Positive electrode active material and method for preparing same

Abstract

Disclosed are a positive electrode active material and a method for preparing same, the positive electrode active material comprising: a composite of a sulfur-based material and a carbon-based conductive material; and a coating layer which coats the entire surface or a part of the surface of the sulfur-based material, wherein the coating layer comprises a first metal sulfide.

Description

Cathode active material and method for manufacturing the same

[0001] This invention relates to a positive electrode active material and a method for manufacturing 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 flammable organic solvents, there is a possibility of overheating and fire in the event of a short circuit.

[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 sulfide-based cathode active material with improved lifespan characteristics.

[0008] Another aspect is to provide a method for manufacturing a sulfide-based cathode active material with improved lifespan characteristics.

[0009] According to one embodiment, an anode active material is provided, comprising a composite of a sulfur-based material and a carbon-based conductive material; and a coating layer covering the entire surface or a portion of the surface of the sulfur-based material; wherein the coating layer comprises a first metal sulfide.

[0010] According to another embodiment, the composite comprises a sulfide-based material and a first metal sulfide, wherein the sulfide-based material is S8, Li2S n (1 ≤ n ≤ 8, where n is an integer) or a combination thereof, wherein the first metal sulfide is TiS x (0 < x ≤ 2, x is an integer), V2S x (0 < x ≤ 5, x is an integer), CrS x (0 < x ≤ 3, x is an integer), ZrS x (0 < x ≤ 2, x is an integer), Nb2S x (0 < x ≤ 2, x is an integer), MoS x (0 < x ≤ 3, x is an integer), HfS x (0 < x ≤ 2, x is an integer) Ta2S x (0 < x ≤ 5, x is an integer), WS x A positive active material is provided, comprising (0 < x ≤ 2, where x is an integer) or a combination thereof.

[0011] According to another embodiment, a method for manufacturing an anode active material is provided, comprising mixing a composition for forming a sulfide-based material, a carbon-based conductive material, and a metal sulfide precursor; wherein the metal sulfide precursor comprises one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

[0012] According to one aspect, by using a positive electrode active material according to one embodiment, it is possible to provide an all-solid-state battery with improved capacity and lifespan characteristics.

[0013] Figure 1 schematically shows the structure of a secondary battery according to one embodiment.

[0014] FIGS. 2 and 3 schematically show the structure of a positive electrode active material according to an exemplary embodiment.

[0015] FIG. 4 is a cross-sectional view of an all-solid-state battery according to another embodiment.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0021] In this disclosure, “alloy” means a mixture of two or more metals.

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

[0023] In the present disclosure, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0024] 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.

[0025] 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.

[0026] In this disclosure, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery.

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

[0028] In this disclosure, “cathode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0029] In this disclosure, the term “composite” refers to a material in which two or more materials are combined to form physically and chemically different phases, thereby exhibiting a more effective function.

[0030] FIG. 1 is a conceptual diagram briefly illustrating a secondary battery according to one embodiment. Referring to FIG. 1, the secondary battery may include a positive electrode (100), a negative electrode (200), and an electrolyte layer (300).

[0031] The positive electrode (100) and the negative electrode (200) may be spaced apart from each other with an electrolyte layer (300) in between. The electrolyte layer (300) may be placed between the positive electrode (100) and the negative electrode (200).

[0032] The electrolyte layer (300) may include an electrolyte as a medium for transferring lithium ions between the positive electrode (100) and the negative electrode (200). Depending on the type of secondary battery, the electrolyte may include a liquid electrolyte, a solid electrolyte, a gel electrolyte, etc. Depending on the type of secondary battery, the electrolyte layer (300) may further include a separator.

[0033] positive electrode (100)

[0034] The positive electrode (100) may include a positive electrode current collector (110) and a positive electrode active material layer (120) formed on the positive electrode current collector (110). The positive electrode active material layer (120) may include a positive electrode active material and may further include a binder and / or a conductive material. As an example, the positive electrode (100) may further include an additive that can serve as a sacrificial electrode.

[0035] The above binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0036] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0037] The positive current collector (110) may provide a reference surface on which the positive active material layer (120) is placed. The positive current collector (110) 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. In another embodiment, 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.

[0038] The positive active material layer (120) may include, for example, a positive active material and a solid electrolyte. The solid electrolyte included in the positive active material layer may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymeric solid electrolyte, or a combination thereof.

[0039] Sulfide-based solid electrolytes are, for example, 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-n 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≤m≤2, 0≤n≤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.

[0040] Sulfide-based solid electrolytes can be manufactured by processing starting materials, such as Li2S or P2S5, using methods such as melt quenching or mechanical milling. Additionally, heat treatment may be performed after such processing. Sulfide-based solid electrolytes may be amorphous, crystalline, or a mixture thereof. Sulfide-based solid electrolytes may, for example, contain at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. Sulfide-based solid electrolytes may, for example, contain Li2S-P2S5. When using a material containing Li2S-P2S5 as a sulfide-based solid electrolyte, the 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.

[0041] The sulfide-based solid electrolyte 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. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and penetration of the solid electrolyte separator by lithium can be suppressed more effectively.

[0042] The content of the solid electrolyte included in the positive active material layer (120) may be, for example, 1 wt% to 50 wt%, 10 wt% to 45 wt%, 20 wt% to 40 wt%, or 25 wt% to 35 wt% of the total weight of the positive active material layer (120).

[0043] The content of the positive active material included in the positive active material layer (120) may be, for example, 30 wt% to 95 wt%, 40 wt% to 85 wt%, 50 wt% to 80 wt%, or 60 wt% to 75 wt% of the total weight of the positive active material layer (120).

[0044] A positive electrode active material and a method for manufacturing the same according to exemplary embodiments are described in more detail below.

[0045] [Cathode active material]

[0046] Referring to FIG. 2, one form of a positive electrode active material according to the present disclosure will be described in detail.

[0047] A positive electrode active material according to one embodiment comprises a composite (1) of a sulfur-based material and a carbon-based conductive material; and a coating layer (2) covering the entire surface or a part of the surface of the sulfur-based material; wherein the coating layer (2) comprises a first metal sulfide.

[0048] Referring to FIG. 2, the positive active material may include a composite (1) and a coating layer (2) disposed continuously or discontinuously along the surface of the composite (1). According to one embodiment, the coating layer (2) may cover all or part of the composite (1). According to one embodiment, the coating layer (2) may coat the entire surface or part of the surface of a sulfide-based material. The composite (1) may include a sulfide-based material and a carbon-based conductive material. The coating layer (2) may include a first metal sulfide. Although the sulfide-based material is an insulator with almost no electrical conductivity, it forms the composite (1) together with the carbon-based conductive material and, by providing the coating layer (2) described above, an effective conductive network can be formed. As a result, by providing a positive electrode containing such a positive active material, it is possible to manufacture a secondary battery having improved lifespan characteristics and high rate characteristics, reduced volume expansion of the electrode terminal, increased composite density, and high energy density characteristics.

[0049] The theoretical basis for the excellent effect provided by the cathode active material according to one embodiment is explained below; however, this is intended to aid in understanding the creative concept and is not intended to limit the creative concept in any way.

[0050] A positive electrode active material according to one embodiment may include a composite of a sulfur-based material and a carbon-based conductive material.

[0051] Sulfide-based materials may contain elemental sulfur (S). Sulfur is attracting attention as a next-generation cathode material due to its high theoretical capacity (1,672 mAh / g), its abundance on Earth, and its relatively low cost. In one embodiment, the elemental sulfur (S) is S8 and Li2S n It may exist in a form including at least one of (1 ≤ n ≤ 8, where n is an integer). That is, the sulfide-based material according to one embodiment is S8, Li2Sn It may include (1 ≤ n ≤ 8, where n is an integer) or a combination thereof. A sulfide-based material undergoes a continuous oxidation / reduction reaction of sulfur and / or lithium sulfide. For example, the reaction process of lithium polysulfide and lithium sulfide by the continuous reduction reaction of sulfur in the sulfide-based material can be expressed as S8→Li2S8→Li2S6→Li2S4→Li2S2→Li2S, etc. In this process, lithium ions move between the anode and cathode, and at the same time, electrons move through an external circuit, which can generate an electric current. A sulfide-based material according to one embodiment may include Li2S. For example, the reaction process of lithium polysulfide and lithium sulfide by the continuous oxidation reaction of Li2S in the sulfide-based material can be expressed as Li2S→Li2S2→Li2S4→Li2S6→Li2S8→S8, etc. In this process, lithium ions move between the anode and cathode, and at the same time, electrons move through an external circuit, which can store energy.

[0052] The content of the sulfide-based material included in the composite may be, for example, 20 to 80 wt%, 30 to 70 wt%, 35 to 65 wt%, or 40 to 60 wt% of the total weight of the positive active material layer. If the content of the sulfide-based material increases excessively, the electronic conductivity of the composite decreases, which may increase the internal resistance of the positive active material. If the content of the sulfide-based material decreases excessively, the energy density of the secondary battery may decrease.

[0053] Carbon-based conductive materials are materials containing carbon atoms, and any material used as a conductive material in the relevant technical field is acceptable. Carbon-based conductive materials may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. Carbon-based conductive materials may be, for example, a sintered product of a carbon precursor. Carbon-based conductive materials may be, for example, carbon nanostructures. Carbon nanostructures may be, for example, one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, or a combination thereof. Carbon-based conductive materials may include, for example, carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, graphene, or a combination thereof. Carbon-based conductive materials may be, for example, porous carbon-based materials or non-porous carbon-based materials. Porous carbon-based materials may include, for example, periodic and regular two-dimensional or three-dimensional pores. Porous carbon-based materials may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, and channel black; graphite, activated carbon, or a combination thereof. The form of the carbon-based conductive material may be, for example, particle form, sheet form, flake form, etc., but is not limited to these; any form used as a carbon-based conductive material in the relevant technical field is possible.

[0054] The content of the carbon-based conductive material included in the composite may be, for example, 1 to 20 wt%, 1 to 15 wt%, or 5 to 10 wt% of the total weight of the positive electrode active material layer. If the content of the carbon-based conductive material increases excessively, the energy density of the secondary battery may decrease. If the content of the carbon-based conductive material decreases excessively, the electronic conductivity of the composite decreases, and the internal resistance of the positive electrode active material may increase.

[0055] The content ratio of the sulfide-based material and the carbon-based conductive material included in the composite may be 1:1 to 50:1, 1:1 to 25:1, 2:1 to 25:1, 3:1 to 25:1, 3:1 to 20:1, or 4:1 to 10:1 by weight. By satisfying the content ratio of the sulfide-based material and the carbon-based conductive material within the above ranges, the electronic conductivity of the composite can be improved, and the specific capacity of the positive active material can be improved, thereby improving the energy density of the secondary battery.

[0056] A composite of a sulfide-based material and a carbon-based conductive material may include, for example, a solid solution of the sulfide-based material and the carbon-based conductive material. A composite of a sulfide-based material and a carbon-based conductive material may include, for example, a solid solution of the sulfide-based material and the carbon-based conductive material including a coating layer. By including a solid solution of the sulfide-based material and the carbon-based conductive material in the composite, the electronic conductivity of the composite of the sulfide-based material and the carbon-based conductive material may be increased. For example, the electronic conductivity of the solid solution may be enhanced compared to the electronic conductivity of the sulfide-based material by carbon disposed within the crystallites of the sulfide-based material. Consequently, the electronic conductivity of the composite of the sulfide-based material and the carbon-based conductive material is enhanced, and the internal resistance of the composite of the sulfide-based material and the carbon-based conductive material may be reduced.

[0057] A composite according to another embodiment may further include a metal halide salt. That is, a composite according to another embodiment may be a composite of a sulfide-based material, a metal halide salt, and a carbon-based conductive material. The ionic conductivity of the composite may be further enhanced by including such a metal halide salt.

[0058] A composite of a sulfide-based material, a metal halide salt, and a carbon-based conductive material may include, for example, a solid solution of the sulfide-based material, the metal halide salt, and the carbon-based conductive material. By including a solid solution of the sulfide-based material, the metal halide salt, and the carbon-based conductive material, the ionic conductivity of the composite of the sulfide-based material, the metal halide salt, and the carbon-based conductive material may be increased. For example, by including lithium ions disposed within the crystallites of the sulfide-based material, the metal halide salt, and the carbon-based conductive material in the solid solution of the sulfide-based material, the metal halide salt, and the carbon-based conductive material, the ionic conductivity of the solid solution of the sulfide-based material, the metal halide salt, and the carbon-based conductive material may be enhanced compared to the ionic conductivity of the sulfide-based material. Consequently, the ionic conductivity of the composite of the sulfide-based material, the metal halide salt, and the carbon-based conductive material may be enhanced, and the internal resistance of the composite of the sulfide-based material, the metal halide salt, and the carbon-based conductive material may be reduced.

[0059] The content ratio of the sulfide-based material and the metal halide salt included in the composite may be 1:1 to 100:1, 2:1 to 50:1, 3:1 to 25:1, 3:1 to 20:1, or 4:1 to 10:1 by weight. By satisfying the content ratio of the sulfide-based material and the metal halide salt within the above ranges, the ionic conductivity of the composite can be improved, and the specific capacity of the positive electrode active material can be improved, thereby improving the energy density of the secondary battery.

[0060] The content of the metal halide salt included in the composite may be, for example, 0 to 30 wt%, 0 to 20 wt%, or 0 to 10 wt% of the total weight of the anode active material layer. The content of the metal halide salt included in the composite may be, for example, 1 to 30 wt%, 1 to 20 wt%, or 1 to 10 wt% of the total weight of the composite. The content of the metal halide salt included in the composite may be, for example, 3 to 30 wt%, 3 to 20 wt%, or 5 to 10 wt% of the total weight of the composite. If the content of the metal halide salt increases excessively, the energy density may decrease.

[0061] Metal halide salts may include alkali metal salts and boron group metal salts. That is, a composite according to another embodiment may be a composite of a sulfide-based material, an alkali metal salt, a boron group metal salt, and a carbon-based conductive material. The ionic conductivity of the composite may be further enhanced by including such alkali metal salts. By including such boron group metal salts, the composite may easily accommodate volume changes of the anode active material, thereby suppressing the occurrence of cracks within the anode active material.

[0062] The content ratio of the alkali metal salt and boron group metal salt included in the metal halide salt may be 1:1 to 1:10, 1:1 to 1:5, or 1:2 to 1:4 by weight. The content ratio of the alkali metal salt and boron group metal salt included in the metal halide salt may be 5:1 to 1:5, 3:1 to 1:3, or 2:1 to 1:2 by molar ratio. By satisfying the content ratio of the alkali metal salt and boron group metal salt within the above ranges, the ionic conductivity of the composite can be improved, and the occurrence of cracks inside the anode active material can be suppressed by easily accommodating volume changes of the anode active material.

[0063] The alkali metal salt may be a binary compound composed of, for example, an alkali metal and one element selected from Group 17 of the periodic table. The alkali metal salt may be, for example, a lithium salt. The alkali metal salt may include, for example, LiF, LiCl, LiBr, LiI, or a combination thereof. Such alkali metal salts can form a complex with a sulfide-based material to improve the ionic conductivity of the positive electrode active material.

[0064] Boron group metal salts may be binary compounds composed, for example, of a boron group metal and one element selected from Group 17 of the periodic table. Boron group metal salts may include, for example, AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TlF3, TlCl3, TlBr3, TlI3, or combinations thereof. These boron group metal salts can form complexes with sulfide-based materials to maintain a constant overall shape of the cathode active material and lower interfacial resistance.

[0065] Referring to FIG. 2, the coating layer (2) may include a first metal sulfide. Depending on its shape, the first metal sulfide can create a space into which ions can be inserted, thereby improving the ion conductivity of the coating layer (2). As ions are inserted or emitted, the first metal sulfide can undergo an oxidation-reduction reaction to store and release charges, thereby improving the electron conductivity of the coating layer (2). The positive electrode active material containing such a coating layer (2) can have improved electrochemical properties.

[0066] The first metal sulfide in the coating layer (2) can have various shapes of structures.

[0067] The first metal sulfide may, for example, have a particle form (zero-dimensional). When the first metal sulfide has a particle form, the average particle size (D50) may be 1 nm to 1 µm, 1 nm to 500 nm, 1 nm to 200 nm, 1 nm to 100 nm, 1 nm to 70 nm, 1 nm to 50 nm, 1 nm to 30 nm, 3 nm to 30 nm, 3 nm to 25 nm, 5 nm to 25 nm, 5 nm to 20 nm, or 7 nm to 20 nm. Since the first metal sulfide has a particle size in this nano range, it can be uniformly coated on the composite without aggregation to form a coating layer (2).

[0068] The first metal sulfide may have a nanorod form (one-dimensional), for example. When the first metal sulfide has a nanorod form, it may have a length corresponding to the longitudinal direction and a diameter corresponding to the transverse direction perpendicular to the longitudinal direction. When the first metal sulfide has a nanorod form, the aspect ratio (length:diameter) may be 2:1 to 100,000:1, 2:1 to 10,000:1, 2:1 to 1,000:1, or 2:1 to 100:1. When the first metal sulfide has a nanorod form, the length of the first metal sulfide may be 0.1 to 50 μm or 1 to 5 μm. When the first metal sulfide has a nanorod form, the thickness of the first metal sulfide may be 0.01 to 10 μm or 0.01 to 1 μm.

[0069] The first metal sulfide may have a layered structure (two-dimensional), for example. When the first metal sulfide has a layered structure, it may have an interlayer spacing. The interlayer spacing of the first metal sulfide may be, for example, 0.1 to 1 nm, 0.3 to 0.9 nm, 0.5 to 0.85 nm, or 0.6 to 0.8 nm. If the interlayer spacing of the first metal sulfide exceeds the above range, it may be structurally unstable and unable to maintain the layered structure. If the interlayer spacing of the first metal sulfide is less than the above range, ion insertion may be difficult, and the ion conductivity may be low.

[0070] The first metal sulfide is TiS x (0 < x ≤ 2, x is an integer), V2S x (0 < x ≤ 5, x is an integer), CrS x (0 < x ≤ 3, x is an integer), ZrS x (0 < x ≤ 2, x is an integer), Nb2S x (0 < x ≤ 2, x is an integer), MoS x (0 < x ≤ 3, x is an integer), HfS x (0 < x ≤ 2, x is an integer) Ta2S x (0 < x ≤ 5, x is an integer), WS x It may include (0 < x ≤ 2, where x is an integer) or a combination thereof. A first metal sulfide according to one embodiment is, for example, TiS x (0 < x ≤ 2, x is an integer), ZrS x (0 < x ≤ 2, x is an integer), MoS x It may include (0 < x ≤ 3, x is an integer) or a combination thereof.

[0071] The content ratio of the sulfide-based material to the first metal sulfide may be 10:1 to 1:1, 5:1 to 1:1, or 4:1 to 2:1 by weight. By satisfying the content ratio of the sulfide-based material to the first metal sulfide within the above range, the ionic conductivity of the positive electrode active material can be improved, and the specific capacity of the positive electrode active material can be improved, thereby improving the energy density of the secondary battery.

[0072] The content of the first metal sulfide included in the composite may be, for example, 1 to 40 wt%, 1 to 30 wt%, 5 to 30 wt%, or 10 to 25 wt% of the total weight of the positive electrode active material layer. If the content of the first metal sulfide increases excessively, the energy density of the secondary battery may decrease. If the content of the first metal sulfide decreases excessively, the ionic conductivity of the positive electrode active material decreases, and the internal resistance may increase.

[0073] According to one embodiment, the weight ratio of the metal halide salt to the first metal sulfide (MS) may be 1:0.2 to 1:30, 1:0.5 to 1:20, 1:1 to 1:10, 1:1 to 1:5, 1:1 to 1:3, or 1:1 to 1:2.

[0074] The content ratio of the carbon-based conductive material and the first metal sulfide may be 1:1 to 1:10, 1:2 to 1:10, or 1:2 to 1:5 by weight. By satisfying the content ratio of the carbon-based conductive material and the first metal sulfide within the above range, the ionic conductivity and electronic conductivity of the positive electrode active material can be improved.

[0075] According to another embodiment, the coating layer (2) may further include a second metal sulfide. The second metal sulfide is LiTiS x (0 < x ≤ 2, x is an integer), LiV2S x (0 < x ≤ 5, x is an integer), LiCrS x (0 < x ≤ 3, x is an integer), LiZrS x(0 < x ≤ 2, x is an integer), LiNb2S x (0 < x ≤ 2, x is an integer), LiMoS x (0 < x ≤ 3, x is an integer), LiHfS x (0 < x ≤ 2, x is an integer) LiTa2S x (0 < x ≤ 5, x is an integer), LiWS x It may include (0 < x ≤ 2, where x is an integer) or a combination thereof. The second metal sulfide according to one embodiment is LiTiS x (0 < x ≤ 2, x is an integer), LiZrS x (0 < x ≤ 2, x is an integer), LiMoS x It may include (0 < x ≤ 3, where x is an integer) or a combination thereof. The content of the second metal sulfide may be equal to or less than the content of the first metal sulfide.

[0076] With reference to FIG. 3, another form of a positive electrode active material according to the present disclosure will be described in detail. Since the above description can be applied as is to configurations using the same names and symbols, redundant descriptions will be omitted and the differences will be explained in detail.

[0077] A positive electrode active material according to one embodiment comprises a composite (1) of a sulfide-based material (SM) and a first metal sulfide (MS); wherein the sulfide-based material is S8, Li2S n (1 ≤ n ≤ 8, where n is an integer) or a combination thereof, wherein the first metal sulfide is TiS x (0 < x ≤ 2, x is an integer), V2S x (0 < x ≤ 5, x is an integer), CrS x (0 < x ≤ 3, x is an integer), ZrS x (0 < x ≤ 2, x is an integer), Nb2S x (0 < x ≤ 2, x is an integer), MoS x(0 < x ≤ 3, x is an integer), HfS x (0 < x ≤ 2, x is an integer) Ta2S x (0 < x ≤ 5, x is an integer), WS x It may include (0 < x ≤ 2, x is an integer) or a combination thereof.

[0078] Referring to FIG. 3, the composite (1) containing the positive electrode active material may be formed by combining two or more different materials to form physically and chemically different phases. The two or more different materials may include a sulfide-based material (SM) and a first metal sulfide (MS). That is, the positive electrode active material according to one embodiment may include a composite of a sulfide-based material (SM) and a first metal sulfide (MS). A detailed description of the sulfide-based material (SM) and the first metal sulfide (MS) will be omitted below, as the above description can be applied as is.

[0079] The content of the sulfide-based material (SM) included in the composite may be, for example, 20 to 80 wt%, 30 to 70 wt%, 35 to 65 wt%, or 40 to 60 wt% of the total weight of the positive active material layer. If the content of the sulfide-based material (SM) increases excessively, the electronic conductivity of the composite decreases, which may increase the internal resistance of the positive active material. If the content of the sulfide-based material (SM) decreases excessively, the energy density of the secondary battery may decrease.

[0080] The content of the first metal sulfide (MS) included in the composite may be, for example, 1 to 40 wt%, 1 to 30 wt%, 5 to 30 wt%, or 10 to 25 wt% of the total weight of the positive electrode active material layer. If the content of the first metal sulfide (MS) increases excessively, the energy density of the secondary battery may decrease. If the content of the first metal sulfide (MS) decreases excessively, the ionic conductivity of the positive electrode active material decreases, and the internal resistance may increase.

[0081] The content ratio of the sulfide-based material (SM) and the first metal sulfide (MS) may be 10:1 to 1:1, 5:1 to 1:1, or 4:1 to 2:1 by weight. By satisfying the content ratio of the sulfide-based material (SM) and the first metal sulfide (MS) within the above range, the ionic conductivity of the positive electrode active material can be improved, and the specific capacity of the positive electrode active material can be improved, thereby improving the energy density of the secondary battery.

[0082] A composite of a sulfide-based material (SM) and a first metal sulfide (MS) may include, for example, a solid solution of the sulfide-based material (SM) and the first metal sulfide (MS). By including a solid solution of the sulfide-based material (SM) and the first metal sulfide (MS) in the composite of the sulfide-based material (SM) and the first metal sulfide (MS), the electronic conductivity of the composite of the sulfide-based material (SM) and the first metal sulfide (MS) may be increased. For example, the electronic conductivity of the solid solution may be enhanced compared to the electronic conductivity of the sulfide-based material (SM) by the metal sulfide disposed within the crystallites of the sulfide-based material (SM). Consequently, the electronic conductivity of the composite of the sulfide-based material (SM) and the first metal sulfide (MS) is enhanced, and the internal resistance of the composite of the sulfide-based material (SM) and the first metal sulfide (MS) may be reduced.

[0083] A composite according to another embodiment may further include a metal halide salt. The metal halide salt may include an alkali metal salt and a boron group metal salt. A composite according to one embodiment may be a composite of a sulfide-based material (SM), a metal halide salt, and a first metal sulfide (MS). The ionic conductivity may be further enhanced by the composite including such a metal halide salt. A composite of a sulfide-based material (SM), a metal halide salt, and a first metal sulfide (MS) may include, for example, a solid solution of the sulfide-based material (SM), the metal halide salt, and the first metal sulfide (MS). According to one embodiment, the weight ratio of the metal halide salt to the first metal sulfide (MS) may be 1:0.2 to 1:30, 1:0.5 to 1:20, 1:1 to 1:10, 1:1 to 1:5, 1:1 to 1:3, or 1:1 to 1:2.

[0084] A composite according to another embodiment may further include a carbon-based conductive material. The carbon-based conductive material may include carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, or a combination thereof. A composite according to one embodiment may be a composite of a sulfide-based material (SM), a carbon-based conductive material, and a first metal sulfide (MS). The electron conductivity may be further enhanced by the composite including such a carbon-based conductive material. A composite of a sulfide-based material (SM), a carbon-based conductive material, and a first metal sulfide (MS) may include, for example, a solid solution of a sulfide-based material (SM), a carbon-based conductive material, and a first metal sulfide (MS). A weight ratio of the carbon-based conductive material and the first metal sulfide (MS) according to one embodiment may be 10:1 to 1:10, 5:1 to 1:5, 4:1 to 1:4, or 2:1 to 1:2.

[0085] A composite according to another embodiment may be a composite of a sulfide-based material (SM), a carbon-based conductive material, a metal halide salt, and a first metal sulfide (MS). The composite of the sulfide-based material (SM), the carbon-based conductive material, the metal halide salt, and the first metal sulfide (MS) may include, for example, a solid solution of the sulfide-based material (SM), the carbon-based conductive material, the metal halide salt, and the first metal sulfide (MS).

[0086] A composite according to another embodiment may further include a second metal sulfide. The second metal sulfide is LiTiS x (0 < x ≤ 2, x is an integer), LiV2S x (0 < x ≤ 5, x is an integer), LiCrS x (0 < x ≤ 3, x is an integer), LiZrS x (0 < x ≤ 2, x is an integer), LiNb2S x (0 < x ≤ 2, x is an integer), LiMoS x (0 < x ≤ 3, x is an integer), LiHfS x (0 < x ≤ 2, x is an integer) LiTa2S x (0 < x ≤ 5, x is an integer), LiWS x It may include (0 < x ≤ 2, x is an integer) or a combination thereof.

[0087] cathode (200)

[0088] A negative electrode (200) according to one embodiment may include a negative electrode current collector (210). In a negative electrode (200) according to one embodiment, lithium metal and / or a lithium alloy may be deposited on the negative electrode current collector (210) by charging. In this case, the lithium metal and / or lithium alloy may act as a lithium reservoir. That is, a secondary battery according to one embodiment may be a lithium metal battery.

[0089] The negative current collector (210) may provide a reference surface on which a lithium metal layer (230) or a negative coating layer (220) is disposed. The negative current collector (210) may include, for example, a material that does not react with lithium, that is, does not form any alloys or 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.

[0090] 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.

[0091] A secondary battery according to one embodiment may further include a negative coating layer (220) on a negative current collector (210). The negative coating layer (220) may be configured to allow lithium metal to grow between the negative current collector (210) and the negative coating layer (220) and / or within the negative coating layer (220) during charging of the secondary battery. The negative coating layer (220) may serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites. The negative coating layer (220) may include, for example, a metal-carbon composite.

[0092] The metal-carbon composite included in the cathode coating layer (220) is a cathode material capable of forming 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. By having the average particle size of the metal-carbon composite 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.

[0093] A metal-carbon composite may include, for example, metal particles and a carbonaceous material. The metal particles and the carbonaceous material may each have a particle form, for example. A metal-carbon composite may be, for example, a simple mixture of metal particles and a carbonaceous material. The metal particles within the metal-carbon composite may include at least one metal or metalloid selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). However, this is not limited thereto, and any metal or metalloid used in the art to form an alloy or compound with lithium is acceptable. The carbonaceous material within the metal-carbon composite may include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. The carbonaceous material within the metal-carbon composite may be amorphous carbon. The carbonaceous material within 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 carbonaceous material within 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 2It can be / g. The BET specific surface area of ​​porous carbon can be measured, for example, according to ISO 9277:2022.

[0094] The mixing ratio of metal particles and carbon-based material included in the cathode coating layer (220) can be, for example, 1:10 to 2:1, 1:5 to 1:1, or 1:4 to 1:2 by weight.

[0095] The metal-carbon composite may be, for example, a composite of metal particles and a carbon-based material. The carbon-based material may be, for example, a carbon-based support. The metal-carbon composite may include, for example, a carbon-based support and metal particles supported on the carbon-based support. By having such a structure, the localization of metal particles within the cathode coating layer (220) is prevented and a uniform distribution can be obtained. Consequently, the cycle characteristics of the all-solid-state battery including the cathode coating layer (220) can be further improved.

[0096] Metal particles supported on a carbon-based support may include, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metal may include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn). The metal oxide may include, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, tellurium (Te) oxide, and zinc (Zn) oxide. The metal oxide may include, for example, Au x O y (0 <x≤2, 0<y≤3), Pt x O y (0 <x≤1, 0<y≤2), Pd x O y (0 <x≤1, 0<y≤1), Si x Oy (0 <x≤1, 0<y≤2), Ag x The y (0 <x≤2, 0<y≤1), Al x The y (0 <x≤2, 0<y≤3), Bi x The y (0 <x≤2, 0<y≤3), Sn x The y (0 <x≤1, 0<y≤2), Te x The y (0 <x≤1,0<y≤3), Zn x The y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속 산화물의 복합체는 예를 들어 Au와 Au x The y (0 <x≤2, 0<y≤3)의 복합체, Pt와 Pt x The y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x The y (0 <x≤1, 0<y≤1)의 복합체, Si와 Si x The y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x The y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x The y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x The y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x The y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x The y (0 <x≤1, 0<y≤3), Zn과 Zn x The y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0097] A carbon-based support is, for example, amorphous carbon. Amorphous carbon is, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofiber (CNF), carbon nanotube (CNT), etc., but is not necessarily limited to these, and any carbon classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0098] The binder included in the cathode 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.

[0099] The cathode coating layer (220) may further include other additives in addition to the metal-carbon composite. The cathode coating layer (220) may further include at least one additive selected from the group consisting of, for example, fillers, coating agents, dispersants, and ion-conducting aids.

[0100] The cathode 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 cathode coating layer (220) may act as a reaction site where the formation of lithium metal begins within the cathode coating layer (220), act as a space where the formed lithium metal is stored, or act as a path for transporting lithium ions. The solid electrolyte may be omitted.

[0101] FIG. 4 is a cross-sectional view of a secondary battery according to an exemplary embodiment. Referring to FIG. 4, a 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 negative electrode coating layer (220). The lithium metal layer (230) may be a configuration 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 negative electrode coating layer (220) by charging.

[0102] 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 may be, 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; any alloy used as a lithium alloy in the relevant technical field may be possible. The lithium metal layer (230) may be composed of one of these alloys or lithium, or may be composed of various types of alloys. The lithium metal layer (230) may be, for example, a plated layer. The lithium metal layer (230) may be, for example, deposited between the negative electrode coating layer (220) and the negative electrode current collector (210) during the charging process of an all-solid-state battery.

[0103] 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 negative electrode coating layer (220) before assembly of the all-solid-state battery. When the lithium metal layer (230) is placed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the all-solid-state 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 negative electrode coating layer (220) before assembly of the all-solid-state battery.

[0104] When a lithium metal layer (230) is precipitated by charging after assembly of the all-solid-state battery, the energy density of the all-solid-state battery can be increased because the lithium metal layer (230) is not included during assembly of the all-solid-state battery. When charging the all-solid-state battery, it can be charged beyond the charging capacity of the negative electrode coating layer (220). That is, the negative electrode coating layer (220) can be overcharged. At the beginning of charging, lithium can be absorbed in the negative electrode coating layer (220). If charging is performed beyond the capacity of the negative electrode 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.

[0105] 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 solid-state battery. In addition, since the negative electrode coating layer (220) covers the lithium metal layer (230), the negative electrode coating layer (220) can protect the lithium metal layer (230) and simultaneously suppress the precipitation growth of lithium dendrites. Therefore, the negative electrode coating layer (220) can suppress short circuits and capacity degradation of the solid-state battery and improve the cycle characteristics of the solid-state battery.

[0106] When a lithium metal layer (230) is formed by charging after assembly of the all-solid-state battery, the negative electrode, i.e., the negative electrode current collector (210) and the negative electrode 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 all-solid-state battery.

[0107] electrolyte layer (300)

[0108] Referring to FIG. 1, the electrolyte layer (300) may include an electrolyte disposed between the anode (100) and the cathode (200). The electrolyte may include, for example, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0109] Solid electrolytes may include, for example, sulfide-based solid electrolytes, oxide-based solid electrolytes, polymeric solid electrolytes, or combinations thereof.

[0110] Since the above description can be applied as is to the solid electrolyte containing the positive active material layer (120) for the sulfide-based solid electrolyte, the description of the overlapping parts will be omitted.

[0111] 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 Aly 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.

[0112] 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.

[0113] 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 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.

[0114] Gel electrolytes are, for example, polymeric gel electrolytes. Gel electrolytes can have a gel state without, for example, containing polymers.

[0115] 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.

[0116] The electrolyte layer (300) may include, for example, a binder. The binder included in the 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 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 coating layer (220). The binder may be omitted.

[0117] The binder content included in the electrolyte layer (300) is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% based on the total weight of the electrolyte layer (300).

[0118] [Method for manufacturing positive electrode active material]

[0119] To manufacture a positive electrode active material, a composition for forming a sulfide-based material, a carbon-based conductive material, and a metal sulfide precursor are mixed. For example, the metal sulfide precursor may include one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

[0120] The composition for forming sulfide-based materials is S8, Li2S n It may include (1 ≤ n ≤ 8, where n is an integer) or a combination thereof. For example, the composition for forming a sulfide-based material may include Li2S. The composition for forming a sulfide-based material according to one embodiment may further include a metal halide salt. The metal halide salt may include an alkali metal salt and a boron group metal salt. For example, the alkali metal salt may include LiF, LiCl, LiBr, LiI, or a combination thereof, and the boron group metal salt may include AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TlF3, TlCl3, TlBr3, TlI3, or a combination thereof. The composition for forming a sulfide-based material according to one embodiment may include a Li2S-LiI-AlI3 complex.

[0121] Since the details regarding carbon-based conductive materials described above can be applied directly to carbon-based conductive materials, a detailed explanation will be omitted.

[0122] The metal sulfide precursor may include one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W. For example, the metal sulfide precursor may include the form of a salt containing one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W. A metal sulfide precursor according to one embodiment is (NH4)2MoS4, (NH4)6Mo7O 24· 4H2O,MoCl n , TiCl n , ZrCl n or may include a combination thereof (1 ≤ n ≤ 10, n is an integer).

[0123] A method for manufacturing a positive electrode active material according to one form of the present disclosure may include: mechanically milling a sulfide-based material forming composition to form a first-1 composition; dry-mix coating or wet-mix coating of the first-1 composition and the metal sulfide precursor to form a first-2 composition; and injecting a carbon-based conductive material into the first-2 composition and mechanically milling it.

[0124] The composition of 1-1 may have the form of a composite of a sulfur-based material. The detailed description of the sulfur-based material may be applied as described above.

[0125] The 1-1 composition can be formed by mechanically milling a composition for forming a sulfide-based material. For example, the 1-1 composition can be formed by first ball milling a composition for forming a sulfide-based material. According to one embodiment, the first ball milling can be performed for 1 to 20 hours at 100 to 1000 rpm. For example, the first ball milling can be performed at 200 to 800 rpm, 300 to 700 rpm, or 400 to 600 rpm. For example, the first ball milling can be performed for 1 to 16 hours, 2 to 12 hours, or 3 to 10 hours.

[0126] The 1-2 composition may have a form comprising a coating layer covering the entire surface or a part of the surface of the 1-1 composition. The coating layer may include a metal sulfide. The detailed description of the coating layer and the metal sulfide may be applied as described above.

[0127] The first-2 composition can be formed by dry mixing coating or wet mixing coating of a metal sulfide precursor onto the first-1 composition. The first-2 composition according to one embodiment can be formed by wet mixing coating of a metal sulfide precursor onto the first-1 composition. The wet mixing coating may be applied using a general method for forming a coating layer on an anode active material, but is not necessarily limited thereto. For example, the wet mixing coating may be applied using a coating method selected from dip coating, spray coating, or slot die coating.

[0128] A positive electrode active material according to one embodiment can be manufactured by injecting a carbon-based conductive material into the first-2 composition and mechanically milling it. For example, a positive electrode active material can be manufactured by secondary ball milling of the first-2 composition. According to one embodiment, the secondary ball milling can be performed at 100 to 1000 rpm for 1 to 20 hours. For example, the secondary ball milling can be performed at 200 to 800 rpm, 300 to 700 rpm, or 400 to 600 rpm. For example, the secondary ball milling can be performed for 1 to 16 hours, 2 to 12 hours, or 3 to 10 hours.

[0129] The positive active material produced by this manufacturing method includes a coating layer covering the entire surface or a part of the surface of a composite of a sulfur-based material and a carbon-based conductive material, and the coating layer may include a metal sulfide.

[0130] A method for manufacturing another type of positive electrode active material according to the present disclosure may include forming a 2-1 composition by mechanically milling a sulfide-based material forming composition and a metal sulfide precursor; and injecting a carbon-based conductive material into the 2-1 composition and mechanically milling it.

[0131] The composition of 2-1 may have a composite form of a sulfur-based material and a metal sulfide. The detailed description of the sulfur-based material and the metal sulfide may be applied as described above.

[0132] The composition of 2-1 can be formed by mechanically milling a composition for forming a sulfide-based material and a metal sulfide together. For example, the composition of 2-1 can be formed by first ball milling a composition for forming a sulfide-based material and a metal sulfide together. According to one embodiment, the first ball milling can be performed at 100 to 1000 rpm for 1 to 20 hours. For example, the first ball milling can be performed at 200 to 800 rpm, 300 to 700 rpm, or 400 to 600 rpm. For example, the first ball milling can be performed for 1 to 16 hours, 2 to 12 hours, or 3 to 10 hours.

[0133] A positive electrode active material according to one embodiment can be manufactured by injecting a carbon-based conductive material into the composition of 2-1 and mechanically milling it. For example, a positive electrode active material can be manufactured by secondary ball milling of the composition of 2-1. According to one embodiment, the secondary ball milling can be performed for 1 to 20 hours at 100 to 1000 rpm. For example, the secondary ball milling can be performed at 200 to 800 rpm, 300 to 700 rpm, or 400 to 600 rpm. For example, the secondary ball milling can be performed for 1 to 16 hours, 2 to 12 hours, or 3 to 10 hours.

[0134] The cathode active material produced by this manufacturing method may include a composite of a sulfur-based material and a metal sulfide.

[0135] 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.

[0136]

[0137] (Manufacturing of positive electrode active material)

[0138] Preparation Example 1: Composite of Li2S and CNF having a MoS2 coating layer

[0139] Li2S was mechanically milled using a ball mill. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G. 10 mmol of the milled Li2S was dispersed in an ethyl acetate solvent. Subsequently, 1 mmol of MoCl4 precursor was slowly added to the Li2S dispersion and mixed to ensure that a sufficient coating layer was formed on the surface of Li2S. At this time, mixing was continued until the weight ratio of Li2S to MoS2 reached 50:25. The weight ratio of Li2S to MoS2 in the formed composite can be varied by adjusting the initial molar ratio of Li2S and MoS2 and the mixing time.

[0140]

[0141] A Li2S composite with a coating layer and CNF were mixed in a weight ratio of 75:5. The mixture was mechanically milled using a ball mill to prepare a Li2S-CNF composite containing a MoS2 coating layer. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G.

[0142] A composite of Li2S containing a MoS2 coating layer and CNF was used as the positive active material.

[0143] Preparation Example 2: Composite of Li2S and CNF having a MoS2 coating layer

[0144] A positive electrode active material was prepared in the same manner as in Preparation Example 1, except that a coating layer was sufficiently formed on the surface of Li2S until the weight ratio of Li2S to MoS2 was 40:20, and the Li2S composite with the coating layer formed was mixed with CNF in a weight ratio of 60:10.

[0145] Preparation Example 3: Composite of a Li2S-LiI-AlI3 complex having a MoS2 coating layer and CNF

[0146] Li2S, LiI, and AlI3 were mixed in a weight ratio of 50:3.34:6.66, respectively. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3 composite. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G.

[0147] 10 mmol of milled Li2S-LiI-AlI3 was dispersed in an ethyl acetate solvent. Then, MoCl4 precursor was slowly added to the Li2S-LiI-AlI3 complex dispersion and mixed until the weight ratio of the Li2S-LiI-AlI3 complex to MoS2 was 60:15, and a sufficient coating layer was formed on the surface of the Li2S-LiI-AlI3 complex.

[0148] A composite with a coating layer and CNF were mixed in a weight ratio of 75:5. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3-CNF composite containing a MoS2 coating layer. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G.

[0149] A composite of a Li2S-LiI-AlI3 complex containing a MoS2 coating layer and CNF was used as the positive active material.

[0150] Preparation Example 4: Composite of a Li2S-LiI-AlI3 complex having a MoS2 coating layer and CNF

[0151] A positive electrode active material was prepared in the same manner as in Preparation Example 3, except that Li2S, LiI, and AlI3 were mixed in a weight ratio of 40:3.34:6.66, respectively, a MoS2 coating layer was formed on the surface of the Li2S-LiI-AlI3 composite until the weight ratio of Li2S to MoS2 became 40:10, and the Li2S-LiI-AlI3 composite with the formed MoS2 coating layer was mixed with CNF in a weight ratio of 60:10.

[0152] Preparation Example 5: Li2S-LiI-AlI3-MoS2 composite

[0153] Li2S, LiI, AlI3, and MoS2 were mixed in a weight ratio of 40:6.68:13.32:10, respectively. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3-MoS2 composite. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G. The Li2S-LiI-AlI3-MoS2 composite was used as the cathode active material.

[0154] Preparation Example 6: Li2S-LiI-AlI3-MoS2-CNF composite

[0155] Li2S, LiI, AlI3, and MoS2 were mixed in a weight ratio of 40:6.68:13.32:8, respectively. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3-MoS2 composite. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G.

[0156] The composite and CNF were mixed in a weight ratio of 68:2. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3-MoS2-CNF composite containing a MoS2 coating layer. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G. The Li2S-LiI-AlI3-MoS2-CNF composite was used as the cathode active material.

[0157] Preparation Example 7: Li2S-LiI-AlI3-MoS2-CNF composite

[0158] A positive electrode active material was prepared in the same manner as in Preparation Example 6, except that Li2S, LiI, AlI3, and MoS2 were mixed in a weight ratio of 40:6.68:13.32:5, respectively, and the composite and CNF were mixed in a weight ratio of 65:5.

[0159] Preparation Example 8: Li2S-LiI-AlI3-MoS2-CNF composite

[0160] A positive electrode active material was prepared in the same manner as in Preparation Example 6, except that Li2S, LiI, AlI3, and MoS2 were mixed in a weight ratio of 40:6.68:13.32:2, respectively, and the composite and CNF were mixed in a weight ratio of 62:8.

[0161] Comparative Preparation Example 1: Li2S-CNF composite

[0162] A positive electrode active material was prepared in the same manner as in Preparation Example 1, except that a MoS2 coating layer was not formed and Li2S:CNF were mixed in a weight ratio of 60:10.

[0163] Comparative Preparation Example 2: Li2S-LiI-AlI3-CNF composite

[0164] A positive electrode active material was prepared in the same manner as in Preparation Example 3, except that a MoS2 coating layer was not formed and Li2S:LiI:AlI3:CNF were mixed in a weight ratio of 50:3.34:6.66:10, respectively.

[0165] The composition of the positive electrode active material prepared in Preparation Examples 1 to 8 and Comparative Preparation Examples 1 to 2, the content (wt%) of the solid electrolyte included in the positive electrode active material layer, and the coating layer are shown in Table 1 below. For the content of the solid electrolyte included in the positive electrode active material layer and the composition ratio of the positive electrode active material, refer to 'Preparation of Positive Electrolytes' described below.

[0166] Cathode active material composition (wt% ratio) Solid electrolyte content (wt%) Coating layer Preparation Example 1 Li2S:CNF:MoS2 (coating) (50:5:25) 20 ○ Preparation Example 2 Li2S:CNF:MoS2 (coating) (40:10:20) 30 ○ Preparation Example 3 Li2S:LiI:AlI3:CNF:MoS2 (coating) (50:3.34:6.66:5:15) 20 ○ Preparation Example 4 Li2S:LiI:AlI3:CNF:MoS2 (coating) (40:3.34:6.66:10:10) 30 ○ Preparation Example 5 Li2S:LiI:AlI3:MoS2 (composite) (40:6.68:13.32:10) 30 × Preparation Example 6 Li2S:LiI:AlI3:MoS2:CNF (complex) (40:6.68:13.32:8:2) 30× Preparation Example 7 Li2S:LiI:AlI3:MoS2:CNF (complex) (40:6.68:13.32:5:5) 30× Preparation Example 8 Li2S:LiI:AlI3:MoS2:CNF (complex) (40:6.68:13.32:2:8) 30× Comparative Preparation Example 1 Li2S:CNF (60:10) 30× Comparative Preparation Example 2 Li2S:LiI:AlI3:CNF (50:3.34:6.66:10) 30×

[0167] (Manufacturing of positive and secondary batteries)

[0168] Example 1

[0169] (Anode manufacturing)

[0170] As the positive active material, the positive active material prepared in Preparation Example 1 was prepared. As the solid electrolyte, Li6PS5Cl (D50=3.0 μm, crystalline), which is an argyrodite-type crystal, was prepared. As the binder, PTFE was prepared. These materials were mixed in a weight ratio of positive active material : solid electrolyte : binder = 80 : 20 : 1.2 to prepare a positive composite. The positive composite was obtained by dry mixing using a ball mill.

[0171] An anode was manufactured 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. The thickness of the anode 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. The area of ​​the anode active material layer and the anode current collector were the same.

[0172] (Cathode manufacturing)

[0173] A SUS foil with a thickness of 10 μm was prepared as a cathode current collector. 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.

[0174] 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 a PVDF binder (Kureha # 9300) was added to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while gradually adding NMP to it. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold-roll-pressed to flatten the surface, thereby preparing a cathode having a cathode coating layer / cathode current collector structure. 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.

[0175] (Preparation of solid electrolyte layer)

[0176] A mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of a solid electrolyte (D50=3.0 (m, crystalline)) which is an argyrodite-type crystal. 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 a laminate was prepared by drying in air at a temperature of 80 °C for 10 minutes. A solid electrolyte layer was prepared by vacuum drying the prepared laminate at 80 °C for 2 hours.

[0177] (Manufacturing of all-solid-state batteries)

[0178] A solid electrolyte layer was placed on the cathode such that the cathode coating layer contacted the solid electrolyte layer, and an anode was placed on the solid electrolyte layer. The prepared laminate was subjected to plate pressing at 85 °C and a pressure of 500 MPa for 30 min. This pressing treatment sintered the solid electrolyte layer, thereby improving battery characteristics. 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.

[0179] An all-solid-state secondary battery was manufactured by placing a pressurized laminate into a pouch and vacuum sealing it. Parts of the positive and negative current collectors were extended outside the sealed battery to be used as the positive and negative terminals.

[0180] Examples 2 to 8

[0181] A positive electrode and an all-solid-state secondary battery were prepared in the same manner as in Example 1, except that the positive electrode active materials prepared in Preparation Examples 2 to 8 were each used.

[0182] Comparative Examples 1 to 2

[0183] A positive electrode and an all-solid-state secondary battery were manufactured in the same manner as in Example 1, except that the positive electrode active materials prepared in Comparative Manufacturing Examples 1 and 2 were used, respectively.

[0184]

[0185] Evaluation Example 1: Charge / Discharge Test

[0186] The charge-discharge characteristics of the all-solid-state batteries prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were evaluated by the following charge-discharge test.

[0187] The charge / discharge test was performed by placing the all-solid-state secondary battery in a constant temperature bath at 45°C.

[0188] The first cycle involved charging at a constant current of 0.1 C for 10 hours until the battery voltage reached 2.5 V to 2.8 V. Subsequently, discharging was performed at a constant current of 0.1 C for 10 hours until the battery voltage reached 0.3 V.

[0189] The value obtained by dividing the discharge capacity of the first cycle by the anode mass is shown as the specific capacity in Table 2 below. The value obtained by multiplying the discharge capacity of the first cycle by the ratio of the Li2S content in the electrode is shown as the electrode capacity in Table 2 below.

[0190] The initial efficiency was calculated by the following mathematical formula 1 and is shown in Table 2 below.

[0191] <Mathematical Formula 1>

[0192] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0193]

[0194] After the second cycle, charging and discharging were performed up to 300 cycles under the same conditions as the first cycle. The number of cycles refers to the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity (SOH 80%) after the second cycle. It was assumed that the life characteristics were superior as the number of cycles increased.

[0195]

[0196] Capacity [mAh / g Li2S ] Electrode Capacity [mAh / g] Initial Efficiency [%] Number of Cycles [@SOH 80%, cycles] Example 1 8 10 40 58 7200 Example 2 8 10 32 48 6200 Example 3 7 80 39 08 8210 Example 4 7 70 308 85185 Example 5 7 50 30 82155 Example 6 7 60 30 48 3160 Example 7 7 80 3128 3170 Example 8 7 40 29 68 2148 Comparative Example 1 2 10 126 408 Comparative Example 2 7 50 37 58 6140

[0197] It was confirmed that Examples 1 to 8 exhibited superior lifespan characteristics compared to Comparative Examples 1 and 2. This is attributed to the improved stability resulting from the metal sulfide coating a composite containing a sulfide-based material or the metal sulfide forming a composite together with a sulfide-based material.

[0198] 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. A composite of a sulfur-based material and a carbon-based conductive material; and It includes a coating layer covering the entire surface or a portion of the surface of the above-mentioned sulfide-based material; The above coating layer is an anode active material comprising a first metal sulfide.

2. In Paragraph 1, The above sulfide-based material is S8, Li2S n A positive active material comprising (1 ≤ n ≤ 8, where n is an integer) or a combination thereof.

3. In Paragraph 1, The above carbon-based conductive material is a positive active material comprising carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, graphene, or a combination thereof.

4. In Paragraph 1, The above composite is a positive active material comprising a solid solution of the sulfide-based material including the coating layer and the carbon-based conductive material.

5. In Paragraph 1, The above first metal sulfide is TiS x (0 < x ≤ 2, x is an integer), V2S x (0 < x ≤ 5, x is an integer), CrS x (0 < x ≤ 3, x is an integer), ZrS x (0 < x ≤ 2, x is an integer), Nb2S x (0 < x ≤ 2, x is an integer), MoS x (0 < x ≤ 3, x is an integer), HfS x (0 < x ≤ 2, x is an integer) Ta2S x (0 < x ≤ 5, x is an integer), WS x A positive active material comprising (0 < x ≤ 2, x is an integer) or a combination thereof.

6. In Paragraph 1, The above complex further comprises a metal halide salt; The above metal halide salt is an anode active material comprising an alkali metal salt and a boron group metal salt.

7. In Paragraph 6, The above alkali metal salt comprises LiF, LiCl, LiBr, LiI, or a combination thereof, and The above boron group metal salt comprises AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TlF3, TlCl3, TlBr3, TlI3, or a combination thereof, forming an anode active material.

8. In Paragraph 6, A positive electrode active material having a weight ratio of the metal halide salt and the first metal sulfide of 1:0.2 to 1:

30.

9. In Paragraph 1, The above coating layer further comprises a second metal sulfide; The above second metal sulfide is LiTiS x (0 < x ≤ 2, x is an integer), LiV2S x (0 < x ≤ 5, x is an integer), LiCrS x (0 < x ≤ 3, x is an integer), LiZrS x (0 < x ≤ 2, x is an integer), LiNb2S x (0 < x ≤ 2, x is an integer), LiMoS x (0 < x ≤ 3, x is an integer), LiHfS x (0 < x ≤ 2, x is an integer) LiTa2S x (0 < x ≤ 5, x is an integer), LiWS x A positive active material comprising (0 < x ≤ 2, x is an integer) or a combination thereof.

10. In Paragraph 1, A positive electrode active material having a weight ratio of the carbon-based conductive material and the first metal sulfide of 10:1 to 1:

10.

11. A composite of a sulfide-based material and a first metal sulfide, wherein; The above sulfide-based material is S8, Li2S n (1 ≤ n ≤ 8, n is an integer) or a combination thereof, The above first metal sulfide is TiS x (0 < x ≤ 2, x is an integer), V2S x (0 < x ≤ 5, x is an integer), CrS x (0 < x ≤ 3, x is an integer), ZrS x (0 < x ≤ 2, x is an integer), Nb2S x (0 < x ≤ 2, x is an integer), MoS x (0 < x ≤ 3, x is an integer), HfS x (0 < x ≤ 2, x is an integer) Ta2S x (0 < x ≤ 5, x is an integer), WS x A positive active material comprising (0 < x ≤ 2, x is an integer) or a combination thereof.

12. In Paragraph 11, The above composite is an anode active material comprising a solid solution of the above sulfide-based material and the above first metal sulfide.

13. In Paragraph 11, The above complex further comprises a metal halide salt; The above metal halide salt is an anode active material comprising an alkali metal salt and a boron group metal salt.

14. In Paragraph 13, A positive electrode active material having a weight ratio of the metal halide salt and the first metal sulfide of 1:0.2 to 1:

30.

15. In Paragraph 11, The above composite further comprises a carbon-based conductive material; The above carbon-based conductive material is a positive active material comprising carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, or a combination thereof.

16. In Paragraph 15, A positive electrode active material having a weight ratio of the carbon-based conductive material and the first metal sulfide of 10:1 to 1:

10.

17. In Paragraph 11, The above complex further comprises a second metal sulfide; The above second metal sulfide is LiTiS x (0 < x ≤ 2, x is an integer), LiV2S x (0 < x ≤ 5, x is an integer), LiCrS x (0 < x ≤ 3, x is an integer), LiZrS x (0 < x ≤ 2, x is an integer), LiNb2S x (0 < x ≤ 2, x is an integer), LiMoS x (0 < x ≤ 3, x is an integer), LiHfS x (0 < x ≤ 2, x is an integer) LiTa2S x (0 < x ≤ 5, x is an integer), LiWS x A positive active material comprising (0 < x ≤ 2, x is an integer) or a combination thereof.

18. Mixing a composition for forming a sulfide-based material, a carbon-based conductive material, and a metal sulfide precursor; A method for manufacturing an anode active material, wherein the metal sulfide precursor comprises one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

19. In Paragraph 18, The above mixture is: Forming the 1-1 composition by mechanically milling the above-mentioned sulfide-based material forming composition; Forming a 1-2 composition by dry mixing coating or wet mixing coating of the 1-1 composition and the metal sulfide precursor; and A method for manufacturing an anode active material comprising injecting the carbon-based conductive material into the above-mentioned first and second compositions and mechanically milling.

20. In Paragraph 18, The above mixture is: Forming the 2-1 composition by mechanically milling the above sulfide-based material forming composition and the above metal sulfide precursor; and A method for manufacturing an anode active material comprising injecting the carbon-based conductive material into the above 2-1 composition and mechanically milling it.

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