5 to 3.5 μm.

[0015] The difference between the average particle diameter (D50) of the first solid electrolyte and the average particle diameter (D50) of the second solid electrolyte may be 3 to 5 μm.

[0016] The ratio of the average particle diameter (D50) of the first solid electrolyte to the average particle diameter (D50) of the second solid electrolyte (first solid electrolyte / second solid electrolyte) may be 3.5 to 6.

[0017] The first solid electrolyte and the second solid electrolyte may each independently be a sulfide-based solid electrolyte or a halide-based solid electrolyte.

[0018] The above sulfide-based solid electrolyte may have an argyrodite-based crystal structure.

[0019] The above sulfide-based solid electrolyte can be represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Li x1 P y1 S z1 D w1 M1 a1 M2 a2

[0022] In the above chemical formula 1, D is a halogen element such as F, Cl, Br, I or a combination thereof, M1 is B, Al, Si, Ge, Ga, In, Sn or a combination thereof, M2 is O, N, Se, As, Se, Sb, Sn or a combination thereof, and 4≤x1≤8, 0.5≤y1≤1.5, 3≤z1≤7, 0≤a1≤2, 0≤a2≤2.

[0023] The above halide-based solid electrolyte can be represented by the following chemical formula 2.

[0024] [Chemical Formula 2]

[0025] Li x2 M3 y2 A z2

[0026] In the above chemical formula 2, M3 is Sc, In, Zr, Lu, Er, Y, Ho or a combination thereof, A is a halogen element such as F, Cl, Br, I or a combination thereof, and 1.5≤x2≤3.5, 0.5≤y2≤1.5, 5≤z2≤7.

[0027] The porosity of the above solid electrolyte sheet may be 14% or less.

[0028] The above solid electrolyte sheet may further include a binder.

[0029] The binder may be nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), PTFE, styrene-butadiene-styrene copolymer, acrylic resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or a combination thereof.

[0030] The above solid electrolyte sheet may further include a porous support.

[0031] The above solid electrolyte sheet may have an ionic conductivity of 1.3 mS / cm or more at 30°C.

[0032]

[0033] 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, the solid electrolyte layer including the aforementioned solid electrolyte sheet.

[0034]

[0035] A solid electrolyte sheet according to one embodiment of the present invention includes a first solid electrolyte having a large particle size and a second solid electrolyte having a small particle size, and by controlling the content of the second solid electrolyte, etc., internal pores can be efficiently reduced, thereby improving ionic conductivity.

[0036] In addition, the solid electrolyte sheet according to one embodiment of the present invention can suppress internal short circuits caused by lithium dendrites and improve rate characteristics when applied to an all-solid-state battery due to the above characteristics.

[0037]

[0038] Figure 1 is a cross-sectional SEM image of a solid electrolyte sheet manufactured according to Example 2.

[0039] Figure 2 is a cross-sectional SEM image of a solid electrolyte sheet manufactured according to Example 5.

[0040] Figure 3 is a cross-sectional SEM image of a solid electrolyte sheet manufactured according to Comparative Example 3.

[0041] Figure 4 is a cross-sectional SEM image of a solid electrolyte sheet manufactured according to Comparative Example 6.

[0042]

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0048] 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.

[0049] 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.

[0050]

[0051] 1. Solid electrolyte sheet

[0052] A solid electrolyte sheet according to one embodiment of the present invention can be applied to a solid electrolyte layer in an all-solid-state battery.

[0053] More specifically, a solid electrolyte sheet according to one embodiment of the present invention includes a first solid electrolyte and a second solid electrolyte, wherein the average particle diameter (D50) of the first solid electrolyte is larger than the average particle diameter (D50) of the second solid electrolyte.

[0054] Since the solid electrolyte sheet includes a first solid electrolyte having a large particle size and a second solid electrolyte having a small particle size, the internal voids of the solid electrolyte sheet are reduced, thereby improving the electrical connectivity between the solid electrolyte particle interfaces, thereby improving the ionic conductivity of the solid electrolyte sheet, and when applied to an all-solid-state battery, short circuits can be suppressed. In addition, if there are many internal voids in the solid electrolyte sheet during high-rate charging and discharging, lithium dendrite growth may be accelerated, which may cause a short circuit or reduce the high-rate discharge capacity. Therefore, the solid electrolyte sheet according to the present invention can have improved high-rate discharge capacity (i.e., rate characteristics).

[0055] Meanwhile, in this specification, the average particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) can be measured using, for example, the laser diffraction method.

[0056] At this time, the content of the second solid electrolyte may be 17 to 43 wt% based on the total weight of the first solid electrolyte and the second solid electrolyte, and more specifically, 20 to 40 wt% or 25 to 35 wt%. If the content of the second solid electrolyte is too low, the second solid electrolyte cannot be sufficiently filled between the first solid electrolyte particles having a large particle size, so the effect of reducing the internal voids of the solid electrolyte sheet may be minimal, and thus the effects of improving the ion conductivity of the solid electrolyte, preventing the short circuit of the battery, and improving the rate characteristics may be minimal. If the content of the second solid electrolyte is too high, the number of small-sized second solid electrolyte particles increases too much, resulting in the formation of a wide particle interface, whereby lithium ion mobility may decrease, and thus the ion conductivity and rate characteristics may decrease.

[0057] In addition, the average particle diameter (D50) of the second solid electrolyte may be 0.5 to 3.5 μm, and more specifically, 0.8 to 3.2 μm. If the average particle diameter (D50) of the second solid electrolyte is too small, the interfacial resistance may increase, which may deteriorate the ionic conductivity and rate characteristics of the solid electrolyte. If the average particle diameter (D50) of the second solid electrolyte is too large, the second solid electrolyte may not be sufficiently filled between the first solid electrolyte particles, and the effect of reducing the internal voids of the solid electrolyte sheet may be minimal, thereby deteriorating the ionic conductivity and rate characteristics.

[0058] Additionally, the difference between the average particle diameter (D50) of the first solid electrolyte and the average particle diameter (D50) of the second solid electrolyte may be 3 to 5 μm. Alternatively, the ratio of the average particle diameter (D50) of the first solid electrolyte to the average particle diameter (D50) of the second solid electrolyte (first solid electrolyte / second solid electrolyte) may be 3.5 to 6.

[0059] If the difference in average particle diameters or the average particle size ratio between the first solid electrolyte and the second solid electrolyte is too small, the second solid electrolyte cannot be sufficiently filled between the first solid electrolyte particles, so the effect of reducing the voids inside the solid electrolyte sheet may be minimal, and thus the effects of improving ionic conductivity, short-circuit prevention, and rate characteristics may be minimal. If the difference in average particle diameters or the particle size ratio between the first solid electrolyte and the second solid electrolyte is too large, the filling rate may be low, or the interfacial area may increase, which may lower the ionic conductivity.

[0060] Accordingly, the average particle diameter (D50) of the first solid electrolyte may be 2 to 8 μm, and more specifically, 2 to 6 μm or 4 to 6 μm, considering the average particle diameter (D50) of the second solid electrolyte according to the present invention.

[0061]

[0062] Meanwhile, the first solid electrolyte and the second solid electrolyte may each independently be a sulfide-based solid electrolyte or a halide-based solid electrolyte.

[0063] The above sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (wherein m, n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (where p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga In), Li3PS4, Li7P3S 11 , Li7-x PS 6-x Cl x (However, 0≤x≤2), Li 7-x PS 6-x Br x (where 0≤x≤2), and Li 7-x PS 6-x I x (However, there can be one or more selected from 0≤x≤2).

[0064] The above sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, a heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one of the above-described sulfide-based solid electrolyte materials that contains at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the solid electrolyte may be a material containing Li2S-P2S5.

[0065] From the perspective of more desirable implementation of ionic conductivity, the sulfide-based solid electrolyte may have an argyrodite-based crystal structure.

[0066] A sulfide-based solid electrolyte having an argyrodite crystal structure may contain, for example, Li, P, S, and halogen elements, and may further contain other doping elements as needed. By further including other doping elements in the argyrodite crystal structure, the moisture stability of the solid electrolyte may be improved, or the electrochemical properties, such as the capacity of the battery, may be more preferably realized.

[0067] For example, the sulfide-based solid electrolyte can be represented by the following chemical formula 1.

[0068] [Chemical Formula 1]

[0069] Li x1 P y1 S z1 Dw1 M1 a1 M2 a2

[0070] In the above chemical formula 1, D is a halogen element such as F, Cl, Br, I or a combination thereof, M1 is B, Al, Si, Ge, Ga, In, Sn or a combination thereof, M2 is O, N, Se, As, Se, Sb, Sn or a combination thereof, and 4≤x1≤8, 0.5≤y1≤1.5, 3≤z1≤7, 0≤a1≤2, 0≤a2≤2.

[0071] In addition, the halide-based solid electrolyte can be represented by the following chemical formula 2.

[0072] [Chemical Formula 2]

[0073] Li x2 M3 y2 A z2

[0074] In the above chemical formula 2, M3 is Sc, In, Zr, Lu, Er, Y, Ho or a combination thereof, A is a halogen element such as F, Cl, Br, I or a combination thereof, and 1.5≤x2≤3.5, 0.5≤y2≤1.5, 5≤z2≤7.

[0075]

[0076] Meanwhile, the solid electrolyte sheet according to the present invention includes first and second solid electrolytes having large and small particle sizes as described above, and the content and average particle size (D50) thereof are appropriately controlled within the range according to the present invention, thereby minimizing internal voids.

[0077] Accordingly, the porosity of the solid electrolyte sheet according to the present invention may be 14% or less, and more specifically, 13%, 11%, 9%, or 7% or less. The porosity of the solid electrolyte sheet may be measured by the following method.

[0078] [Formula 1]

[0079] Porosity% ={1 - (V true / V bulk)} × 100

[0080] In the above equation 1, V bulk is the volume of the entire solid electrolyte sheet (in pellet form), and V true is the volume of the solid electrolyte particles themselves, excluding internal voids within the solid electrolyte sheet, measured using a gas pycnometer (Accupyc 1330, Micromeritics) in a high-purity He gas atmosphere of 100% purity.

[0081]

[0082] Meanwhile, the solid electrolyte sheet may further include a binder. By further including a binder in the solid electrolyte sheet, the bonding force between solid electrolyte particles may be improved, and the mechanical strength of the solid electrolyte sheet may be improved.

[0083] The binder may be, but is not limited to, for example, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), PTFE, styrene-butadiene-styrene copolymer, acrylic resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or a combination thereof.

[0084] In addition, the solid electrolyte sheet may further include a porous support. By further including a porous support, the solid electrolyte sheet can sufficiently improve mechanical rigidity and function as a self-supporting membrane.

[0085] The porous support may include, but is not necessarily limited to, a polymer resin made of, for example, polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinylidene fluoride (PVDF), Teflon (PTFE), or a combination thereof.

[0086]

[0087] The solid electrolyte sheet according to the present invention includes first and second solid electrolytes having large and small particle sizes as described above, and the content and average particle size (D50) thereof are appropriately controlled within the range according to the present invention, so that ionic conductivity can be sufficiently improved.

[0088] Accordingly, the solid electrolyte sheet according to the present invention may have an ionic conductivity of 1.3 mS / cm or more at 30°C, and more specifically, 1.4 mS / cm, 1.5 mS / cm or 1.7 mS / cm or more.

[0089]

[0090] 2. Method for manufacturing solid electrolyte sheet

[0091] The solid electrolyte sheet according to the present invention can be manufactured according to the following manufacturing method, which will be described below.

[0092]

[0093] First, a solid electrolyte composition is formed.

[0094] The above solid electrolyte composition may include the first solid electrolyte, the second solid electrolyte, the binder, and the solvent according to the present invention described above.

[0095] The binder may be, but is not limited to, for example, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), PTFE, styrene-butadiene-styrene copolymer, acrylic resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or a combination thereof.

[0096] The solvent may be, for example, xylene, toluene, isobutyl isobutyrate, or a combination thereof, but is not necessarily limited thereto, and any solvent used in the art may be used.

[0097] The above solid electrolyte composition may further include a dispersant that can improve the dispersibility of the solid content in the solid electrolyte composition, and may further include other additives as needed.

[0098]

[0099] Next, the solid electrolyte composition is applied onto a substrate or porous support.

[0100] The above substrate is not particularly limited as long as it is chemically stable with respect to the solid electrolyte composition. For example, the substrate may be, but is not necessarily limited to, PET (polyethylene terephthalate), PEN (polyethylenenaphthalate), PES (polyethersulfone), PC (polycarbonate), PP (polypropylene), or a combination thereof.

[0101] The porous support may include, but is not necessarily limited to, a polymer resin made of, for example, polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinylidene fluoride (PVDF), Teflon (PTFE), or a combination thereof.

[0102] The above application is not particularly limited as long as it is commonly used in the relevant technical field, but may be performed by, for example, a slurry casting method.

[0103]

[0104] Next, the solid electrolyte composition applied on the substrate or porous support is dried to remove the solvent in the solid electrolyte composition, thereby forming a solid electrolyte sheet.

[0105] The drying can be performed, for example, at a temperature of about 20 to 60°C.

[0106]

[0107] 3. All-solid-state battery

[0108] 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, the solid electrolyte layer including the aforementioned solid electrolyte sheet.

[0109] 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.

[0110] The above-mentioned positive electrode active material layer may include, for example, a positive electrode active material and a solid electrolyte. The solid electrolyte included in the positive electrode active material layer may be the same as or different from the solid electrolyte included in the solid electrolyte sheet.

[0111] 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 as a mixture of two or more.

[0112] The above lithium transition metal oxide is, for example, Li a A 1-b B b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α F α(In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoGb O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); A compound represented by any one of the chemical formulas of LiFePO4. In this compound, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of this compound, and it is also possible to use a mixture of the above-mentioned compound and the compound having a coating layer added. The coating layer added to the surface of these compounds includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0113] The positive electrode active material layer may include, for example, a solid electrolyte. The solid electrolyte included in the positive electrode layer may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

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

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

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

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

[0118] The positive electrode collector may be, for example, a plate or foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The thickness of the positive electrode collector may be, for example, 1 um to 100 um, 1 um to 50 um, 5 um to 25 um, or 10 um to 20 um.

[0119]

[0120] 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.

[0121] The above negative electrode active material layer may include, for example, a negative electrode active material and a binder.

[0122] 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.

[0123] The above carbon-based negative electrode active material may be amorphous carbon. The amorphous carbon may include, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., 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 graphite-based carbon.

[0124] The metal / metalloid negative electrode active material includes at least one selected from the group consisting of lithium (Li), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited thereto, and any metal negative electrode active material or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130]

[0131] 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.

[0132]

[0133] Manufacturing Example 1: 1 μm Li 5.7 PS 4.7 Cl 1.3 Manufacturing of argyrodite solid electrolyte

[0134] Li 5.7 PS 4.7 Cl 1.3 was synthesized through a dry method. Specifically, Li2S, P2S5, and LiCl were measured according to the composition, mixed at 300 rpm for 8 hours using a high viscosity mill (Planetary Mill), and then pellets were made at 300 MPa and heat-treated at 550 ℃ in an argon (Ar) atmosphere to obtain Li 5.7 PS 4.7 Cl 1.3 An argyrodite-based solid electrolyte was synthesized. Subsequently, the synthesized solid electrolyte was pulverized through ball milling to an average particle size (D50) of 1 μm.

[0135]

[0136] Manufacturing Example 2: 3 μm Li5.7 PS 4.7 Cl 1.3 Manufacturing of argyrodite solid electrolyte

[0137] A solid electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the synthesized solid electrolyte was pulverized through ball milling to obtain an average particle size (D50) of 3 μm.

[0138]

[0139] Manufacturing Example 3: 5 μm Li 5.7 PS 4.7 Cl 1.3 Manufacturing of argyrodite solid electrolyte

[0140] A solid electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the synthesized solid electrolyte was pulverized through ball milling to obtain an average particle size (D50) of 5 μm.

[0141]

[0142] Manufacturing Example 4: 7 μm Li 5.7 PS 4.7 Cl 1.3 Manufacturing of argyrodite solid electrolyte

[0143] A solid electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the synthesized solid electrolyte was pulverized through ball milling to obtain an average particle size (D50) of 7 μm.

[0144]

[0145] Example 1

[0146] (1) Manufacturing of solid electrolyte sheets

[0147] The solid electrolyte manufactured according to Manufacturing Example 2 was used as a first solid electrolyte, and the solid electrolyte manufactured according to Manufacturing Example 1 was used as a second solid electrolyte. The first solid electrolyte:second solid electrolyte were mixed so that the mixing weight ratio was 80:20, and xylene solvent containing 3 wt% of NBR binder dissolved therein was additionally mixed to form a solid electrolyte composition (slurry).

[0148] Thereafter, the solid electrolyte composition (slurry) was applied onto a PET (polyethylene terephthalate) substrate by blade coating.

[0149] Thereafter, the applied solid electrolyte composition (slurry) was dried at 50°C and then detached from the PET substrate to produce a solid electrolyte sheet.

[0150] (2) All-solid-state battery manufacturing

[0151] The above manufactured solid electrolyte sheet is 0.785 cm 2 After being punched out with an area of ​​1000 sq. m and placed in a pressure cell, a composite electrode was loaded on top of it. The composite electrode was composed of a cathode active material (NCM 811): solid electrolyte (Li 5.7 PS 4.7 Cl 1.3 ): 0.785 cm of cathode slurry mixed with the challenge material (denka black) at a weight ratio of 70:29:1 2 It was manufactured by loading 20.0 mg on the area and densifying to 300 MPa. Afterwards, the Li counter electrode was bonded at 20 MPa with the cathode, and the cell was fastened at the same pressure.

[0152]

[0153] Examples 2 to 6, Comparative Examples 4 to 6

[0154] When manufacturing a solid electrolyte sheet, a solid electrolyte sheet and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the average particle diameter (D50) and mixing weight ratio of the first solid electrolyte and the second solid electrolyte were changed as shown in Table 1 below.

[0155]

[0156] Comparative Examples 1 to 3

[0157] When manufacturing a solid electrolyte sheet, a solid electrolyte sheet and an all-solid-state battery were manufactured in the same manner as in Example 1, except that a single solid electrolyte having a different average particle diameter (D50) was used as shown in Table 1 below.

[0158]

[0159] Table 1 below is a table that summarizes the solid electrolyte particle size and mixing weight ratio in the solid electrolyte sheets of examples and comparative examples.

[0160] Tables 2 and 3 below are tables summarizing the results of evaluating the ionic conductivity and porosity of a solid electrolyte sheet according to Experimental Example 2 described below, and the results of evaluating the rate characteristics of an all-solid-state battery according to Experimental Example 3 described below, respectively.

[0161] First solid electrolyte average particle size (D50) (μm) Second solid electrolyte average particle size (D50) (μm) Second solid electrolyte content (wt%) Difference in average particle size (D50) of first solid electrolyte and second solid electrolyte (μm) First solid electrolyte / second solid electrolyte average particle size (D50) Non-comparative example 11 μm Exclusive comparative example 23 μm Exclusive comparative example 35 μm Exclusive comparative example 4311023Example 1312023Example 2313023Example 3314023Comparative example 5315023Example 4533021.67Example 5513045Comparative example 6515045Example 6713067

[0162] Solid electrolyte sheetAll-solid-state batteryIonic conductivity(mS / cm)Porosity(%)High-rate(1.5C)Discharge capacity(mAh / g)Comparative example 10.417165Comparative example 21.016171Comparative example 31.219ParagraphComparative example 41.2315165Example 11.3213172Example 21.49182Example 31.349.5178Comparative example 51.310176Example 41.610186Example 51.86192Comparative example 61.316176Example 61.912Paragraph

[0163] Experimental Example 1: SEM Image Analysis of Solid Electrolyte Sheets

[0164] SEM (scanning electron microscope) images of cross-sections of solid electrolyte sheets manufactured according to Example 2, Example 5, Comparative Example 3, and Comparative Example 6 were observed, and are shown in FIGS. 1 to 4, respectively, in that order.

[0165] Referring to FIGS. 1 to 4, it was confirmed that the solid electrolyte sheet according to the embodiment had a relatively small pore size in the cross-section of the sheet. On the other hand, it was confirmed that the pores between the solid electrolyte particles of the solid electrolyte sheet according to the comparative example were formed to be larger than those of the embodiment, even when visually observed.

[0166]

[0167] Experimental Example 2: Evaluation of Solid Electrolyte Sheet Properties

[0168] (1) Solid electrolyte sheet ionic conductivity

[0169] The solid electrolyte sheet manufactured according to the examples and comparative examples was used as a working electrode and the cell was fastened at a pressure of 70 MPa using SUS, and then the impedance was measured by applying a voltage of 10 mV at 30°C.

[0170] (2) Solid electrolyte sheet porosity

[0171] The porosity of the solid electrolyte sheet was measured by the following method.

[0172] [Formula 1]

[0173] Porosity% ={1 - (V true / V bulk )} × 100

[0174] In the above equation 1, V bulk is the volume of the entire solid electrolyte sheet (in pellet form), and V true is the volume of the solid electrolyte particles themselves, excluding internal voids within the solid electrolyte sheet, measured using a gas pycnometer (Accupyc 1330, Micromeritics) in a high-purity He gas atmosphere of 100% purity.

[0175]

[0176] Experimental Example 3: Evaluation of All-Solid-State Battery Rate Characteristics

[0177] After manufacturing the all-solid-state battery, it was aged at room temperature for 2 hours and then subjected to initial cycling. Capacity evaluation was performed with 180 mAh / g as the reference capacity, and the charge / discharge conditions were CC / CV 2.5~4.20 V, 1 / 20 C cut-off. One cycle was performed under 0.1 C charge / 0.1 C discharge conditions. At this time, the rate characteristic was evaluated by calculating the discharge capacity at 1.5 C current in the second cycle as a percentage of the discharge capacity in the first cycle.

[0178]

[0179] Referring to Tables 1 and 2, in the case of Examples 1 to 6, where the solid electrolyte sheet includes a first solid electrolyte having a large particle size and a second solid electrolyte having a small particle size, and the content of the second solid electrolyte, etc., is appropriately controlled, it was confirmed that the membrane porosity of the solid electrolyte sheet was generally small, the ionic conductivity was excellent, and the rate characteristics of the all-solid-state battery were excellent.

[0180] On the other hand, in the case of Comparative Examples 1 to 3, when a single solid electrolyte was applied, it was confirmed that the membrane porosity was large, the ionic conductivity was low, and the rate characteristics of the all-solid-state battery deteriorated. In particular, in the case of Comparative Example 3, it was confirmed that a short circuit occurred during high-rate discharge.

[0181] In the case of Comparative Example 4, as a result of the content of the second solid electrolyte being too small, it was confirmed that the porosity of the solid electrolyte sheet increased, the ionic conductivity was increased, and the rate characteristics of the all-solid-state battery deteriorated compared to Examples 1 to 3 in which the same solid electrolyte particle size was applied.

[0182] In the case of Comparative Example 5, it was confirmed that the ionic conductivity of the solid electrolyte sheet was reduced compared to Examples 1 to 3 in which the same solid electrolyte particle size was applied, as a result of the content of the second solid electrolyte being too high.

[0183] In the case of Comparative Example 6, it was confirmed that the porosity of the solid electrolyte sheet increased, the ionic conductivity deteriorated, and the rate characteristics of the all-solid-state battery significantly deteriorated compared to Example 5, where the same solid electrolyte particle size was applied, as a result of the content of the second solid electrolyte being too large.

[0184] Meanwhile, when comparing Examples 2, 4, 5, and 7, it was confirmed that in Example 5, where the difference in average particle diameters (D50) of the first and second solid electrolytes or the average particle diameter (D50) ratio was more appropriately controlled, even though the content of the second solid electrolyte was the same at 30 wt%, the ionic conductivity, porosity, and rate characteristics of the all-solid-state battery of the solid electrolyte sheet were more preferably implemented.

[0185]

[0186] 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.

[0187] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Containing a first solid electrolyte and a second solid electrolyte, The average particle diameter (D50) of the first solid electrolyte is larger than the average particle diameter (D50) of the second solid electrolyte, The content of the second solid electrolyte is 17 to 43 wt% based on the total weight of the first solid electrolyte and the second solid electrolyte, The average particle diameter (D50) of the second solid electrolyte is 0.5 to 3.5 μm. Solid electrolyte sheet.

2. In paragraph 1, A solid electrolyte sheet in which the difference between the average particle diameter (D50) of the first solid electrolyte and the average particle diameter (D50) of the second solid electrolyte is 3 to 5 μm.

3. In paragraph 1, A solid electrolyte sheet in which the ratio of the average particle diameter (D50) of the first solid electrolyte to the average particle diameter (D50) of the second solid electrolyte (first solid electrolyte / second solid electrolyte) is 3.5 to 6.

4. In paragraph 1, A solid electrolyte sheet wherein the first solid electrolyte and the second solid electrolyte are each independently a sulfide-based solid electrolyte or a halide-based solid electrolyte.

5. In paragraph 4, The above sulfide-based solid electrolyte is a solid electrolyte sheet having an argyrodite-based crystal structure.

6. In paragraph 4, The above sulfide-based solid electrolyte is a solid electrolyte sheet represented by the following chemical formula 1: [Chemical Formula 1] The x1 P y1 S z1 D w1 M1 a1 M2 a2 In the above chemical formula 1, D is a halogen element such as F, Cl, Br, I or a combination thereof, M1 is B, Al, Si, Ge, Ga, In, Sn or a combination thereof, M2 is O, N, Se, As, Se, Sb, Sn or a combination thereof, and 4≤x1≤8, 0.5≤y1≤1.5, 3≤z1≤7, 0≤a1≤2, 0≤a2≤2.

7. In paragraph 4, The above halide-based solid electrolyte is a solid electrolyte sheet represented by the following chemical formula 2: [Chemical Formula 2] Li x2 M3 y2 A z2 In the above chemical formula 2, M3 is Sc, In, Zr, Lu, Er, Y, Ho or a combination thereof, A is a halogen element such as F, Cl, Br, I or a combination thereof, and 1.5≤x2≤3.5, 0.5≤y2≤1.5, 5≤z2≤7.

8. In paragraph 1, A solid electrolyte sheet having a porosity of 14% or less.

9. In paragraph 1, The above solid electrolyte sheet is a solid electrolyte sheet further comprising a binder.

10. In paragraph 9, The above binder is a solid electrolyte sheet comprising nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), PTFE, styrene-butadiene-styrene copolymer, acrylic resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or a combination thereof.

11. In paragraph 1, The above solid electrolyte sheet is a solid electrolyte sheet further comprising a porous support.

12. In paragraph 1, The above solid electrolyte sheet is a solid electrolyte sheet having an ionic conductivity of 1.3 mS / cm or more at 30°C.

13. 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, the solid electrolyte layer including the solid electrolyte sheet of claim 1.

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