Solid electrolyte and all-solid-state battery comprising same

Abstract

Provided is a sulfide-based solid electrolyte having improved atmospheric stability. A solid electrolyte comprises lithium (Li), phosphorus (P), sulfur (S), and a halogen element and has an argyrodite-based crystal structure, wherein at least a portion of the crystal structure is doped with oxygen and at least one element selected from Group 13 elements, with a ratio of a peak area at 191.4 (±0.1) eV to a peak area at 189.38 (±0.1) eV in X-ray photoelectron spectroscopy (XPS) being 0.2 to 0.22.

Description

Solid electrolyte and all-solid-state battery including the same

[0001] This description relates to a solid electrolyte and an all-solid-state battery containing the same.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0191003 filed on December 19, 2024, the entire contents of said prior application are incorporated herein by reference.

[0003] With research focusing on the safety issues and energy density of high-capacity batteries, all-solid-state batteries are gaining prominence as next-generation batteries. These all-solid-state batteries significantly improve battery safety by replacing flammable liquid electrolytes, which are prone to explosions, with solid electrolytes. Solid electrolytes used in all-solid-state batteries include oxide-based, sulfide-based, and polymer-based types; among these, active research is being conducted on sulfide-based solid electrolytes, which exhibit the highest ionic conductivity.

[0004] However, sulfide-based solid electrolytes developed to date face difficulties in battery applications due to low moisture stability and redox stability.

[0005] Attempts to dope metal oxides to address this (KR2700195) are being made, but unique material properties are still required.

[0006] One embodiment aims to provide a solid electrolyte with improved moisture stability.

[0007] Another embodiment aims to provide a solid electrolyte battery comprising a solid electrolyte with improved moisture stability.

[0008] According to one embodiment, the solid electrolyte comprises lithium (Li), phosphorus (P), sulfur (S), and halogen elements, has an argyrodite-based crystal structure, at least a portion of the crystal structure is doped with one or more elements selected from group 13 elements and oxygen, and the ratio of the 191.4 (±0.1) eV peak area / 189.38 (±0.1) eV peak area in X-ray Photoelectron Spectroscopy (XPS) is 0.2 to 0.22.

[0009] According to one embodiment, the solid electrolyte has at least a portion of the azirodite-based crystal structure doped with one or more elements selected from group 13 elements and oxygen, and the moisture stability can be improved by the peak ratio of a specific eV in XPS showing a specific value.

[0010] Figure 1 is a graph of XPS analysis of the solid electrolytes prepared in Example 4 and Comparative Example 1.

[0011] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0012] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0013] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0014] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0015] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0016] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0017] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0018] A solid electrolyte according to one embodiment provides a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and halogen elements, having an argyrodite-based crystal structure, wherein at least a portion of the crystal structure is doped with one or more elements selected from group 13 elements and oxygen (O).

[0019] "Doping" can mean not only the substitution of some elements of a compound with new elements, but also that the doped element becomes a component of the compound's crystal phase.

[0020] A sulfide-based solid electrolyte according to one embodiment has an argyrodite-based crystal structure. The argyrodite-based crystal structure has the advantage of high ionic conductivity.

[0021] However, while these azirodite crystal structures possess high ionic conductivity, their conductivity deteriorates due to adverse reactions with moisture when exposed to the atmosphere. Consequently, various approaches, such as metal oxides and halogen compounds, have been attempted to improve moisture stability; however, these methods have faced the problem of significantly degrading ionic conductivity while simultaneously improving moisture stability, leading to a deterioration in cell performance, including capacity and lifespan characteristics of lithium-ion batteries.

[0022] Accordingly, the inventors of the present invention, through repeated research, discovered that atmospheric stability (or moisture stability) is improved by doping at least a portion of the azirodite-based crystal structure with one or more elements selected from Group 13 elements and oxygen, thereby completing the present invention. Group 13 elements are trivalent elements that can increase the concentration of mobile lithium within the crystal structure, and as the oxygen element replaces sulfur, PS has a tighter bond compared to the central element PS4. 4-x O x By forming a tetrahedron, the bonding strength can be maintained better upon exposure to moisture, thereby enabling efficient moisture stability.

[0023] In particular, it can be confirmed that atmospheric stability is further improved when group 13 elements are included and the ratio of the peak area at 191.4 (±0.1) eV to the peak area at 189.38 (±0.1) eV in XPS (X-ray Photoelectron Spectroscopy) is 0.2 to 0.22.

[0024] A sulfide-based solid electrolyte exhibiting such an area ratio can be represented by the following chemical formula 1.

[0025] [Chemical Formula 1]

[0026] Li 7a-ax P a M 2c S 6a-ax O 3c D ax

[0027] In the above chemical formula 1,

[0028] D is F, Cl, Br, I, or a combination thereof, and

[0029] M is B, Al, Ga, In, Ti, or a combination thereof, and

[0030]

[0031] *290.65≤a≤1.2 and,

[0032] 0.8≤x≤2 and,

[0033] 0.026≤c≤0.28.

[0034] M can be most effective with B, which has a small element size.

[0035] If the doping amount is low, the effect on atmospheric stability may be negligible. If the doping amount of a Group 13 element is above a certain value, the doping effect, i.e., the improvement in atmospheric stability, can be maintained. On the other hand, if the doping amount is too high, the basic azirodite crystal structure is significantly deformed, so the doping effect is not realized, and there may be a significant deterioration in the solid electrolyte ionic conductivity or the electrochemical properties of the battery. Therefore, it may be more desirable for the range of c to be 0.135 ≤ c ≤ 0.28.

[0036] Meanwhile, the sulfide-based solid electrolyte according to the present invention may further dope at least a portion of the crystal structure with silicon (Si). As the solid electrolyte is further doped with silicon, the doping effect, such as atmospheric stability, can be further enhanced, and in particular, the lifespan characteristics of the battery can be further improved.

[0037] At this time, silicon can be additionally and independently doped in addition to one or more elements selected from Group 13 elements. At this time, the doping amounts of one or more elements selected from Group 13 elements and silicon do not have a constant correlation but can be randomly adjusted independently of each other. Accordingly, by appropriately adjusting the doping amounts of one or more elements selected from Group 13 elements and silicon independently of each other, the moisture stability effect can be maximized.

[0038] D can be chlorine (Cl). The use of chlorine, in particular among halogen elements, may have the effect of stabilizing the structure of the azirodite-based solid electrolyte, as well as the advantages of being easier to synthesize and cheaper than other elements.

[0039] The above-mentioned sulfide-based solid electrolyte may be in the form of particles or powder, and may be crystalline or amorphous.

[0040] Another embodiment of the present invention provides a method for manufacturing a sulfide-based solid electrolyte comprising the steps of: mixing a lithium-containing sulfide, a phosphorus-containing compound, a halogen raw material, and a doping raw material to form a mixture; and heat-treating the mixture to form a sulfide-based solid electrolyte, wherein the doping raw material comprises a compound containing one or more elements selected from Group 13 elements and a silicon-based compound.

[0041] Hereinafter, a method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention will be described in detail step by step.

[0042] First, a lithium-containing sulfide, a phosphorus-containing compound, a halogen raw material, and a doping raw material are mixed to form a mixture.

[0043] The lithium-containing sulfide may be, for example, one or more of Li2S and Li2S2, but is not limited thereto. More specifically, the lithium-containing sulfide may be Li2S.

[0044] The phosphorus-containing compound may be, for example, one or more of P2S5 and P2O5, but is not limited thereto. More specifically, the phosphorus-containing compound may be P2S5.

[0045] The halogen raw material may be, for example, one or more of LiF, LiCl, LiBr, and LiI, but is not limited thereto.

[0046] The doping raw material includes compounds containing one or more elements selected from Group 13 elements and silicon-based compounds.

[0047] Compounds containing one or more elements selected from Group 13 elements are not particularly limited, but may be, for example, one or more of B2O3, H3BO3, BN, BF3, B4C, BCl3, B2S5, Al2O3, Al2(SO4)3, Al(NO3)3, Al2(SO3)3, AlCl3, Al(OH)3, Ga2O3, In2O3, and TiO2.

[0048] The silicon-based compounds to be additionally mixed are not particularly limited, but may be, for example, one or more of SiO2, SiBr4, SiCl4, Si3N4, SiO, SiC, SiAl CaSiO3, Si2H6, Na2SiO3, TiSiO4, SiCl4, and SiS2.

[0049] The mixing ratio is mixed to be within the range of Chemical Formula 1 above. Preferably, the range of c may be 0.135 ≤ c ≤ 0.28.

[0050] Next, optionally as needed, after the step of forming the mixture, the method may further include a step of compressing the mixture to form pellets.

[0051] At this time, compression can be performed at a pressure of 100 to 500 MPa, specifically 150 to 450 MPa, and more specifically 200 to 400 MPa. If the pressure is too low, a problem may arise where interfacial resistance increases due to insufficient binding between powder particles. On the other hand, if the pressure is too high, the binding between powder particles is already established, so the binding state does not change even if additional pressure is applied, which may cause problems in terms of process efficiency. Therefore, forming pellets at an appropriate pressure is desirable in terms of productivity.

[0052] Next, the mixture is heat-treated to form a sulfide-based solid electrolyte. Of course, if a step of forming pellets is additionally included, the pellets are heat-treated to form a sulfide-based solid electrolyte.

[0053] Heat treatment can be performed at 300 to 800°C, specifically at 400 to 700°C, and more specifically at 500 to 600°C. If the heat treatment temperature is too low, a problem may occur where the heat treatment effect is negligible, and if the heat treatment temperature is too high, a problem may occur where the elements constituting the solid electrolyte vaporize and the solid electrolyte is lost.

[0054] Heat treatment can be performed in an inert gas atmosphere. More specifically, it can be performed in an argon (Ar) atmosphere.

[0055] Another embodiment of the present invention provides an electrochemical cell comprising an anode; a cathode; and a solid electrolyte layer located between the anode and the cathode, wherein at least one of the anode, the cathode, and the solid electrolyte layer comprises the aforementioned solid electrolyte.

[0056] The electrochemical cell is not particularly limited, but it may be, for example, a lithium secondary battery.

[0057] Since the solid electrolyte is as described above, the remaining components will be explained in detail below.

[0058] The positive electrode may include a current collector and a positive electrode active material layer disposed on the current collector, and the positive electrode active material layer may include a positive electrode active material.

[0059] As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used, and specific examples thereof may include compounds represented by any one of the following chemical formulas:

[0060] Li a A 1-b B bD2(wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α T α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B c O 2-α T2(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α T α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Lia Ni 1-b-c Mn b B c O 2-α T2(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2(wherein the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); and LiFePO4.

[0061] In the chemical formula, A is Ni, Co, Mn or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; T is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; I is Cr, V, Fe, Sc, Y or a combination thereof; and J may be V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0062] Of course, compounds having a coating layer on their surface, or compounds having a coating layer mixed with the compound can also be used.

[0063] The coating layer may include at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compounds forming these coating layers may be amorphous or crystalline. As coating elements included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof may be used. For the coating layer formation process, any coating method may be used as long as the compound can be coated using these elements in a way that does not adversely affect the physical properties of the cathode active material (e.g., spray coating, immersion method, etc.). Since this is a matter that is well understood by those skilled in the art, a detailed explanation will be omitted.

[0064] The positive active material layer may further include a conductive material and / or a binder together with the aforementioned positive active material.

[0065] The 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 include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto.

[0066] A conductive material is used to impart conductivity to an electrode, and in a battery being constructed, any electronically conductive material that does not cause chemical changes can be used. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fibers; metal-based materials such as metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive polymer materials such as polyphenylene derivatives; or conductive materials comprising a mixture thereof.

[0067] Aluminum can be used as a current collector, but is not limited to it.

[0068] The cathode comprises a current collector and a cathode active material layer disposed on the current collector, and the cathode active material layer comprises a cathode active material.

[0069] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0070] As a material capable of reversibly intercalating / deintercalating lithium ions, any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries can be used, and representative examples include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0071] As an alloy of lithium metal, an alloy of a metal selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0072] Materials capable of doping and dedoping lithium include Si, SiOx (0 < x < 2), Si-Y alloy (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and at least one of these may also be used in combination with SiO2. The above element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0073] Examples of transition metal oxides include vanadium oxide and lithium vanadium oxide.

[0074] The negative active material layer also includes a binder and may optionally further include a conductive material.

[0075] The binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. Representative examples include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto.

[0076] A conductive material is used to impart conductivity to an electrode, and in a battery being constructed, any electronically conductive material that does not cause chemical changes can be used. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fibers; metal-based materials such as metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive polymer materials such as polyphenylene derivatives; or conductive materials comprising a mixture thereof.

[0077] As a current collector, a material selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof may be used.

[0078] The cathode and anode are manufactured by preparing an active material composition by mixing an active material, a conductive material, and a binder in a solvent, and applying this composition to a current collector. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof is omitted in this specification. The solvent may include N-methylpyrrolidone, but is not limited thereto.

[0079] Another embodiment of the present invention provides an electric vehicle comprising the aforementioned electrochemical cell.

[0080] The embodiments of the present invention will be described in more detail below through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited by the following examples.

[0081] Example 1: Li 6.0 P 1.0 B 0.05 S 5.0 O 0.075 Cl 1.0 Solid Electrolyte Manufacturing

[0082] (1) Preparation of solid electrolyte

[0083] After quantifying the reactants Li2S, P2S5, LiCl, and B2O3, a mixture was formed by mixing them at 300 rpm for about 8 hours using a planetary mill. At this time, the mixing ratio was set so that the molar ratio of Li2PS5Cl to B2O3 was 99:1.

[0084] Next, a pressure of 300 MPa was applied to the mixture to form pellets.

[0085] Next, the pellets are heat-treated at 550°C in an argon (Ar) atmosphere to Li 6.0 P 1.0 B 0.05 S 5.0 O 0.075 Cl 1.0 A solid electrolyte was manufactured.

[0086] (2) Lithium secondary battery manufacturing

[0087] The manufactured solid electrolyte is used as the electrolyte, and Li is used as the positive electrode active material. 6.0 P 1.0 B 0.05 S 5.0 O 0.075 Cl 1.0 A lithium secondary battery was manufactured using an In-Li alloy as the negative electrode active material.

[0088] Example 2: Li 6.0 P 1.0 B 0.16 S 5.0 O 0.24 Cl 1.0 Solid Electrolyte Manufacturing

[0089] Except for adjusting the mixing ratio so that the molar ratio of Li2PS5Cl to B2O3 is 97:3, the procedure was carried out in the same manner as Example 1, and Li 6.0 P 1.0 B 0.16 S 5.0 O 0.24 Cl 1.0 A solid electrolyte and a lithium secondary battery were manufactured.

[0090] Example 3: Li 6.0 P 1.0 B 0.27 S 5.0 O 0.405 Cl 1.0 Solid Electrolyte Manufacturing

[0091] Except for adjusting the mixing ratio so that the molar ratio of Li2PS5Cl to B2O3 is 95:5, the procedure was carried out in the same manner as Example 1, and Li 6.0 P 1.0 B 0.27 O 0.405 Cl 1.0 A solid electrolyte and a lithium secondary battery were manufactured.

[0092] Example 4: Li 6.0 P 1.0 B 0.57 S 5.0 O 0.855 Cl 1.0 Solid Electrolyte Manufacturing

[0093] Except for adjusting the mixing ratio so that the molar ratio of Li2PS5Cl to B2O3 is 90:10, the procedure was carried out in the same manner as Example 1, and Li 6.0 P 1.0 B 0.57 S 5.0 O 0.855 Cl 1.0 A solid electrolyte and a lithium secondary battery were manufactured.

[0094] Example 5: Li 6.0 P 1.0 B 1.3 S 5.0 O 1.95 Cl 1.0 Solid Electrolyte Manufacturing

[0095] Except for adjusting the mixing ratio so that the molar ratio of Li2PS5Cl to B2O3 is 80:20, the procedure was carried out in the same manner as Example 1, and Li 6.0 P 1.0 B 1.3 S 5.0 O 1.95 Cl 1.0 A solid electrolyte and a lithium secondary battery were manufactured.

[0096] Comparative Example 1: Li 6.0 P 1.0 S 5.0 Cl 1.0

[0097] Solid Electrolyte Manufacturing

[0098] Li2S, P2S5, and LiCl were mixed using a planetary mill at 300 rpm for about 8 hours to form a mixture. Next, a pressure of 300 MPa was applied to the mixture to form pellets. Next, the pellets were heat-treated at 550°C in an argon (Ar) atmosphere to produce a Li6PS5Cl solid electrolyte.

[0099] (2) Lithium secondary battery manufacturing

[0100] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the solid electrolyte manufactured above was used.

[0101] Experimental Example 1: XPS Analysis

[0102] X-ray Photoelectron Spectroscopy (XPS) analysis was performed on the solid electrolyte prepared in Example 4 and the solid electrolyte prepared in Comparative Example 1. Peaks appearing at 191.43 eV and 189.38 eV were measured. The results are disclosed in Table 1 below.

[0103] Classification 191.43 eV / 189.38 eV Peak Area Ratio Example 10.2 Example 20.21 Example 30.21 Example 40.22 Example 50.23 Comparative Example 0

[0104] Figure 1 is a graph showing the XPS analysis results of Example 4 and Comparative Example 1. In the undoped case (Comparative Example 1), the peak at 191.43 eV / 189.38 eV was not detected, so the peak area ratio was 0, whereas it can be confirmed that the peak area ratio at 191.43 eV / 189.38 eV is 0.22. Experimental Example 2: Evaluation of Solid Electrolyte Ionic Conductivity and Atmospheric Stability

[0105] Experiments evaluating the ionic conductivity and atmospheric stability of solid electrolytes prepared according to Examples 1 to 5 and Comparative Example 1 were conducted, and the results are shown in Table 2 below. The specific experimental methods are as follows.

[0106] (1) Evaluation of ion conductivity before atmospheric exposure

[0107] After grinding the manufactured solid electrolyte, it was formed into pellets under a pressure of 300 MPa. Then, a cell was fabricated using SUS as the working electrode under a pressure of 70 MPa. After that, the impedance was measured by applying a voltage of 10 mV at 25°C.

[0108] (2) Atmospheric stability assessment

[0109] 1) Evaluation of ion conductivity after atmospheric exposure

[0110] In a dry room with a dew point of about -40℃, 2g of powdered solid electrolyte was left for about 12 hours, then recovered and its impedance was measured.

[0111] 2) Atmospheric stability assessment

[0112] Atmospheric stability was evaluated by converting the ion conductivity after atmospheric exposure relative to the ion conductivity before atmospheric exposure derived above into a percentage (%).

[0113] Classification Atmospheric Stability (%) Example 172 Example 279 Example 384 Example 486 Example 569 Comparative Example 166

[0114] Referring to Table 2, it was confirmed that the solid electrolytes of Examples 1 to 5 generally exhibited superior atmospheric stability compared to the solid electrolyte of Comparative Example 1. Among them, Examples 1 to 4 demonstrated superior atmospheric stability (%) of 70 or higher. Furthermore, Examples 3 and 4 demonstrated even greater superior atmospheric stability (%) of 80 or higher. Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings; such modifications are also naturally included within the scope of the present invention.

[0115] Therefore, the substantive scope of the present invention shall be defined by the appended claims and their equivalents.

[0116] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

1. Contains lithium (Li), phosphorus (P), sulfur (S), and halogen elements, It has an argyrodite crystal structure, At least a portion of the above crystal structure is doped with one or more elements selected from group 13 elements and oxygen (O), and Sulfide-based solid electrolyte with a 191.4 (±0.1) eV peak area / 189.38 (±0.1) eV peak area ratio of 0.2 to 0.22 in XPS (X-ray Photoelectron Spectroscopy).

2. In Paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte represented by the following chemical formula 1. [Chemical Formula 1] Li 7a-ax P a M 2c S 6a-ax Oh 3c D ax In the above chemical formula 1, D is F, Cl, Br, I, or a combination thereof, and M is B, Al, Ga, In, Ti, or a combination thereof, and 0.65≤a≤1.2 and, 0.8≤x≤2 and, 0.026≤c≤0.

28.

3. In Paragraph 2, A sulfide-based solid electrolyte in which c in Chemical Formula 1 above is 0.135≤c≤0.

28.

4. In Paragraph 1, The above Group 13 element is a sulfide-based solid electrolyte in which boron is the element.

5. Anode; cathode; and An all-solid-state battery comprising a solid electrolyte layer according to any one of claims 1 to 4, located between the anode and the cathode.

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