Positive electrode active material layer and secondary battery comprising same

Abstract

Disclosed are a positive electrode active material layer and a secondary battery comprising same, the positive electrode active material layer comprising: a lithium-containing sulfide-based positive electrode active material; a sulfide-based solid electrolyte; an ionic liquid comprising a lithium salt and a non-aqueous organic solvent; and an ion-conductive binder comprising an ether-based polymer and a fluorine-based polymer.

Description

Positive active material layer and secondary battery including the same

[0001] The invention relates to a positive electrode active material layer and a secondary battery containing the same.

[0002] Recently, driven by industrial demands, the development of batteries with high energy density and safety is actively underway. For example, lithium batteries are being put into practical use not only in information and communication devices but also in the automotive sector. In the automotive field, safety is considered particularly important because it is directly related to human life.

[0003] Since lithium batteries use an electrolyte containing a flammable organic solvent, there is a possibility of overheating and fire if a short circuit occurs.

[0004] All-solid-state batteries using a solid electrolyte instead of a liquid electrolyte are being proposed.

[0005] By not using flammable organic solvents, all-solid-state batteries can significantly reduce the likelihood of fire or explosion in the event of a short circuit. These batteries can greatly enhance safety compared to lithium batteries that use liquid electrolytes.

[0006] Secondary batteries use sulfur-based materials as cathode active materials to increase capacity. Using sulfur-based materials allows for a higher theoretical energy capacity compared to lithium-ion batteries, and the low cost of sulfur-based materials can lower the manufacturing cost of secondary batteries.

[0007] One aspect is to provide a positive electrode active material layer capable of suppressing the effect of volume change of the positive electrode active material during charging and discharging.

[0008] Another aspect is to provide a secondary battery capable of suppressing degradation of battery performance even when charging and discharging at low voltage.

[0009] According to one embodiment, a positive electrode active material layer is provided, comprising: a lithium-containing sulfide-based positive electrode active material; a sulfide-based solid electrolyte; an ionic liquid comprising a lithium salt and a non-aqueous organic solvent; and an ionic conductive binder comprising an ether-based polymer and a fluorine-based polymer.

[0010] According to another embodiment, a secondary battery is provided comprising a positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the positive electrode comprises the positive electrode active material layer described above.

[0011] According to one aspect, by employing a positive active material layer comprising an ionic liquid and a solid electrolyte, it is possible to provide a secondary battery in which performance degradation due to volume change of the positive active material during charging and discharging is suppressed.

[0012] FIG. 1 is a cross-sectional view of a secondary battery according to an exemplary embodiment.

[0013] Figure 2 is an enlarged schematic diagram showing area A of Figure 1 enlarged.

[0014] FIG. 3 is a cross-sectional view of a secondary battery according to another exemplary embodiment.

[0015] The present inventive concept described below is subject to various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments and should be understood to include all modifications, equivalents, or substitutions that fall within the scope of the description of the present inventive concept.

[0016] The terms used below are used merely to describe specific embodiments and are not intended to limit the creative concept. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the following, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, components, materials, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, components, materials, or combinations thereof. The “ / ” used below may be interpreted as “and” or “or” depending on the context.

[0017] In the drawings, thicknesses have been enlarged or reduced to clearly represent various layers and regions. Throughout the specification, the same reference numerals have been used for similar parts. Throughout the specification, when a part such as a layer, film, region, or plate is described as being “on” or “above” another part, this includes not only cases where it is directly above another part but also cases where there is another part in between. Throughout the specification, terms such as “first,” “second,” etc., may be used to describe various components, but the components should not be limited by these terms. In this specification and drawings, components having substantially the same functional configuration are referred to by the same reference numerals to avoid redundant descriptions.

[0018] In the present disclosure, the “size” of a particle is, for example, the “particle diameter” of the particle. The “particle diameter” of the particle represents the average diameter when the particle is spherical and represents the average major axis length when the particle is non-spherical. The particle diameter of the particle can be measured using a particle size analyzer (PSA). The “particle diameter” of the particle is, for example, the average particle diameter. The average particle diameter is, for example, the median particle diameter (D50). The median particle diameter (D50) is the particle size corresponding to the 50% cumulative volume calculated from the side of the particle having a small particle size in the particle size distribution measured, for example by laser diffraction.

[0019] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0020] In this disclosure, “alloy” means a mixture of two or more metals.

[0021] In the present disclosure, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0022] In the present disclosure, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0023] In the present disclosure, “lithiation” and “to lithiate” refer to the process of adding lithium to a positive electrode active material or a negative electrode active material.

[0024] In the present disclosure, “delithiation” and “to delithiate” refer to the process of removing lithium from a positive electrode active material or a negative electrode active material.

[0025] In this disclosure, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery.

[0026] In this disclosure, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0027] In this disclosure, “cathode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0028] In the present disclosure, each of the phrases such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0029] A positive electrode active material layer and a secondary battery including the same according to exemplary embodiments are described in more detail below.

[0030] Lithium-sulfur batteries using sulfur-based materials as the cathode active material undergo volume expansion and contraction due to the formation and decomposition of lithium sulfide (Li2S) during the charging and discharging process. This can lead to poor contact or mechanical stress at the electrode-electrolyte interface. Such volume changes can result in performance degradation and reduced lifespan of the all-solid-state battery.

[0031] FIG. 1 is a cross-sectional view of a secondary battery according to an exemplary embodiment. Referring to FIG. 1, a secondary battery according to an exemplary embodiment may include a positive electrode (100); a negative electrode (200); and a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200).

[0032] [anode]

[0033] Referring to FIG. 1, a positive electrode (100) according to one embodiment may include a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on one or both sides of the positive electrode current collector (110).

[0034] The positive current collector (110) may provide a reference surface on which the positive active material layer (120) is placed. The positive current collector may include, for example, a plate or foil comprising indium (In), copper (Cu), magnesium (Mg), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive current collector (110) may be omitted. Although not illustrated, a carbon layer with a thickness of 0.1 μm to 4 μm may be further disposed between the positive current collector (110) and the positive active material layer (120) to increase the bonding strength between the positive current collector (110) and the positive active material layer (120). The carbon layer may include amorphous carbon, crystalline carbon, etc.

[0035] FIG. 2 is a schematic cross-sectional view showing an enlarged view of region A of FIG. 1. Referring to FIG. 2, the positive active material layer (120) may include a lithium-containing sulfide-based positive active material (AML); a sulfide-based solid electrolyte (SE); an ionic liquid (LE) comprising a lithium salt and a non-aqueous organic solvent; and an ion-conducting binder (ICB) comprising an ether-based polymer (EP) and a fluorine-based polymer (FP). The non-aqueous organic solvent may include an ether-based solvent.

[0036] Referring to FIG. 2, the lithium-containing sulfide-based cathode active material (AML) is an electrode material to which lithium is added, for example, to a sulfur-based cathode active material. The sulfur-based cathode active material includes, for example, a sulfur-based material, a sulfur-based material-containing composite, or a combination thereof. The sulfur-based material is, for example, inorganic sulfur, Li2S n (n>1), it may be a disulfide compound, an organic sulfur compound, a carbon-sulfur polymer, or a combination thereof. The sulfur-based material-containing composite may be inorganic sulfur, Li2S n(n>1), it may be a composite containing a disulfide compound, an organic sulfur compound, a carbon-sulfur polymer, or a combination thereof. The sulfur-based material-containing composite may include, for example, a composite of a sulfur-based material and carbon, a composite of a sulfur-based material, carbon and a solid electrolyte, a composite of a sulfur-based material and a solid electrolyte, a composite of a sulfur-based material and a metal carbide, a composite of a sulfur-based material, carbon and a metal carbide, a composite of a sulfur-based material and a metal nitride, a composite of a sulfur-based material, carbon and a metal nitride, or a combination thereof. Since the lithium-containing sulfide-based cathode active material (AML) provides a higher discharge capacity per unit weight compared to oxide-based cathode active materials, the energy density per unit weight of a secondary battery containing the lithium-containing sulfide-based cathode active material can be improved.

[0037] The lithium-containing sulfide-based cathode active material (AML) may include, for example, Li2S, a Li2S-containing composite, or a combination thereof. By including Li2S, a Li2S-containing composite, or a combination thereof having high capacity as the lithium-containing sulfide-based cathode active material (AML), the use of lithium metal can be omitted during the manufacture of the secondary battery. Since lithium metal has high reactivity and great ductility, it can reduce mass production efficiency during battery manufacturing. Therefore, the mass production efficiency of the secondary battery can be improved. Since lithium metal is omitted from the negative electrode layer, the volume of the negative electrode (200) is reduced, thereby improving the energy density per unit volume of the secondary battery and allowing for the configuration of a secondary battery with a simpler structure.

[0038] A lithium-containing sulfide-based cathode active material (AML) undergoes delithiation during initial charging, for example, and then increases in volume through lithiation during subsequent discharge. Since the volume of the lithium-containing sulfide-based cathode active material (AML) changes while maintaining ion and / or electron transport pathways through conductive materials placed around the lithium-containing sulfide-based cathode active material (AML), the likelihood of the ion and / or electron transport pathways being severed is low.

[0039] The particle size of the lithium-containing sulfide-based cathode active material (AML) may be, for example, 1 μm to 10 μm, 2 μm to 8 μm, or 3 μm to 7 μm. By having the lithium-containing sulfide-based cathode active material (AML) have a particle size within this range, the cycle characteristics of the secondary battery containing the lithium sulfide-based cathode active material (AML) can be further improved.

[0040] A Li2S-containing composite is, for example, a composite of Li2S and a conductive material. The conductive material is, for example, an ionic conductive material containing a metallic or metalloid element; and an electronic conductive material containing carbon; or a combination thereof.

[0041] The Li2S-containing composite can impart ion conductivity to the lithium-containing sulfide-based cathode active material (AML) by including an ion-conducting material containing a metal or metalloid element.

[0042] An ion-conducting material according to one embodiment may include an alkali metal salt. By including an alkali metal salt in the ion-conducting material, the Li2S-containing composite can improve ion conductivity. The alkali metal salt may include, for example, LiF, LiCl, LiBr, LiI, or a combination thereof. The Li2S-containing composite including the alkali metal salt may be, for example, Li2S-LiF, Li2S-LiCl, Li2S-LiBr, or Li2S-LiI.

[0043] An ion-conducting material according to another embodiment may further include a boron group metal salt. By including a boron group metal salt in the ion-conducting material, the Li2S-containing composite can maintain its overall shape and lower the interfacial resistance. The boron group metal salt may include, for example, AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TlF3, TlCl3, TlBr3, TlI3, or a combination thereof. Li2S-containing complexes containing boron group metal salts may be, for example, Li2S-AlF3, Li2S-AlCl3, Li2S-AlBr3, Li2S-AlI3, Li2S-GaF3, Li2S-GaCl3, Li2S-GaBr3, Li2S-GaI3, Li2S-InF3, Li2S-InCl3, Li2S-lnBr3, Li2S-lnI3, Li2S-TlF3, Li2S-TlCl3, or Li2S-TlBr3, Li2S-TlI3.

[0044] An ion-conducting material according to another embodiment may include an alkali metal salt and a boron group metal salt. By including an alkali metal salt and a boron group metal salt in the ion-conducting material, the Li2S-containing composite can have improved ion conductivity while simultaneously lowering interfacial resistance. Li2S-containing complexes comprising alkali metal salts and boron group metal salts are, for example, Li2S-LiF-AlF3, Li2S-LiF-AlCl3, Li2S-LiF-AlBr3, Li2S-LiF-AlI3, Li2S-LiF-GaF3, Li2S-LiF-GaCl3, Li2S-LiF-GaBr3, Li2S-LiF-GaI3, Li2S-LiF-InF3, Li2S-LiF-InCl3, Li2S-LiF-InBr3, Li2S-LiF-InI3, Li2S-LiF-TlF3, Li2S-LiF-TlCl3, Li2S-LiF-TlBr3, Li2S-LiF-TlI3, Li2S-LiCl-AlF3, Li2S-LiCl-AlCl3, Li2S-LiCl-AlBr3, Li2S-LiCl-AlI3, Li2S-LiCl-GaF3, Li2S-LiCl-GaCl3, Li2S-LiCl-GaBr3, Li2S-LiCl-GaI3, Li2S-LiCl-InF3, Li2S-LiCl-InCl3, Li2S-LiCl-InBr3, Li2S-LiCl-InI3, Li2S-LiCl-TlF3, Li2S-LiCl-TlCl3, Li2S-LiCl-TlBr3, Li2S-LiCl-TlI3, Li2S-LiBr-AlF3, Li2S-LiBr-AlCl3, Li2S-LiBr-AlBr3, Li2S-LiBr-AlI3, Li2S-LiBr-GaF3, Li2S-LiBr-GaCl3, Li2S-LiBr-GaBr3, Li2S-LiBr-GaI3, Li2S-LiBr-InF3, Li2S-LiBr-InCl3, Li2S-LiBr-InBr3, Li2S-LiBr-InI3, Li2S-LiBr-TlF3, Li2S-LiBr-TlCl3, Li2S-LiBr-TlBr3, Li2S-LiBr-TlI3, Li2S-LiI-AlF3, Li2S-LiI-AlCl3,It may be Li2S-LiI-AlBr3, Li2S-LiI-AlI3, Li2S-LiI-GaF3, Li2S-LiI-GaCl3, Li2S-LiI-GaBr3, Li2S-LiI-GaI3, Li2S-LiI-InF3, Li2S-LiI-InCl3, Li2S-LiI-InBr3, Li2S-LiI-InI3, Li2S-LiI-TlF3, Li2S-LiI-TlCl3, Li2S-LiI-TlBr3 or Li2S-LiI-TlI3.

[0045] The Li2S-containing composite can impart electronic conductivity to the lithium-containing sulfide-based cathode active material (AML) by including an electronically conductive material containing carbon. The carbon may be, for example, any material containing carbon atoms that is used as a conductive material in the art. The carbon may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon may be, for example, a calcined product of a carbon precursor. The carbon may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof. The carbon may be, for example, porous carbon or non-porous carbon. Porous carbon may include, for example, periodic and regular two-dimensional or three-dimensional pores. Porous carbon may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, Channel black; graphite, activated carbon, or a combination thereof. The form of carbon may be, for example, particle form, sheet form, flake form, etc., but is not limited thereto; any form used as carbon in the relevant technical field is possible. The method for manufacturing the Li2S and carbon composite may be a dry method, a wet method, or a combination thereof, but is not limited thereto; and the method for manufacturing the Li2S and carbon composite in the relevant technical field may be, for example, milling, heat treatment, deposition, etc., but is not necessarily limited thereto; any method used in the relevant technical field is possible. Li2S-containing complexes comprising alkali metal salts, boron group metal salts, and carbon are, for example, Li2S-LiF-AlF3-CNF, Li2S-LiF-AlCl3-CNF, Li2S-LiF-AlBr3-CNF, Li2S-LiF-AlI3-CNF, Li2S-LiF-GaF3-CNF, Li2S-LiF-GaCl3-CNF, Li2S-LiF-GaBr3-CNF,Li2S-LiF-GaI3-CNF, Li2S-LiF-InF3-CNF, Li2S-LiF-InCl3-CNF, Li2S-LiF-InBr3-CNF, Li2S-LiF-InI3-CNF, Li2S-LiF-TlF3-CNF, Li2S-LiF-TlCl3-CNF, Li2S-LiF-TlBr3-CNF, Li2S-LiF-TlI3-CNF, Li2S-LiCl-AlF3-CNF, Li2S-LiCl-AlCl3-CNF, Li2S-LiCl-AlBr3-CNF, Li2S-LiCl-AlI3-CNF, Li2S-LiCl-GaF3-CNF, Li2S-LiCl-GaCl3-CNF, Li2S-LiCl-GaBr3-CNF, Li2S-LiCl-GaI3-CNF, Li2S-LiCl-InF3-CNF, Li2S-LiCl-InCl3-CNF, Li2S-LiCl-InBr3-CNF, Li2S-LiCl-InI3-CNF, Li2S-LiCl-TlF3-CNF, Li2S-LiCl-TlCl3-CNF, Li2S-LiCl-TlBr3-CNF, Li2S-LiCl-TlI3-CNF, Li2S-LiBr-AlF3-CNF, Li2S-LiBr-AlCl3-CNF, Li2S-LiBr-AlBr3-CNF, Li2S-LiBr-AlI3-CNF, Li2S-LiBr-GaF3-CNF, Li2S-LiBr-GaCl3-CNF, Li2S-LiBr-GaBr3-CNF, Li2S-LiBr-GaI3-CNF, Li2S-LiBr-InF3-CNF, Li2S-LiBr-InCl3-CNF, Li2S-LiBr-InBr3-CNF, Li2S-LiBr-InI3-CNF, Li2S-LiBr-TlF3-CNF, Li2S-LiBr-TlCl3-CNF, Li2S-LiBr-TlBr3-CNF, Li2S-LiBr-TlI3-CNF, Li2S-LiI-AlF3-CNF, Li2S-LiI-AlCl3-CNF, Li2S-LiI-AlBr3-CNF, Li2S-LiI-AlI3-CNF, Li2S-LiI-GaF3-CNF, Li2S-LiI-GaCl3-CNF, Li2S-LiI-GaBr3-CNF, Li2S-LiI-GaI3-CNF,It may be Li2S-LiI-InF3-CNF, Li2S-LiI-InCl3-CNF, Li2S-LiI-InBr3-CNF, Li2S-LiI-InI3-CNF, Li2S-LiI-TlF3-CNF, Li2S-LiI-TlCl3-CNF, Li2S-LiI-TlBr3-CNF, or Li2S-LiI-TlI3-CNF.

[0046] The content of the lithium-containing sulfide-based positive active material (AML) included in the positive active material layer (120) may be, for example, 50 to 95 weight%, 60 to 90 weight%, or 65 to 85 weight% of the total weight of the positive active material layer (120).

[0047] Referring to FIG. 2, the positive active material layer (120) may include a sulfide-based solid electrolyte (SE) having excellent lithium ion conductivity characteristics. The sulfide-based solid electrolyte (SE) is, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX (wherein 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 (In the above formula, m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (In the above formula, p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li + 12-n-x A n+ X 2- 6-x Y - x(In the above formula, A is one of P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is one of S, Se, or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, and 1≤n≤5, 0≤x≤2) Li 7-m M m PS 6-n X n (In the above formula, M is one of Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, Sc, Y, Ti, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Mn, Tc, Re, Bh, Ru, Os, Hs, Co, Rh, Ir, Mt, Ni, Pd, Pt, Ds, Au, Rg, Cd, Hg, or Cn, X is one of F, Cl, Br, or I, 0 <n≤2, 0<x≤2), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x It may include (0≤x≤2) or a combination thereof.

[0048] Sulfide-based solid electrolytes (SE) can be manufactured by processing starting materials, such as Li2S or P2S5, by methods such as melt quenching or mechanical milling. Additionally, heat treatment may be performed after such processing. Sulfide-based solid electrolytes (SE) may be amorphous, crystalline, or a mixture thereof. Sulfide-based solid electrolytes (SE) may, for example, contain at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. Sulfide-based solid electrolytes (SE) may, for example, contain Li2S-P2S5. When using a material containing Li2S-P2S5 as a sulfide-based solid electrolyte (SE), the mixed molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 20 : 80 to 90 : 10, 25 : 75 to 90 : 10, 30 : 70 to 70 : 30, and 40 : 60 to 60 : 40.

[0049] The particle size of the sulfide-based solid electrolyte (SE) may be, for example, 0.1 μm to 5 μm, 0.5 μm to 4 μm, or 1 μm to 3 μm. By having the sulfide-based solid electrolyte (SE) have a particle size within this range, the cycle characteristics of the secondary battery containing the sulfide-based solid electrolyte (SE) can be further improved.

[0050] The sulfide-based solid electrolyte (SE) may be, for example, an argyrodite-type solid electrolyte. The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc.

[0051] The content of the sulfide-based solid electrolyte (SE) included in the positive active material layer (120) may be, for example, 3 to 30 weight%, 10 to 30 weight%, or 10 to 20 weight% of the total weight of the positive active material layer (120).

[0052] Referring to FIG. 2, the positive electrode active material layer (120) may include an ionic liquid (LE). Although the lithium-containing sulfide-based positive electrode active material (AML) and the sulfide-based solid electrolyte (SE) can increase the contact area when pressure is applied due to their flexible properties, voids are inevitably created because they are solids, and these voids may act as resistance elements in terms of ion conductivity. Referring to FIG. 2, the present disclosure can reduce the interfacial resistance between the positive electrode active material (AML) and the sulfide-based solid electrolyte (SE) and improve ion conductivity by filling these voids with an ionic liquid (LE) containing a lithium salt and a non-aqueous organic solvent. As a result, a secondary battery comprising a solid electrolyte layer (300) between the positive electrode (100) and the negative electrode (200) can be provided, which can suppress the degradation of battery performance even when charging and discharging at low pressure.

[0053] The lithium salt contained in the ionic liquid (LE) may be a lithium salt having strong resistance to moisture. The lithium salt may include, for example, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium nitrate (LiNO3), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium fluoride (LiF), or a combination thereof.

[0054] The concentration of the lithium salt can be 0.1 M to 6.0 M. When the concentration of the lithium salt is within the above range, lithium ions can move effectively as the ionic liquid (LE) has appropriate conductivity.

[0055] The non-aqueous organic solvents included in the ionic liquid (LE) may include ether-based solvents. Ether-based solvents have high stability with sulfur and lithium metals and excellent solubility for lithium polysulfides. Ether-based solvents include, for example, monoglyme (1G), diglyme (2G), tetraglyme (4G), dibutyl ether, diethoxyethane, diethyl ether, dipropyl ether, triethylene glycol dimethyl ether (Triglyme), pentaethylene glycol dimethyl ether, dioxane, methyl tetrahydrofuran, ethylene glycol diethyl ether, 1,2-dimethoxypropane, trimethoxymethane, and 2-methyl tetrahydrofuran. It may include Tetrahydrofuran, 2,5-Dimethyl Tetrahydrofuran, Tetrahydrofuran (THF), or a combination thereof.

[0056] The content of the ionic liquid (LE) included in the positive active material layer (120) may be, for example, 1 to 15 weight%, 3 to 8 weight%, or 4 to 6 weight% of the total weight of the positive active material layer (120).

[0057] Referring to FIG. 2, the positive active material layer (120) may include an ion-conducting binder (ICB). The ion-conducting binder (ICB) can improve ion conductivity within the positive active material layer (120) by forming an ion conduction path between the positive active material and the solid electrolyte. The ion-conducting binder (ICB) can support or absorb an ionic liquid (LE) to suppress the ionic liquid (LE) from flowing out from the positive active material layer (120) to the solid electrolyte layer (300).

[0058] The ion-conducting binder (ICB) may include ether-based polymers (EP) and fluorine-based polymers (FP).

[0059] Ether-based polymers (EPs) provide excellent ionic conductivity due to their structural characteristics and can strengthen contact between the anode active material layer and the solid electrolyte through flexible molecular chains. Since ether-based polymers (EPs) have strong interactions with ionic liquids, they can help the ionic liquids be stably supported within the anode active material layer. Ether-based polymers (EPs) can absorb ionic liquids (LEs) and swell.

[0060] Ether-based polymers (EP) may include, for example, polyethylene oxide (PEO), polypropylene oxide (PPO), polymethylene oxide (PMO), polybutylene oxide (PBO), polytetrahydrofuran (PTHF), polyethylene glycol (PEG), poly(oxyethylene) (POE), epoxy resins, polyoxymethylene (POM), or combinations thereof.

[0061] Fluorine-based polymers (FP) have excellent chemical stability and heat resistance, so even when the positive active material layer (120) is manufactured dry, the reaction with impurities can be minimized and the quality of the electrode plate can be improved. Fluorinated polymers (FP) may include, for example, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy alkane (PFA), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), fluoroethylene vinyl ether (FEVE), tetrafluoroethylene hexafluoropropylene vinylidene fluoride (THV), or combinations thereof.

[0062] The ion-conducting binder (ICB) can improve the mechanical strength and chemical stability of the positive active material layer (120) formed through a dry process by simultaneously including the ether-based polymer (EP) and the fluorine-based polymer (FP), and at the same time, effectively prevent the leakage of the ionic liquid (LE) by containing the ionic liquid (LE) within the positive active material layer (120).

[0063] In the ion-conducting binder (ICB), the molar ratio of the ether-based polymer and the fluorine-based polymer (FP), respectively, may be 5:1 to 1:5, 3:1 to 1:3, or 2:1 to 1:2.

[0064] The content of the ion-conducting binder (ICB) included in the positive active material layer (120) may be, for example, 0.1 to 5 weight% or 0.5 to 2 weight% of the total weight of the positive active material layer (120).

[0065] The weight ratio of the ionic liquid (LE) and the solid electrolyte (SE) included in the positive active material layer (120) may be, for example, 1:1 to 1:20, 1:1 to 1:10, 1:1 to 1:5, or 1:2 to 1:4. By having the weight ratio of the ionic liquid (LE) and the solid electrolyte (SE) within the above ranges, the positive active material layer (120) can have high ionic conductivity at the interface while maintaining the stability of the solid electrolyte (SE).

[0066] The weight ratio of the ion-conducting binder (ICB) and the ionic liquid (LE) included in the positive active material layer (120) may be, for example, 1:1 to 1:20, 1:1 to 1:15, 1:1 to 1:10, or 1:2 to 1:9. By having the weight ratio of the ion-conducting binder (ICB) and the ionic liquid (LE) within the above ranges, the leakage of the ionic liquid (LE) can be effectively reduced while maintaining high ionic conductivity at the interface.

[0067] The weight ratio of the sulfide-based solid electrolyte (SE) and the lithium-containing sulfide-based positive electrode active material (AML) included in the positive electrode active material layer (120) may be, for example, 1:1 to 1:20, 1:1 to 1:10, or 1:2 to 1:9. By having the weight ratio of the sulfide-based solid electrolyte (SE) and the lithium-containing sulfide-based positive electrode active material (AML) within the above ranges, the energy density of the secondary battery can be improved while having high ionic conductivity.

[0068] [Anode Manufacturing Method]

[0069] A method for manufacturing a positive electrode according to one embodiment of the present disclosure comprises: preparing a slurry comprising a lithium-containing sulfide-based positive electrode active material, a sulfide-based solid electrolyte, and an ion-conducting binder, applying it to a positive electrode current collector, and drying it to form a positive electrode composite layer; and absorbing an ionic liquid comprising a lithium salt and an organic solvent into the positive electrode composite layer to form a positive electrode active material layer. First, the positive electrode active material layer is formed by a slurry coating method and dried to form a solid active material layer. Then, an ionic liquid is prepared and the dried positive electrode active material layer is supported in the ionic liquid, or the ionic liquid is appropriately sprayed or immersed into the positive electrode active material layer to ensure sufficient absorption by the binder. At this time, the ion-conducting binder efficiently absorbs the ionic liquid to allow the ionic liquid to penetrate uniformly into the positive electrode active material layer, thereby improving the electrochemical properties of the positive electrode active material layer and forming an ion conduction path that promotes the movement of lithium ions. As a result, the ionic liquid is evenly absorbed into the positive electrode active material layer, thereby forming a positive electrode layer capable of maximizing conductivity and ion conductivity.

[0070] A method for manufacturing a positive electrode according to another embodiment of the present disclosure comprises: dry-mixing a lithium-containing sulfide-based positive electrode active material, a sulfide-based solid electrolyte, and an ion-conducting binder to produce a positive electrode composite powder, applying it to a positive electrode current collector, and pressing it to form a positive electrode composite layer; and absorbing an ionic liquid containing a lithium salt and an organic solvent into the positive electrode composite layer to form a positive electrode active material layer. First, the positive electrode active material layer is formed by a dry coating method, and then an ionic liquid is prepared to support the positive electrode active material layer in the ionic liquid, or the ionic liquid is appropriately sprayed or immersed into the positive electrode active material layer to ensure sufficient absorption by the binder. At this time, the ion-conducting binder efficiently absorbs the ionic liquid to allow the ionic liquid to penetrate uniformly into the positive electrode active material layer, thereby improving the electrochemical properties of the positive electrode active material layer and forming an ion conduction path that promotes the movement of lithium ions. As a result, the ionic liquid is evenly absorbed into the positive electrode active material layer, thereby forming a positive electrode layer capable of maximizing conductivity and ion conductivity.

[0071] The positive electrode active material layer may further include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited to these, and any material used as a carbon-based conductive material in the relevant technical field is acceptable. The metal-based conductive material may be metal powder, metal fiber, or a combination thereof, but is not limited to these, and any material used as a metal-based conductive material in the relevant technical field is acceptable. The content of the conductive material included in the positive electrode active material layer may be, for example, 1 wt% to 40 wt%, 5 wt% to 35 wt%, or 10 wt% to 30 wt% of the total weight of the positive electrode active material layer.

[0072] [cathode]

[0073] The negative electrode (200) may include a negative current collector (210). Lithium metal and / or a lithium alloy may be deposited on the negative current collector (210) by charging the negative electrode (200). In this case, the lithium metal and / or the lithium alloy may act as a lithium reservoir. The negative current collector (210) may provide a reference surface on which a lithium metal layer (230) or a coating layer (220) is placed. The negative current collector (210) may include, for example, a material that does not react with lithium, that is, does not form both alloys and compounds with lithium. The material constituting the negative current collector (210) may include at least one metal selected from the group consisting of, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative current collector (210) may be 1 to 20 μm, for example 5 to 15 μm, for example 7 to 10 μm.

[0074] The negative current collector (210) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (210) is, for example, in the form of a plate or foil. In another embodiment, the negative current collector (210) may be omitted.

[0075] The negative electrode (200) may further include a negative electrode current collector (210); and a coating layer (220) disposed on the negative electrode current collector (210). The coating layer (220) may be configured to allow lithium metal to grow between the negative electrode current collector (210) and the coating layer (220) and / or within the coating layer (220) during charging of the secondary battery. The coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0076] The coating layer (220) may include metal particles and / or carbon-based materials.

[0077] The metal particles in the coating layer (220) may be metals or metalloids that form an alloy or compound with lithium. The metal particles may include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), or a combination thereof.

[0078] The carbon-based material in the coating layer (220) may include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. The carbon-based material in the metal-carbon composite may be amorphous carbon. The carbon-based material in the metal-carbon composite may include, for example, carbon black, acetylene black, furnace black, Kettjen black, graphene, or a combination thereof. Amorphous carbon may be carbon that does not have crystallinity or has very low crystallinity. The carbon-based material in the metal-carbon composite may be, for example, porous carbon. The pore volume contained in the porous carbon may be, for example, 0.1 cc / g to 10.0 cc / g, 0.5 cc / g to 5 cc / g, or 0.1 cc / g to 1 cc / g. The average pore diameter contained in the porous carbon may be, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The BET specific surface area of ​​the porous carbon is, for example, 100 m² 2 / g to 3,000 m 2 It can be / g. The BET specific surface area of ​​porous carbon can be measured, for example, according to ISO 9277:2022.

[0079] The metal particles and carbon-based material within the coating layer (220) can form a metal-carbon composite. The metal-carbon composite is a negative electrode material that can form an alloy or compound with, for example, lithium. The metal-carbon composite has, for example, a particle form. The average particle size of the metal-carbon composite having a particle form is, for example, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle size of the metal-carbon composite having a particle form is, for example, 10 nm to 4 μm, 10 nm to 3 μm, 10 nm to 2 μm, 10 nm to 1 μm, or 10 nm to 500 nm, 10 nm to 300 nm, or 10 nm to 100 nm. Since the metal-carbon composite has an average particle size within this range, the reversible absorption and / or desorption of lithium during charging and discharging may be more facilitated. The average particle size of the metal-carbon composite is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

[0080] The mixing ratio of the carbon-based material and the metal particles included in the coating layer (220) may be, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight.

[0081] The coating layer (220) may further include a binder. The binder included in the coating layer (220) 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 to these, and any binder used in the relevant technical field is possible. The binder may be composed of a single binder or a plurality of different binders.

[0082] The coating layer (220) may further include other additives (12) in addition to the metal-carbon composite. The coating layer (220) may further include at least one additive (12) selected from the group consisting of, for example, fillers, coating agents, dispersants, and ion-conducting aids.

[0083] The coating layer (220) may further include a solid electrolyte. The solid electrolyte may be a material selected from, for example, a solid electrolyte included in a solid electrolyte separator. The solid electrolyte included in the coating layer (220) may act as a reaction site where the formation of lithium metal begins within the coating layer (220), act as a space where the formed lithium metal is stored, or act as a pathway for transporting lithium ions. The solid electrolyte may be omitted.

[0084] FIG. 3 is a cross-sectional view of a secondary battery according to another exemplary embodiment. Referring to FIG. 3, the negative electrode (200) according to another embodiment may further include a lithium metal layer (230) disposed between a negative electrode current collector (210) and a coating layer (220). The lithium metal layer (230) may be a component formed by charging the secondary battery. Although not shown in the drawing, the secondary battery may further include a lithium metal layer (230) disposed inside the coating layer (220) by charging. The lithium metal layer (230) may include lithium or a lithium alloy. Since the lithium metal layer (230) is a metal layer containing lithium, it may function as, for example, a lithium reservoir. The lithium alloy is, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., but is not limited to these, and any alloy used as a lithium alloy in the relevant technical field may be possible. The lithium metal layer (230) may be made of one of these alloys or lithium, or may be made of various types of alloys. The lithium metal layer (230) may be, for example, a plated layer. The lithium metal layer (230) may be deposited between the coating layer (220) and the negative current collector (210) during the charging process of a secondary battery, for example.

[0085] In another embodiment, the lithium metal layer (230) within the negative electrode may be provided, for example, between the negative electrode current collector (210) and the coating layer (220) before the assembly of the secondary battery. When the lithium metal layer (230) is placed between the negative electrode current collector (210) and the coating layer (220) before the assembly of the secondary battery, the lithium metal layer (230) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be placed between the negative electrode current collector (210) and the coating layer (220) before the assembly of the secondary battery.

[0086] When a lithium metal layer (230) is precipitated by charging after the assembly of the secondary battery, the energy density of the secondary battery can be increased because the lithium metal layer (230) is not included during the assembly of the secondary battery. When charging the secondary battery, it can be charged beyond the charging capacity of the coating layer (220). That is, the coating layer (220) can be overcharged. At the beginning of charging, lithium can be absorbed in the coating layer (220). If charging is performed beyond the capacity of the coating layer (220), lithium can be precipitated, for example, between the negative electrode coating layer (220) and the negative electrode current collector (210). A lithium metal layer (230) can be formed by the precipitated lithium.

[0087] The lithium metal layer (230) can be composed mainly of lithium (i.e., metallic lithium). During discharge, the lithium in the lithium metal layer (230) can be ionized and move to the positive electrode (100). In other words, lithium can be used as a negative electrode active material in a secondary battery. In addition, since the coating layer (220) covers the lithium metal layer (230), the coating layer (220) can protect the lithium metal layer (230) and at the same time suppress the precipitation growth of lithium dendrites. Therefore, the coating layer (220) can suppress short circuits and capacity degradation of the secondary battery and improve the cycle characteristics of the secondary battery.

[0088] When a lithium metal layer (230) is formed by charging after assembly of the secondary battery, the negative electrode (200), that is, the negative electrode current collector (210) and the coating layer (220) and the region between them may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the secondary battery.

[0089] [Solid Electrolyte Layer]

[0090] The solid electrolyte layer (300) may include a solid electrolyte. The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymeric solid electrolyte, or a combination thereof.

[0091] The sulfide-based solid electrolyte can be selected from among the sulfide-based solid electrolytes included in the anode active material layer (120) described above.

[0092] Oxide-based solid electrolytes are, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. Oxide-based solid electrolytes are produced, for example, by sintering.

[0093] Oxide-based solid electrolytes are, for example, Li7La3Zr2O 12(LLZO) and Li 3+x La3Zr 2-a M a O 12 (M-doped LLZO, M=Ga, W, Nb, Ta, or Al(0 <a<2, 0≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체 전해질이다.

[0094] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or comprise a polymer having ion-conducting functional groups. The polymer solid electrolyte may, for example, be a polymer electrolyte that is in a solid state at 25°C and 1 atm. The polymer solid electrolyte may, for example, not contain a liquid.The polymeric solid electrolyte comprises a polymer, wherein the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), poly(methylmethacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), Polyaniline, Polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, Sulfonated poly(ether ether ketone) (SPEEK), Sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), Sulfonated poly(arylether ketone) (SPAEK), Poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), Poly(styrene sulfonate) (PSS), Lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +It may be ) or a combination thereof, but is not limited thereto, and any that are used in polymer electrolytes in the relevant technical field are permitted. Any lithium salt that can be used as a lithium salt in the relevant technical field is permitted. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F2 x+1 SO2)(C y F 2y+1 The polymer may be SO2)(x and y are each 1 to 20), LiCl, LiI, or a mixture thereof. The polymer included in the polymer solid electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight-average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1,000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0095] Gel electrolytes are, for example, polymeric gel electrolytes. Gel electrolytes can have a gel state without, for example, containing polymers.

[0096] Polymer gel electrolytes may, for example, comprise a liquid electrolyte and a polymer, or comprise an organic solvent and a polymer having ion-conducting functional groups. Polymer gel electrolytes may, for example, be polymer electrolytes in a gel state at 25°C and 1 atm. Polymer gel electrolytes may, for example, have a gel state without containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from the polymers used in solid polymer electrolytes. The organic solvent may be selected from the organic solvents used in liquid electrolytes. The lithium salt may be selected from the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt or a room-temperature molten salt that has a melting point below room temperature, consists solely of ions, and is in a liquid state at room temperature. The ionic liquid comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N -It may include one or more compounds selected from those containing one or more anions selected from among. The polymer solid electrolyte may form a polymer gel electrolyte by impregnating it into a liquid electrolyte in a secondary battery, for example. The polymer gel electrolyte may further include inorganic particles. The polymer included in the polymer gel electrolyte may be a compound containing, for example, 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight-average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0097] The solid electrolyte layer (300) may be impermeable to lithium polysulfide. Therefore, side reactions between the lithium polysulfide generated during the charging and discharging of the sulfide-based positive electrode active material and the negative electrode layer can be blocked. Accordingly, the cycle characteristics of the secondary battery including the solid electrolyte layer (300) can be improved.

[0098] The solid electrolyte layer (300) may include, for example, a binder. The binder included in the solid electrolyte layer (300) may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these and any binder used in the relevant technical field is possible. The binder of the solid electrolyte layer (300) may be the same as or different from the binder included in the positive electrode active material layer (120) and the negative electrode active material layer (220). The binder may be omitted.

[0099] The binder content included in the solid electrolyte layer (300) is 0.1 to 10 wt%, 1 to 5 wt%, 1 to 3 wt%, or 1 to 2 wt% with respect to the total weight of the solid electrolyte layer (300).

[0100] The creative idea is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the creative idea and do not limit the scope of the creative idea to these examples alone.

[0101] Example 1

[0102] (Cathode layer manufacturing)

[0103] A SUS foil with a thickness of 10 μm was prepared as a cathode current collector. In addition, carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle diameter of about 60 nm were prepared as the composition of the cathode coating layer.

[0104] 4 g of a mixed powder, prepared by mixing carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1, was placed in a container, and 4 g of an NMP solution containing 7 wt% of PVDF binder (Kureha # 9300) was added to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while gradually adding NMP (N-methyl-2-pyrrolidone) to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater and dried in air at 80°C for 10 minutes to prepare a laminate. The prepared laminate was vacuum dried at 40°C for 10 hours. The dried laminate was cold-roll-pressed to flatten the surface of the cathode coating layer to fabricate the cathode layer. The thickness of the cathode coating layer was approximately 15 μm. The surface area of ​​the cathode coating layer and the cathode current collector were the same.

[0105] (Preparation of solid electrolyte layer)

[0106] A mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of an argyrodite-type crystal Li6PS5Cl solid electrolyte (D50 = 3.0 μm, crystalline) to the solid electrolyte. A slurry was prepared by stirring while adding octyl acetate to the prepared mixture. The prepared slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, and dried in air at 80°C for 10 minutes to obtain a laminate. The obtained laminate was vacuum dried at 80°C for 2 hours. A solid electrolyte layer was prepared by the above process.

[0107] (Manufacturing of the anode layer)

[0108] A Li2S-LiI-AlI3-CNF composite, a lithium-containing sulfide-based cathode active material, was prepared as the cathode active material. The Li2S-LiI-AlI3-CNF composite was prepared as follows. Li2S, LiI, and AlI3 were mixed in a weight ratio of 50:5:15. The mixture was mechanically milled using a ball mill to prepare the Li2S-LiI-AlI3 composite. The milling conditions were 25 ℃ and 450 rpm for 10 hours. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-AlI3 composite thus prepared was mixed with carbon nanofiber (CNF) in a weight ratio of 70:10. The mixture was mechanically milled using a ball mill to prepare the Li2S-LiI-AlI3-CNF composite. The milling conditions were 25 ℃ and 450 rpm for 10 hours. The milling energy applied to the sample during milling was 20 G.

[0109] As a solid electrolyte, a Li6PS5Cl sulfide-based solid electrolyte (D50 = 1.0 μm, crystalline) which is an argyrodite-type crystal was prepared.

[0110] As an ionic liquid, the lithium salt LiTFSI was prepared by dissolving it in Diglyme (2G), an ether-based solvent, at a concentration of 2.0 M.

[0111] An ion-conducting binder was prepared by mixing PTFE and PEO in a 1:1 molar ratio as binders.

[0112] A cathode mixture was prepared by mixing these materials in a weight ratio of cathode active material : solid electrolyte : binder = 80 : 15 : 1. The cathode mixture was obtained by dry mixing using a mixer.

[0113] An anode composite layer was prepared by placing the anode composite on one side of an anode current collector made of aluminum foil coated with carbon on one side and performing a plate press at a pressure of 200 MPa for 10 minutes. An anode active material layer was prepared by spraying an ionic liquid onto the prepared anode composite layer to ensure sufficient absorption between the layers of the anode composite layer. The composition ratio of the formed anode active material layer, based on weight ratio, was anode active material : solid electrolyte : ionic liquid : binder = 80 : 15 : 4 : 1. The thickness of the anode layer was approximately 120 μm. The thickness of the anode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0114] (Manufacturing of all-solid-state batteries)

[0115] Referring to Fig. 1, a solid electrolyte layer was placed on the cathode layer such that a cathode coating layer contacted the solid electrolyte layer, and an anode layer was placed on the solid electrolyte layer. The prepared laminate was placed in a pouch and vacuum-sealed. The vacuum-sealed pouch was subjected to Warm Isostatic Press (WIP) treatment at 85°C and a pressure of 500 MPa for 30 minutes to manufacture an all-solid-state battery. This pressurization treatment sintered the solid electrolyte layer and improved interfacial contact, thereby enhancing battery characteristics. Parts of the positive and negative current collectors were extended outside the sealed battery to serve as positive and negative layer terminals. The thickness of the sintered solid electrolyte layer was approximately 45 μm. The density of the Li6PS5Cl solid electrolyte, an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc.

[0116] Example 2

[0117] A positive electrode layer and an all-solid-state battery were prepared in the same manner as in Example 1, except that the composition ratio of the positive electrode active material layer was changed to positive electrode active material : solid electrolyte : ionic liquid : binder = 80 : 15 : 4.5 : 0.5 based on weight ratio.

[0118] Example 3

[0119] A positive electrode layer and an all-solid-state battery were prepared in the same manner as in Example 1, except that the composition ratio of the positive electrode active material layer was changed to positive electrode active material : solid electrolyte : ionic liquid : binder = 80 : 15 : 3 : 2 based on weight ratio.

[0120] Comparative Example 1 - Ionic liquid free

[0121] A positive electrode layer and an all-solid-state battery were prepared in the same manner as in Example 1, except that the composition ratio of the positive electrode active material layer was changed to positive electrode active material : solid electrolyte : binder = 80 : 19 : 1 based on weight ratio.

[0122] Comparative Example 2 - Fluorinated polymer binder alone (PTFE)

[0123] A positive electrode layer and an all-solid-state battery were prepared in the same manner as in Example 1, except that PTFE was used as a binder.

[0124] Comparative Example 3 - Fluorine-based polymer binder free

[0125] A positive electrode layer and an all-solid-state battery were prepared in the same manner as in Example 1, except that SBR and PEO were mixed in a 1:1 molar ratio as binders.

[0126]

[0127] Evaluation example

[0128] The charge-discharge characteristics of the all-solid-state batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by the following charge-discharge test. The charge-discharge test was performed in a constant temperature bath at 45°C after mounting the all-solid-state battery on a dedicated jig capable of adjusting the confining pressure. The test was conducted under confining pressure conditions of 2.0 MPa and 0.5 MPa, respectively.

[0129] Charging was performed in CC mode. Charging was carried out at 0.1 C until the battery voltage reached 2.8 V, and discharging was carried out in CC mode at 0.05 C until it reached 1.0 V.

[0130] The above charge-discharge test was repeated until the SOH reached 80%, and the charge capacity, discharge capacity, and SOH were measured for each cycle.

[0131] The electrode capacity (mAh / g) was derived from the discharge capacity of the first cycle and is shown in Table 1 below.

[0132] The discharge capacity of the second cycle and the discharge capacity of the first cycle were substituted into the following mathematical formula 1 to derive the rate characteristic (%), which is shown in Table 1 below.

[0133] <Mathematical Formula 1>

[0134] Rate Characteristic [%] = [Discharge Capacity in 2nd Cycle / Discharge Capacity in 1st Cycle] × 100 (%)

[0135] The number of cycles until the SOH reaches 80% was defined as the life characteristic (@SOH 80%, cycles), and this is shown in Table 1 below.

[0136]

[0137] Confining pressure = 2 MPa Confining pressure = 0.5 MPa Electrode capacity (mAh / g) Rate characteristic (%) Lifespan characteristic (@SOH 80%, cycles) Electrode capacity (mAh / g) Rate characteristic (%) Lifespan characteristic (@SOH 80%, cycles) Example 15 1199.532249399.1297 Example 248999.228346698.9265 Example 349799.330148599289 Comparative Example 146298.624444698.2225 Comparative Example 245198.526243398238 Comparative Example 340598.221238797.8199

[0138] Referring to Table 1, it was confirmed that Examples 1 to 3 exhibited superior electrode capacitance, rate characteristics, and life characteristics compared to Comparative Examples 1 to 3. In particular, Examples 1 to 3 maintained relatively high performance in electrode capacitance, rate characteristics, and life characteristics even under low-pressure driving conditions with a confining pressure of 0.5 MPa, and excellent stability and design flexibility were confirmed, as the difference in performance with respect to the confining pressure condition of 2.0 MPa was not significant.

[0139] Although exemplary embodiments have been described in detail with reference to the attached drawings, the present creative idea is not limited to such examples. It is obvious that a person skilled in the art to which the present creative idea belongs can derive various variations or modifications within the scope of the technical idea described in the patent claims, and these also naturally fall within the technical scope of the present creative idea.

Claims

1. Lithium-containing sulfide-based cathode active material; Sulfide-based solid electrolytes; An ionic liquid comprising a lithium salt and a non-aqueous organic solvent; and A positive electrode active material layer comprising an ion-conducting binder comprising an ether-based polymer and a fluorine-based polymer.

2. In Paragraph 1, The above ether-based polymer is an anode active material layer that absorbs the above ionic liquid and swells.

3. In Paragraph 1, The above-mentioned non-aqueous organic solvent includes an ether-based solvent, and The above ether-based solvents are Monoglyme (1G), Diglyme (2G), Triglyme (3G), Tetraglyme (4G), Dibutyl Ether, Diethoxyethane, Diethyl Ether, Dipropyl Ether, Pentaethylene Glycol Dimethyl Ether, Dioxane, Methyl Tetrahydrofuran, Ethylene Glycol Diethyl Ether, 1,2-Dimethoxypropane, Trimethoxymethane, 2-Methyl Tetrahydrofuran, and 2,5-Dimethyl A positive electrode active material layer comprising tetrahydrofuran (2,5-Dimethyl Tetrahydrofuran), tetrahydrofuran (Tetrahydrofuran, THF), or a combination thereof.

4. In Paragraph 1, The above-mentioned fluorine-based polymer comprises polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy alkane (PFA), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), fluoroethylene vinyl ether (FEVE), tetrafluoroethylene hexafluoropropylene vinylidene fluoride (THV), or a combination thereof, forming an anode active material layer.

5. In Paragraph 1, The above ether-based polymer comprises polyethylene oxide (PEO), polypropylene oxide (PPO), polymethylene oxide (PMO), polybutylene oxide (PBO), polytetrahydrofuran (PTHF), polyethylene glycol (PEG), poly(oxyethylene) (POE), epoxy resins, polyoxymethylene (POM), or a combination thereof, forming an anode active material layer.

6. In Paragraph 1, The above lithium salt comprises lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium nitrate (LiNO3), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium fluoride (LiF), or a combination thereof, forming an anode active material layer.

7. In Paragraph 1, The above sulfide-based solid electrolyte is Li3PO4-Li2SO4, 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 (In the above formula, m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (In the above formula, p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li + 12-n-x A n+ X 2- 6-x Y - x (In the above formula, A is one of P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is one of S, Se, or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, and 1≤n≤5, 0≤x≤2) Li 7-m M m PS 6-n X n (In the above formula, M is one of Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, Sc, Y, Ti, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Mn, Tc, Re, Bh, Ru, Os, Hs, Co, Rh, Ir, Mt, Ni, Pd, Pt, Ds, Au, Rg, Cd, Hg, or Cn, X is one of F, Cl, Br, or I, 0 <n≤2, 0<x≤2), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x A positive active material layer comprising (0≤x≤2) or a combination thereof.

8. In Paragraph 1, The above lithium-containing sulfide-based cathode active material includes a Li2S-containing complex, and The above Li2S-containing composite is a positive active material layer, which is a composite of Li2S and a conductive material.

9. In Paragraph 8, The above conductive material comprises an ion-conducting material containing a metal or metalloid element; and an electron-conducting material containing carbon, forming an anode active material layer.

10. In Paragraph 9, The above ion-conducting material is an anode active material layer comprising an alkali metal salt and a boron group metal salt.

11. In Paragraph 1, A positive electrode active material layer, wherein the weight ratio of the ionic liquid and the sulfide-based solid electrolyte is 1:1 to 1:

20.

12. In Paragraph 1, A positive active material layer, wherein the weight ratio of the ion-conducting binder and the ionic liquid is 1:1 to 1:

20.

13. In Paragraph 1, With respect to the total weight of the above positive active material layer: The content of the above lithium-containing sulfide-based cathode active material is 50 to 95 weight% The content of the above sulfide-based solid electrolyte is 3 to 30 weight%, The content of the above ionic liquid is 1 to 15 weight%, A positive active material layer comprising 0.1 to 5 weight% of the ion-conducting binder.

14. In Paragraph 1, The particle size of the above lithium-containing sulfide-based cathode active material is 1 μm to 10 μm, A positive electrode active material layer having a particle size of 0.1 μm to 5 μm of the above sulfide-based solid electrolyte.

15. In Paragraph 1, A positive electrode active material layer, wherein the weight ratio of the sulfide-based solid electrolyte and the lithium-containing sulfide-based positive electrode active material is 1:1 to 1:

20.

16. In Paragraph 1, A positive active material layer in which the molar ratio of the ether-based polymer to the fluorine-based polymer in the above ion-conducting binder is 5:1 to 1:

5.

17. Anode; cathode; and A solid electrolyte layer disposed between the anode and the cathode, wherein The above positive electrode comprises the positive electrode active material layer of claim 1, a secondary battery.

18. In Paragraph 17, The above solid electrolyte layer comprises a sulfide-based solid electrolyte, and The above sulfide-based solid electrolyte is Li3PO4-Li2SO4, 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 (In the above formula, m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (In the above formula, p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li + 12-n-x A n+ X 2- 6-x Y - x (In the above formula, A is one of P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is one of S, Se, or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, and 1≤n≤5, 0≤x≤2) Li 7-m M m PS 6-n X n (In the above formula, M is one of Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, Sc, Y, Ti, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Mn, Tc, Re, Bh, Ru, Os, Hs, Co, Rh, Ir, Mt, Ni, Pd, Pt, Ds, Au, Rg, Cd, Hg, or Cn, X is one of F, Cl, Br, or I, 0 <n≤2, 0<x≤2), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x A secondary battery comprising (0≤x≤2) or a combination thereof.

19. In Paragraph 17, The above cathode comprises a cathode current collector; and a coating layer disposed on the cathode current collector, and The above coating layer is: Metal particles comprising gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof; and A secondary battery comprising a carbon-based material including amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

20. In Paragraph 19, A secondary battery further comprising a lithium metal layer disposed between the above-mentioned negative current collector and the above-mentioned coating layer.

Images