Dry positive electrode film, and dry positive electrode and all-solid-state secondary battery comprising same

Abstract

Disclosed are a dry positive electrode film, a dry positive electrode including the same, and an all-solid-state secondary battery. The dry positive electrode film includes a dry positive electrode active material, a dry sulfide-based solid electrolyte, and a dry binder, in which the dry positive electrode active material includes a composite of Li2S, a lithium salt (LiaXb), and a carbonaceous material (C), the composite is represented by Li2S-LiaXb-C (1 < = a < = 5, 1 < = b < = 5), and X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure described herein relate to a dry cathode film, and a dry cathode and a full solid-state secondary battery each including the dry cathode film. BACKGROUND

[0002] To meet the miniaturization and high performance of one or more suitable devices, high energy density of a secondary battery and miniaturization and weight reduction are becoming important. For example, a high capacity secondary battery is becoming important.

[0003] An electrode manufactured from a slurry containing a solvent can be manufactured using an excess amount of an organic solvent. Therefore, a dry method that does not require such an organic solvent is being studied in the manufacture of an electrode. SUMMARY

[0004] TECHNICAL PROBLEM An aspect according to one or more embodiments relates to a dry cathode film having improved mechanical properties and reduced specific resistivity by including a Li2S-lithium salt-carbonaceous material composite and a dry binder that binds these substances.

[0005] An aspect according to one or more embodiments relates to a dry cathode including the dry cathode film.

[0006] An aspect according to one or more embodiments relates to a full solid-state secondary battery including the dry cathode film.

[0007] TECHNICAL SOLUTION According to one or more embodiments, the dry cathode film includes: a dry cathode active material, a dry sulfide-based solid electrolyte, and a dry binder, wherein the dry cathode active material includes a composite of Li2S, a lithium salt (Li a X b ), and a carbonaceous material (C), the composite is represented by Li2S-Li a X b -C (wherein 1≤a≤5 and 1≤b≤5), and X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or any combination thereof.

[0008] According to one or more embodiments, the dry cathode includes: a cathode current collector; and The aforementioned dry positive electrode membrane is disposed on at least one side (e.g., one side or both sides (e.g., opposite sides)) of the positive electrode current collector.

[0009] According to one or more embodiments, the all-solid-state secondary battery includes: Positive electrode, negative electrode, and electrolyte layer disposed between the positive and negative electrodes. Among them, the positive electrode is the aforementioned dry positive electrode, and The negative electrode includes a negative electrode current collector and a first negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0010] Technical effect Depending on the circumstances, a dry cathode film with improved mechanical properties and reduced specific resistivity can be provided by including a Li2S-lithium salt-carbon material composite and a dry binder that bonds these materials.

[0011] By including this dry cathode membrane, an all-solid-state secondary battery with increased specific capacity and improved cycle characteristics can be provided. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0013] Figure 2 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0014] Figure 3 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

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

[0016] Figure 5 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0017] Figure 6 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0018] Figure 7 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Detailed Implementation

[0019] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Furthermore, it will be further understood that terms (such as those defined in common dictionaries) shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field and shall not be interpreted in an idealized or overly formalized sense, unless expressly defined herein.

[0020] Example embodiments will be described herein with reference to schematic cross-sectional views of preferred embodiments. Thus, variations in the illustrated shapes will be anticipated due to, for example, manufacturing techniques and / or tolerances. Therefore, example embodiments should not be construed as limited to the shapes of the areas shown herein, but will include shape deviations caused, for example, by manufacturing processes. For example, areas shown or described as flat may generally have rough and / or non-linear characteristics. Furthermore, sharp corners shown in the figures may be rounded (rounded). Therefore, the areas shown in the figures are schematic in nature, and their shapes are not intended to show the actual shape of the areas of the device, nor are they intended to limit the scope of the claims.

[0021] However, this disclosure may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. The embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art. The same reference numerals in the drawings denote the same elements.

[0022] It will be understood that when an element is referred to as being "on" another element, the element may be directly on the other element, or there may be (multiple) intermediary elements between them. Conversely, when an element is referred to as being "directly on" another element, there are no intermediary elements between them.

[0023] Although the terms “first,” “second,” “third,” etc., may be used herein to describe one or more suitable elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or portion from another region, layer, or portion. Therefore, without departing from the teachings herein, the first element, first component, first region, first layer, or first portion discussed may be referred to as a second element, second component, second region, second layer, or second portion.

[0024] The terminology used herein is for descriptive purposes only and is not intended to limit this disclosure. As used herein, unless otherwise stated, expressions used in the singular may include the expression “at least one.” “At least one” should not be construed as singular. As used herein, the term “and / or” may include any and all combinations of one or more of the associated listed items. Terms such as “comprising” and / or “having” are intended to indicate the presence of the features, regions, integrals, processes, components, and / or elements disclosed in the specification, and are not intended to exclude the possibility that one or more other features, regions, integrals, processes, components, and / or elements may be present or added. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are also intended to include the plural forms. Furthermore, when describing embodiments of this disclosure, the use of “may” refers to “one or more embodiments of this disclosure.”

[0025] Spatially relative terms such as “below,” “under,” “lower,” “above,” “upper,” or “upper” may be used herein to readily describe the relationship between one element or feature and another element(s) as shown in the accompanying drawings. It will be understood that, in addition to the orientations depicted in the drawings, the spatially relative terms are intended to also cover different orientations of the device during use or operation. For example, if (e.g., when) the device in the drawings is flipped, an element described as “below” other elements or features will subsequently be oriented “above” other elements or features. Thus, the exemplified phrase “below” can include both above and below orientations (e.g., both above and below orientations). The device may be otherwise oriented (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0026] In this disclosure, the term "dry" or "dry" can refer to a state intended to avoid contact with solvents, such as processing solvents, or a state intended to be solvent-free. For example, a dry positive electrode active material can refer to a positive electrode active material intended to avoid contact with solvents or a positive electrode active material intended to be solvent-free. For example, a dry solid electrolyte can refer to a solid electrolyte intended to avoid contact with solvents or a solid electrolyte intended to be solvent-free. For example, a dry conductive material can refer to a conductive material intended to avoid contact with solvents or a conductive material intended to be solvent-free. For example, a dry binder can refer to an binder intended to avoid contact with solvents or a binder intended to be solvent-free. For example, a binder that does not mix with a solvent but is liquid at room temperature can be a dry binder.

[0027] In this disclosure, the term "group" may refer to a group of elements numbered 1 to 18 in the periodic table, classified according to the classification system of the International Union of Pure and Applied Chemistry ("IUPAC").

[0028] In this disclosure, the term "particle size" can refer to the average diameter of spherical particles or the average length of the major axis of non-spherical particles. Particle size can be measured using a particle size analyzer (PSA). "Particle size" can be, for example, the average particle size. The "average particle size" can be, for example, the median particle size (D50).

[0029] D50 can refer to the particle size corresponding to 50% of the particles in a cumulative distribution curve measured by laser diffraction, in which particles are accumulated in order of particle size from smallest to largest.

[0030] D90 can refer to the particle size corresponding to 90% of the particles in a cumulative distribution curve measured by laser diffraction, in which particles are accumulated in order of particle size from smallest to largest.

[0031] D10 can refer to the particle size corresponding to 10% of the particles in a cumulative distribution curve measured by laser diffraction, in which particles are accumulated in order of particle size from smallest to largest.

[0032] In this disclosure, the term "metal" can include metals and metalloids (such as silicon and germanium) that are in elemental or ionic states.

[0033] In this disclosure, the term "alloy" may refer to a mixture of two or more metals.

[0034] In this disclosure, the term "electrode active material" can refer to a material used for an electrode that allows for lithiation and delithiation.

[0035] In this disclosure, the term "positive electrode active material" may refer to a material used for a positive electrode that allows for lithiation and delithiation.

[0036] In this disclosure, the term "negative electrode active material" may refer to a material used for a negative electrode that allows for lithiation and delithiation.

[0037] In this disclosure, the term "lithiation" and its variations may refer to the process of adding lithium to an electrode active material.

[0038] In this disclosure, the term "delithiation" and its variations may refer to the process of removing lithium from an electrode active material.

[0039] In this disclosure, the term "charging" and its variations may refer to the process by which a battery supplies electrochemical energy.

[0040] In this disclosure, the term "discharge" and its variations may refer to the process of removing electrochemical energy from a battery.

[0041] In this disclosure, the terms "positive electrode" and "positive electrode" can refer to an electrode that undergoes electrochemical reduction and lithiation during discharge.

[0042] In this disclosure, the terms "negative electrode" and "negative electrode" can refer to an electrode that undergoes electrochemical oxidation and delithiation during discharge.

[0043] While some embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that may not currently be foreseen or possibly not be foreseen by the applicant or others skilled in the art. The appended claims, both as filed and as may be amended, are intended to cover all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0044] In the following description, the dry positive electrode film according to the embodiments, the dry positive electrode including the dry positive electrode film, and the all-solid-state secondary battery will be described in more detail.

[0045] [Dry positive electrode film] [Dry cathode film: a composite of Li2S, lithium salt, and carbonaceous materials] The dry cathode film according to the embodiments may include a dry cathode active material, a dry sulfide solid electrolyte, and a dry binder. The dry cathode active material may include a Li2S-lithium salt-carbon material composite.

[0046] By incorporating a Li₂S-lithium salt-carbonaceous material composite, the dry cathode active material can provide increased discharge capacity, enhanced ionic conductivity, and improved electronic conductivity. Because the composite includes Li₂S, which can act as a lithium source, the supply of a lithium source in the anode is unnecessary (e.g., can be excluded). As a result, the energy density of the all-solid-state secondary battery can be increased. However, sulfur (i.e., S) does not contain lithium and cannot act as a lithium source, so providing a lithium source in the anode may be critical or necessary. Because the composite includes a lithium salt, the ionic conductivity of the dry cathode active material can be improved, and the internal resistance of the dry cathode film including the dry cathode active material can be reduced. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be improved. Because the composite includes a carbonaceous material, the electronic conductivity of the dry cathode active material can be improved, and the internal resistance of the dry cathode film including the dry cathode active material can be reduced. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be improved. Because the composite includes a carbonaceous material, the adhesion strength between the composite and the dry binder can be further improved. Therefore, mechanical properties of the dry positive electrode film, such as tensile strength, can be further improved. The dry binder is discontinuously bonded to portions of the surface of multiple dry positive electrode active material particles, thus effectively suppressing the increase in internal resistance of the dry positive electrode film. However, wet binders are coated onto a large area of ​​the surface of multiple positive electrode active material particles during the process of dissolving in a solvent and drying, which can significantly increase the internal resistance of the dry positive electrode film. On the other hand, because the dry positive electrode film includes a dry sulfide-based solid electrolyte, the ionic conductivity of the dry positive electrode film can be further improved. As a result, the internal resistance of the dry positive electrode film can be further reduced. Because the internal resistance of the dry positive electrode film is reduced and its mechanical properties are improved, the specific capacity and / or cycle characteristics of the all-solid-state secondary battery including the dry positive electrode film according to this disclosure can be improved.

[0047] Li₂S-lithium salt-carbon material composites can be made from Li₂S-Li a X b -C (where 1≤a≤5 and 1≤b≤5) represents X. X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or any combination thereof. For example, a can be 1, 2, 3, 4, or 5. For example, b can be 1, 2, 3, 4, or 5. C can refer to carbonaceous materials that are essentially composed of carbon atoms.

[0048] The size (e.g., average diameter or average major axis) of the Li2S crystallites obtained in the X-ray diffraction (XRD) spectrum of the Li2S-lithium salt-carbon composite can be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of the Li2S crystallites obtained in the XRD spectrum of the Li2S-lithium salt-carbon composite can be, for example, about 1 nm to about 20 nm, about 1 nm to about 15 nm, or about 3 nm to about 10 nm. Because the Li2S-lithium salt-carbon composite includes Li2S crystallites and the size of the Li2S crystallites is reduced to 20 nm or less, the volume change of the Li2S crystallites can be reduced during charge and discharge. For example, due to the reduced size of the Li2S crystallites, the volume change of a single Li2S crystallite can be reduced, resulting in a reduction in the overall volume change of the Li2S-lithium salt-carbon composite during charge and discharge. For example, due to the reduced size of Li2S crystallites, the grain boundaries between multiple Li2S crystallites readily adapt to the volume changes of the Li2S crystallites during charge and discharge, thus reducing the volume change of the Li2S-lithium salt-carbon composite during charge and discharge. This reduces the likelihood of defects such as cracks caused by the volume changes of the composite during charge and discharge. Because the dry cathode film includes the Li2S-lithium salt-carbon composite, the cycle characteristics of all-solid-state secondary batteries including the dry cathode film can be improved. With the Li2S crystallites reduced to 20 nm, the contact area between Li2S and the lithium salt and / or carbonaceous materials can be further increased. This further increase in the contact area between Li2S and the lithium salt and / or carbonaceous materials improves the reversibility of electrode reactions in all-solid-state secondary batteries including the Li2S-lithium salt-carbon composite.

[0049] The Li₂S-lithium salt-carbon composite material can include, for example, a solid solution of Li₂S and a lithium salt. Because the Li₂S-lithium salt-carbon composite material includes a solid solution of Li₂S and a lithium salt, its ionic conductivity can be further improved. For example, because the solid solution of Li₂S and a lithium salt includes lithium atoms located within Li₂S microcrystals, the ionic conductivity of the solid solution of Li₂S and a lithium salt can be increased compared to the ionic conductivity of Li₂S alone. As a result, the ionic conductivity of the Li₂S-lithium salt-carbon composite material can be improved, and its internal resistance can be reduced. Because the dry cathode film includes such a composite, its internal resistance can be further reduced. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be further improved.

[0050] Li2S-lithium salt-carbon composites can be distinguished from simple mixtures of Li2S, lithium salt, and carbonaceous materials. In simple mixtures of Li2S, lithium salt, and carbonaceous materials, a dense interface cannot be maintained between the Li2S, lithium salt, and carbonaceous materials, thus providing high interfacial resistance and leading to a deterioration in the lifetime characteristics of all-solid-state secondary batteries.

[0051] Li₂S-lithium salt-carbonaceous material composites may include Li₂S. Due to the high theoretical capacity of Li₂S, all-solid-state secondary batteries with high energy density can be provided. However, due to the low ionic and / or electronic conductivity of Li₂S, composites containing lithium salts and carbonaceous materials can be formed to overcome these drawbacks. In the Li₂S-lithium salt-carbonaceous material composite, the amount of Li₂S can be, for example, about 50 wt% to about 80 wt%, about 50 wt% to about 75 wt%, or about 50 wt% to about 70 wt%, based on the total weight of the Li₂S-lithium salt-carbonaceous material composite. If (for example) the amount of Li₂S is too high, it may be difficult to improve the ionic and / or electronic conductivity of Li₂S. If (for example) the amount of Li₂S is too low, the energy density of the secondary battery may decrease.

[0052] The Li2S-lithium salt-carbon composite material may include a lithium salt. The lithium salt may be, for example, a compound that does not contain sulfur (S). The lithium salt may be, for example, a binary compound or a ternary compound. The lithium salt may be, for example, a binary compound composed of lithium and one element selected from groups 13 to 17 of the periodic table. The lithium salt may be, for example, a ternary compound composed of lithium and two elements selected from groups 13 to 17 of the periodic table. The binary compound may include, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or any combination thereof. By including such a binary compound, the composite may have further improved ionic conductivity. By including such a composite (i.e., a dry cathode active material), the dry cathode film may have further reduced internal resistance. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be further improved. Ternary compounds can include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or any combination thereof. By including such ternary compounds, the composite can have improved ionic conductivity. By including such composites (i.e., dry cathode active materials), the dry cathode film can have further reduced internal resistance. As a result, the cycle characteristics of all-solid-state secondary batteries including dry cathode films can be further improved. In the Li₂S-lithium salt-carbon composite, based on the total weight of the Li₂S-lithium salt-carbon composite, the amount of lithium salt can be from about 1 wt% to about 40 wt%, from about 5 wt% to about 35 wt%, from about 10 wt% to about 35 wt%, from about 15 wt% to about 35 wt%, from about 20 wt% to about 35 wt%, or from about 25 wt% to about 35 wt%. If (for example, when) the amount of lithium salt is too high, the energy density of the all-solid-state secondary battery may decrease. If (for example, when) the amount of lithium salt is too low, the ionic conductivity of the Li₂S-lithium salt-carbon composite may deteriorate, leading to an increase in the internal resistance of the dry cathode film. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry cathode film may deteriorate.

[0053] In a Li₂S-lithium salt-carbon composite, the molar ratio of Li₂S to lithium salt can be, for example, about 50:50 to about 95:5, about 60:40 to about 95:5, about 60:40 to about 90:10, about 65:35 to about 90:10, about 65:35 to about 85:15, or about 70:30 to about 85:15. In a Li₂S-lithium salt-carbon composite, the molar ratio of Li₂S to lithium salt can be, for example, about 50:50 to about 95:5, about 50:50 to about 90:10, about 50:50 to about 85:15, about 50:50 to about 80:20, about 50:50 to about 75:25, or about 50:50 to about 70:30. If (for example, when) the molar ratio of Li₂S to lithium salt is within the above ranges, the cycle characteristics of the all-solid-state lithium battery, including the dry cathode film, can be further improved. If, for example, the molar ratio of Li₂S is too high, the effect of lithium salt on increasing ionic conductivity will be negligible. If, for example, the molar ratio of Li₂S is too high, the energy density of lithium batteries including dry cathode active materials may decrease.

[0054] The Li2S-lithium salt-carbonaceous material composite includes carbonaceous materials. Carbonaceous materials can be, for example, any material comprising carbon atoms and generally used in the art as a conductive material. Carbonaceous materials can be, for example, crystalline carbon, amorphous carbon, or any combination thereof. Carbonaceous materials can be, for example, calcined products of carbon precursors. Carbonaceous materials can be, for example, carbon nanostructures. Carbon nanostructures can be, for example, one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, or any combination thereof. Carbon nanostructures can be, for example, carbon nanotubes, carbon nanofibers, carbon nanoribbons, carbon nanorods, graphene, or any combination thereof. Carbonaceous materials can be, for example, porous or non-porous carbonaceous materials. Porous carbonaceous materials can include, for example, periodic and regular two-dimensional or three-dimensional pores. Porous carbonaceous materials can be, for example, carbon black (such as Ketjen black, acetylene black, superconducting acetylene black (Denka black), thermally cracked carbon black, and channel black), graphite, activated carbon, or any combination thereof. The carbonaceous material can be in particulate, sheet, or flake form, but is not limited thereto, and any material commonly used as a carbonaceous material in the art can be used. Based on the total weight of the composite, the amount of carbonaceous material included in the Li₂S-lithium salt-carbonaceous material composite can be, for example, about 1 wt% to 20 wt%, about 5 wt% to 20 wt%, or about 10 wt% to 20 wt%. If (for example, when) the amount of carbonaceous material is excessively increased, the energy density of the dry cathode film and the all-solid-state secondary battery may decrease. If (for example, when) the amount of carbonaceous material is excessively decreased, the electronic conductivity of the Li₂S-lithium salt-carbonaceous material composite may decrease, leading to an increase in the internal resistance of the dry cathode film. As a result, the cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0055] Lithium salts and carbonaceous materials can each have a Mohs hardness greater than that of Li₂S. Li₂S can have a Mohs hardness of, for example, 0.6 or less. The Mohs hardness of lithium salts can be 0.7 or greater, 0.8 or greater, 0.9 or greater, 1.0 or greater, 1.5 or greater, or 2.0 or greater. If (for example, when) the Mohs hardness of lithium salts is within the above ranges, Li₂S can be more easily pulverized during the grinding process, and a solid solution of Li₂S and lithium salts can be formed more easily. The Mohs hardness of LiI can be, for example, 2.0. Carbonaceous materials can have a Mohs hardness of 0.7 or greater, 0.8 or greater, 0.9 or greater, 1.0 or greater, 1.2 or greater, or 1.5 or greater. If (for example, when) the Mohs hardness of carbonaceous materials is within the above ranges, Li₂S can be more easily pulverized during the grinding process, and a Li₂S-lithium salt-carbonaceous material composite can be formed more easily. Carbon nanofibers (CNFs) can have a Mohs hardness of, for example, 1.5.

[0056] Carbonaceous materials can include, for example, fibrous carbonaceous materials. Because the Li₂S-lithium salt-carbonaceous material composite includes fibrous carbonaceous materials, the electronic conductivity of the Li₂S-lithium salt-carbonaceous material composite can be further improved. Because the Li₂S-lithium salt-carbonaceous material composite includes fibrous carbonaceous materials, electron conduction from the surface to the interior of the Li₂S-lithium salt-carbonaceous material composite can be facilitated. Dry cathode films including Li₂S-lithium salt-carbonaceous material composites can have reduced internal resistance, and all-solid-state secondary batteries including dry cathode films can have further improved cycle characteristics.

[0057] The fibrous carbonaceous material can have an aspect ratio of, for example, 2 or greater, 3 or greater, 4 or greater, 5 or greater, 10 or greater, or 20 or greater. The fibrous carbonaceous material can have an aspect ratio of, for example, about 2 to about 30, about 3 to about 30, about 4 to about 30, about 5 to about 30, about 10 to about 30, or about 20 to about 30. The fibrous carbonaceous material can have an aspect ratio of, for example, about 2 to about 30, about 2 to about 20, about 2 to about 10, about 2 to about 8, about 2 to about 5, or about 2 to about 4. If (for example, when) the aspect ratio of the fibrous carbonaceous material is within the above ranges, the overall electronic conductivity of the Li₂S-lithium salt-carbonaceous material composite can be improved, and the local inhomogeneity of electronic conductivity in the Li₂S-lithium salt-carbonaceous material composite can be further reduced.

[0058] Fibrous carbonaceous materials may include, for example, carbon nanostructures. Carbon nanostructures may include, for example, carbon nanofibers (CNF), carbon nanotubes (CNT), carbon nanoribbons, carbon nanorods, or any combination thereof.

[0059] Carbon nanostructures can be primary carbon nanostructures (e.g., primary particles) formed by a single carbon nanostructure and secondary carbon nanostructures (e.g., secondary particles) formed by multiple carbon nanostructures aggregated together.

[0060] Primary carbon nanostructures may have diameters (e.g., average diameter or average major axis) ranging from about 1 nm to about 200 nm, about 1 nm to about 150 nm, about 1 nm to about 100 nm, about 1 nm to about 50 nm, about 1 nm to about 30 nm, or about 1 nm to about 20 nm. Primary carbon nanostructures may have lengths (e.g., average length) ranging from about 10 nm to about 2 μm, about 10 nm to about 1.5 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 400 nm, about 10 nm to about 300 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. The diameter and length of the primary carbon nanostructures may be measured by images obtained using scanning electron microscopy (SEM) or transmission electron microscopy (TEM). In some embodiments, the diameter and / or length of the primary carbon nanostructures may be measured by laser diffraction.

[0061] Secondary carbon nanostructures are structures formed by the aggregation of primary carbon nanostructures, wholly or partially, in bundle or rope form. Secondary carbon nanostructures can include, for example, bundle-type (or rope-type) carbon nanostructures, rope-type (or rope-type) carbon nanostructures, or any combination thereof. Secondary carbon nanostructures can have diameters (e.g., average diameter or average major axis) ranging from about 2 nm to about 200 nm, about 3 nm to about 150 nm, about 5 nm to about 100 nm, about 5 nm to about 50 nm, about 5 nm to about 30 nm, or about 5 nm to about 20 nm. Secondary carbon nanostructures can have lengths (e.g., average length) ranging from about 20 nm to about 2 μm, about 30 nm to about 1.5 μm, about 50 nm to about 1 μm, about 50 nm to about 500 nm, about 50 nm to about 400 nm, about 50 nm to about 300 nm, about 50 nm to about 200 nm, or about 50 nm to about 100 nm. The diameter and length of the secondary carbon nanostructures can be measured by images obtained using SEM or optical microscopy. In some embodiments, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be dispersed in a solvent or the like to convert it into a primary carbon nanostructure, which can then be used to prepare Li₂S-lithium salt-carbon composite materials.

[0062] The particle size of the dry positive electrode active material (i.e., the particle size of the Li2S-lithium salt-carbonaceous material composite) (e.g., average diameter or average long axis) can be, for example, 10 μm or less, 8 μm or less, 5 μm or less, 4 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less. The particle size of the composite can be, for example, about 1 μm to about 10 μm, about 2 μm to about 10 μm, about 2 μm to 8 μm, or about 3 μm to about 8 μm. The particle size of the Li2S-lithium salt-carbonaceous material composite can be, for example, about 0.1 μm to about 10 μm, about 0.1 μm to about 8 μm, about 0.1 μm to about 5 μm, about 0.1 μm to about 4 μm, about 0.1 μm to about 2 μm, about 0.1 μm to about 1.5 μm, or about 0.1 μm to about 1 μm. If the particle size of the Li2S-lithium salt-carbon composite is within the aforementioned range (e.g., when), volume change during charge and discharge can be suppressed, and degradation of the dry cathode active material during charge and discharge can be suppressed. If the particle size of the Li2S-lithium salt-carbon composite is excessively increased (e.g., when), the volume change of the Li2S-lithium salt-carbon composite may increase during charge and discharge, leading to accelerated degradation of the dry cathode active material. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry cathode active material may deteriorate. Therefore, the cycle characteristics (e.g., lifetime characteristics) of the all-solid-state secondary battery including the dry cathode active material of this disclosure can be improved. The particle size of the Li2S-lithium salt-carbon composite can be measured using laser diffraction or scanning electron microscopy (SEM). The particle size of the Li2S-lithium salt-carbon composite can be the arithmetic mean of the particle sizes of multiple particles measured from a scanning electron microscope image using software.

[0063] The particle size of Li2S included in the composite (i.e., the particle size of Li2S included in the composite) (e.g., average diameter or average major axis) can be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The particle size of Li2S can be, for example, about 0.1 μm to about 2 μm, about 0.1 μm to about 1.5 μm, or about 0.1 μm to about 1 μm. If (e.g., when) the particle size of Li2S is within the above ranges, volume change can be suppressed during charge and discharge, thus suppressing the degradation of the dry cathode active material including the composite during charge and discharge. If (e.g., when) the particle size of Li2S is excessively increased, the volume change of the composite during charge and discharge may increase, leading to accelerated degradation of the dry cathode active material including the composite. As a result, the cycle characteristics of the secondary battery including the dry cathode active material may deteriorate.

[0064] Based on 100 parts by weight of the composite, the Li2S-lithium salt-carbonaceous material composite may include, for example, about 10 parts by weight to about 80 parts by weight of Li2S, about 1 part by weight to about 40 parts by weight of lithium salt, and about 1 part by weight to about 20 parts by weight of carbonaceous material. Based on 100 parts by weight of the composite, the amount of Li2S included in the Li2S-lithium salt-carbonaceous material composite may be, for example, about 10 parts by weight to about 80 parts by weight, about 20 parts by weight to about 70 parts by weight, about 30 parts by weight to about 60 parts by weight, or about 40 parts by weight to about 60 parts by weight. Based on 100 parts by weight of the composite, the amount of lithium salt included in the Li2S-lithium salt-carbonaceous material composite may be, for example, about 10 parts by weight to about 40 parts by weight, about 15 parts by weight to about 40 parts by weight, about 20 parts by weight to about 40 parts by weight, or about 25 parts by weight to about 35 parts by weight. Based on 100 parts by weight of the composite, the amount of carbonaceous material included in the Li2S-lithium salt-carbonaceous material composite can be, for example, from about 1 part by weight to about 20 parts by weight, from about 5 parts by weight to about 20 parts by weight, or from about 5 parts by weight to about 15 parts by weight. If (for example, when) the Li2S-lithium salt-carbonaceous material composite comprises the composition of Li2S, lithium salt and carbonaceous material, then the dry cathode film comprising the Li2S-lithium salt-carbonaceous material composite can have excellent ionic conductivity and / or electronic conductivity.

[0065] The ionic conductivity of the Li₂S-lithium salt-carbon composite material can be, for example, 1 × 10⁻⁶ at 25 °C. -5 S / cm or greater, 2×10 -5 S / cm or greater, 4×10 -5 S / cm or greater, 6×10 -5 S / cm or greater, 8×10 -5 S / cm or greater, or 1×10 -4 S / cm or greater. Ionic conductivity can be measured, for example, by electrochemical impedance spectroscopy, DC polarization, etc. If (for example, when) the ionic conductivity of the Li₂S-lithium salt-carbon composite is within the above range, the internal resistance of the dry cathode film including the Li₂S-lithium salt-carbon composite can be further reduced. The cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be improved.

[0066] The electronic conductivity of the Li₂S-lithium salt-carbon composite material can be, for example, 1 × 10⁻⁶ at 25 °C. -5 S / cm or greater, 2×10 -5 S / cm or greater, 4×10 -5 S / cm or greater, 6×10 -5 S / cm or greater, 8×10 -5 S / cm or greater, or 1×10 -4S / cm or greater. Electronic conductivity can be measured, for example, by electrochemical impedance spectroscopy, DC polarization methods, etc. If (for example, when) the electronic conductivity of the Li₂S-lithium salt-carbon composite is within the above range, the internal resistance of the dry cathode film including the Li₂S-lithium salt-carbon composite can be further reduced. The cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be improved.

[0067] Based on the total weight of the dry cathode film, the amount of the Li2S-lithium salt-carbon composite material can be, for example, about 50 wt% to about 95 wt%, about 50 wt% to about 80 wt%, about 55 wt% to about 80 wt%, about 60 wt% to about 80 wt%, about 65 wt% to about 80 wt%, or about 70 wt% to about 80 wt%. If (for example, when) the amount of the Li2S-lithium salt-carbon composite material is too high, the volume change of the dry cathode during discharge may increase excessively, thus potentially degrading the cycle characteristics of the all-solid-state secondary battery. If (for example, when) the amount of the Li2S-lithium salt-carbon composite material is too low, the energy density of the all-solid-state secondary battery may decrease.

[0068] [Dry positive electrode film: sulfide-based solid electrolyte] The dry positive electrode film includes a dry sulfide-based solid electrolyte. The sulfide-based solid electrolyte may include, for example, at least one selected from the following: Li₂S-P₂S₅, Li₂S-P₂S₅-LiX (where X is a halogen atom), 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 (Where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (Where p and q are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In), Li 7-x PS 6-x Cl x (where 0≤x≤2), Li 7-x PS 6-x Br x (where 0 ≤ x ≤ 2) and Li 7-x PS 6- x I x(Where, 0 ≤ x ≤ 2). Sulfide solid electrolytes can be prepared by treating starting materials such as Li₂S and / or P₂S₅ through melt quenching or mechanical grinding. Heat treatment can be performed after such treatment. Sulfide solid electrolytes can be in amorphous or crystalline form or a mixture thereof. Sulfide solid electrolytes can, for example, include at least sulfur (S), phosphorus (P), and lithium (Li) as components. Sulfide solid electrolytes can include, for example, Li₂S-P₂S₅. If (e.g., when) a material including Li₂S-P₂S₅ is used as a sulfide solid electrolyte material, the molar ratio of Li₂S to P₂S₅ can be, for example, about 20:80 to about 90:10, about 25:75 to about 90:10, about 30:70 to about 70:30, or about 40:60 to about 60:40.

[0069] Sulfide solid electrolytes may include, for example, solid electrolytes of the sulfide-germanium type (or class) represented by Formula 1: Formula 1 Li + 12-n-x A n+ X 2- 6-x Y - x In Formula 1, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is S, Se, or Te, and Y is Cl, Br, I, F, CN, OCN, SCN, or N3, where 1 ≤ n ≤ 5 and 0 ≤ x ≤ 2. Sulfide solid electrolytes can be compounds of the sulfide-germanium type (or class) including, for example, at least one selected from the following (e.g., sulfide-germanium compounds): Li 7- x PS 6-x Cl x (where 0≤x≤2), Li 7-x PS 6-x Br x (where 0 ≤ x ≤ 2) and Li 7-x PS 6-x I x (Where, 0≤x≤2). Sulfide solid electrolytes can be compounds of the sulfide-germanium type (or class) including, for example, at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I.

[0070] Australite-type (or similar) solid electrolytes can have densities ranging from 1.5 g / cc to 2.0 g / cc. Because australite-type (or similar) solid electrolytes have densities of 1.5 g / cc or greater, they can reduce the internal resistance of all-solid-state secondary batteries and effectively suppress the permeation of solid membranes.

[0071] The sulfide solid electrolyte included in the dry positive electrode film may be the same as or different from the sulfide solid electrolyte included in the electrolyte layer.

[0072] The average particle size D50 of the sulfide-based solid electrolyte included in the dry positive electrode film can be smaller than the average particle size D50 of the sulfide-based solid electrolyte included in the electrolyte layer. For example, the average particle size D50 of the sulfide-based solid electrolyte included in the dry positive electrode film can be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average particle size D50 of the sulfide-based solid electrolyte included in the electrolyte layer 30. The average particle size D50 can be, for example, the median particle size D50. The median particle size D50 can be the particle size corresponding to 50% of the cumulative volume calculated from the smallest particle in the particle size distribution measured, for example, by laser diffraction.

[0073] Based on the total weight (100 wt%) of the dry cathode film, the amount of sulfide-based solid electrolyte included in the dry cathode film can be approximately 5 wt% to approximately 45 wt%, approximately 15 wt% to approximately 40 wt%, approximately 20 wt% to approximately 40 wt%, or approximately 25 wt% to approximately 40 wt%. If (for example, when) the dry cathode film includes sulfide-based solid electrolyte in amounts within the above ranges, the dry cathode film can provide reduced internal resistance and improved ionic conductivity. If (for example, when) the amount of sulfide-based solid electrolyte is too low, the internal resistance of the dry cathode film can increase, leading to a deterioration in the cycle characteristics of the all-solid-state secondary battery. If (for example, when) the amount of sulfide-based solid electrolyte is too high, the energy density of the all-solid-state secondary battery may decrease.

[0074] [Dry cathode film: dry binder] The dry positive electrode film may include a dry binder. The dry binder may be, for example, a binder that is not impregnated with, dissolved in, or dispersed in a processing solvent during the process of manufacturing the dry positive electrode film. The dry binder may be, for example, a binder that does not include a processing solvent or is not in contact with a processing solvent during the process of manufacturing the dry positive electrode film. The dry binder may be, for example, a fibrillated binder or a fibrous binder. The fibrillated binder or fibrous binder can serve as a porous matrix that supports and binds the dry positive electrode active material and other components included in the dry positive electrode film. The fibrillated binder or fibrous binder is bonded to multiple dry positive electrode active materials in a discontinuous manner on the surface of the dry positive electrode active material without agglomerating with each other, thus effectively suppressing the increase in internal resistance of the dry positive electrode film. Based on SEM images of the cross-section of the dry positive electrode, it can be confirmed that the fibrillated binder or fibrous binder has a fibrous form. The fibrillated binder or fibrous binder may have an aspect ratio of, for example, 10 or greater, 20 or greater, 50 or greater, or 100 or greater.

[0075] Examples of dry binders may include, but are not limited to, polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, polyvinylidene fluoride (PVDF), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and / or one or more copolymers thereof, and any binder suitable for use in the manufacture of dry electrodes may also be used. For example, dry binders may include fluorinated binders. Fluorinated binders may be, for example, polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, or polyvinylidene fluoride (PVDF).

[0076] Dry adhesives may have glass transition temperatures (T0) of, for example, about -30°C to about 150°C, about 15°C to about 150°C, about 15°C to about 130°C, about 50°C to about 130°C, about 100°C to about 130°C, or about 120°C to about 130°C. g The dry adhesive may have, for example, a glass transition temperature (T0) of about -30°C to about 150°C, about -30°C to about 100°C, about -30°C to about 50°C, about -30°C to about 15°C, about -30°C to about -10°C, or about -30°C to about -20°C. g The glass transition temperature of polytetrafluoroethylene (PTFE) can be, for example, from 120°C to about 130°C. If (for example, when) the dry binder has a glass transition temperature within the above range, fibrillated or fibrous binders can be more easily obtained during the process of manufacturing the dry electrode.

[0077] Based on the total weight of the dry cathode film, the amount of dry binder can be, for example, about 0.1 wt% to about 5 wt%, about 0.5 wt% to about 5 wt%, about 1 wt% to about 5 wt%, or about 1 wt% to about 3 wt%. If (for example, when) the amount of dry binder included in the dry cathode film is within the above range, the adhesive strength of the dry cathode film can be improved, and the high energy density of the dry cathode film can be maintained.

[0078] [Dry cathode film: conductive material] The dry positive electrode film may also include, for example, a conductive material. The conductive material may be, for example, a dry conductive material. The dry conductive material may be, for example, a conductive material that is not impregnated with a processing solvent, is not dissolved in a processing solvent, or is not dispersed in a processing solvent during the process of manufacturing the dry positive electrode film. The dry conductive material may be, for example, a conductive material that does not include a processing solvent or is not in contact with a processing solvent during the process of manufacturing the dry positive electrode film. The dry conductive material may include, for example, a carbonaceous conductive material. The carbonaceous conductive material may include, for example, fibrous carbonaceous material having an aspect ratio of 10 or greater, particulate carbonaceous material having an aspect ratio of less than 10, or a combination thereof.

[0079] Fibrous carbonaceous materials with an aspect ratio of 10 or greater can be, for example, carbon fibers, carbon nanotubes, or carbon nanoribbons, but are not limited thereto, and any material available in the art as a carbonaceous conductive material can also be used. Fibrous carbonaceous conductive materials can be distinguished from the carbonaceous materials constituting the dry cathode active material in terms of simple mixing with the dry cathode active material.

[0080] Examples of particulate carbonaceous materials having an aspect ratio of less than 10 may include, but are not limited to, carbon black, acetylene black, Ketjen black, natural graphite, and artificial graphite, and any carbonaceous conductive material commonly available in the art may also be used. The aspect ratio of the particulate carbonaceous material may, for example, be from about 1 to about 7, from about 1 to about 5, from about 1 to about 3, or from about 1 to about 2.

[0081] Based on the total weight of the dry positive electrode film, the amount of dry conductive material included in the dry positive electrode film can be, for example, from about 0.1 wt% to about 5 wt%, from about 0.5 wt% to about 5 wt%, or from about 1 wt% to about 5 wt%. If (for example, when) the amount of dry conductive material included in the dry positive electrode film is within the above range, the dry positive electrode film can have further improved conductivity, and the all-solid-state secondary battery including the dry positive electrode film can have further improved cycle characteristics. Dry conductive material may not be provided.

[0082] [Dry cathode film: other additives] In addition to the positive electrode active material, solid electrolyte, binder and conductive material, the dry positive electrode film may also include additives such as fillers, coatings, dispersants and ion-conducting agents.

[0083] The fillers, coatings, dispersants, and ion-conducting additives included in the dry cathode film can be any suitable materials commonly used in the cathode of an all-solid-state secondary battery.

[0084] [Dry cathode film: Physical properties] The dry positive electrode film can be, for example, a self-standing membrane. For instance, the dry positive electrode film can have a membrane shape without utilizing a support. Therefore, the dry positive electrode film can be placed on the positive current collector after being prepared as a separate self-standing membrane. The dry positive electrode film prepared by the dry process does not include any intentionally added processing solvent. For example, the dry electrode film does not include residual processing solvent. Although trace amounts of unintended solvent may remain in the dry positive electrode film, this solvent is not an intentionally added processing solvent. Therefore, the dry positive electrode film can be distinguished from the wet positive electrode film, which is prepared by mixing the components with a processing solvent, drying the mixture, and removing all or part of the processing solvent.

[0085] The dry cathode film can have a thickness of, for example, about 50 μm to about 500 μm, about 50 μm to about 400 μm, about 50 μm to about 300 μm, or about 50 μm to about 250 μm. If the dry cathode film is too thin, the number of current collectors may increase, and therefore the energy density per unit volume of the all-solid-state secondary battery may decrease. If the dry cathode film is too thick, the internal resistance of the dry cathode may increase, and therefore the cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0086] The dry positive electrode film can have a tensile strength of, for example, 500 kPa or greater, 700 kPa or greater, or 900 kPa or greater at 25°C. The dry positive electrode film can also have a tensile strength of approximately 500 kPa to approximately 5000 kPa, approximately 700 kPa to approximately 5000 kPa, approximately 700 kPa to approximately 3000 kPa, approximately 700 kPa to approximately 2000 kPa, or approximately 900 kPa to approximately 2000 kPa at 25°C. If the tensile strength of the dry positive electrode film is within the above ranges, the structural stability of the dry positive electrode film can be improved. Therefore, because the stable three-dimensional conductive network of the dry positive electrode film is maintained during the charge and discharge process, the reversibility of the electrode reaction can be improved. If the dry positive electrode film has such a high tensile strength, the mechanical strength of the dry positive electrode film can be improved. Because the dry cathode film can possess improved mechanical strength, localized degradation caused by volume changes during charge and discharge can be suppressed in both the dry cathode film and the all-solid-state secondary battery comprising it. As a result, the cycle characteristics of the all-solid-state secondary battery can be improved. If, for example, the tensile strength of the dry cathode film is too low, defects such as cracks and fractures may occur during the manufacturing process of the all-solid-state secondary battery or during its charge and discharge process, leading to a decrease in the yield of the all-solid-state secondary battery. The tensile strength (tensile strength at break) of the dry cathode film can be measured, for example, according to the ASTM D412 method.

[0087] The dry positive electrode film can have a surface resistivity of, for example, 70 Ω / sq or less, 60 Ω / sq or less, 50 Ω / sq or less, 40 Ω / sq or less, or 35 Ω / sq or less at 25 °C. The surface resistivity of the dry positive electrode film at 25 °C and 1 atm can be, for example, about 0.1 Ω / sq to about 70 Ω / sq, about 0.5 Ω / sq to about 60 Ω / sq, 1 Ω / sq to about 50 Ω / sq, about 1 Ω / sq to about 40 Ω / sq, or about 1 Ω / sq to about 35 Ω / sq. Because the dry positive electrode film has this reduced surface resistivity, the surface resistance, interfacial resistance, and / or internal resistance of the dry positive electrode film can be reduced. Therefore, the cycle characteristics of all-solid-state secondary batteries including dry positive electrode films can be further improved. The surface resistivity of the dry positive electrode film can be measured, for example, according to ASTM D257 or IEC 62631-3-1 methods.

[0088] [Dry positive electrode] [Dry cathode: Cathode active material layer] The dry positive electrode according to an embodiment may include: a positive current collector; and a positive active material layer disposed on at least one side of the positive current collector. The positive active material layer may include the aforementioned dry positive electrode film. By including the aforementioned dry positive electrode film, the dry positive electrode can have a further reduced internal resistance. Therefore, the cycle characteristics of the secondary battery including the dry positive electrode can be further improved.

[0089] Reference Figures 1 to 7 The dry positive electrode 10 may include a positive current collector 11 and a positive active material layer 12 disposed on at least one side of the positive current collector 11. The positive active material layer 12 may include the dry positive electrode membrane described above.

[0090] [Dry cathode: Cathode current collector] The positive current collector 11 may be, for example, in the form of a plate or foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof. The positive current collector 11 may not be provided. The positive current collector 11 may have a thickness of, for example, about 1 μm to about 100 μm, about 1 μm to about 50 μm, about 5 μm to about 25 μm, or about 10 μm to about 20 μm.

[0091] The positive current collector 11 may include, for example, a substrate film and a metal layer disposed on at least one side of the substrate film. The substrate film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or any combination thereof. The substrate film may be, for example, an insulator. Because the substrate film includes an insulating thermoplastic polymer, the substrate film can soften or liquefy in the event of a short circuit to stop the operation of the battery, thus suppressing a rapid increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or alloys thereof. The metal layer, acting as an electrochemical fuse, can be cut off in the event of an overcurrent to prevent or reduce a short circuit. By controlling the thickness of the metal layer, the limiting current and the maximum current can be adjusted. The metal layer may be plated or deposited on the substrate film. As the thickness of the metal layer decreases, the limiting current and / or maximum current of the positive electrode current collector 11 decreases, thereby improving the stability of the lithium battery under short-circuit conditions (e.g., during a short circuit). Lead tabs can be added to the metal layer for external connections. The lead tabs can be welded to the metal layer or metal layer / substrate film stack structure by ultrasonic welding, laser welding, spot welding, etc. The metal layer can be electrically connected to the lead tabs when the substrate film and / or metal layer melts during welding. A metal sheet can also be added between the metal layer and the lead tabs for a stronger weld between them. The metal sheet can be a sheet of the same material as the metal layer. The metal sheet can be, for example, metal foil and metal mesh. The metal sheet can be, for example, Al foil, copper foil, and stainless steel (SUS) foil. By placing the metal sheet on the metal layer and performing welding, the lead tabs can be welded to a metal sheet / metal layer stack structure or a metal sheet / metal layer / substrate film stack structure. When the substrate film, metal layer, and / or metal sheet melt during soldering, the metal layer or metal layer / metal sheet stack structure can be electrically connected to the lead patch. Metal sheets and / or lead patches can also be added to a portion of the metal layer. The substrate film can have a thickness of, for example, about 1 μm to about 50 μm, about 1.5 μm to about 50 μm, about 1.5 μm to about 40 μm, or about 1 μm to about 30 μm. If, for example, the thickness of the substrate film is within the above ranges, the weight of the electrode assembly can be reduced more effectively. The melting point of the substrate film can be, for example, about 100°C to about 300°C, about 100°C to about 250°C, or about 100°C to about 200°C. If, for example, the substrate film has a melting point within the above ranges, the substrate film can melt during the soldering process to readily bond to the lead patch.To improve the adhesion between the substrate film and the metal layer, the substrate film can be surface-treated, such as by corona treatment. The thickness of the metal layer can be, for example, about 0.01 μm to about 3 μm, about 0.1 μm to about 3 μm, about 0.1 μm to about 2 μm, or about 0.1 μm to about 1 μm. If (for example, when) the thickness of the metal layer is within the above range, the stability of the electrode assembly can be obtained while maintaining the conductivity of the electrode assembly. The thickness of the metal sheet can be, for example, about 2 μm to about 10 μm, about 2 μm to about 7 μm, or about 4 μm to about 6 μm. If (for example, when) the thickness of the metal sheet is within the above range, the metal layer can be more easily connected to the lead tab. If (for example, when) the positive electrode current collector 11 has the above structure, the weight of the positive electrode can be reduced, thereby increasing the energy density of the positive electrode and the lithium battery.

[0092] [Dry cathode: intermediate layer] The dry positive electrode may include a positive current collector and a dry positive electrode film, and may also include an intermediate layer disposed between the positive current collector and the dry positive electrode film (i.e., the dry positive electrode active material layer). An intermediate layer may be omitted.

[0093] An intermediate layer can be disposed on at least one side of, for example, the positive current collector. By disposing the intermediate layer on at least one side of the positive current collector, the bonding strength between the positive current collector and the dry positive electrode film can be further improved.

[0094] The thickness of the intermediate layer can be, for example, about 0.01% to about 30%, about 0.1% to about 30%, about 0.5% to about 30%, about 1% to about 25%, about 1% to about 20%, about 1% to about 15%, about 1% to about 10%, about 1% to about 5%, or about 1% to about 3% of the thickness of the positive electrode current collector. The thickness of the intermediate layer can be, for example, about 10 nm to about 5 μm, about 50 nm to about 5 μm, about 200 nm to about 4 μm, about 500 nm to about 3 μm, about 500 nm to about 2 μm, about 500 nm to about 1.5 μm, or about 700 nm to about 1.3 μm. If (for example, when) the intermediate layer has a thickness within the above range, the bonding strength between the positive electrode current collector and the dry positive electrode film can be further increased, and the increase in interface resistance can be suppressed.

[0095] The intermediate layer may include, for example, a carbonaceous conductive material. The carbonaceous conductive material included in the intermediate layer may be selected from the carbonaceous conductive materials used in the dry electrode film. The intermediate layer may include the same carbonaceous conductive material as used in the dry electrode film. Because the intermediate layer includes a carbonaceous conductive material, it may be, for example, a conductive layer.

[0096] [Dry cathode: First inactive component] Reference Figures 4 to 7The positive electrode 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one side of the positive electrode current collector 11. A first inactive member 40 may be disposed on one side surface of the positive electrode 10. (Refer to...) Figure 4 and Figure 6 The first inactive component 40 may be disposed on at least one side of each of the positive electrode active material layer 12 and the positive electrode current collector 11. (Refer to...) Figure 5 and 7 The first inactive component 40 may be located on one side surface of the positive electrode active material layer 12 and disposed between the electrolyte layer 30 and the positive electrode current collector 11 facing the electrolyte layer 30. The first inactive component 40 may not be disposed on the side surface of the positive electrode current collector 11. The electrolyte layer 30 may be, for example, a solid electrolyte layer.

[0097] If (for example, when) the positive electrode 10 includes the first inactive component 40, the occurrence of cracks in the electrolyte layer 30 can be suppressed during the manufacture and / or charge / discharge of the all-solid-state secondary battery 1, thereby improving the cycle characteristics of the all-solid-state secondary battery 1. In an all-solid-state secondary battery 1 that does not include the first inactive component 40, substantially uneven pressure may be applied to the electrolyte layer 30 in contact with the positive electrode 10 during the manufacture and / or charge / discharge of the all-solid-state secondary battery 1, resulting in cracks in the electrolyte layer 30, thus lithium metal growth, thereby increasing the possibility of a short circuit.

[0098] In the all-solid-state secondary battery 1, the thickness of the first inactive component 40 can be greater than or the same as the thickness of the positive electrode active material layer 12. For example, in the all-solid-state secondary battery 1, the thickness of the first inactive component 40 can be substantially the same as the thickness of the positive electrode 10. If (for example, when) the thickness of the first inactive component 40 is the same as the thickness of the positive electrode 10, a substantially uniform pressure can be applied between the positive electrode 10 and the electrolyte layer 30, and the positive electrode 10 can be in sufficiently close contact with the electrolyte layer 30, thereby reducing the interfacial resistance between the positive electrode 10 and the electrolyte layer 30. The electrolyte layer 30 can be sufficiently sintered during the pressing / manufacturing process of the all-solid-state secondary battery 1, thus reducing the internal resistance of the electrolyte layer 30 and the all-solid-state secondary battery 1 including it.

[0099] The first inactive component 40 can be in contact with the solid electrolyte layer 30 while surrounding the side surface of the positive electrode 10. If (e.g., when) the first inactive component 40 is in contact with the electrolyte layer 30 while surrounding the side surface of the positive electrode 10, cracking caused by pressure differences in the electrolyte layer 30, which is not in contact with the positive electrode 10, can be effectively suppressed during the pressing process. The first inactive component 40 around the side surface of the positive electrode 10 (e.g., surrounding the side surface of the positive electrode 10) can be separated from the negative electrode 20 (e.g., the first negative electrode active material layer 22). The first inactive component 40 can be in contact with the electrolyte layer 30 while surrounding the side surface of the positive electrode 10, and can be separated from the negative electrode 20. Therefore, the possibility of a short circuit caused by physical contact between the positive electrode 10 and the first negative electrode active material layer 22, or the possibility of a short circuit caused by lithium overcharging, can be suppressed. For example, if (e.g., when) the first inactive component 40 is disposed on one side surface of the positive electrode active material layer 12 and one side surface of the positive electrode current collector 11, the possibility of a short circuit caused by the contact between the positive electrode current collector 11 and the negative electrode 20 can be suppressed more effectively.

[0100] Reference Figures 4 to 7 The first inactive member 40 can extend from one side surface of the positive electrode 10 to the end of the electrolyte layer 30. By extending the first inactive member 40 to the end of the electrolyte layer 30, cracks generated in the end of the electrolyte layer 30 can be suppressed. The end of the electrolyte layer 30 can be the outermost portion in contact with the side surface of the electrolyte layer 30. The first inactive member 40 can extend to the outermost portion in contact with the side surface of the solid electrolyte layer 30. The first inactive member 40 can be separate from the negative electrode 20 (e.g., the first negative electrode active material layer 22). The first inactive member 40 can extend to the end of the electrolyte layer 30 but not in contact with the negative electrode 20. The first inactive member 40 can fill the space between one side surface of the positive electrode 10 and the end of the electrolyte layer 30.

[0101] Reference Figures 4 to 7 The width of the first inactive member 40 extending from one side surface of the positive electrode 10 to the end of the electrolyte layer 30 can be, for example, about 1% to about 30%, about 1% to about 25%, about 1% to about 20%, about 1% to about 15%, about 1% to about 10%, or about 1% to about 5% of the width of the positive electrode 10 between one side and the other side facing that side. If (for example) the width of the first inactive member 40 is too large, the energy density of the all-solid-state secondary battery 1 may be reduced. If (for example) the width of the first inactive member 40 is too small, the effect of the first inactive member 40 will be negligible.

[0102] The area of ​​the positive electrode 10 can be smaller than the area of ​​the electrolyte layer 30 in contact with the positive electrode 10. A first inactive member 40 arranged around the side surface of the positive electrode 10 can compensate for the area difference between the positive electrode 10 and the electrolyte layer 30. Since the area of ​​the first inactive member 40 compensates for the difference between the area of ​​the positive electrode 10 and the area of ​​the electrolyte layer 30, cracks in the electrolyte layer 30 caused by pressure difference during the pressing process can be effectively suppressed. For example, the sum of the area of ​​the positive electrode 10 and the area of ​​the first inactive member 40 can be the same as the area of ​​the electrolyte layer 30. The electrolyte layer 30 can be, for example, a solid electrolyte layer.

[0103] The area of ​​the positive electrode 10 can be, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area of ​​the electrolyte layer 30. The area of ​​the positive electrode 10 can be, for example, about 50% to less than 100%, about 50% to about 99%, about 55% to about 98%, about 60% to about 97%, about 70% to about 96%, about 80% to about 95%, or about 85% to about 95% of the area of ​​the electrolyte layer 30.

[0104] If (for example, when) the area of ​​the positive electrode 10 is equal to or greater than the area of ​​the electrolyte layer 30, the likelihood of a short circuit caused by physical contact between the positive electrode 10 and the first negative electrode active material layer 22, or by overcharging of lithium, may increase. The area of ​​the positive electrode 10 may, for example, be the same as the area of ​​the positive electrode active material layer 12. The area of ​​the positive electrode 10 may, for example, be the same as the area of ​​the positive electrode current collector 11.

[0105] The area of ​​the first inactive component 40 may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the area of ​​the positive electrode 10. The area of ​​the first inactive component 40 may be, for example, about 1% to about 50%, about 5% to about 40%, about 5% to about 30%, about 5% to about 20%, or about 5% to about 15% of the area of ​​the positive electrode 10.

[0106] The area S1 of the positive electrode 10 can be smaller than the area S4 of the negative electrode current collector 21. The area S1 of the positive electrode 10 can, for example, be smaller than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area S4 of the negative electrode current collector 21. The area S1 of the positive electrode 10 can, for example, be about 50% to less than 100%, about 50% to about 99%, about 55% to about 98%, about 60% to about 97%, about 70% to about 96%, about 80% to about 95%, or about 85% to about 95% of the area S4 of the negative electrode current collector 21. The area S4 of the negative electrode current collector 21 can, for example, be the same as the area of ​​the negative electrode 20. The area S4 of the negative electrode current collector 21 can, for example, be the same as the area of ​​the first negative electrode active material layer 22.

[0107] As used herein, “identical” area, length, width, thickness, and / or shape can include all cases where the area, length, thickness, and / or shape are “substantially identical” except where the area, length, thickness, and / or shape has been intentionally modified. “Identical” area, length, width, and / or thickness can include, for example, a range of unintended differences in area, length, width, and / or thickness between objects being compared that are less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0108] The thickness of the first inactive component 40 may, for example, be greater than the thickness of the first negative electrode active material layer 22. The thickness of the first negative electrode active material layer 22 may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the first inactive component 40. The thickness of the first negative electrode active material layer 22 may be approximately 1% to approximately 50%, approximately 1% to approximately 40%, approximately 1% to approximately 30%, approximately 1% to approximately 20%, or approximately 1% to approximately 10% of the thickness of the first inactive component 40.

[0109] The first inactive component 40 can be a gasket. By using a gasket as the first inactive component 40, cracks that occur in the electrolyte layer 30 due to pressure differences during the pressing process can be more effectively suppressed.

[0110] The first inactive component 40 may have, for example, a single-layer structure. In some embodiments, although not shown in the figures, the first inactive component 40 may have a multi-layer structure. In a first inactive component 40 with a multi-layer structure, the individual layers may have different compositions. The first inactive component 40 with a multi-layer structure may have a two-layer, three-layer, four-layer, or five-layer structure. The first inactive component 40 with a multi-layer structure may include, for example, at least one adhesive layer and at least one support layer. The adhesive layer can effectively prevent or reduce the separation of the positive electrode 10 from the electrolyte layer 30 caused by volume changes of the positive electrode 10 during the charge and discharge process of the all-solid-state secondary battery 1, and provides adhesive strength between the support layer and other layers, thereby increasing the thin strength of the first inactive component 40. The support layer can provide support for the first inactive component 40 to prevent or reduce the application of significantly uneven pressure to the electrolyte layer 30 during the pressing process or charge and discharge process, and to prevent or reduce deformation of the all-solid-state secondary battery 1.

[0111] The first inactive component 40 can be, for example, a flame-retardant inactive component. Because the flame-retardant inactive component provides flame retardancy, thermal runaway and ignition of the all-solid-state secondary battery 1 can be prevented or reduced. As a result, the safety of the all-solid-state secondary battery 1 can be further improved. The flame-retardant inactive component absorbs moisture remaining in the all-solid-state secondary battery 1, thus preventing or reducing the degradation of the all-solid-state secondary battery 1 and improving its lifespan characteristics.

[0112] The flame-retardant inactive component may include, for example, a matrix and a filler. The matrix may include, for example, a substrate and a reinforcing material. The matrix may include, for example, a fiber substrate and a fiber reinforcing material. By including a substrate, the matrix can be elastic. Therefore, the matrix can effectively adapt to volume changes during the charging and discharging of the all-solid-state secondary battery 1 and can be arranged in one or more suitable locations. The substrate included in the matrix may include, for example, a first fiber material. If (e.g., when) the substrate includes a first fiber material, the volume change of the positive electrode 10 can be effectively adapted during the charging and discharging of the all-solid-state secondary battery 1, and deformation of the first inactive component 40 caused by the volume change of the positive electrode 10 can be effectively suppressed. The first fiber material may be, for example, a material with an aspect ratio of 5 or greater, 20 or greater, or 50 or greater. The first fiber material may be, for example, a material with an aspect ratio of about 5 to about 1000, about 20 to about 1000, or about 50 to about 1000. The first fiber material may be, for example, an insulating material. Because the first fiber material is an insulating material, short circuits between the positive electrode 10 and the negative electrode 20 caused by lithium dendrites or the like formed during the charging and discharging process of the all-solid-state secondary battery 1 can be effectively suppressed. The first fiber material may include, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conducting polymer fibers. Because the matrix includes a reinforcing material, the strength of the matrix can be increased. Therefore, the matrix can prevent or reduce excessive volume changes during the charging and discharging of the all-solid-state secondary battery 1 and prevent or reduce deformation of the all-solid-state secondary battery. The reinforcing material included in the matrix may include, for example, a second fiber material. Because the reinforcing material includes a second fiber material, the strength of the matrix can be increased more uniformly. The second fiber material may be, for example, a material with an aspect ratio of 3 or greater, 5 or greater, or 10 or greater. The second fiber material may be, for example, a material with an aspect ratio of about 3 to about 100, about 5 to about 100, or about 10 to about 100. The second fiber material may be, for example, a flame-retardant material. Because the second fiber material is a flame-retardant material, it can effectively prevent or reduce ignition caused by thermal runaway during the charging and discharging process of the all-solid-state secondary battery 1 or by external impact. The second fiber material may be, for example, glass fiber, metal oxide fiber, and ceramic fiber.

[0113] In addition to the matrix, the flame-retardant inactive component may also include a filler. The filler may be located inside the matrix, on the surface of the matrix, or both inside and on the surface of the matrix (e.g., simultaneously inside and on the surface of the matrix). The filler may be, for example, an inorganic material. The filler included in the flame-retardant inactive component may be, for example, a hygroscopic agent. The filler may absorb moisture, for example, at temperatures below 100°C to remove residual moisture in the all-solid-state secondary battery 1, thereby preventing or reducing the degradation of the all-solid-state secondary battery 1. If (e.g., when) the temperature of the all-solid-state secondary battery 1 exceeds 150°C due to thermal runaway during the charge-discharge process of the all-solid-state secondary battery 1 or due to external impact, the filler may release the absorbed moisture, thereby effectively suppressing ignition of the all-solid-state secondary battery 1. For example, the filler may be, for example, a flame retardant. The filler may be, for example, a hygroscopic metal hydroxide. The metal hydroxide included in the filler may be, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, Ti(OH)3, Zr(OH)4, Al(OH)3, or any combination thereof. Based on 100 parts by weight of the flame-retardant inactive component 40, the amount of filler included in the flame-retardant inactive component may be, for example, about 10 parts by weight to about 80 parts by weight, about 20 parts by weight to about 80 parts by weight, about 30 parts by weight to about 80 parts by weight, about 40 parts by weight to about 80 parts by weight, about 50 parts by weight to about 80 parts by weight, about 60 parts by weight to about 80 parts by weight, or about 65 parts by weight to about 80 parts by weight.

[0114] Flame-retardant inactive components may also include, for example, adhesives. Adhesives may include, for example, curable polymers or non-curable polymers. Curable polymers may be polymers that are cured by heat and / or pressure. Curable polymers may be, for example, solids at room temperature. Flame-retardant inactive components include, for example, hot-pressed curable polymers and / or their cured products. Hot-pressed curable polymers may be, for example, TSA-66 manufactured by Toray.

[0115] In addition to the substrate, reinforcing material, filler, and binder described above, the flame-retardant inactive component may also include other materials. The flame-retardant inactive component may also include at least one selected from, for example, paper, insulating polymers, ionically conductive polymers, insulating inorganic materials, oxide solid electrolytes, and sulfide solid electrolytes. The insulating polymer may be, for example, an olefin polymer, such as polypropylene (PP) and polyethylene (PE).

[0116] The density of the substrate or reinforcing material included in the flame-retardant inactive component may be, for example, about 10% to about 300%, about 10% to about 150%, about 10% to about 140%, about 10% to about 130%, or about 10% to about 120% of the density of the positive active material included in the positive active material layer 12.

[0117] The first inactive component 40 may be a component that does not include an electrochemically active material (such as an electrode active material). The electrode active material may be a material that allows lithium insertion / extraction. Apart from the electrode active material, the first inactive component 40 may be formed of any material commonly used in the art.

[0118] [All-solid-state rechargeable battery] The all-solid-state secondary battery according to an embodiment may include: a positive electrode; a negative electrode; and an electrolyte layer disposed between the positive and negative electrodes. The positive electrode may be the aforementioned dry positive electrode. The negative electrode may include a negative electrode current collector and a first negative electrode active material layer disposed on one side of the negative electrode current collector.

[0119] Reference Figures 1 to 7 The all-solid-state secondary battery 1 may include: a positive electrode 10; a negative electrode 20; and an electrolyte layer 30 disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10 may include a dry positive electrode. The negative electrode 20 may include a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on one side of the negative electrode current collector 21.

[0120] [positive electrode] Refer to the previously described dry positive electrode.

[0121] [negative electrode] [Negative electrode: Negative electrode active material] Reference Figures 1 to 7 The negative electrode 20 may include a first negative electrode active material layer 22. The first negative electrode active material layer 22 may include, for example, a negative electrode active material and a binder.

[0122] The negative electrode active material included in the first negative electrode active material layer 22 can be, for example, a material for the negative electrode that allows the formation of alloys or compounds with lithium.

[0123] The negative electrode active material included in the first negative electrode active material layer 22 can, for example, be in particulate form. The particulate form of the negative electrode active material can have an average particle size of, 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 particulate form of the negative electrode active material can have an average particle size of, for example, about 10 nm to about 4 μm, about 10 nm to about 3 μm, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 300 nm, or about 10 nm to about 100 nm. If (for example, when) the average particle size of the negative electrode active material is within the above ranges, reversible adsorption and / or desorption of lithium can occur more easily during charge and discharge. The average particle size of the negative electrode active material can be, for example, the median diameter D50 measured using a laser particle size analyzer.

[0124] The negative electrode active material included in the first negative electrode active material layer 22 may include at least one selected from, for example, carbonaceous negative electrode active materials and metallic or quasi-metallic negative electrode active materials.

[0125] Carbonaceous anode active materials may include, for example, amorphous carbon, crystalline carbon, porous carbon, or any combination thereof.

[0126] The carbonaceous negative electrode active material can be, for example, amorphous carbon. Amorphous carbon can be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), or graphene, but is not limited thereto; any carbon classified as amorphous carbon in the art can also be used. Amorphous carbon can be carbon that is non-crystalline or has very low crystallinity, and can be distinguished from crystalline carbon or graphitic carbon.

[0127] The carbonaceous anode active material can be, for example, porous carbon. The pore volume in the porous carbon can be, for example, about 0.1 cc / g to about 10.0 cc / g, about 0.5 cc / g to about 5 cc / g, or about 0.1 cc / g to about 1 cc / g. The porous carbon can have, for example, an average pore size of about 1 nm to about 50 nm, about 1 nm to about 30 nm, or about 1 nm to about 10 nm. The porous carbon can have, for example, an average pore size of about 100 nm. 2 / g to approximately 3000m 2 / g BET specific surface area.

[0128] Metallic or quasi-metallic anode active materials may include, but are not limited to, at least one selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any suitable metallic or quasi-metallic anode active material that forms an alloy or compound with lithium may also be used. For example, because Ni does not form an alloy with lithium, nickel (Ni) is not a metallic anode active material.

[0129] The first negative electrode active material layer 22 may include one type (or kind) of negative electrode active material or a mixture of multiple different negative electrode active materials. For example, the first negative electrode active material layer 22 may include only amorphous carbon, or it may include at least one selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). In some embodiments, the first negative electrode active material layer 22 may include amorphous carbon and a mixture of at least one selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of amorphous carbon and gold, etc., in the mixture may be, for example, about 99:1 to about 1:99, about 10:1 to about 1:2, about 5:1 to about 1:1, or about 4:1 to about 2:1. However, the mixing ratio is not limited to this, but is selected according to the desired characteristics of the all-solid-state secondary battery 1. Due to the composition of the negative electrode active material, the cycle characteristics of the all-solid-state secondary battery 1 can be further improved.

[0130] The negative electrode active material included in the first negative electrode active material layer 22 may comprise, for example, a mixture of first particles formed of amorphous carbon and second particles formed of metal or metalloid. The metal or metalloid may include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The metalloid may be, for example, a semiconductor. Based on the total weight of the mixture, the amount of the second particles may be from about 1 to about 99 wt%, from about 1 wt% to about 60 wt%, from about 8 wt% to about 60 wt%, from about 10 wt% to about 50 wt%, from about 15 wt% to about 40 wt%, or from about 20 wt% to about 30 wt%. If (for example, when) the amount of the second particles is within the above ranges, the cycle characteristics of the all-solid-state secondary battery 1 may be further improved.

[0131] In some embodiments, the first negative electrode active material layer 22 may include a composite negative electrode active material. The composite negative electrode active material may include, for example, a carbonaceous support and a metal negative electrode active material supported on the carbonaceous support. If (e.g., when) the composite negative electrode active material has such a structure, localization of the metal negative electrode active material in the first negative electrode active material layer can be suppressed and a substantially uniform distribution can be obtained. As a result, the cycle characteristics of the all-solid-state secondary battery 1 including the first negative electrode active material layer 22 can be further improved.

[0132] The metal negative electrode active material supported on a carbonaceous carrier may include, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or any 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 (where 0 < x ≤ 2 and 0 < y ≤ 3), Pt x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), Pd x O y (where 0 < x ≤ 1 and 0 < y ≤ 1), Si x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), Ag x O y (where 0 < x ≤ 2 and 0 < y ≤ 1), Al x O y (where 0 < x ≤ 2 and 0 < y ≤ 3), Bi x O y (where 0 < x ≤ 2 and 0 < y ≤ 3), Sn x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), Te x O y (where 0 < x ≤ 1 and 0 < y ≤ 3), Zn x O y (where 0 < x ≤ 1 and 0 < y ≤ 1), or any combination thereof. The composite of a metal and a metal oxide may include, for example, a composite of Au and Au x O y (where 0 < x ≤ 2 and 0 < y ≤ 3), a composite of Pt and Pt x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), a composite of Pd and Pd x O y (where 0 < x ≤ 1 and 0 < y ≤ 1), a composite of Si and Si x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), a composite of Ag and Ag x O y (where 0 < x ≤ 2 and 0 < y ≤ 1), a composite of Al and Al x Oy a composite of (where 0 < x ≤ 2 and 0 < y ≤ 3), Bi and Bi x O y a composite of (where 0 < x ≤ 2 and 0 < y ≤ 3), Sn and Sn x O y a composite of (where 0 < x ≤ 1 and 0 < y ≤ 2), Te and Te x O y a composite of (where 0 < x ≤ 1 and 0 < y ≤ 3), Zn and Zn x O y a composite of (where 0 < x ≤ 1 and 0 < y ≤ 1), or any combination thereof.

[0133] The carbonaceous carrier can be, for example, amorphous carbon. The amorphous carbon can be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), or carbon nanotubes (CNT), but is not limited thereto, and any carbon classified as amorphous carbon in the art can also be used. The amorphous carbon can be carbon that does not have crystallinity or has very low crystallinity and can be distinguished from crystalline carbon or graphite-like carbon. The carbonaceous material can be, for example, a carbonaceous negative electrode active material.

[0134] The composite negative electrode active material can be in the form of particles, for example. The composite negative electrode active material in the form of particles can have a particle size of, for example, about 10 nm to about 4 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. If (for example, when) the average particle size of the composite negative electrode active material is within the above range, reversible adsorption and / or desorption of lithium can occur more easily during charge and discharge. The metal negative electrode active material supported on the carrier can be in the form of particles, for example. The metal negative electrode active material can have a particle size of, for example, about 1 nm to about 200 nm, about 1 nm to about 150 nm, about 5 nm to about 100 nm, or about 10 nm to about 50 nm. The carbonaceous carrier can be in the form of particles, for example. The carbonaceous carrier can have a particle size of, for example, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. If (for example, when) the carbonaceous carrier has a particle size within the above range, the carbonaceous carrier can be more uniformly arranged in the first negative electrode active material layer. The carbonaceous carrier can be, for example, nanoparticles having a particle size of 500 nm or less. The particle sizes of the composite negative electrode active material, the metal negative electrode active material, and the carbonaceous carrier can be, for example, average particle sizes. The average particle size can be, for example, the median diameter D50 measured using a laser particle size analyzer. In some embodiments, the average particle size can be automatically determined or manually determined using software based on guidelines from electron microscope images, for example.

[0135] [Negative electrode: binder] The binder included in the first negative electrode active material layer 22 may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, or polymethyl methacrylate, but is not limited thereto, and any binder commonly available in the art may also be used. The binder may be used alone or in combination of several different binders.

[0136] Because the first negative electrode active material layer 22 includes a binder, it can be stably positioned on the negative electrode current collector 21. Although the volume and / or relative position of the first negative electrode active material layer 22 may change, cracking can be suppressed within it during the charge-discharge process. For example, if (e.g., when) the first negative electrode active material layer 22 does not include a binder, it would easily separate from the negative electrode current collector 21. Separation of the first negative electrode active material layer 22 from the negative electrode current collector 21 could expose areas of the negative electrode current collector 21 to the electrolyte layer 30, increasing the likelihood of a short circuit. The first negative electrode active material layer 22 can be prepared, for example, by applying a slurry containing materials constituting the first negative electrode active material layer 22 to the negative electrode current collector 21 and drying the slurry. By adding a binder to the first negative electrode active material layer 22, the negative electrode active material can be stably dispersed in the slurry. For example, if (e.g., when) the paste is applied to the negative electrode current collector 21 by screen printing, it may be possible to suppress or reduce screen clogging (e.g., clogging by aggregates of negative electrode active material).

[0137] [Anode: Other additives] The first negative electrode active material layer 22 may also include additives used in the all-solid-state secondary battery 1, such as fillers, coatings, dispersants, and ion conduction aids.

[0138] [Negative electrode: Solid electrolyte] The first negative electrode active material layer 22 may further include a solid electrolyte. The solid electrolyte may be selected from those included in the electrolyte layer 30. The solid electrolyte included in the first negative electrode active material layer 22 can serve as a reaction site for initiating the formation of lithium metal in the first negative electrode active material layer 22, as a space for storing the formed lithium metal, or as a pathway for transporting lithium ions. A solid electrolyte may not be provided.

[0139] In the first negative electrode active material layer 22, for example, the amount of solid electrolyte may be higher in the region adjacent to the electrolyte layer 30 and lower in the region adjacent to the negative electrode current collector 21. In the first negative electrode active material layer 22, the solid electrolyte may have, for example, a concentration gradient, such that the concentration decreases from the region adjacent to the electrolyte layer 30 to the region adjacent to the negative electrode current collector 21.

[0140] [Negative Electrode: First Negative Electrode Active Material Layer] The ratio of the initial charge capacity B of the first negative electrode active material layer 22 to the initial charge capacity A of the positive electrode active material layer, B / A, can be from approximately 0.005 to approximately 0.45. The initial charge capacity of the positive electrode active material layer 12 can be determined from the first open-circuit voltage relative to Li / Li + The initial charging capacity of the first negative electrode active material layer 22 can be determined at the maximum charging voltage relative to the second open-circuit voltage. + Determined at 0.01V.

[0141] The maximum charging voltage can be determined by the type (or variety) of the positive electrode active material. The maximum charging voltage can be, for example, 1.5V, 2.0V, 2.5V, 3.0V, 3.5V, 4.0V, 4.2V, or 4.3V. For example, the maximum charging voltage of Li₂S or a Li₂S complex relative to Li / Li⁺ can be 2.5V. For example, the maximum charging voltage of Li₂S or a Li₂S complex relative to Li / Li⁺ can be... +The initial charge capacity (B) of the first negative electrode active material layer 22 to the initial charge capacity (A) of the positive electrode active material layer (B / A) can be, for example, about 0.01 to about 0.3, about 0.01 to about 0.2, or about 0.05 to about 0.1. The initial charge capacity (mAh) of the positive electrode active material layer 12 can be obtained by multiplying the specific charge capacity (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer 12. If (for example, when) one or more suitable types (species) of positive electrode active material are used, the specific charge capacity × mass value for all positive electrode active materials is calculated separately, and the sum of the values ​​can be considered as the initial charge capacity of the positive electrode active material layer 12. The initial charge capacity of the first negative electrode active material layer 22 can be calculated in substantially the same manner. The initial charge capacity of the first negative electrode active material layer 22 can be obtained by multiplying the specific charge capacity (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer 22. If (for example, when) one or more suitable types (species) of negative electrode active materials are used, the specific charge capacity × mass value for each negative electrode active material is calculated separately, and the sum of the values ​​can be considered as the initial charge capacity of the first negative electrode active material layer 22. The specific charge capacity of the positive and negative electrode active materials can be measured using an all-solid-state half-cell using lithium metal as the counter electrode. The initial charge capacity of the positive electrode active material layer 12 and the first negative electrode active material layer 22 can be measured using an all-solid-state half-cell at a constant current density (e.g., 0.1 mA / cm²). 2 Direct measurement is possible under these conditions. It can measure voltages from the first open-circuit voltage (OCV) to the maximum charging voltage (e.g., 3.0V relative to Li / Li). + The positive electrode of the cell can be measured at its operating voltage. The negative electrode (e.g., lithium metal) can be measured at operating voltages ranging from a second open-circuit voltage (OCV) to 0.01V. For example, an all-solid-state half-cell including a positive electrode active material layer can be measured at 0.1 mA / cm². 2 A constant current is applied from the first open-circuit voltage to 3.0V, and the all-solid-state half-cell, including the first negative electrode active material layer, can be charged at 0.1mA / cm. 2 A constant current is applied to charge the circuit from the second open-circuit voltage to 0.01V. The current density during charging at a constant current can be, for example, 0.2 mA / cm². 2 or 0.5mA / cm 2 An all-solid-state half-cell, including a positive electrode active material layer, can be charged, for example, from a first open-circuit voltage to 2.5V, 2.0V, 3.5V, or 4.0V. The maximum charging voltage of the positive electrode active material can be determined by the maximum voltage of the battery that meets the safety conditions according to JISC8712:2015 of the Japanese Standards Institute.

[0142] If (for example, when) the first negative electrode active material layer 22 has too low an initial charge capacity, the thickness of the first negative electrode active material layer 22 will become too small. Therefore, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 during repeated charge and discharge processes may damage the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If (for example, when) the first negative electrode active material layer 22 has too high a charge capacity, the energy density of the all-solid-state secondary battery 1 will decrease. Therefore, the internal resistance of the all-solid-state secondary battery 1 may increase due to the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0143] The thickness of the first negative electrode active material layer 22 can be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 can be, for example, about 1% to about 50%, about 1% to about 40%, about 1% to about 30%, about 1% to about 20%, about 1% to about 10%, or about 1% to about 5% of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 can be, for example, about 1 μm to about 20 μm, about 2 μm to about 15 μm, or about 3 μm to about 10 μm. If (for example, when) the first negative electrode active material layer 22 has too small a thickness, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 may damage the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If (for example, when) the first negative electrode active material layer 22 has too large a thickness, the energy density of the all-solid-state secondary battery 1 may decrease, and the internal resistance of the all-solid-state secondary battery 1 may increase due to the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If (for example, when) the thickness of the first negative electrode active material layer 22 decreases, for example, the initial charging capacity of the first negative electrode active material layer 22 will also decrease.

[0144] [Negative Electrode: Second Negative Electrode Active Material Layer] Reference Figure 3The all-solid-state secondary battery 1 may further include, for example, a second negative electrode active material layer 24 disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 after charging. The second negative electrode active material layer 24 may be a metal layer comprising lithium or a lithium alloy. The metal layer may include lithium or a lithium alloy. Therefore, the second negative electrode active material layer 24, as a lithium-containing metal layer, can be used as a lithium storage device. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, or a Li-Si alloy, but is not limited thereto; any lithium alloy commonly available in the art may also be used. The second negative electrode active material layer 24 may be formed from a single alloy, lithium, or a combination of one or more suitable types (types) of alloys. The second negative electrode active material layer 24 may be, for example, a plating. For example, the second negative electrode active material layer 24 may be plated between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charge and discharge process of the all-solid-state secondary battery 1.

[0145] The thickness of the second negative electrode active material layer 24 is not limited, but can be, for example, about 1 μm to about 500 μm, about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 1 μm to about 100 μm, or about 1 μm to about 50 μm. If (for example, when) the thickness of the second negative electrode active material layer 24 is too small, it may be difficult to obtain the function of the second negative electrode active material layer 24 as a lithium storage device. If (for example, when) the thickness of the second negative electrode active material layer 24 is too large, the mass and volume of the all-solid-state secondary battery 1 increase, and therefore the cycle characteristics of the all-solid-state secondary battery 1 may deteriorate.

[0146] In some embodiments, in the all-solid-state secondary battery 1, a second negative electrode active material layer 24 may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembling the all-solid-state secondary battery 1. If (for example, when) the second negative electrode active material layer 24 is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembling the all-solid-state secondary battery 1, the second negative electrode active material layer 24, as a metal layer including lithium, can be used as a lithium storage device. For example, a lithium foil may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembling the all-solid-state secondary battery 1.

[0147] If, for example, the second negative electrode active material layer 24 is deposited by charging after assembling the all-solid-state secondary battery 1, the energy density of the all-solid-state secondary battery 1 can be increased because the second negative electrode active material layer 24 is not included during the assembly of the all-solid-state secondary battery 1. While charging the all-solid-state secondary battery 1, it is possible to charge beyond the charging capacity of the first negative electrode active material layer 22. For example, the first negative electrode active material layer 22 can be overcharged. During the initial charging, lithium can be adsorbed onto the first negative electrode active material layer 22. The negative electrode active material included in the first negative electrode active material layer 22 can form an alloy or compound with lithium ions that have migrated from the positive electrode 10. If, for example, the first negative electrode active material layer 22 is overcharged beyond its capacity, lithium can be deposited on the rear surface of the first negative electrode active material layer 22 (i.e., between the negative electrode current collector 21 and the first negative electrode active material layer 22), and a metal layer corresponding to the second negative electrode active material layer 24 can be formed by the deposited lithium. The second negative electrode active material layer 24 can be a metal layer mainly composed of lithium (i.e., lithium metal). These results are achieved because the negative electrode active material included in the first negative electrode active material layer 22 comprises materials that form alloys or compounds with lithium. During discharge, the lithium in the first negative electrode active material layer 22 and the second negative electrode active material layer 24 (i.e., the metal layer) can be ionized to migrate in the direction toward the positive electrode 10. Therefore, lithium can be utilized as the negative electrode active material in the all-solid-state secondary battery 1. For example, because the second negative electrode active material layer 24 is coated with the first negative electrode active material layer 22, the first negative electrode active material layer 22 can serve as a protective layer for the second negative electrode active material layer 24 (i.e., the metal layer) to prevent or reduce the formation and growth of lithium dendrites. Therefore, short circuits and capacity reduction can be suppressed in the all-solid-state secondary battery 1, thus improving the cycle characteristics of the all-solid-state secondary battery 1. If, for example, the second negative electrode active material layer 24 is set by charging after assembling the all-solid-state secondary battery 1, then the negative electrode 20 (i.e., the negative electrode current collector 21, the first negative electrode active material layer 22, and the region therebetween) can be a Li-free region that does not include lithium (Li) in the early stages of charging or after the all-solid-state secondary battery 1 has been fully discharged.

[0148] [Negative electrode: Negative electrode current collector] The negative electrode current collector 21 can be formed of, for example, a material that does not react with lithium (i.e., a material that does not form alloys or compounds with lithium). The material constituting the negative electrode current collector 21 can be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not limited thereto, and any material commonly used as an electrode current collector in the art can also be used. The negative electrode current collector 21 can be formed of one metal selected from the above-mentioned metals, or an alloy or coating material of two or more metals. The negative electrode current collector 21 can be, for example, in the form of a plate or foil.

[0149] Reference Figure 2 The all-solid-state secondary battery 1 may further include a thin film 23 comprising elements capable of forming an alloy with lithium, on one side of the negative electrode current collector 21. The thin film 23 may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The thin film 23 may include, for example, elements capable of forming an alloy with lithium. Examples of elements capable of forming an alloy with lithium include gold, silver, zinc, tin, indium, silicon, aluminum, and bismuth, but are not limited thereto, and any suitable element capable of forming an alloy with lithium may also be used. The thin film 23 may be formed from any metal or an alloy of one or more suitable types (classes) of metals. By disposing of the thin film 23 on one surface of the negative electrode current collector 21, the second negative electrode active material layer 24 deposited between the thin film 23 and the first negative electrode active material layer 22 can become flatter, thereby further improving the cycle characteristics of the all-solid-state secondary battery 1.

[0150] For example, the thin film 23 may have a thickness of about 1 nm to about 800 nm, about 10 nm to about 700 nm, about 50 nm to about 600 nm, or about 100 nm to about 500 nm. If the thickness of the thin film 23 is less than 1 nm, it may be difficult to obtain the functionality of the thin film 23. If the thickness of the thin film 23 is too large, the amount of lithium adsorbed by the thin film 23 and deposited in the negative electrode is reduced, thus the energy density of the all-solid-state secondary battery 1 may be reduced and the cycle characteristics of the all-solid-state secondary battery 1 may be degraded. The thin film 23 may be formed on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, or deposition. However, the method is not limited to this, and any method commonly used in the art to form the thin film 23 may be used.

[0151] In one or more embodiments, the negative current collector 21 may include, for example, a substrate film and a metal layer disposed on at least one side (e.g., one side or both sides (e.g., opposite sides)) of the substrate film. The substrate film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or any combination thereof. The polymer may be an insulating polymer. If (e.g., when) the substrate film comprises an insulating thermoplastic polymer, the substrate film may soften or liquefy in the event of a short circuit to stop the operation of the battery, thereby suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The negative current collector 21 may also include a metal sheet and / or lead terminals. For a detailed description of the substrate film, metal layer, metal sheet, and lead terminals of the negative current collector 21, refer to the positive current collector 11 described above. If (for example, when) the negative electrode current collector 21 has the above structure, the weight of the negative electrode can be reduced, thereby increasing the energy density of the negative electrode and the lithium battery.

[0152] [Negative electrode layer: Second inactive component] Reference Figures 6 to 7 The all-solid-state secondary battery 1 may also include a second inactive component 50 disposed on the other side of the negative electrode current collector 21.

[0153] The difference between the second inactive member 50 and the first inactive member 40 may be that the second inactive member 50 is conductive (e.g., a conductor) by additionally including a conductive material. The second inactive member 50 may be, for example, a conductive flame-retardant inactive member.

[0154] For example, the conductive material can be graphite, carbon black, acetylene black, Ketjen black, superconducting acetylene black, carbon fiber, carbon nanotubes (CNTs), graphene, metal fiber, or metal powder. At 25°C, the second inactive component 50 can have an electronic conductivity that is, for example, 100 times, 1000 times, or 10000 times, or greater than that of the first inactive component 40.

[0155] The second inactive component 50 may include, for example, a matrix, a filler, and a conductive material. The matrix may include, for example, a substrate and a reinforcing material. The second inactive component 50 may also include fillers, binders, etc. Based on 100 parts by weight of the second inactive component 50, the amount of conductive material included in the second inactive component 50 may be, for example, about 1 part by weight to about 30 parts by weight, about 1 part by weight to about 20 parts by weight, about 1 part by weight to about 15 parts by weight, about 1 part by weight to about 10 parts by weight, about 5 parts by weight to about 40 parts by weight, about 5 parts by weight to about 30 parts by weight, or about 5 parts by weight to about 35 parts by weight.

[0156] The second inactive component 50 may have a Young's modulus, for example, smaller than that of the negative electrode current collector 21. The Young's modulus of the second inactive component 50 may be, for example, 50% or less, 30% or less, 10% or less, or 5% or less of the Young's modulus of the negative electrode current collector 21. The Young's modulus of the second inactive component 50 may be, for example, about 0.01% to about 50%, about 0.1% to about 30%, about 0.1% to about 10%, or about 1% to about 5% of the Young's modulus of the negative electrode current collector 21. The Young's modulus of the second inactive component 50 may, for example, be 100 MPa or less, 50 MPa or less, 30 MPa or less, 10 MPa or less, or 5 MPa or less. The Young's modulus of the second inactive component 50 may be, for example, about 0.01 MPa to about 100 MPa, about 0.1 MPa to about 50 MPa, about 0.1 MPa to about 30 MPa, about 0.1 MPa to about 10 MPa, or about 1 MPa to about 5 MPa.

[0157] If (for example, when) the second inactive component 50, 50a, or 50b is conductive (e.g., a conductor), it can perform the function of the second inactive component 50. Because the second inactive component 50 has a lower Young's modulus than the negative electrode current collector 21, it can more effectively accommodate volume changes in the negative electrode layer 20 during the charge and discharge of the all-solid-state secondary battery 1. As a result, the second inactive component 50 can effectively reduce the internal stress caused by the volume changes of the all-solid-state secondary battery 1 during the charge and discharge of the all-solid-state secondary battery 1, and thus can further improve the cycle characteristics of the all-solid-state secondary battery 1.

[0158] The thickness of the second inactive component 50 can, for example, be greater than the thickness of the first negative electrode active material layer 22. Because the second inactive component 50 has a greater thickness than the first negative electrode active material layer 22, it can more effectively accommodate volume changes in the negative electrode 20 during charging and discharging. The thickness of the first negative electrode active material layer 22 can be 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the second inactive component 50. The thickness of the first negative electrode active material layer 22 can be, for example, about 1% to about 50%, about 1% to about 40%, about 1% to about 30%, about 1% to about 20%, or about 1% to about 10% of the thickness of the second inactive component 50. The thickness of the second inactive component 50 can be, for example, about 1 μm to about 300 μm, about 10 μm to about 300 μm, about 50 μm to about 300 μm, or about 100 μm to about 200 μm. If the second inactive member 50 has too little thickness, it may not provide its intended effect. If the second inactive member 50 has too much thickness, the energy density of the all-solid-state secondary battery 1 may decrease. The shape of the second inactive member 50 is not limited and can be selected according to the shape of the all-solid-state secondary battery 1. The second inactive member 50 may be in the form of, for example, a sheet, rod, or gasket. The second inactive member 50 may be disposed on one surface or (e.g., simultaneously) on both surfaces of an all-solid-state secondary battery 1. The second inactive member 50 may be disposed, for example, between multiple stacked all-solid-state secondary batteries 1. For example, the second inactive member 50 may be disposed between multiple stacked all-solid-state secondary batteries 1, on the uppermost surface, and / or the lowermost surface.

[0159] [Electrolyte layer] [Electrolyte layer: Electrolyte] Reference Figures 3 to 7 The electrolyte layer 30 may include an electrolyte disposed between the positive electrode 10 and the negative electrode 20. The electrolyte may include, for example, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0160] Solid electrolytes may include, for example, sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or any combination thereof.

[0161] Solid electrolytes can be, for example, sulfide-based solid electrolytes. For a description of sulfide-based solid electrolytes, refer to the description of the dry cathode film above.

[0162] Oxide solid electrolytes can be, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12(where 0 < x < 2 and 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT, where 0 ≤ x < 1 and 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 (where 0 < x < 2 and 0 < y < 3), Li[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Polymer solid electrolytes may include, for example, mixtures of lithium salts and polymers, or polymers having ion-conducting functional groups. Polymer solid electrolytes may be, for example, solid polymer electrolytes at 25°C and 1 atm. Polymer solid electrolytes may not contain (e.g., may exclude) liquids. Polymer solid electrolytes may include polymers. Polymers can be, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), PVDF-HFP copolymer, 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(methyl methacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylene dioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(aryl ether ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazolidinebenzisoquinolinone)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylanthracene-2-sulfonate (DPASLi) + Lithium salts may be any combination thereof, but are not limited thereto, and any compound commonly used as a polymer electrolyte in the art may be used. The lithium salt may also be any lithium salt commonly used in the art. For example, the lithium salt may be LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are 1 to 20), LiCl, LiI, or any mixture thereof. The polymer included in the polymer solid electrolyte can be, for example, a compound comprising 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The polymer included in the polymer solid electrolyte can have, for example, a weight-average molecular weight of 1000 Daltons (Da) or greater, 10,000 Da or greater, 100,000 Da or greater, or 1,000,000 Da or greater.

[0165] Gel electrolytes can be, for example, polymer gel electrolytes. Gel electrolytes can have a gel state without including polymers.

[0166] Polymer gel electrolytes may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having ionicly conductive functional groups. A polymer gel electrolyte may be, for example, a polymer electrolyte in a gel state at 25°C and 1 atm. A polymer gel electrolyte may have, for example, a gel state without including a liquid. The liquid electrolyte used in a polymer gel electrolyte may be, for example, a mixture of an ionic liquid and a lithium salt; 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 a polymer gel electrolyte may be selected from polymers used in polymer solid electrolytes. The organic solvent may be selected from organic solvents used in liquid electrolytes. The lithium salt may be selected from lithium salts used in polymer solid electrolytes. An ionic liquid may refer to a salt that is liquid at room temperature, consists only of ions, and has a melting point at room temperature or is a molten salt at room temperature. Ionic liquids may include, for example, at least one compound comprising: a) at least one cation selected from ammonium, pyrrolidineonium, pyridinium, pyrimidineonium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazineonium, phosphonium, sulfonium, triazolium, and any mixture thereof; and b) a cation selected from BF4. - PF6 - AsF6 - SbF6 - AlCl4 - HSO4 - ClO4 - CH3SO3 - CF3CO2 - Cl - ,Br - I - SO4 - CF3SO3 - (FSO2)2N - (C2F2SO2)2N - (C2F5SO2)(CF3SO2)N - and (CF3SO2)2N -At least one anion is present. The polymer solid electrolyte can be impregnated with a liquid electrolyte in a secondary battery to form a polymer gel electrolyte. The polymer gel electrolyte may also include inorganic particles. The polymer included in the polymer gel electrolyte may be, for example, a compound comprising 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The polymer included in the polymer gel electrolyte may have a weight-average molecular weight, for example, 500 Da or greater, 1000 Da or greater, 10,000 Da or greater, 100,000 Da or greater, or 1,000,000 Da or greater.

[0167] [Electrolyte layer: binder] The electrolyte layer 30 may include, for example, an adhesive. The adhesive included in the electrolyte layer 30 may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene, but is not limited thereto, and any adhesive commonly available in the art may be used. The adhesive of the electrolyte layer 30 may be the same as or different from the adhesive included in the positive electrode active material layer 12 and the first negative electrode active material layer 22. An adhesive may not be provided.

[0168] Based on the total weight of the electrolyte layer 30, the amount of binder included in the electrolyte layer 30 may be from about 0.1 wt% to about 10 wt%, from about 0.1 wt% to about 5 wt%, from about 0.1 wt% to about 3 wt%, from about 0.1 wt% to about 1 wt%, from about 0 wt% to about 0.5 wt%, or from about 0 wt% to 0.1 wt%.

[0169] Invention Model In the following description, one or more exemplary embodiments of the present disclosure will be described in more detail with reference to the following examples and comparative examples. However, these examples are not intended to limit the purpose and scope of the one or more exemplary embodiments.

[0170] (Preparation of positive electrode active material) Preparation Example 1: Li2S-LiI-CNF Complex (First process) Li₂S and LiI were mixed at a weight ratio of 30:20. The Li₂S-LiI composite was prepared by mechanically grinding the mixture using a ball mill. The grinding conditions were 25°C, 600 rpm, and 10 hours. The grinding energy applied to the sample during grinding was 28 G.

[0171] (Second process) The Li₂S-LiI composite was mixed with carbon nanofibers (CNF) at a weight ratio of 50:10. The Li₂S-LiI-CNF composite was prepared by mechanically milling the mixture using a ball mill. The milling conditions were 25°C, 600 rpm, and 10 hours. The milling energy applied to the sample during milling was 28 G. The Li₂S-LiI-CNF composite was used as the positive electrode active material.

[0172] Li2S has a Mohs hardness of 0.6, LiI has a Mohs hardness of 2.0, and CNF has a Mohs hardness of 1.5.

[0173] Comparative preparation example 1: S-CNT-Li6PS5Cl complex (First process) Sulfur (S) and CNTs were mixed at a weight ratio of 25:25. The S-CNT composite was prepared by mechanically grinding the mixture using a ball mill. The grinding conditions were 25°C, 600 rpm, and 10 hours.

[0174] (Second process) The S-CNT composite and Li6PS5Cl were mixed at a weight ratio of 50:50. The S-CNT-Li6PS5Cl composite was prepared by mechanically grinding the mixture using a ball mill. The grinding conditions were 25°C, 600 rpm, and 10 hours.

[0175] The S-CNT-Li6PS5Cl complex was used as the positive electrode active material.

[0176] (Manufacturing of dry cathode film, dry cathode and all-solid-state secondary battery) Example 1: Dry, Li2S-LiI-CNF:SE:PTFE=60:39:1 (Preparation of dry positive electrode film) The Li₂S-LiI-CNF composite prepared in Preparation Example 1 was used as the dry positive electrode active material. Li₆PS₅Cl (D₅₀ = 3.0 μm, crystalline) was prepared as the dry solid electrolyte, either argyrocerite-type or microcrystalline. PTFE was prepared as the dry binder.

[0177] Prepare dry positive electrode active material and dry solid electrolyte at a weight ratio of 60:39, add them to a blade mixer and mix for 2 minutes to prepare the first mixture.

[0178] Prepare a first mixture and dry binder at a weight ratio of 99:1, add them to a blade mixer, and mix for 20 seconds to prepare a second mixture.

[0179] The second mixture was further mixed using a kneader and passed through calendering rolls to prepare a dry positive electrode film (self-standing film) in sheet form with a thickness of about 100 μm.

[0180] In the dry positive electrode film, the weight ratio of positive electrode active material: solid electrolyte: binder is 60:39:1. Fibrillation is performed during the additional mixing and calendering processes using a kneader.

[0181] (Preparation of dry cathode) A dry positive electrode is prepared by depositing a dry positive electrode film on one side of a positive electrode current collector formed from an Al foil coated with carbon. The thickness of the carbon-coated Al foil is approximately 20 μm. The thickness of the carbon coating is approximately 1 μm.

[0182] The area of ​​the positive electrode active material layer (dry positive electrode film) is the same as the area of ​​the positive electrode current collector.

[0183] (Preparation of the negative electrode) Prepare a 10 μm thick SUS foil as the negative electrode current collector. Prepare carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle size of about 60 nm as the negative electrode active materials.

[0184] A powder mixture of 4g of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was added to a container, and 4g of an N-methyl-2-pyrrolidone (NMP) solution including 7wt% PVDF binder (Kureha #9300) was added to prepare a mixed solution. NMP was gradually added to the mixed solution while stirring to prepare a slurry. The prepared slurry was coated onto an SUS sheet using a rod coater and dried in air at 80°C for 10 minutes, followed by vacuum drying at 40°C for 10 hours to prepare a stacked structure. The surface of the prepared stacked structure was planarized by cold rolling to prepare a negative electrode with a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 15μm. The area of ​​the first negative electrode active material layer was the same as the area of ​​the negative electrode current collector.

[0185] (Preparation of solid electrolyte layer) A solid electrolyte of Li6PS5Cl (D50 = 3.0 μm, crystalline) was prepared as a sulforaphite-germanium-type (or similar) microcrystalline material. 1.5 parts by weight of acrylic binder were added to 98.5 parts by weight of the solid electrolyte to prepare a mixture. Octyl acetate was added to the prepared mixture while stirring to prepare a slurry. The prepared slurry was applied to a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate using a bar coater and dried in air at 80°C for 10 minutes to obtain a stacked structure. The prepared stacked structure was dried in vacuum at 80°C for 2 hours, and the solid electrolyte layer was separated from the PET substrate to prepare the solid electrolyte layer.

[0186] (First inactive component) A pulp prepared by mixing pulp fibers (cellulose fibers), glass fibers, aluminum hydroxide (Al(OH)3), acrylic binder and solvent is formed into a gasket and the solvent is removed therefrom to prepare a flame-retardant inactive component.

[0187] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder is 20:8:70:2. The inactive component has a thickness of 120 μm.

[0188] Before arranging the prepared flame-retardant inactive components on the solid electrolyte layer, a heat treatment was performed in a vacuum at 80°C for 5 hours to remove moisture and other substances from the flame-retardant inactive components.

[0189] (Second inactive component) The second inactive component is prepared in essentially the same manner as the method for preparing the first inactive component, except that the pulp comprising pulp fibers (cellulose fibers), glass fibers, aluminum hydroxide (Al(OH)3), acrylic binder and solvent is formed into a sheet.

[0190] The second inactive component can be used as an elastic sheet.

[0191] (Preparation of all-solid-state secondary batteries) Reference Figure 3A solid electrolyte layer is disposed on the negative electrode, such that a first negative electrode active material layer is in contact with the solid electrolyte layer, and a positive electrode is disposed on the solid electrolyte layer. A gasket is arranged around the positive electrode to surround it and contact the solid electrolyte layer, thus fabricating a stacked structure. The gasket has a thickness of approximately 120 μm. A flame-retardant inactive component is used as the gasket. The gasket is positioned to contact the side surfaces of the positive electrode and the solid electrolyte layer. The positive electrode is located in the central region of the solid electrolyte layer, and the gasket is positioned to surround the positive electrode and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode is approximately 90% of the area of ​​the solid electrolyte layer, and the gasket is positioned over the entire remaining 10% of the area of ​​the solid electrolyte layer over which the positive electrode is not positioned. The gasket is the first inactive component.

[0192] The prepared stacked structure was pressed for 30 minutes at 85°C and 500 MPa using a plate press. This pressing process sintered the solid electrolyte layer to improve battery characteristics. The sintered solid electrolyte layer had a thickness of approximately 45 μm. The silage-germanium sulfide (or similar) crystalline Li6PS5Cl solid electrolyte included in the sintered solid electrolyte layer had a density of 1.6 g / cc. The area of ​​the solid electrolyte layer was the same as that of the negative electrode.

[0193] A second inactive component having the same area and shape as the stacked structure is additionally disposed on the outer surface of the negative electrode current collector of the pressed stacked structure.

[0194] A stacked structure with a second inactive component is added to the bag and vacuum-sealed to prepare an all-solid-state secondary battery. The portions of the positive and negative current collectors extend to the outside of the sealed battery to serve as the positive and negative terminals, respectively.

[0195] Example 2: Dry, Li2S-LiI-CNF:SE:PTFE=70:29:1 Except that the weight ratio of positive electrode active material: solid electrolyte: binder in the dry positive electrode film is 70:29:1, the dry positive electrode film, dry positive electrode and all-solid-state secondary battery are prepared in essentially the same manner as in Example 1.

[0196] Example 3: Dry, Li2S-LiI-CNF:SE:PTFE=80:19:1 Except that the weight ratio of positive electrode active material: solid electrolyte: binder in the dry positive electrode film is 80:19:1, the dry positive electrode film, dry positive electrode and all-solid-state secondary battery are prepared in essentially the same manner as in Example 1.

[0197] Example 4: Dry, Li2S-LiI-CNF:SE:PTFE=60:38:2 Except that the weight ratio of positive electrode active material: solid electrolyte: binder in the dry positive electrode film is 60:38:2, the dry positive electrode film, dry positive electrode and all-solid-state secondary battery are prepared in essentially the same manner as in Example 1.

[0198] Refer to Example 1 The all-solid-state secondary battery was prepared in essentially the same manner as in Example 1, except that the first inactive component was omitted.

[0199] Refer to Example 2 The all-solid-state secondary battery was prepared in essentially the same manner as in Example 1, except that the first inactive component was omitted.

[0200] Comparison Example 1: Wet, Li2S-LiI-CNF:SE:PVDF-HFP=60:39:1 Except for the wet positive electrode prepared according to the following method, the all-solid-state secondary battery was prepared in essentially the same manner as in Example 1.

[0201] (Preparation of wet cathode) The Li₂S-LiI-CNF composite prepared in Preparation Example 1 was used as the positive electrode active material. Li₆PS₅Cl (D₅₀ = 3.0 μm, crystalline) was prepared as a sulforaphite-germanium oxide or microcrystalline solid electrolyte. A PVDF-HFP solution was prepared as a binder. Octyl acetate was added to a mixture of the positive electrode active material, solid electrolyte, and binder in a weight ratio of 60:39:1 while stirring to prepare a positive electrode active material slurry.

[0202] The positive electrode active material slurry was coated onto one side of an Al foil positive electrode current collector with a thickness of 20 μm and dried. Then, it was dried in a vacuum oven at 80 °C for 4 hours to prepare a stacked structure in which the positive electrode active material layer is disposed on the positive electrode current collector.

[0203] The area of ​​the positive electrode active material layer is the same as the area of ​​the positive electrode current collector.

[0204] Comparison Example 2: Dry, S-CNT-Li6PS5Cl:PTFE=99:1 Except for the preparation of the dry cathode according to the following method, the all-solid-state secondary battery is prepared in essentially the same manner as in Example 1.

[0205] (Preparation of dry cathode) The S-CNT-Li6PS5Cl composite prepared in Comparative Preparation Example 1 was prepared as the dry positive electrode active material. PTFE was prepared as the dry binder.

[0206] Prepare dry positive electrode active material and dry binder at a weight ratio of 99:1, add them to a blade mixer, and mix for 5 minutes to prepare a mixture.

[0207] The mixture is placed on one side of a stainless steel (SUS) substrate and rolled to prepare a dry positive electrode.

[0208] Comparison Example 3: Dry, no adhesive The dry positive electrode film is prepared in essentially the same manner as in Example 1, except that no binder is used.

[0209] Evaluation Example 1: XRD Analysis and SEM Analysis The bare Li₂S and pulverized Li₂S used in the preparation of Example 1, as well as the Li₂S-LiI-C composite prepared in Example 1, were evaluated by measuring XRD spectra via Cu Kα radiation. The measurement results are shown in Table 1. The size and lattice constant of the Li₂S crystallites were derived from the first peak observed in the obtained XRD spectra at a diffraction angle (2θ) corresponding to the crystal plane (111) at 27° ± 2.0°.

[0210] The pulverized Li₂S was prepared by grinding under the same conditions as the first process in Preparation Example 1, except that the mixture of Li₂S and LiI mixed in a 30:20 weight ratio was replaced with pure Li₂S. No second process was performed.

[0211] The bare Li₂S and pulverized Li₂S used in the preparation of Example 1, as well as the Li₂S-LiI-CNF complex prepared in Example 1, were evaluated as follows: the particle size (i.e., D50 particle size) of the complex and the particle size of Li₂S in the complex were measured using a laser-based particle size analyzer (PSA) and a scanning electron microscope (SEM). The measurement results are shown in Table 1.

[0212] [Table 1]

[0213] As shown in Table 1, compared with the size of bare Li2S particles and Li2S crystallites, the size of Li2S particles and Li2S crystallites of the Li2S-LiI-CNF composite prepared in Example 1 are significantly reduced.

[0214] Although not shown in Table 1, the Li2S-LiI-CNF composite prepared in Example 1 has a larger lattice constant than that of bare Li2S.

[0215] The increased lattice constant of the Li2S-LiI-CNF complex compared to that of bare Li2S is attributed to the presence of LiI dissolved within the Li2S microcrystals. Therefore, the formation of a solid solution of Li2S and LiI in the Li2S-LiI-CNF complex is confirmed.

[0216] Although not shown in Table 1, the composite of Preparation Example 1 has a particle size of approximately 5 μm.

[0217] Evaluation Example 2: Measurement of Tensile Strength at Break The tensile strength at break of the dry positive electrode films prepared in Example 1 and Comparative Example 3 was measured according to ASTM D 412 method, and the results are shown in Table 2.

[0218] The wet positive electrode prepared in Comparative Example 1 cannot form a self-standing film, therefore the tensile strength at break cannot be measured.

[0219] The prepared dry positive electrode film was cut into strips with a width of 15 mm and a length of 50 mm. Each strip was gripped at both ends in the longitudinal direction in a tensile strength tester (e.g., simultaneously), with the distance between the chucks set to 10 mm. The tensile strength was then measured at 23 °C and a speed of 5 mm / min to obtain the tensile strength at break [kPa]. The measurement results are shown in Table 2.

[0220] [Table 2]

[0221] As shown in Table 2, the dry cathode film of Example 1 exhibits excellent or suitable tensile strength.

[0222] In the dry cathode film of Example 1, the dispersibility of the dry binder was improved, and the adhesion uniformity between the positive electrode active material and the dry binder was also improved. As a result, the overall mechanical strength of the cathode film of Example 1 was improved.

[0223] In the dry cathode film of Comparative Example 3, which does not include the binder, the mechanical strength is significantly degraded, making it impossible to measure the mechanical strength.

[0224] Evaluation Example 2: Measurement of Surface Resistivity The surface resistivity of the dry positive electrode films prepared in Example 1 and Comparative Example 2 was measured using the 4-probe method according to ASTM D 257, and the results are shown in Table 3.

[0225] [Table 3]

[0226] As shown in Table 3, the dry positive electrode film of Example 1 has a lower surface resistivity than the dry positive electrode film of Comparative Example 2.

[0227] The dry cathode film of Comparative Example 2, which includes sulfur (S) as the positive electrode active material, is considered to have a higher surface resistivity than the dry cathode film of Example 1, which includes a Li2S-lithium salt-carbon material composite as the positive electrode active material.

[0228] Sulfur (S) has ~10 -30 Its electronic conductivity of S / cm is lower than that of Li₂S (~10). -13 S / cm).

[0229] Evaluation Example 3: Charge / Discharge Test The charge / discharge characteristics of the all-solid-state secondary batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were evaluated by the following charge / discharge tests. The all-solid-state secondary batteries were placed in a constant temperature bath at 45°C for the charge / discharge tests.

[0230] The first cycle was performed by charging the battery at a constant current of 0.05C for 20 hours until the battery voltage reached 2.8V. Subsequently, the battery was discharged at a constant current of 0.05C for 20 hours until the battery voltage reached 1.0V.

[0231] The second cycle was performed by charging the battery at a constant current of 0.05C for 20 hours until the battery voltage reached 2.8V. Subsequently, the battery was discharged at a constant current of 0.05C for 20 hours until the battery voltage reached 1.0V.

[0232] A third cycle was performed at a constant current of 0.1C for 10 hours until the battery voltage reached 2.8V. Subsequently, the battery was discharged at a constant current of 0.1C for 10 hours until the battery voltage reached 1.0V.

[0233] Starting from the fourth cycle, 20 charge-discharge cycles were performed under the same conditions as the third cycle. The measurement results are shown in Table 2. Capacity retention is defined as shown in Equation 1.

[0234] Equation 1 Capacity retention rate [%] = [Discharge capacity at 23rd cycle / Charge capacity at 3rd cycle] × 100 [Table 4]

[0235] As shown in Table 4, compared with the all-solid-state secondary battery of Comparative Example 1 which uses a wet positive electrode, the all-solid-state secondary batteries of Examples 1 to 4 using a dry positive electrode exhibit improved discharge capacity and lifetime characteristics.

[0236] Therefore, it has been confirmed that because dry cathodes have lower internal resistance than wet cathodes, they provide improved reversibility of electrode reactions.

[0237] Compared with the all-solid-state secondary battery of Comparative Example 2 which uses S-CNT-Li6PS5Cl composite positive electrode active material, the all-solid-state secondary batteries of Examples 1 to 4 which use Li2S-LiI-CNF composite positive electrode active material exhibit improved discharge capacity and lifetime characteristics.

[0238] Therefore, it has been confirmed that the Li2S-lithium salt-carbon composite provides improved charge-discharge characteristics compared to the S-solid electrolyte-carbon composite.

[0239] Although not shown in Table 2, the all-solid-state secondary battery of Reference Example 1, which does not include the first inactive component, and the all-solid-state secondary battery of Reference Example 2, which does not include the second inactive component, exhibit relatively poorer lifetime characteristics than the all-solid-state secondary battery of Example 1.

[0240] In some examples, it was confirmed that in the all-solid-state secondary batteries of Examples 1 to 4, a lithium metal layer serving as a second negative electrode active material layer was formed between the first negative electrode active material layer and the negative electrode current collector after initial charging. The formation of the second negative electrode active material layer was confirmed by cross-sectional images of the all-solid-state secondary batteries obtained by SEM.

[0241] List of reference numerals for key components 1 All-solid-state secondary battery 10 positive electrode 11 Positive current collector 12 Positive active material layer 20 negative electrode 21 negative electrode current collector 22 First negative electrode active material layer 23 Thin film 24 Second negative electrode active material layer 30 Electrolyte layer 40 First inactive component 50 Second inactive component.

[0242] Industry applicability Depending on the circumstances, dry cathode films with improved mechanical properties and reduced specific resistivity can be provided by including Li2S-lithium salt-carbon material composites and dry binders that bind these materials.

[0243] By including this dry cathode membrane, an all-solid-state secondary battery with increased specific capacity and improved cycle characteristics can be provided.

Claims

1. A dry cathode film comprising: a dry cathode active material; a dry sulfide-based solid electrolyte; and a dry binder, The dry positive electrode active material includes a composite of Li2S, a lithium salt (Li a X b ) and a carbonaceous material (C). The composite is composed of Li2S-Li a X b - C (wherein 1≤a≤5 and 1≤b≤5) represents, and X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof.

2. The dry cathode film of claim 1, wherein, a size of a Li2S crystallite obtained in an X-ray diffraction (XRD) spectrum of the composite is 20 nm or less, and the composite further comprises a solid solution of Li2S and a lithium salt.

3. The dry cathode film of claim 1, wherein, the lithium salt is a binary compound or a ternary compound, wherein the binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or a combination thereof, and the ternary compound comprises Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or a combination thereof.

4. The dry cathode film of claim 1, wherein, in the composite, a molar ratio of the Li2S to the lithium salt is 50:50 to 95:

5.

5. The dry cathode film of claim 1, wherein, the lithium salt and the carbonaceous material each have a Mohs hardness greater than a Mohs hardness of the Li2S, and the lithium salt and the carbonaceous material each have a Mohs hardness of 0.7 or more.

6. The dry cathode film of claim 1, wherein, the carbonaceous material comprises a fibrous carbonaceous material, the fibrous carbonaceous material comprises a carbon nanostructure, wherein the carbon nanostructure comprises a carbon nanofiber, a carbon nanotube, a carbon nanoribbon, a carbon nanorod, or a combination thereof, and an amount of the carbonaceous material is 1 wt% to 20 wt% based on a total weight of the composite.

7. The dry cathode film of claim 1, wherein, based on 100 parts by weight of the composite, the composite comprises 50 parts by weight to 80 parts by weight of the Li2S, 1 part by weight to 40 parts by weight of the lithium salt, and 1 part by weight to 20 parts by weight of the carbonaceous material.

8. The dry cathode film of claim 1, wherein, a size of a particle of the composite is 10 µm or less, and an amount of the composite is 50 wt% to 80 wt% based on a total weight of the dry cathode film.

9. The dry cathode film of claim 1, wherein, The dry sulfide-based solid electrolyte includes at least one selected from the group consisting of Li2S-P2S5; Li2S-P2S5-LiX, wherein X is a halogen; Li2S-P2S5-Li2O; Li2S-P2S5-Li2O-LiI; Li2S-SiS2; Li2S-SiS2-LiI; Li2S-SiS2-LiBr; Li2S-SiS2-LiCl; Li2S-SiS2-B2S3-LiI; Li2S-SiS2-P2S5-LiI; Li2S-B2S3; Li2S-P2S5-Z m S n wherein m and n are positive numbers, and Z is Ge, Zn, or Ga; Li2S-GeS2; Li2S-SiS2-Li3PO4; Li2S-SiS2-Li p MO q wherein p and q are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In; Li 7-x PS 6-x Cl x wherein 0≤x≤2; Li 7-x PS 6-x Br x wherein 0≤x≤2; and Li 7-x PS 6-x I x wherein 0≤x≤2, the sulfide-based solid electrolyte comprises a argyrodite-type solid electrolyte, the argyrodite-type solid electrolyte comprises at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I, and the argyrodite-type solid electrolyte has a density of 1.5 g / cc to 2.0 g / cc.

10. The dry cathode film of claim 1, wherein, the dry binder comprises a fibrillated binder, the dry binder comprises a fluorine-based binder, the dry binder has a glass transition temperature (Tg) of 15 °C to 130 °C, and the dry binder has a glass transition temperature (Tg) of 15 °C to 130 °C, and The amount of the dry binder is 0.1 wt% to 5 wt% based on the total weight of the dry cathode film.

11. The dry cathode film of claim 1, wherein, The dry cathode film is a self-standing film, The dry cathode film does not contain residual processing solvent, and The dry cathode film has a thickness of 50 pm to 500 pm.

12. The dry cathode film of claim 1, wherein, The dry cathode film has a tensile strength of 500 kPa to 5000 kPa, and The dry cathode film has a surface resistivity of 70 W / sq or less.

13. A dry cathode comprising: a cathode current collector; and The dry cathode film according to claim 1 on at least one side of the cathode current collector.

14. The dry cathode of claim 13, wherein, The cathode current collector comprises a base film and a metal layer on at least one side of the base film, wherein the base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof, and the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, and there is also an intermediate layer between the cathode current collector and the dry cathode film, and wherein the intermediate layer comprises a carbonaceous conductive material.

15. A full solid-state secondary battery comprising: a cathode; an anode; and an electrolyte layer between the cathode and the anode, wherein the cathode is the dry cathode according to claim 13, and the anode comprises an anode current collector and a first anode active material layer on at least one side of the anode current collector.

16. The all-solid-state secondary battery according to claim 15, wherein The first anode active material layer comprises an anode active material and a binder, and wherein the anode active material is in the form of particles, and the average particle size of the particles of the anode active material is 4 pm or less.

17. The all-solid-state secondary battery according to claim 16, wherein The anode active material comprises at least one selected from a carbonaceous anode active material and a metal or metalloid anode active material, The carbonaceous anode active material comprises amorphous carbon, crystalline carbon, porous carbon, or a combination thereof, The metal or metalloid anode active material comprises gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof, The anode active material comprises a mixture of first particles of amorphous carbon and second particles of a metal or metalloid, and The amount of the second particles is 1 wt% to 60 wt% based on the total weight of the mixture.

18. The full solid-state secondary battery according to claim 15, further comprising a second anode active material layer between the anode current collector and the first anode active material and / or between the anode current collector and the electrolyte layer, wherein The second anode active material layer is a metal layer, and the metal layer comprises lithium or a lithium alloy.

19. The all-solid-state secondary battery according to claim 15, wherein, The electrolyte layer comprises a solid electrolyte, a gel electrolyte, or a combination thereof, The solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof, and The gel electrolyte includes a polymer gel electrolyte. 20.The all-solid-state secondary battery of claim 15, further comprising at least one of a first inactive member on a first side surface of the positive electrode and a second inactive member on a second side of the negative electrode, wherein, The first and second inactive members include electrically conductive, fire-retardant, inactive members.

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