Solid electrolyte and all-solid-state battery including same

Abstract

The present disclosure relates to a solid electrolyte which is a composite including a first glass ceramic compound and a second glass ceramic compound.

Description

Technical Field

[0001] This disclosure relates to a solid electrolyte and an all-solid-state battery including the solid electrolyte. Background Technology

[0002] Currently, commercially available lithium-ion batteries are manufactured using liquid electrolytes, which pose a high risk of explosion and fire, especially when the battery is damaged due to external impact.

[0003] Therefore, all-solid-state batteries based on solid electrolytes are being actively developed to improve battery stability, and they are attracting significant attention as the next generation of batteries. In particular, all-solid-state batteries hold enormous potential in the electric vehicle (EV) and energy storage system (ESS) markets, where battery safety is directly linked to property and personal injury, and related research is actively underway. In addition to medium and large-sized batteries for EVs and ESS, small all-solid-state batteries are also under development and are expected to begin mass production in the near future.

[0004] Due to the characteristics of membrane-free all-solid-state batteries, the development of solid electrolytes with high ionic conductivity and low electronic conductivity is crucial. Furthermore, to improve the efficiency of all-solid-state battery manufacturing processes, it is essential to be able to dry, plasticize, and sinter at low temperatures. Among currently promising solid electrolyte candidates, lithium lanthanum zirconium oxide with a garnet structure has shown high ionic conductivity and is suitable for use as an electrolyte in all-solid-state batteries. However, the high sintering temperature exceeding 1000°C offers extremely limited improvement in the density between the solid electrolyte layer and the electrode active material particles. Summary of the Invention

[0005] Technical issues This disclosure aims to provide a solid electrolyte with excellent ionic conductivity and low firing temperature, as well as an all-solid-state battery including the solid electrolyte.

[0006] Solution to the problem Embodiments of this disclosure provide a solid electrolyte, which is a composite comprising a first glass-ceramic compound and a second glass-ceramic compound.

[0007] The first glass-ceramic compound may be a Na superionic conductor (NASICON) structure compound or a garnet structure compound.

[0008] The Na superionic conductor compound can be represented by the following chemical formula 1: [Chemical Formula 1] Li a1 M1 b1 Alc1 (PO4) d1 In chemical formula 1, M1 is a dopant element, and M1 is Ti, Ga or a combination thereof, 1≤a1≤1.5, 0.1≤b1≤2.5, 0≤c1≤1.5, and 3.5≤d1≤4.5.

[0009] The garnet-structured compound can be represented by the following chemical formula 2: [Chemical Formula 2] Li a2 La b2 Zr c2 M2 d2 O e2 In chemical formula 2, M2 is a dopant element, and M2 is Ga, Al, Rb, Ti or a combination thereof, 5.5≤a2≤7.5, 2.5≤b2≤3.5, 1.5≤c2≤2.5, 0≤d2≤1, 11.5≤e2≤12.5.

[0010] The second glass-ceramic compound includes Li, B, O and halogens, and may also include at least one of Ga, Zn, Mg, Al, Ge, Si, Ti, P and Bi.

[0011] The second glass-ceramic compound can be represented by the following chemical formula 3.

[0012] [Chemical Formula 3] Li a3 B b3 O c3 D d3 M3 e3 In chemical formula 3, D is a halogen element, and D is F, Cl, Br, I or a combination thereof, M3 is Ga, Zn, Mg, Al, Ge, Si, Ti, P, Bi or a combination thereof, 3≤a3≤4, 3.5≤b3≤5.5, 11.5≤c3≤12.5, 0≤d3≤1, 1.5≤e3≤3.5.

[0013] Based on the total volume of the solid electrolyte, the volume percentage of the first glass-ceramic compound can be greater than or equal to 51%.

[0014] Based on the total volume of the solid electrolyte, the volume percentage of the second glass-ceramic compound may be less than or equal to 49%.

[0015] The lithium-ion conductivity of the first glass-ceramic compound may be greater than that of the second glass-ceramic compound.

[0016] The electronic conductivity of the second glass-ceramic compound may be less than that of the first glass-ceramic compound.

[0017] The first glass-ceramic compound has a lithium-ion conductivity at 25°C greater than or equal to 1.0 × 10⁻⁶. -5 S / cm.

[0018] The lithium-ion conductivity of the second glass-ceramic compound at 25°C can be less than or equal to 1.0 × 10⁻⁶. -5 S / cm.

[0019] The electronic conductivity of the first glass-ceramic compound at 25°C can be greater than or equal to 2.0 × 10⁻⁶. -10 S / cm.

[0020] The electronic conductivity of the second glass-ceramic compound at 25°C can be less than or equal to 2.0 × 10⁻⁶. -10 S / cm.

[0021] Another embodiment of this disclosure provides an all-solid-state battery, the all-solid-state battery including a positive electrode layer, a negative electrode layer and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer includes the aforementioned solid electrolyte.

[0022] The positive electrode layer may include a current collector and a positive electrode active material layer located on the current collector, and the negative electrode layer may include a current collector and a negative electrode active material layer located on the current collector, and the positive electrode active material layer or the negative electrode active material layer may include the aforementioned solid electrolyte.

[0023] Beneficial effects of the invention The solid electrolyte according to embodiments of this disclosure is a composite of two different glass-ceramic compounds, thereby exhibiting excellent ionic conductivity and reducing the sintering temperature during the fabrication of all-solid-state batteries. Therefore, the manufacturing process cost of all-solid-state batteries can be reduced, and the density between the solid electrolyte layer and the electrode active material particles can be improved. Attached Figure Description

[0024] Figure 1 The image shows a SEM image of the solid electrolyte prepared according to Example 1. Detailed Implementation

[0025] The present disclosure will be described in detail below with reference to the accompanying drawings, in which embodiments of the disclosure are illustrated. The drawings and description are intended to be illustrative rather than restrictive in nature. Throughout the specification, the same reference numerals denote the same elements. The drawings are intended only to facilitate understanding of the exemplary embodiments disclosed herein, and it will be understood that the technical concepts disclosed herein are not limited to the drawings and include all variations, equivalents, or alternatives within the scope of the concepts and techniques of this disclosure. In the drawings, some components are shown enlarged, omitted, or schematically, and the dimensions of the individual components do not necessarily reflect their actual dimensions.

[0026] In addition, unless explicitly stated otherwise, the words “including” and variations such as “containing” or “having” will be understood to imply the inclusion of the stated elements but not the exclusion of any other elements.

[0027] Throughout this specification, "stack direction" refers to the direction in which the constituent elements are stacked sequentially, and can also be a "thickness direction" perpendicular to the wide surface (main surface) of the on-sheet constituent element, which corresponds to the T-axis direction. Furthermore, "side" refers to a direction extending parallel to the wide surface (main surface) from the edge of the on-sheet constituent element; this can be a "planar direction" and corresponds to the L-axis direction in the accompanying drawings.

[0028] In this specification, "solid electrolyte" refers to a material that can conduct electric current through the movement of solid lithium ions.

[0029] As used herein, "ionic conductivity" is an indicator that measures the tendency of a material to conduct ions, and it theoretically increases proportionally to the concentration, charge, and charge mobility of ions.

[0030] 1. Solid electrolytes The solid electrolyte according to embodiments of this disclosure is a composite comprising a first glass-ceramic compound and a second glass-ceramic compound.

[0031] As used herein, “glass-ceramic” means a material containing an amorphous phase and one or more crystalline phases by heating and processing an amorphous glass to precipitate a crystalline phase (i.e., partial crystallization), and having both amorphous and crystalline properties.

[0032] Additionally, as used herein, "amorphous glass" refers to glass that does not exhibit diffraction peaks indicating a crystal during X-ray diffraction analysis, i.e., it does not have a crystalline phase and is highly transparent.

[0033] At this point, the first glass-ceramic compound can be a Na superionic conductor (NASICON) structure compound or a garnet structure compound.

[0034] More specifically, compounds with the NASICON structure can be represented by the following chemical formula 1: [Chemical Formula 1] Li a1 M1 b1 Al c1 (PO4) d1 In chemical formula 1, M1 is a dopant element, and M1 is Ti, Ga or a combination thereof, and 1≤a1≤1.5, 0.1≤b1≤2.5, 0≤c1≤1.5, 3.5≤d1≤4.5.

[0035] More specifically, garnet-structured compounds can be represented by the following chemical formula 2: [Chemical Formula 2] Li a2 La b2 Zr c2 M2 d2 O e2 In chemical formula 2, M2 is a dopant element, and M2 is Ga, Al, Rb, Ti or a combination thereof, 5.5≤a2≤7.5, 2.5≤b2≤3.5, 1.5≤c2≤2.5, 0≤d2≤1, 11.5≤e2≤12.5.

[0036] In addition, the second glass-ceramic compound includes Li, B, O and halogens, and may also include at least one of Ga, Zn, Mg, Al, Ge, Si, Ti, P and Bi.

[0037] More specifically, the second glass-ceramic compound can be represented by the following chemical formula 3: [Chemical Formula 3] Li a3 B b3 O c3 D d3 M3 e3 In Equation 3, D is a halogen element, and D is F, Cl, Br, I or a combination thereof, M3 is Ga, Zn, Mg, Al, Ge, Si, Ti, P, Bi or a combination thereof, 3≤a3≤4, 3.5≤b3≤5.5, 11.5≤c3≤12.5, 0≤d3≤1, 1.5≤e3≤3.5.

[0038] Typically, when amorphous glass undergoes crystallization and transforms into glass ceramic, its ionic conductivity tends to decrease.

[0039] On the other hand, the first and second glass-ceramic compounds having the above-described compositions can exhibit high ionic conductivity because glass ceramics exhibit the characteristics of oxide crystals. Furthermore, during the sintering process, the first and second glass-ceramic compounds with the above-described compositions are amorphous before reaching the crystallization temperature, which promotes their combination with other compounds, resulting in favorable sintering behavior. Upon completion of sintering, a solid electrolyte in the form of a composite material with high ionic conductivity can be obtained.

[0040] At this point, the lithium-ion conductivity of the first glass-ceramic compound can be greater than that of the second glass-ceramic compound. Furthermore, the crystallization temperature of the first glass-ceramic compound is higher than that of the second glass-ceramic compound, therefore, the sintering temperature can be higher. In other words, according to this disclosure, the solid electrolyte is a composite of a first glass-ceramic compound with high ionic conductivity but a high sintering temperature and a second glass-ceramic compound with relatively low ionic conductivity but a low sintering temperature, thereby uniformly realizing the advantages of both the first and second glass-ceramic compounds.

[0041] In other words, the solid electrolyte according to this disclosure is a composite of a first glass-ceramic compound and a second glass-ceramic compound, thus exhibiting excellent ionic conductivity and allowing for a lower sintering temperature during the manufacture of all-solid-state batteries. Therefore, the manufacturing process cost of all-solid-state batteries can be reduced, and the density between the solid electrolyte layer and the electrode active material particles can be improved.

[0042] At this point, based on the total volume of the solid electrolyte, the volume percentage of the first glass-ceramic compound can be greater than or equal to 51%, more specifically, the volume percentage can be from 51% to 99%, or the volume percentage can be from 80% to 97%. Additionally, based on the total volume of the solid electrolyte, the volume percentage of the second glass-ceramic compound can be less than or equal to 49%, more specifically, the volume percentage can be from 1% to 49%, or the volume percentage can be from 3% to 20%. If the volume of the first glass-ceramic compound is too large, the sintering temperature of the solid electrolyte may increase, and there may be a problem of reduced ionic conductivity due to incomplete sintering. If the volume of the second glass-ceramic compound is too large, there may be a problem of reduced ionic conductivity of the solid electrolyte.

[0043] Furthermore, the electronic conductivity of the second glass-ceramic compound can be lower than that of the first glass-ceramic compound. Therefore, by reducing the electron mobility efficiency at the grain boundaries of the solid electrolyte, the following advantages can be achieved: reducing the growth of lithium dendrites generated by the binding of electrons and lithium ions within the solid electrolyte.

[0044] More specifically, the lithium-ion conductivity of the first glass-ceramic compound at 25°C can be greater than or equal to 1.0 × 10⁻⁶. -5 S / cm, and more specifically, it can be 1.0 × 10⁻⁶. -5 S / cm up to 4.0×10 -4 S / cm.

[0045] Furthermore, the lithium-ion conductivity of the second glass-ceramic compound at 25°C can be less than or equal to 1.0 × 10⁻⁶. -5 S / cm, and more specifically, it can be 1.0 × 10⁻⁶. -5 S / cm up to 1.0×10 -5 S / cm.

[0046] Furthermore, the electronic conductivity of the first glass-ceramic compound at 25°C can be greater than or equal to 2.0 × 10⁻⁶. -10 S / cm, and more specifically, it can be 2.0 × 10⁻⁶. -10 S / cm up to 5.0×10 -10 S / cm.

[0047] The electronic conductivity of the second glass-ceramic compound at 25°C can be less than or equal to 2.0 × 10⁻⁶. -10 S / cm, and more specifically, it can be 1.0 × 10⁻⁶. -10 S / cm up to 2.0×10 -10 S / cm.

[0048] 2. All-solid-state battery Another embodiment of this disclosure provides an all-solid-state battery, which includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer includes the aforementioned solid electrolyte.

[0049] More specifically, the positive electrode layer may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

[0050] For example, the positive electrode active material layer may include a positive electrode active material and a solid electrolyte. The solid electrolyte included in the positive electrode active material layer may be the same as or different from the solid electrolyte included in the solid electrolyte sheet.

[0051] The positive electrode active material is a material capable of reversibly inserting and deintercalating lithium ions. Positive electrode active materials may include, but are not limited to, lithium transition metal oxides (such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM)), lithium manganese oxide, lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, vanadium oxide, etc. Any material in the art that can be used as a positive electrode active material may be used. The positive electrode active material may be used alone or in a mixture of two or more of the above.

[0052] Lithium transition metal oxides may include, for example: Li a A 1-b B b D2 (where 0.90≤a≤1 and 0≤b≤0.5); Li a E 1-b B b O 2-c D c (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05); LiE 2-b B b O 4-c D c (Where, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Co b B c O 2-α F α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Co b B c O 2-α F2 (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mn b B c D α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Mn b B c O 2-α F α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mn b B c O 2-α F2 (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b Ec G d O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c Mn d G e O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2 (where 0.90≤a≤1, 0.001≤b≤0.1); Li a CoG b O2 (where 0.90≤a≤1, 0.001≤b≤0.1); Li a MnG b O2 (where 0.90≤a≤1, 0.001≤b≤0.1); Li a Mn2G b O4 (where 0.90≤a≤1, 0.001≤b≤0.1); compounds represented by any of the following chemical formulas: 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); LiFePO4. In these compounds, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. Compounds with surface coatings, or mixtures of the above compounds and coating compounds, can be used. For example, the coating added to the surface of such a compound may include compounds of oxides of coating elements, hydroxides of coating elements, hydroxyoxides of coating elements, oxycarbonates of coating elements, or hydroxycarbonates of coating elements. The compound constituting the coating may be amorphous or crystalline. Coating elements included in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or combinations thereof. The method of forming the coating may be a suitable method that will not adversely affect the physical properties of the positive electrode active material. Coating methods may include, for example, spraying, dipping, etc. Since specific coating methods are well understood by those skilled in the art, detailed descriptions will be omitted.

[0053] The positive electrode active material layer may include, for example, a solid electrolyte. The solid electrolyte included in the positive electrode layer may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0054] The positive electrode active material layer may include, for example, an adhesive. The adhesive may include, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not necessarily limited to these. Any material that can be used as an adhesive in the art may be used.

[0055] The positive electrode active material layer may include, for example, a conductive material. Conductive materials may include, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fibers, metal powders, etc., but are not limited thereto. Any material that can be used as a conductive material in the art can be used.

[0056] For example, in addition to the aforementioned positive electrode active material, solid electrolyte, binder and conductive material, the positive electrode active material layer may further include additives such as fillers, coating agents, dispersants, ion conductivity enhancers and so on.

[0057] Known materials commonly used in electrodes for all-solid-state secondary batteries can be used as the positive electrode active material layer, including fillers, coating agents, dispersants, ion conductivity enhancers, etc.

[0058] For example, a plate of foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof can be used as the positive electrode current collector. The thickness of the positive electrode current collector can be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0059] More specifically, the negative electrode layer may include a negative electrode current collector and a layer of negative electrode active material disposed on the negative electrode current collector.

[0060] The negative electrode active material layer may include, for example, a negative electrode active material and an adhesive.

[0061] The negative electrode active material may include, for example, carbon-based negative electrode active materials, metal / metal-like negative electrode active materials, or combinations thereof.

[0062] Carbon-based anode active materials can be amorphous carbon. Amorphous carbon can include, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, etc., but is not limited to these. Any material classified as amorphous carbon in the art can be used. Amorphous carbon is carbon with little or no crystallinity, and in this respect, it can be distinguished from crystalline carbon or graphite-based carbon.

[0063] Metal / metal-like anode active materials may include, but are not limited to, at least one selected from lithium (Li), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Any material in the art that can be used as a metal anode active material or metal-like anode active material capable of forming alloys or compounds with lithium may be used.

[0064] The adhesive included in the negative electrode active material layer may include, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto. Any material that can be used as an adhesive in the art can be used. The adhesive may be used alone or in combination with a variety of adhesives that are different from each other.

[0065] When the negative electrode active material layer includes a binder, the negative electrode active material layer can be stably positioned on the negative electrode current collector. Furthermore, although the volume and / or relative position of the negative electrode active material layer changes during charging and discharging, breakage of the negative electrode active material layer can still be suppressed.

[0066] The negative electrode active material layer may also include additives, such as fillers, coating agents, dispersants, ion conductivity enhancers, etc., used in conventional all-solid-state batteries.

[0067] The negative electrode active material layer may also include, for example, a solid electrolyte. In this case, the solid electrolyte included in the negative electrode layer may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0068] The all-solid-state battery may further include a second negative electrode active material layer disposed between the negative electrode current collector and the negative electrode active material layer during charging. The second negative electrode active material layer may be deposited between the negative electrode current collectors during charging, or it may be disposed on the negative electrode active material layer during electrode assembly. This second negative electrode active material layer may be a metal layer comprising lithium or a lithium alloy. The lithium alloy may include, for example, Li-Al alloys, Li-Sn alloys, Li-In alloys, Li-Ag alloys, Li-Au alloys, Li-Zn alloys, Li-Ge alloys, Li-Si alloys, etc., but is not limited thereto. Any material in the art that can be used as a lithium alloy may be used. The second negative electrode active material layer may utilize one of these alloys and / or a lithium composition, or it may utilize several types of alloys and / or a lithium composition.

[0069] For example, the negative electrode current collector can be formed using a material that does not react with lithium (i.e., a material that does not form an alloy or compound with lithium). The negative electrode current collector may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), etc., but is not limited to these. Any material in the art that can be used as an electrode current collector can be used. The negative electrode current collector can be formed using one of the above-mentioned metals, an alloy of two or more of the above-mentioned metals, or a coating material. For example, the negative electrode current collector can be in the form of a plate or foil.

[0070] In the following, embodiments of the present disclosure will be described in more detail by way of examples. However, the following examples are merely preferred examples of the present disclosure, and the present disclosure is not limited to the following examples.

[0071] Preparation Example 1 (First Glass-Ceramic Compound A) Ti(OC3H) as a raw material is added according to the target stoichiometric ratio. 12 4. LiNO3, Al(NO3)3 and NH4H2PO4 were mixed and then calcined at 1300°C to prepare a compound having a NASICON structure represented by LiTi2Al(PO4)3.

[0072] Preparation Example 2 (First Glass-Ceramic Compound B) Li₂CO₃, La₂O₃, and Zr(OC₂H₅)₄, as raw materials, are added and mixed according to the target stoichiometric ratio, and then calcined at 1300°C to prepare a product with Li₇La₃Zr₂O₄ composition. 12 The compound represented by the garnet structure.

[0073] Preparation Example 3 (First Glass-Ceramic Compound C) Li₂CO₃, La₂O₃, Zr(OC₂H₅)₄, and Ga₂O₃, as raw materials, are added and mixed according to the target stoichiometric ratio, and then calcined at 1300°C to prepare a product with Li₂CO₃ as the raw material. 6.4 Ga 0.2 La3Zr2O 12 Compounds representing the garnet structure.

[0074] Preparation Example 4 (First Glass-Ceramic Compound D) Li₂CO₃, La₂O₃, Zr(OC₂H₅)₄, and Al₂O₃, as raw materials, are added and mixed according to the target stoichiometric ratio, and then calcined at 1300°C to prepare a product with Li₂CO₃ as the raw material. 6.4 Al 0.2 La3Zr2O 12 Compounds representing the garnet structure.

[0075] Preparation Example 5 (Second Glass-Ceramic Compound E) Li₂CO₃, B₂O₃, Al₂O₃, Ga₂O₃, and LiCl, as raw materials, are added and mixed according to the target stoichiometric ratio, and then calcined at 1300℃ to prepare Li₄B₄Ga₃O₃. 12 Cl represents compounds.

[0076] Preparation Example 6 (Second Glass-Ceramic Compound F) After adding Li₂CO₃, B₂O₃, Al₂O₃, ZnO, and LiCl as raw materials according to the target stoichiometric ratio and mixing them, Li₄B₄Zn₃O₄ was prepared at a temperature of 1300℃. 12 Cl represents compounds.

[0077] Preparation Example 7 (Second Glass-Ceramic Compound G) After adding Li₂CO₃, B₂O₃, Al₂O₃, MgO, and LiCl as raw materials according to the target stoichiometric ratio and mixing them, Li₄B₄Mg₃O₃ was prepared at a temperature of 1300℃. 12 Cl represents compounds.

[0078] Preparation Example 8 (Second Glass-Ceramic Compound H) After adding Li₂CO₃, B₂O₃, Al₂O₃, MgO, Ga₂O₃, and LiCl as raw materials according to the target stoichiometric ratio and mixing them, Li₄B₄Mg₂GaO₃ was prepared at a temperature of 1300℃. 12 Cl represents compounds.

[0079] Preparation Example 9 (Second Glass-Ceramic Compound I) After adding Li₂CO₃, B₂O₃, Al₂O₃, and LiCl as raw materials according to the target stoichiometric ratio and mixing them, Li₄B₄Al₃O₃ was prepared at a temperature of 1300℃. 12 Cl represents compounds.

[0080] Example 1 (1) Preparation of solid electrolytes The solid electrolyte layer was prepared by mixing 51% by volume of a first glass-ceramic compound B with an average particle size (D50) of 10 μm prepared by Preparation Example 2 and 49% by volume of a second glass-ceramic compound I with an average particle size (D50) of 5 μm prepared by Preparation Example 9, and mixing total solid electrolyte compound: binder (polymethyl methacrylate): solvent (dihydroterpineol) in a weight ratio of 100:10:150 and drying the mixture, and then sintering the mixture at a sintering temperature of 500°C for 10 minutes.

[0081] (2) All-solid-state battery manufacturing All-solid-state batteries are manufactured by applying a solid electrolyte layer, a positive electrode layer with a lithium cobalt oxide positive electrode active material layer, and a negative electrode layer with a graphite negative electrode active material layer.

[0082] Examples 2 to 10 Solid electrolytes and all-solid-state batteries are manufactured in the same manner as in Example 1, except that the types of the first glass-ceramic compound and the second glass-ceramic compound that are combined to form the solid electrolyte are different, as shown in Table 2 below.

[0083] Comparative Example 1 The all-solid-state battery was manufactured in the same manner as in Example 1, except that the second glass-ceramic compound I prepared in Preparation Example 9 was used alone as the solid electrolyte.

[0084] Comparative Examples 2 to 5 The all-solid-state battery was manufactured in the same manner as in Comparative Example 1, except that the type of the second glass-ceramic compound used alone as the solid electrolyte was different, as shown in Table 2 below.

[0085] Experimental Example 1: Evaluation of the ionic and electronic conductivity of the solid electrolyte prepared in the example. The lithium-ion conductivity, electronic conductivity, and sintering temperature of each solid electrolyte prepared in Preparation Examples 1 to 9 were evaluated and are shown in Table 1 below.

[0086] (Table 1)

[0087] Experimental Example 2: Evaluation of SEM Images of Solid Electrolytes Evaluation of scanning electron microscope (SEM) images of the solid electrolyte prepared according to Example 1, and in Figure 1 As shown in the image.

[0088] Reference Figure 1 As can be seen, the composite solid electrolyte based on the mixed sintered body of Example 1 exhibits excellent sinterability, and the crystalline glass with excellent ionic conductivity is uniformly distributed. Furthermore, since these two types of combined solid electrolytes have different physical and chemical properties, they are easily distinguishable in the SEM images.

[0089] Experimental Example 3: Evaluation of Sintering Temperature of Solid Electrolyte and Capacity Characteristics of All-Solid-State Batteries The sintering temperatures of the solid electrolytes manufactured according to the example and comparative examples were evaluated, and the initial capacity characteristics of the all-solid-state batteries manufactured according to the example and comparative examples were also evaluated, as shown in Table 2 below. For the initial capacity characteristics, batteries were manufactured, aged at 25°C for 12 hours, and then subjected to charge-discharge tests at 25°C. To evaluate the initial capacity, 200 mAh / g was used as a reference capacity, and the battery was charged to 4.25V at a constant current of 0.1C, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, the battery was allowed to rest for 10 minutes, and then discharged at a constant current of 0.1C with a reference capacity of 200 mAh / g until it reached 2.5V.

[0090] (Table 2)

[0091] Referring to Table 2, in Examples 1 to 10 where the first glass-ceramic compound and the second glass-ceramic compound are combined, it can be seen that the initial charge capacity and initial discharge capacity are improved compared to Comparative Example 1, which uses only the second glass-ceramic compound. Therefore, it can be seen that the ionic conductivity of the composite solid electrolyte is improved compared to the solid electrolyte alone. Furthermore, it can be seen that the sintering temperature of the composite solid electrolytes in Examples 1 to 10 is significantly lower than that of the first glass-ceramic compound alone.

[0092] Therefore, it can be seen that the solid electrolyte according to this disclosure has excellent ionic conductivity and lower sintering temperature due to the combination of the first glass-ceramic compound and the second glass-ceramic compound.

[0093] While this disclosure has been described in conjunction with what is now considered to be actual embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments, but rather, on the contrary, is intended to cover various variations and equivalents included within the spirit and scope of the appended claims.

[0094] Therefore, the actual scope of this disclosure will be defined by the appended claims and their equivalents.

Claims

1. A solid electrolyte, said solid electrolyte being a composite comprising a first glass-ceramic compound and a second glass-ceramic compound.

2. The solid electrolyte according to claim 1, wherein, The first glass-ceramic compound is a Na superionic conductor (NASICON) structure compound or a garnet structure compound.

3. The solid electrolyte according to claim 2, wherein, The Na superionic conductor compound is represented by the following chemical formula 1: [Chemical Formula 1] That a1 M1 b1 Al c1 (PO4) d1 In chemical formula 1, M1 is a dopant element, and M1 is Ti, Ga or a combination thereof, 1≤a1≤1.5, 0.1≤b1≤2.5, 0≤c1≤1.5, and 3.5≤d1≤4.

5.

4. The solid electrolyte according to claim 2, wherein, The garnet-structured compound is represented by the following chemical formula 2: [Chemical Formula 2] Li a2 La b2 Zr c2 M2 d2 O e2 In chemical formula 2, M2 is a dopant element, and M2 is Ga, Al, Rb, Ti or a combination thereof, 5.5≤a2≤7.5, 2.5≤b2≤3.5, 1.5≤c2≤2.5, 0≤d2≤1, 11.5≤e2≤12.

5.

5. The solid electrolyte according to claim 1, wherein, The second glass-ceramic compound includes Li, B, O and halogens, and also includes at least one of Ga, Zn, Mg, Al, Ge, Si, Ti, P and Bi.

6. The solid electrolyte according to claim 1, wherein, The second glass-ceramic compound is represented by the following chemical formula 3: [Chemical Formula 3] Read a3 B b3 Oh c3 D d3 M3 e3 In chemical formula 3, D is a halogen element, and D is F, Cl, Br, I or a combination thereof, M3 is Ga, Zn, Mg, Al, Ge, Si, Ti, P, Bi or a combination thereof, 3≤a3≤4, 3.5≤b3≤5.5, 11.5≤c3≤12.5, 0≤d3≤1, 1.5≤e3≤3.

5.

7. The solid electrolyte according to claim 1, wherein, Based on the total volume of the solid electrolyte, the volume percentage of the first glass-ceramic compound is greater than or equal to 51%.

8. The solid electrolyte according to claim 1, wherein, Based on the total volume of the solid electrolyte, the volume percentage of the second glass-ceramic compound is less than or equal to 49%.

9. The solid electrolyte according to claim 1, wherein, The lithium-ion conductivity of the first glass-ceramic compound is greater than that of the second glass-ceramic compound.

10. The solid electrolyte according to claim 1, wherein, The electronic conductivity of the second glass-ceramic compound is less than that of the first glass-ceramic compound.

11. The solid electrolyte according to claim 1, wherein, The first glass-ceramic compound has a lithium-ion conductivity at 25°C greater than or equal to 1.0 × 10⁻⁶. -5 S / cm.

12. The solid electrolyte according to claim 1, wherein, The lithium-ion conductivity of the second glass-ceramic compound at 25°C is less than or equal to 1.0 × 10⁻⁶. -5 S / cm.

13. The solid electrolyte according to claim 1, wherein, The first glass-ceramic compound has an electronic conductivity at 25°C greater than or equal to 2.0 × 10⁻⁶. -10 S / cm.

14. The solid electrolyte according to claim 1, wherein, The electronic conductivity of the second glass-ceramic compound at 25°C is less than or equal to 2.0 × 10⁻⁶. -10 S / cm.

15. An all-solid-state battery, comprising: A positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer comprises the solid electrolyte according to claim 1.

16. The all-solid-state battery according to claim 15, wherein, The positive electrode layer includes a current collector and a positive electrode active material layer located on the current collector, and the negative electrode layer includes a current collector and a negative electrode active material layer located on the current collector. The positive electrode active material layer or the negative electrode active material layer includes the solid electrolyte according to claim 1.

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