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

Abstract

Disclosed are dry positive electrode film, and dry positive electrode and all-solid secondary battery comprising same, the dry positive electrode film comprising dry positive active material, dry sulfide-based solid electrolyte, and a dry binder, wherein the dry positive active material comprises a composite of Li2S, lithium salt (LiaXb), and carbon-based material (C), the composite being expressed by Li2S-LiaXb-C (1≤a≤5, 1≤b≤5) and X being 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

Dry cathode film, dry cathode and all-solid-state secondary battery containing the same

[0001] The present invention relates to a dry cathode film, a dry cathode including the same, and an all-solid-state secondary battery.

[0002] To accommodate the miniaturization and high-performance of various devices, secondary batteries are becoming increasingly important, not only for their miniaturization and weight reduction, but also for their high energy density. In other words, high-capacity secondary batteries are becoming increasingly important.

[0003] Electrodes manufactured from slurries containing solvents typically use excessive amounts of organic solvent during electrode manufacture. The application of a dry process that eliminates the use of organic solvents during electrode manufacture is being considered.

[0004] One aspect is to provide a dry cathode film having improved mechanical properties and reduced resistivity by including a composite of Li2S-lithium salt-carbon material and a dry binder binding them.

[0005] Another aspect is to provide a dry cathode comprising the above dry cathode film.

[0006] Another aspect is to provide an all-solid-state secondary battery including the above dry positive electrode film.

[0007] According to the implementation example

[0008] It includes a dry cathode active material, a dry sulfide-based solid electrolyte, and a dry binder.

[0009] The above dry cathode active material is Li2S and lithium salt (Li a X b ) and a composite of carbon-based material (C),

[0010] The above complex is Li2S-Li a X b -C (1≤a≤5, 1≤b≤5) is expressed as

[0011] A dry cathode film is provided, wherein 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.

[0012] According to another implementation example,

[0013] anode current collector; and

[0014] A dry cathode is provided, which includes a dry cathode film according to the above, which is disposed on one or both sides of the cathode current collector.

[0015] According to another implementation example,

[0016] A cathode; an anode; and an electrolyte layer disposed between the anode and the cathode,

[0017] The above positive electrode is a dry positive electrode according to the above,

[0018] An all-solid-state secondary battery is provided, wherein the negative electrode includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0019] According to one aspect, it is possible to provide a dry cathode film having improved mechanical properties and reduced resistivity by including a composite of Li2S-lithium salt-carbon material and a dry binder binding them.

[0020] By providing such a dry cathode film, it is possible to provide an all-solid-state secondary battery with increased specific capacity and cycle characteristics.

[0021] Figure 1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0022] Figure 2 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0023] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0024] Fig. 4 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0025] Figure 5 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0026] Figure 6 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0027] Fig. 7 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used in this disclosure have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure pertains. Furthermore, terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0029] Exemplary embodiments are described in this disclosure with reference to cross-sectional drawings that are schematic representations of idealized embodiments. As such, variations from the shapes depicted are to be expected, for example, as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described in this disclosure should not be construed as limited to the specific shapes of regions as depicted in this disclosure, but should encompass variations in shapes resulting from, for example, manufacturing. For example, regions depicted or described as flat may typically have rough and / or non-linear features. Moreover, angles depicted as sharp may be rounded. Therefore, the regions depicted in the drawings are schematic in nature, and their shapes are not intended to depict the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0030] This creative idea may be embodied in many different forms and should not be construed as limited to the embodiments described in this disclosure. These embodiments are provided so that this disclosure will be thorough and complete, and so that it will fully convey the scope of the creative idea to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0031] When a component is referred to as being "on" another component, it can be understood that it is either directly on top of the other component or that other components may be intervening between them. Conversely, when a component is referred to as being "directly on" another component, no intervening components are present.

[0032] Although terms such as "first," "second," "third," etc. may be used herein to describe various components, elements, regions, layers, and / or zones, these components, elements, regions, layers, and / or zones should not be limited by these terms. These terms are only used to distinguish one component, element, region, layer, or zone from another component, element, region, layer, or zone. Thus, a first component, element, region, layer, or zone described below may be referred to as a second component, element, region, layer, or zone without departing from the teachings of this disclosure.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms including "at least one," unless the content clearly dictates otherwise. "At least one" should not be construed as limiting to the singular. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The terms "comprises" and / or "comprising" as used in the detailed description specify the presence of stated features, regions, integers, steps, operations, components, and / or ingredients, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, ingredients, and / or groups thereof.

[0034] Spatially relative terms such as "below," "under," "lower," "above," "upper," and the like may be used herein to readily describe the relationship of one component or feature to another. It will be understood that spatially relative terms are intended to encompass different orientations of the device when in use or operation in addition to the orientations depicted in the drawings. For example, if the device in the drawings were turned over, a component described as "below" or "below" another component or feature would then be oriented "above" the other component or feature. Thus, the exemplary term "below" can encompass both the above and below orientations. The device may be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein may be interpreted accordingly.

[0035] In the present disclosure, "dry" or "dry" means a state in which there is no intentional contact with a solvent such as a process solvent, or a state in which there is no intentional inclusion of a solvent. For example, a dry cathode active material means a cathode active material that is not intentionally in contact with a solvent or a cathode active material that is not intentionally in contact with a solvent. For example, a dry solid electrolyte means a solid electrolyte that is not intentionally in contact with a solvent or a solid electrolyte that is not intentionally in contact with a solvent. For example, a dry conductive material means a conductive material that is not intentionally in contact with a solvent or a conductive material that is not intentionally in contact with a solvent. For example, a dry binder means a conductive material that is not intentionally in contact with a solvent or a binder that is not intentionally in contact with a solvent. For example, a binder that is liquid at room temperature without being mixed with a solvent is a dry binder.

[0036] In this disclosure, "group" means a group of the periodic table of elements according to the International Union of Pure and Applied Chemistry ("IUPAC") Group 1-18 classification system.

[0037] In this disclosure, “particle diameter” refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter can be measured using a particle size analyzer (PSA). The “particle diameter” is, for example, the average particle diameter. The “average particle diameter” is, for example, D50, the median particle diameter.

[0038] D50 is the size of the particle corresponding to 50% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0039] D90 is the size of the particle corresponding to 90% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0040] D10 is the size of the particle corresponding to 10% of the cumulative volume, calculated from the particle side with a small particle size in the particle size distribution measured by laser diffraction.

[0041] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0042] In this disclosure, “alloy” means a mixture of two or more metals.

[0043] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0044] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0045] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0046] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0047] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0048] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0049] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0050] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0051] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0052] While specific implementations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or unforeseen may occur to the applicant or those skilled in the art. Accordingly, the appended claims, as filed and as amended, are intended to encompass all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0053]

[0054] Hereinafter, a dry cathode film, a dry cathode including the same, and an all-solid-state secondary battery according to exemplary embodiments are described in more detail.

[0055] [Dry cathode film]

[0056] [Dry cathode film: composite of Li2S, lithium salt, and catalytic material]

[0057] A dry cathode film according to an embodiment includes a dry cathode active material, a dry sulfide-based solid electrolyte, and a dry binder. The dry cathode active material includes a composite of Li2S, a lithium salt, and a carbon-based material.

[0058] A dry cathode active material comprising a composite of Li2S, a lithium salt, and a carbon-based material can provide enhanced discharge capacity and enhanced ionic and electronic conductivities. Since the composite comprises Li2S and Li2S can act as a lithium source, the provision of a lithium source in the negative electrode can be omitted. Consequently, the energy density of an all-solid-state secondary battery can be improved. In contrast, sulfur (i.e., S) does not contain lithium and cannot act as a lithium source, thus essentially requiring the provision of a lithium source in the negative electrode. Since the composite comprises a lithium salt, the ionic conductivity of the dry cathode active material can be improved, and the internal resistance of a dry cathode film comprising the dry cathode active material can be reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery comprising a dry cathode film can be improved. Since the composite comprises a carbon-based material, the electronic conductivity of the dry cathode active material can be improved, and the internal resistance of a dry cathode film comprising the dry cathode active material can be reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including a dry cathode film can be improved. Since the composite includes a carbon-based material, the bonding strength between the composite and the dry binder can be further enhanced. Therefore, the mechanical properties, such as the tensile strength, of the dry cathode film can be further improved. Since the dry binder intermittently binds to some portions of the surfaces of the plurality of dry cathode active material particles, the increase in internal resistance of the dry cathode film caused by the dry binder can be effectively suppressed. In contrast, the wet binder can significantly increase the internal resistance of the dry cathode film by being widely coated on the surfaces of the plurality of cathode active material particles during the drying process after being dissolved in a solvent. Since the dry cathode film includes a dry sulfide-based solid electrolyte, the ionic conductivity of the dry cathode film can be further improved. Consequently, the internal resistance of the dry cathode film can be further reduced.By reducing the internal resistance of the dry positive electrode film and improving the mechanical properties, the specific capacity and / or cycle characteristics of an all-solid-state secondary battery including the dry positive electrode film of the present disclosure can be improved.

[0059] Li2S and lithium salt (Li a X b ) and a carbon-based material (C) are composites, for example, Li2S-Li a X b -C is represented by (1≤a≤5, 1≤b≤5). 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. a is, for example, 1, 2, 3, 4 or 5. b is, for example, 1, 2, 3, 4 or 5. C refers to a carbonaceous material consisting essentially of carbon atoms.

[0060] The size (e.g., average diameter or average major axis) of Li2S crystallites obtained from an XRD spectrum of a composite of Li2S, a lithium salt, and a carbon-based material may be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of Li2S crystallites obtained from an X-ray diffraction (XRD) spectrum of a composite of Li2S, a lithium salt, and a carbon-based material may be, for example, 1 to 20 nm, 1 to 15 nm, or 3 to 10 nm. The composite of Li2S, a lithium salt, and a carbon-based material includes Li2S crystallites, and when the size of the Li2S crystallites is reduced to 20 nm or less, a volume change of the Li2S crystallites during charge and discharge can be alleviated. For example, as the size of Li2S crystallites decreases, the volume change caused by a single Li2S crystallite decreases, so that the overall volume change of the composite of Li2S, lithium salt, and carbon-based material during charge and discharge can be alleviated. For example, as the size of Li2S crystallites decreases, the grain boundaries between multiple Li2S crystallites can more easily accommodate the volume change of the Li2S crystallites during charge and discharge, so that the volume change of the composite of Li2S-lithium salt-carbon-based material can be alleviated during charge and discharge. The possibility of defects such as cracks occurring due to the volume change of the composite during charge and discharge can be reduced. By including the composite of Li2S, lithium salt, and carbon-based material in the dry cathode film, the cycle characteristics of an all-solid-state secondary battery including the dry cathode film can be improved. By reducing the size of Li2S crystallites by 20 nm, the contact area between Li2S and lithium salt and / or carbon-based material can be further increased. The reversibility of electrode reactions in an all-solid-state secondary battery comprising a composite of Li2S, a lithium salt, and a carbon-based material can be improved by further increasing the contact area between Li2S and a lithium salt and / or a carbon-based material.

[0061] The composite of Li2S, a lithium salt, and a carbon-based material may include, for example, a solid solution of Li2S and a lithium salt. By including the solid solution of Li2S and a lithium salt in the composite of Li2S, a lithium salt, and a carbon-based material, the ionic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material may be further increased. For example, by including lithium atoms arranged within Li2S crystallites in the solid solution of Li2S and a lithium salt, the ionic conductivity of the solid solution of Li2S and a lithium salt may be improved compared to the ionic conductivity of Li2S. Consequently, the ionic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material may be improved, and the internal resistance of the composite of Li2S, a lithium salt, and a carbon-based material may be reduced. By including such a composite in the dry cathode film, the internal resistance of the dry cathode film may be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a dry cathode film may be further improved.

[0062] A composite of Li2S, a lithium salt, and a carbon-based material is distinct from a simple mixture of Li2S, an alkali metal salt, and a carbon-based material. A simple mixture of Li2S, an alkali metal salt, and a carbon-based material fails to maintain a dense interface between the Li2S, the alkali metal salt, and the carbon-based material, resulting in high interfacial resistance and consequently degrading the life characteristics of an all-solid-state secondary battery.

[0063] A composite of Li2S, a lithium salt, and a carbon-based material includes Li2S. Since Li2S has a high theoretical capacity, an all-solid-state secondary battery having a high energy density can be provided. However, since Li2S has low ionic conductivity and / or electronic conductivity, a composite is formed with a lithium salt and a carbon-based material to overcome this drawback. In the composite of Li2S, a lithium salt, and a carbon-based material, the content of Li2S may be, for example, 50 to 80 wt%, 50 to 75 wt%, or 50 to 70 wt% of the total weight of the composite of Li2S, a lithium salt, and a carbon-based material. If the content of Li2S is excessively increased, it may not be easy to improve the ionic conductivity and / or electronic conductivity of Li2S. If the content of Li2S is excessively low, the energy density of the all-solid-state secondary battery may be reduced.

[0064] A composite of Li2S, a lithium salt, and a carbon-based material includes a lithium salt. A lithium salt is, 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 of elements. 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 of elements. The binary compound may include, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or a combination thereof. By including such a binary compound in the composite, the ionic conductivity of the composite may be further improved. By including such a complex, i.e., a dry cathode active material, in the dry cathode film, the internal resistance of the dry cathode film can be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a dry cathode film can be further improved. The ternary compound may include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or a combination thereof. By including such a ternary compound in the complex, the ionic conductivity of the complex can be further improved. By including such a complex, i.e., a dry cathode active material in the dry cathode film, the internal resistance of the dry cathode film can be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a dry cathode film can be further improved.In the composite of Li2S, a lithium salt, and a carbon-based material, the content of the lithium salt may be, for example, 1 to 40 wt%, 5 to 35 wt%, 10 to 35 wt%, 15 to 35 wt%, 20 to 35 wt%, or 25 to 35 wt% of the total weight of the composite of Li2S, a lithium salt, and a carbon-based material. If the content of the lithium salt is excessively increased, the energy density of the all-solid-state secondary battery may decrease. If the content of the lithium salt is excessively low, the ionic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material may decrease, which may increase the internal resistance of the dry positive electrode film. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry positive electrode film may deteriorate.

[0065] In the composite of Li2S, a lithium salt, and a carbon-based material, the molar ratio of Li2S and a lithium salt may be, for example, 50:50 to 95:5, 60:40 to 95:5, 60:40 to 90:10, 65:35 to 90:10, 65:35 to 85:15, or 70:30 to 85:15. In the composite of Li2S, a lithium salt, and a carbon-based material, the molar ratio of Li2S and a lithium salt may be, for example, 50:50 to 95:5, 50:50 to 90:10, 50:50 to 85:15, 50:50 to 80:20, 50:50 to 75:25, or 50:50 to 70:30. By maintaining the molar ratio of Li2S and lithium salt within this range, the cycle characteristics of an all-solid-state lithium battery including a dry cathode film can be further improved. If the molar ratio of Li2S is excessively high, the ionic conductivity enhancement effect of the lithium salt may be minimal. If the molar ratio of Li2S is excessively high, the energy density of a lithium battery including a composite cathode active material may be reduced.

[0066] The composite of Li2S, a lithium salt, and a carbon-based material includes a carbon-based material. The carbon-based material may be, for example, any material containing carbon atoms that is used as a conductive material in the art. The carbon-based material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon-based material may be, for example, a sintered product of a carbon precursor. The carbon-based material may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof. The carbon-based material may be, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon-based material may be, for example, carbon black such as Ketjen Black, acetylene black, Denka Black, thermal black, channel black, etc.; graphite, activated carbon, or a combination thereof. The form of the carbon-based material may be, for example, particle form, sheet form, flake form, etc., but is not limited thereto, and any carbon-based material used in the art may be used. The content of the carbon-based material included in the composite of Li2S, lithium salt, and carbon-based material may be, for example, 1 to 20 wt%, 5 to 20 wt%, or 10 to 20 wt% of the total weight of the composite. If the content of the carbon-based material increases excessively, the energy density of the dry cathode film and the all-solid-state secondary battery may decrease. If the content of the carbon-based material decreases excessively, the electronic conductivity of the composite of Li2S, lithium salt, and carbon-based material may decrease, which may increase the internal resistance of the dry cathode film. As a result, the cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0067] The Mohs hardness of the lithium salt and the carbon-based material may be greater than that of Li2S. The Mohs hardness of Li2S is, for example, 0.6 or less. The Mohs hardness of the lithium salt may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. When the lithium salt has a Mohs hardness in this range, the pulverization of Li2S can be performed more easily during the milling process, and a solid solution of Li2S and the lithium salt can be formed more easily. The Mohs hardness of LiI is, for example, 2.0. The Mohs hardness of the carbon-based material may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, or 1.5 or more, respectively. Since the carbon-based material has a Mohs hardness in this range, the grinding of Li2S can be performed more easily during the milling process, and a composite of Li2S, a lithium salt, and a carbon-based material can be formed more easily. The modal hardness of carbon nanofibers (CNF) is, for example, 1.5.

[0068] The carbon-based material may include, for example, a fibrous carbon-based material. By including the fibrous carbon-based material in the composite of Li2S, a lithium salt, and a carbon-based material, the electronic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material can be further improved. By including the fibrous carbon-based material in the composite of Li2S, a lithium salt, and a carbon-based material, electronic conduction can be more easily performed from the surface to the inside of the composite of Li2S, a lithium salt, and a carbon-based material. The internal resistance of a dry cathode film including a composite of Li2S, a lithium salt, and a carbon-based material can be reduced, and the cycle characteristics of an all-solid-state secondary battery including a dry cathode film can be further improved.

[0069] The aspect ratio of the fibrous carbon-based material can be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. When the fibrous carbon-based material has an aspect ratio in this range, the overall electronic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material is improved, and the imbalance of local electronic conductivity within the composite of Li2S, a lithium salt, and a carbon-based material can be further alleviated.

[0070] The fibrous carbon-based material may include, for example, carbon nanostructures. The carbon nanostructures may include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanobelts, carbon nanorods, or combinations thereof.

[0071] Carbon nanostructures can form primary carbon nanostructures (e.g., primary particles) composed of a single carbon nanostructure and secondary carbon nanostructures (e.g., secondary particles) composed of multiple carbon nanostructures aggregated together.

[0072] The diameter (e.g., average diameter or average principal axis) of the primary carbon nanostructure can be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length (e.g., average length) of the primary carbon nanostructure can be, for example, 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure can be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructures can be measured by laser diffraction.

[0073] Secondary carbon nanostructures are, for example, structures formed by assembling primary carbon nanostructures in whole or in part to form bundles or bundle-type structures. The secondary carbon nanostructures may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or combinations thereof. The diameter (for example, average diameter or average principal axis) of the secondary carbon nanostructures may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length (e.g., average length) of the secondary carbon nanotube structures can be, for example, 20 nm to 2 ㎛, 30 nm to 1.5 ㎛, 50 nm to 1 ㎛, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructures can be measured from scanning electron microscope (SEM) images or optical microscopes. Alternatively, the diameter and / or length of the secondary carbon nanostructures can be measured by laser diffraction. The secondary carbon nanostructures can be converted into primary carbon nanostructures, for example, by dispersing them in a solvent or the like, and then used to prepare a composite of Li2S, a lithium salt, and a carbon-based material.

[0074] The particle size (e.g., average diameter or average principal axis) of the dry cathode active material, i.e., the particle size of the composite of Li2S, lithium salt, and carbon-based material, may 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 size of the composite particles may be, for example, 1 to 10 μm, 2 to 10 μm, 2 to 8 μm, or 3 to 8 μm. The size of the composite particles of Li2S, lithium salt, and carbon-based material may be, for example, 0.1 to 10 μm, 0.1 to 8 μm, 0.1 to 5 μm, 0.1 to 4 μm, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm. Since the composite particles of Li2S, lithium salt, and carbon-based material have sizes in this range, the volume change during charge and discharge is suppressed, thereby suppressing the deterioration of the dry cathode active material during charge and discharge. If the size of the composite particles of Li2S, lithium salt, and carbon-based material increases excessively, the volume change of the composite of Li2S, lithium salt, and carbon-based material increases during charge and discharge, thereby accelerating the deterioration of the dry cathode active material. Therefore, the cycle characteristics of an all-solid-state secondary battery including such a dry cathode active material may deteriorate. Therefore, the cycle characteristics, for example, the life characteristics, of an all-solid-state secondary battery including the dry cathode active material of the present disclosure can be improved. The size of the composite particles of Li2S, lithium salt, and carbon-based material can be measured using, for example, laser diffraction, a scanning electron microscope, or the like. The size of the composite of Li2S, lithium salt, and carbon-based material is, for example, the arithmetic mean value of the particle diameters of a plurality of particles measured using software from a scanning electron microscope image.

[0075] The size of the Li2S particles included in the composite (e.g., the average diameter or average principal axis), that is, the size of the Li2S particles included in the composite, may be, for example, 2 ㎛ or less, 1.5 ㎛ or less, or 1 ㎛ or less. The size of the Li2S particles may be, for example, 0.1 to 2 ㎛, 0.1 to 1.5 ㎛, or 0.1 to 1 ㎛ or less. Since the Li2S particles have a size in this range, the volume change during charge and discharge is suppressed, and thus the deterioration of the dry cathode active material including the composite during charge and discharge can be suppressed. If the size of the Li2S particles increases excessively, the volume change of the composite during charge and discharge may increase, and thus the deterioration of the dry cathode active material including the composite may be accelerated. As a result, the cycle characteristics of a secondary battery including such a dry cathode active material may deteriorate.

[0076] For example, the composite of Li2S, a lithium salt, and a carbon-based material may contain 10 to 80 parts by weight of Li2S, 1 to 40 parts by weight of the lithium salt, and 1 to 20 parts by weight of the carbon-based material, relative to 100 parts by weight of the composite. The Li2S content included in the composite of Li2S, a lithium salt, and a carbon-based material may be, for example, 10 to 80 parts by weight, 20 to 70 parts by weight, 30 to 60 parts by weight, or 40 to 60 parts by weight of Li2S, relative to 100 parts by weight of the composite. The lithium salt content included in the composite of Li2S, a lithium salt, and a carbon-based material may be, for example, 10 to 40 parts by weight, 15 to 40 parts by weight, 20 to 40 parts by weight, or 25 to 35 parts by weight of the lithium salt, relative to 100 parts by weight of the composite. The content of the carbon-based material included in the composite of Li2S, a lithium salt, and a carbon-based material may be, for example, 1 to 20 parts by weight, 5 to 20 parts by weight, or 5 to 15 parts by weight of the carbon-based material per 100 parts by weight of the composite. Since the composite of Li2S, a lithium salt, and a carbon-based material has a composition of Li2S, an alkali metal salt, and a carbon-based material within this range, a dry positive electrode film including the composite of Li2S, a lithium salt, and a carbon-based material can provide excellent ionic conductivity and / or electronic conductivity.

[0077] The ionic conductivity of a composite of Li2S, lithium salt, and carbon material is, for example, 1×10 at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4It can be S / cm or more. The ionic conductivity can be measured using, for example, electrochemical impedance spectroscopy, direct current polarization method, etc. Since the composite of Li2S, lithium salt, and carbon-based material has an ionic conductivity in this range, the internal resistance of the dry cathode film including the composite of Li2S, lithium salt, and carbon-based material can be further reduced. The cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be improved.

[0078] The electronic conductivity of a composite of Li2S, lithium salt, and carbon-based material is, for example, 1×10 at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4 It can be S / cm or more. The electronic conductivity can be measured using, for example, electrochemical impedance spectroscopy, DC polarization method, etc. Since the composite of Li2S, lithium salt, and carbon-based material has an electronic conductivity in this range, the internal resistance of the dry cathode film including the composite of Li2S, lithium salt, and carbon-based material can be further reduced. The cycle characteristics of the all-solid-state secondary battery including the dry cathode film can be improved.

[0079] The content of the composite of Li2S, lithium salt, and carbon-based material may be, for example, 50 to 95 wt%, 50 to 80 wt%, 55 to 80 wt%, 60 to 80 wt%, 65 to 80 wt%, or 70 to 80 wt% of the total weight of the dry positive electrode film. If the content of the composite of Li2S, lithium salt, and carbon-based material increases excessively, the volume change of the dry positive electrode may increase excessively during charge and discharge, which may deteriorate the cycle characteristics of the all-solid-state secondary battery. If the content of the composite of Li2S, lithium salt, and carbon-based material decreases excessively, the energy density of the all-solid-state secondary battery may decrease.

[0080] [Dry anode film: sulfide-based solid electrolyte]

[0081] The dry cathode film includes a dry sulfide-based solid electrolyte. The sulfide-based solid electrolyte is, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x(0≤x≤2) is at least one selected from. The sulfide-based solid electrolyte can be manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, heat treatment can be performed after the treatment. The sulfide-based solid electrolyte can be amorphous, crystalline, or a mixture thereof. The sulfide-based solid electrolyte can include, for example, sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. The sulfide-based solid electrolyte can include, for example, Li2S-P2S5. When using a material containing Li2S-P2S5 as a sulfide-based solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0082] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

[0083] <Chemical Formula 1>

[0084] Li + 12-n-x A n+ X 2- 6-x Y - x

[0085] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1≤n≤5, 0≤x≤2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Brx , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound (e.g., an argyrodite compound) including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0086] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte separator by lithium dendrites can be more effectively suppressed.

[0087] The sulfide-based solid electrolyte included in the dry cathode film may be the same as or different from the sulfide-based solid electrolyte included in the electrolyte layer.

[0088] The sulfide-based solid electrolyte included in the dry positive electrode film may have a smaller D50 average particle size than the sulfide-based solid electrolyte included in the electrolyte layer. For example, the D50 average particle size of the sulfide-based solid electrolyte included in the dry positive electrode film may 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 D50 average particle size of the sulfide-based solid electrolyte included in the electrolyte layer (30). The D50 average particle size is, for example, a median particle diameter (D50). The median particle diameter (D50) is the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by, for example, a laser diffraction method.

[0089] The content of the sulfide-based solid electrolyte included in the dry positive electrode film may be 5 to 45 wt%, 15 to 40 wt%, 20 to 40 wt%, or 25 to 40 wt% of the total weight of the dry positive electrode film. By including the sulfide-based solid electrolyte in this range, the dry positive electrode film can provide reduced internal resistance and improved ionic conductivity. If the content of the sulfide-based solid electrolyte is excessively reduced, the internal resistance of the dry positive electrode film increases, which may deteriorate the cycle characteristics of the all-solid-state secondary battery. If the content of the sulfide-based solid electrolyte is excessively increased, the energy density of the all-solid-state secondary battery may be reduced.

[0090] [Dry cathode film: dry binder]

[0091] The dry cathode film includes a dry binder. A dry binder is, for example, a binder that is not impregnated, dissolved, or dispersed in a process solvent during the manufacturing process of the dry cathode film. A dry binder is, for example, a binder that does not contain or come into contact with a process solvent during the manufacturing process of the dry cathode film. The dry binder is, for example, a fibrillated binder or a fibrous binder. The fibrillated binder or the fibrous binder can serve as a porous matrix that supports and binds the dry cathode active material and other components included in the dry cathode film. The fibrillated binder or the fibrous binder is intermittently arranged on the surface of the dry cathode active material without agglomeration, thereby binding a plurality of dry cathode active materials, thereby effectively suppressing an increase in the internal resistance of the dry cathode film caused by the dry binder. A fibrous binder or fibrous binder can be identified as having a fibrous form, for example, as shown in a scanning electron microscope image of a cross-section of a dry anode. The fibrous binder or fibrous binder has an aspect ratio of, for example, 10 or more, 20 or more, 50 or more, or 100 or more.

[0092] Dry binders include, but are not limited to, any binder used in the manufacture of dry electrodes, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexapropylene (PVDF-HFP) copolymer, polyvinylidene fluoride (PVDF), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or copolymers thereof. The dry binder may include, in particular, a fluorinated binder. Fluorinated binders include, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexapropylene (PVDF-HFP) copolymer, or polyvinylidene fluoride (PVDF).

[0093] Glass transition temperature (T) of dry binder g ) can be, for example, -30°C to 150°C, 15°C to 150°C, 15°C to 130°C, 50°C to 130°C, 100°C to 130°C, or 120°C to 130°C. The glass transition temperature (T of the dry binder g) can be, for example, -30°C to 150°C, -30°C to 100°C, -30°C to 50°C, -30°C to 15°C, -30°C to -10°C, or -30°C to -20°C. The glass transition temperature of polytetrafluoroethylene (PTFE) is, for example, 120 to 130°C. Since the dry binder has a glass transition temperature in this range, a fiberized binder or a fibrous binder can be more easily obtained during the dry electrode manufacturing process. The glass transition temperature of the dry binder can be measured, for example, by a Differential Scanning Calorimeter (DSC), a Dynamic Mechnaical Analyzer (DMA), a Thermochemical Analyzer (TMA), and / or a Thermogravimetric Analyzer (TGA).

[0094] The content of the dry binder is, for example, 0.1 to 5 wt%, 0.5 to 5 wt%, 1 to 5 wt%, or 1 to 3 wt% based on the total weight of the dry positive electrode film. By including the dry binder in this range in the dry positive electrode film, the bonding strength of the dry positive electrode film is improved, and the dry positive electrode film can maintain an increased energy density.

[0095] [Dry anode film: conductive material]

[0096] The dry cathode film may further comprise, for example, a conductive material. The conductive material is, for example, a dry conductive material. A dry conductive material is, for example, a conductive material that is not impregnated, dissolved, or dispersed in a process solvent during the manufacturing process of the dry cathode film. A dry conductive material is, for example, a conductive material that does not contain or come into contact with a process solvent during the manufacturing process of the dry cathode film. The dry conductive material comprises, for example, a carbon-based conductive material. The carbon-based conductive material comprises, for example, a fibrous carbon-based material having an aspect ratio of 10 or greater, a particulate carbon-based material having an aspect ratio of less than 10, or a combination thereof. The aspect ratio of the fibrous carbon-based material, e.g., the ratio of the diameter to the length of the fibrous carbon-based material, can be determined, for example, from an SEM image.

[0097] Fibrous carbon-based materials with an aspect ratio of 10 or greater include, but are not limited to, carbon fibers, carbon nanotubes, and carbon nanobelts, and any material used as a carbon-based conductive material in the relevant technical field may be used. Fibrous carbon-based material conductive materials are distinguished from carbon-based materials that form part of a dry cathode active material in that they are simply mixed with the dry cathode active material.

[0098] Particulate carbon-based materials having an aspect ratio of less than 10 include, but are not limited to, carbon black, acetylene black, Ketjen black, natural graphite, artificial graphite, etc., and any material used as a carbon-based conductive material in the relevant technical field may be used. The aspect ratio of the particulate carbon-based material is, for example, 1 to 7, 1 to 5, 1 to 3, or 1 to 2.

[0099] The content of the dry conductive material included in the dry positive electrode film is, for example, 0.1 to 5 wt%, 0.5 to 5 wt%, or 1 to 5 wt% based on the total weight of the dry positive electrode film. By further including the dry conductive material in this range in the dry positive electrode film, the electronic conductivity of the dry positive electrode film is further improved, and the cycle characteristics of an all-solid-state secondary battery including the dry positive electrode film can be further improved. The dry conductive material may be omitted.

[0100] [Dry Anode Film: Other Additives]

[0101] In addition to the above-described positive electrode active material, solid electrolyte, binder, and conductive agent, the dry positive electrode film may further include additives such as fillers, coating agents, dispersants, and ion conductive aids.

[0102] As fillers, coating agents, dispersants, ion conductive aids, etc. that can be included in the dry cathode film, known materials generally used in the cathode of an all-solid-state secondary battery can be used.

[0103] [Dry cathode film: physical properties]

[0104] Dry cathode films are, for example, self-standing films. Dry cathode films can maintain a film form without a support, for example. Therefore, dry cathode films can be prepared as separate self-standing films and then placed on a cathode current collector. Since dry cathode films are manufactured through a dry process, they do not contain any intentionally added process solvents. For example, they do not contain residual processing solvents. While trace amounts of unintended solvents may remain in dry cathode films, these solvents are not intentionally added process solvents. Therefore, dry cathode films are distinguished from wet cathode films, which are manufactured by mixing components and process solvents and then drying to remove some or all of the process solvent.

[0105] The thickness of the dry positive electrode film may be, for example, 50 to 500 μm, 50 to 400 μm, 50 to 300 μm, or 50 to 250 μm. If the thickness of the dry positive electrode film is too thin, the number of current collectors increases, which may lower the energy density per unit volume of the all-solid-state secondary battery. If the thickness of the dry positive electrode film is too large, the internal resistance of the dry positive electrode increases, which may lower the cycle characteristics of the all-solid-state secondary battery.

[0106] The tensile strength of the dry positive electrode film can be, for example, 500 kPa or more, 700 kPa or more, or 900 kPa or more at 25°C. The tensile strength of the dry positive electrode film can be, for example, 500 kPa to 5000 kPa, 700 kPa to 5000 kPa, 700 kPa to 3000 kPa, 700 kPa to 2000 kPa, or 900 kPa to 2000 kPa at 25°C. When the dry positive electrode film has a tensile strength in this range, the structural stability of the dry positive electrode film can be improved. Therefore, the dry positive electrode film can maintain a stable three-dimensional conductive network during the charge / discharge process, thereby improving the reversibility of the electrode reaction. When the dry positive electrode film has a high tensile strength in this range, the mechanical strength of the dry positive electrode film can be improved. Since the dry cathode film has improved mechanical strength, local deterioration due to volume change during charge and discharge of a dry cathode having the dry cathode film and an all-solid-state secondary battery including the same can be suppressed. As a result, the cycle characteristics of the all-solid-state secondary battery can be improved. If the tensile strength of the dry cathode film is excessively low, defects such as cracks and cuts may occur during the manufacturing process or charge and discharge process of the all-solid-state secondary battery, which may reduce the yield of the all-solid-state secondary battery. The tensile strength at break of the dry cathode film can be measured, for example, according to ASTM D412.

[0107] The surface resistivity of the dry positive electrode film may be, 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 may be, for example, 0.1 to 70 Ω / sq, 0.5 to 60 Ω / sq, 1 to 50 Ω / sq, 1 to 40 Ω / sq, or 1 to 35 Ω / sq at 25°C and 1 atm. When the dry positive electrode film has a reduced surface resistivity in this range, the surface resistance, interfacial resistance, and / or internal resistance of the dry positive electrode film may be reduced. Therefore, the cycle characteristics of an all-solid-state secondary battery including such a dry positive electrode film may be further improved. The surface resistivity of a dry cathode film can be measured, for example, according to ASTM D257 or IEC 62631-3-1.

[0108]

[0109] [Dry anode]

[0110] [Dry cathode: cathode active material layer]

[0111] According to one embodiment, a dry positive electrode comprises: a positive electrode current collector; and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector. The positive electrode active material layer comprises the above-described dry positive electrode film. By including the above-described dry positive electrode film, the dry positive electrode can have further reduced internal resistance. Accordingly, the cycle characteristics of a secondary battery including the dry positive electrode can be further improved.

[0112] Referring to FIGS. 1 to 7, a dry positive electrode (10) includes a positive electrode current collector (11); and a positive electrode active material layer (12) disposed on one or both sides of the positive electrode current collector (11). The positive electrode active material layer (12) includes the above-described dry positive electrode film.

[0113] [Dry anode: anode current collector]

[0114] The positive electrode collector (11) uses a plate or foil made of, for example, 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. The positive electrode collector (11) may be omitted. The thickness of the positive electrode collector (11) is, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0115] The cathode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base 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 a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies, thereby blocking battery operation and 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 an alloy thereof. The metal layer can act as an electrochemical fuse and be cut off in case of overcurrent to prevent a short circuit. The limit current and the maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or the maximum current of the positive electrode current collector (11) decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added on the metal layer for connection to the outside. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and lithium battery.

[0116] [Dry anode: interlayer]

[0117] A dry cathode may further include, for example, a cathode current collector; and an interlayer disposed between the cathode current collector and the dry cathode film (i.e., the dry cathode active material layer). The interlayer may be omitted.

[0118] The interlayer is disposed, for example, on one or both sides of the positive electrode collector. By disposing the interlayer on one or both sides of the positive electrode collector, the bonding strength between the positive electrode collector and the dry positive electrode film can be further enhanced.

[0119] The thickness of the intermediate layer is, for example, 0.01 to 30%, 0.1 to 30%, 0.5 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10%, 1 to 5%, or 1 to 3% of the thickness of the positive electrode collector. The thickness of the intermediate layer is, for example, 10 nm to 5 ㎛, 50 nm to 5 ㎛, 200 nm to 4 ㎛, 500 nm to 3 ㎛, 500 nm to 2 ㎛, 500 nm to 1.5 ㎛, or 700 nm to 1.3 ㎛. When the intermediate layer has a thickness in this range, the bonding force between the positive electrode collector and the dry positive electrode film is further improved, and an increase in interfacial resistance is suppressed.

[0120] The intermediate layer includes, for example, a carbon-based conductive material. The carbon-based conductive material included in the intermediate layer may be selected from carbon-based conductive materials used in dry electrode films. The intermediate layer may include the same carbon-based conductive material as the carbon-based conductive material used in the dry electrode film. By including a carbon-based conductive material in the intermediate layer, the intermediate layer may be, for example, a conductive layer.

[0121] [Dry anode: first inert member]

[0122] Referring to FIGS. 4 to 7, the positive electrode (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one side of the positive electrode current collector. A first inactive member (40) is disposed on one side of the positive electrode (10). Referring to FIGS. 4 and 6, the first inactive member (40) is disposed on one side of the positive electrode active material layer (12) and the positive electrode current collector (11). Referring to FIGS. 5 and 7, the first inactive member (40) is disposed on one side of the positive electrode active material layer (12) and between the electrolyte layer (30) and the positive electrode current collector (11) facing the electrolyte layer (30). The first inactive member (40) is not disposed on one side of the positive electrode current collector (11). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0123] By including the first inert member (40), cracking of the electrolyte layer (30) is prevented during the manufacture and / or charging / discharging of the all-solid-state secondary battery (1), and as a result, the cycle characteristics of the all-solid-state secondary battery (2) are improved. In the all-solid-state secondary battery (1) that does not include the first inert member (40), when the manufacture and / or charging / discharging of the all-solid-state secondary battery (1) is performed, uneven pressure is applied to the electrolyte layer (30) in contact with the positive electrode (10), which increases the possibility of cracking in the electrolyte layer (30), and thus, a short circuit may occur due to the growth of lithium metal through the crack.

[0124] In the all-solid-state secondary battery (1), the thickness of the first inert member (40) is greater than or equal to the thickness of the positive electrode active material layer (12). Alternatively, in the all-solid-state secondary battery (1), the thickness of the first inert member (40) is substantially equal to the thickness of the positive electrode (10). Since the thickness of the first inert member (40) is equal to the thickness of the positive electrode (10), a uniform pressure is applied between the positive electrode (10) and the electrolyte layer (30), and the positive electrode (10) and the electrolyte layer (30) are sufficiently adhered to each other, so that the interfacial resistance between the positive electrode (10) and the electrolyte layer (30) can be reduced. In addition, since the electrolyte layer (30) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state secondary battery (1), the internal resistance of the electrolyte layer (30) and the all-solid-state secondary battery (1) including the same is reduced.

[0125] The first inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the electrolyte layer (30). Since the first inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the electrolyte layer (30), cracks in the electrolyte layer (30) that occur due to a pressure difference during the pressing process in the electrolyte layer (30) that does not come into contact with the positive electrode (20) can be effectively suppressed. The first inert member (40) surrounds the side surface of the positive electrode (10) and is separated from the negative electrode (20), more specifically, the first negative electrode active material layer (22). The first inert member (40) surrounds the side surface of the positive electrode (10), comes into contact with the electrolyte layer (30), and is separated from the negative electrode (20). Therefore, the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or a short circuit occurring due to overcharging of lithium, etc., is suppressed. For example, the first inert member (40) is disposed on one side of the positive electrode active material layer (12) and simultaneously disposed on one side of the positive electrode current collector (11), thereby more effectively suppressing the possibility of a short circuit occurring due to contact between the positive electrode current collector (11) and the negative electrode (20).

[0126] Referring to FIGS. 4 to 7, the first inert member (40) extends from one side of the positive electrode (30) to the end of the electrolyte layer (30). By extending the first inert member (40) to the end of the electrolyte layer (30), cracks occurring at the end of the electrolyte layer (30) can be suppressed. The end of the electrolyte layer (30) is the outermost part that is in contact with the side of the electrolyte layer (30). The first inert member (40) extends to the outermost part that is in contact with the side of the electrolyte layer (30). The first inert member (40) is separated from the negative electrode (20), more specifically, from the first negative electrode active material layer (22). The first inert member (40) extends to the end of the electrolyte layer (30), but does not contact the negative electrode (20). The first inert member (40) fills a space extending from, for example, one side of the anode (30) to the end of the electrolyte layer (30).

[0127] Referring to FIGS. 4 to 7, the width of the first inert member (40) extending from one side of the positive electrode (10) to the end of the electrolyte layer (30) is, for example, 1 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10%, or 1 to 5% of the width between one side of the positive electrode (10) and the other side opposite to the one side. If the width of the first inert member (40) is excessively large, the energy density of the all-solid-state secondary battery (1) is reduced. If the width of the first inert member (40) is excessively small, the effect of arranging the first inert member (40) is minimal.

[0128] The area of ​​the anode (10) is smaller than the area of ​​the electrolyte layer (30) in contact with the anode (10). The first inert member (40) is arranged to surround the side of the anode (10) to compensate for the area difference between the anode (10) and the electrolyte layer (30). Since the area of ​​the first inert member (40) compensates for the difference between the area of ​​the anode (10) and the area of ​​the electrolyte layer (30), cracks in the electrolyte layer (30) caused by the pressure difference during the pressing process are effectively suppressed. For example, the sum of the area of ​​the anode (10) and the area of ​​the first inert member (40) is equal to the area of ​​the electrolyte layer (30). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0129] The area of ​​the anode (10) is, 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 anode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area of ​​the electrolyte layer (30).

[0130] If the area of ​​the positive electrode (10) is equal to or larger than the area of ​​the electrolyte layer (30), the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or overcharging of lithium increases. The area of ​​the positive electrode (10) is, for example, equal to the area of ​​the positive electrode active material layer (12). The area of ​​the positive electrode (10) is, for example, equal to the area (11) of the positive electrode current collector.

[0131] The area of ​​the first inert member (40) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the area of ​​the anode (10). The area of ​​the first inert member (40) is, for example, 1% to 50%, 5% to 40%, 5% to 30%, 5% to 20%, or 5% to 15% of the area of ​​the anode (10).

[0132] The area (S1) of the positive electrode (10) is smaller than the area (S4) of the negative electrode current collector (21). The area (S1) of the positive electrode (10) is, for example, less 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) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area (S4) of the negative electrode current collector (21). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the negative electrode (20). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the first negative electrode active material layer (22).

[0133] As used herein, “same” area, length, width, thickness, and / or shape includes all instances of having “substantially the same” area, length, width, thickness, and / or shape, except where the area, length, width, thickness, and / or shape are intentionally different from each other. “Same” area, length, width, and / or thickness includes a range where the unintentional difference in the area, length, width, and / or thickness of the compared objects is, for example, less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0134] The thickness of the first inert member (40) is, for example, greater than the thickness of the first negative electrode active material layer (22). The thickness of the first negative electrode active material layer (22) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the first inert member (40). The thickness of the first negative electrode active material layer (22) is, for example, 1% to 50%, 1% to 40%, 1% to 30%, 1% to 20%, or 1% to 10% of the thickness of the first inert member (40).

[0135] The first inert member (40) may be a gasket. By using a gasket as the first inert member (40), cracks in the electrolyte layer (30) caused by a pressure difference during the pressing process can be effectively suppressed.

[0136] The first inert member (40) has, for example, a single-layer structure. Alternatively, although not shown in the drawing, the first inert member (40) may have a multi-layer structure. In the first inert member (40) having a multi-layer structure, each layer may have a different composition. The first inert member having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. The first inert member (40) having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers. The adhesive layer effectively prevents, for example, a separation between the positive electrode (10) and the electrolyte layer (30) due to a volume change of the positive electrode (10) occurring during the charge / discharge process of the all-solid-state secondary battery (10), and improves the film strength of the first inert member (40) by providing a bonding force between the support layer and other layers. The support layer provides support to the first inert member (40), prevents unevenness of pressure applied to the electrolyte layer (30) during the pressurization process or the charge / discharge process, and prevents deformation of the shape of the all-solid-state secondary battery (1) being manufactured.

[0137] The first inert member (40) is, for example, a flame-retardant inert member. The flame-retardant inert member provides flame retardancy, thereby preventing thermal runaway and ignition of the all-solid-state secondary battery (1). Consequently, the safety of the all-solid-state secondary battery (1) is further enhanced. The flame-retardant inert member absorbs residual moisture within the all-solid-state secondary battery (1), thereby preventing deterioration of the all-solid-state secondary battery (1), thereby improving the lifespan characteristics of the all-solid-state secondary battery (1).

[0138] The flame-retardant inert member includes, for example, a matrix and a filler. The matrix includes, for example, a substrate and a reinforcing material. The matrix includes, for example, a fibrous substrate and a fibrous reinforcing material. Since the matrix includes the substrate, the matrix can have elasticity. Therefore, the matrix can effectively accommodate volume changes during charge and discharge of the all-solid-state secondary battery (1) and can be arranged at various positions. The substrate included in the matrix includes, for example, a first fibrous material. Since the substrate includes the first fibrous material, the volume changes of the positive electrode (30) occurring during charge and discharge of the all-solid-state secondary battery (1) can be effectively accommodated and deformation of the first inert member (40) due to the volume changes of the positive electrode (30) can be effectively suppressed. The first fibrous material is, for example, a material having an aspect ratio of 5 or more, 20 or more, or 50 or more. The first fibrous material is, for example, a material having an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. Since the first fibrous material is an insulating material, a short circuit between the positive electrode (30) and the negative electrode (20) caused by lithium dendrites, etc., generated during the charge and discharge process of the all-solid-state secondary battery (1) can be effectively prevented. The first fibrous material includes, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conductive polymer fibers. The strength of the matrix is ​​improved by the inclusion of a reinforcing material in the matrix. Therefore, the matrix can prevent excessive volume change during charge and discharge of the all-solid-state secondary battery (1) and deformation of the all-solid-state secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material. Since the reinforcing material includes the second fibrous material, the strength of the matrix can be increased more uniformly. The second fibrous material is, for example, a material having an aspect ratio of 3 or more, 5 or more, or 10 or more.The first fibrous material is, for example, a material having an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame-retardant material. Since the second fibrous material is a flame-retardant material, ignition due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or due to external impact can be effectively suppressed. The second fibrous material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc.

[0139] The flame-retardant inert member includes a filler in addition to a matrix. The filler may be disposed within the matrix, on the surface of the matrix, or on both the interior and the surface. The filler is, for example, an inorganic material. The filler included in the flame-retardant inert member is, for example, a moisture getter. The filler removes moisture remaining in the all-solid-state secondary battery (1) by adsorbing moisture, for example, at a temperature below 100°C, thereby preventing deterioration of the all-solid-state secondary battery (1). In addition, when the temperature of the all-solid-state secondary battery (1) increases to 150°C or higher due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or an external impact, the filler releases the adsorbed moisture, thereby effectively suppressing ignition of the all-solid-state secondary battery (1). That is, the filler is, for example, a flame retardant. The filler is, for example, a metal hydroxide having moisture adsorption properties. The metal hydroxide contained in the filler is, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, TI(OH)3, Zr(OH)4, Al(OH)3, or a combination thereof. The content of the filler contained in the flame-retardant inert member is, for example, 10 to 80 parts by weight, 20 to 80 parts by weight, 30 to 80 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, 60 to 80 parts by weight, or 65 to 80 parts by weight, based on 100 parts by weight of the flame-retardant inert member (4).

[0140] The flame-retardant inert member may further comprise, for example, a binder. The binder may comprise, for example, a curable polymer or a non-curable polymer. A curable polymer is a polymer that cures by heat and / or pressure. A curable polymer is, for example, a solid at room temperature. The flame-retardant inert member may comprise, for example, a heat-pressure curable film and / or a cured product thereof. An example of a heat-pressure curable polymer is TSA-66 from Toray.

[0141] The flame-retardant inert member may additionally include other materials in addition to the above-described substrate, reinforcing material, filler, and binder. The flame-retardant inert member may further include one or more selected from among paper, an insulating polymer, an ion-conducting polymer, an insulating inorganic material, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

[0142] The density of the substrate or the density of the reinforcing material included in the flame-retardant inert member may be, for example, 10% to 300%, 10% to 150%, 10% to 140%, 10% to 130%, or 10% to 120% of the density of the positive electrode active material included in the positive electrode active material layer (12).

[0143] The first inert member (40) is a member that does not contain an electrochemically active material, for example, an electrode active material. The electrode active material is a material that absorbs / releases lithium. The first inert member (40) is a member made of a material other than the electrode active material and used in the relevant technical field.

[0144]

[0145] [All-solid-state secondary battery]

[0146] An all-solid-state secondary battery according to one embodiment includes a positive electrode; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode. The positive electrode is the dry positive electrode described above. The negative electrode includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0147] Referring to FIGS. 1 to 7, an all-solid-state secondary battery (1) includes 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) includes a dry positive electrode. The negative electrode (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector.

[0148] [anode]

[0149] Refer to the dry anode described above.

[0150] [cathode]

[0151] [Cathode: Cathode active material]

[0152] Referring to FIGS. 1 to 7, the negative electrode (20) includes a first negative electrode active material layer (22). The first negative electrode active material layer (22) includes, for example, a negative electrode active material and a binder.

[0153] The negative electrode active material included in the first negative electrode active material layer (22) is, for example, a negative electrode material that can form an alloy or compound with lithium.

[0154] The negative electrode active material included in the first negative electrode active material layer (22) has, for example, a particle form. The average particle diameter of the negative electrode active material having a particle form is, for example, 4 ㎛ or less, 3 ㎛ or less, 2 ㎛ or less, 1 ㎛ or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle diameter of the negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 3 ㎛, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 300 nm, or 10 nm to 100 nm. When the negative electrode active material has an average particle diameter in this range, reversible absorption and / or desorption of lithium can be facilitated during charge and discharge. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

[0155] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or metalloid negative electrode active material.

[0156] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0157] The carbon-based negative electrode material is, in particular, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene, and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0158] The carbon-based negative electrode active material may be, for example, porous carbon. The porous carbon has a pore volume of, for example, 0.1 cc / g to 10.0 cc / g, 0.5 cc / g to 5 cc / g, or 0.1 cc / g to 1 cc / g. The porous carbon has an average pore diameter of, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The porous carbon has a BET surface area of, for example, 100 m 2 / g to 3000 m 2 / g is.

[0159] The metal or metalloid negative electrode active material includes, but is not limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium and therefore is not a metal negative electrode active material.

[0160] The first negative electrode active material layer (22) includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the first negative electrode active material layer (22) includes only amorphous carbon, or includes at least one selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the first negative electrode active material layer (22) includes a mixture of amorphous carbon and at least one selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture of amorphous carbon and gold, etc., is a weight ratio, for example, 99:1 to 1:99, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to this range and is selected according to the required characteristics of the all-solid-state secondary battery (1). When the negative electrode active material has this composition, the cycle characteristics of the all-solid-state secondary battery (1) are further improved.

[0161] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid. The metal or metalloid includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the metalloid is a semiconductor. The content of the second particles is 1 to 99 wt%, 1 to 60 wt%, 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, an all-solid-state secondary battery (1) are further improved.

[0162] Alternatively, the first negative electrode active material layer (22) includes a composite negative electrode active material. The composite negative electrode active material may include, for example, a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support. Since the composite negative electrode active material has such a structure, the metal-based negative electrode active material can be prevented from being localized within the first negative electrode active material layer and a uniform distribution can be achieved. As a result, the cycle characteristics of the all-solid-state secondary battery (1) including the first negative electrode active material layer (22) are further improved.

[0163] The metal-based negative electrode active material supported on the carbon-based support includes, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metal includes, 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 includes, 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 includes, for example, Au x O y (0 <x≤2, 0<y≤3), Pt x O y (0 <x≤1, 0<y≤2), Pd x O y (0 <x≤1, 0<y≤1), Si x O y (0 <x≤1, 0<y≤2), Ag x O y (0 <x≤2, 0<y≤1), Al x O y (0 <x≤2, 0<y≤3), Bi x O y (0 <x≤2, 0<y≤3), Sn x O y (0 <x≤1, 0<y≤2), Te x O y(0 <x≤1, 0<y≤3), Zn x The y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x The y (0 <x2, 0<y3)의 복합체, Pt와 Pt x The y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x The y (0 <x≤1, 0<y≤1)의 복합체, Si와 Si x The y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x The y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x The y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x The y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x The y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x The y (0 <x≤1, 0<y≤3), Zn과 Zn x The y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0164] The carbonaceous support is, for example, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., and any material classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite carbon. Carbonaceous materials are, for example, carbonaceous negative electrode active materials.

[0165] The composite negative electrode active material may have, for example, a particle form. The particle size of the composite negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. When the composite negative electrode active material has a particle size in this range, reversible absorption and / or desorption of lithium may be facilitated during charge and discharge. The metal-based negative electrode active material supported on the support may have, for example, a particle form. The particle size of the metal-based negative electrode active material may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 5 nm to 100 nm, or 10 nm to 50 nm. The carbon-based support may have, for example, a particle form. The particle size of the carbon-based support may be, for example, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having a particle size in this range, the carbon-based support can be more uniformly arranged within the first negative electrode active material layer. The carbon-based support may be, for example, nanoparticles having a particle size of 500 nm or less. The particle sizes of the composite negative electrode active material, the particle sizes of the metal-based negative electrode active material, and the particle sizes of the carbon-based support are, for example, average particle sizes. The average particle size is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer. Alternatively, the average particle size may be determined automatically using software, for example, from an electron microscope image, or manually by a manual method.

[0166] [Cathode: Binder]

[0167] The binder included in the first negative electrode active material layer (22) is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0168] Since the first negative electrode active material layer (22) includes a binder, the first negative electrode active material layer (22) is stabilized on the negative electrode current collector (21). In addition, cracking of the first negative electrode active material layer (22) is suppressed despite changes in the volume and / or relative position of the first negative electrode active material layer (22) during the charge and discharge process. For example, if the first negative electrode active material layer (22) does not include a binder, the first negative electrode active material layer (22) can be easily separated from the negative electrode current collector (21). As the first negative electrode active material layer (22) is separated from the negative electrode current collector (21), the possibility of a short circuit occurring increases as the negative electrode current collector (21) comes into contact with the electrolyte layer (30) at the exposed portion of the negative electrode current collector (21). The first negative electrode active material layer (22) is manufactured by, for example, applying a slurry in which the material constituting the first negative electrode active material layer (22) is dispersed onto the negative electrode current collector (21) and drying the slurry. By including a binder in the first negative electrode active material layer (22), stable dispersion of the negative electrode active material in the slurry is possible. For example, when applying the slurry onto the negative electrode current collector (21) by screen printing, it is possible to suppress clogging of the screen (for example, clogging by aggregates of the negative electrode active material).

[0169] [Cathode: Other additives]

[0170] The first negative electrode active material layer (22) may further include additives used in a conventional all-solid-state secondary battery (1), such as fillers, coating agents, dispersants, and ion conductive aids.

[0171] [Cathode: Solid electrolyte]

[0172] The first negative electrode active material layer (22) may further include a solid electrolyte. The solid electrolyte may be, for example, a material selected from among the solid electrolytes included in the electrolyte layer (30). The solid electrolyte included in the first negative electrode active material layer (22) may act as a reaction site where lithium metal formation begins within the first negative electrode active material layer (22), a space where the formed lithium metal is stored, or a path for transferring lithium ions. The solid electrolyte may be omitted.

[0173] In the first negative electrode active material layer (22), the content of the solid electrolyte may be high, for example, in an area adjacent to the electrolyte layer (30), and low, for example, in an area adjacent to the negative electrode current collector (21). In the first negative electrode active material layer (22), the solid electrolyte may have a concentration gradient in which the concentration decreases, for example, from an area adjacent to the electrolyte layer (30) to an area adjacent to the negative electrode current collector (21).

[0174] [Cathode: First negative electrode active material layer]

[0175] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer (12) is the first open circuit voltage (1 st Li / Li from open circuit voltage) + The initial charge capacity of the first negative electrode active material layer (22) is determined at the maximum charging voltage. The initial charge capacity of the first negative electrode active material layer (22) is determined at the second open circuit voltage (2 nd Li / Li from open circuit voltage) + It is determined at 0.01 V.

[0176] The maximum charging voltage is determined by the type of cathode active material. The maximum charging voltage can be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charging voltage of Li2S or Li2S composite is Li / Li + can be 2.5 V for Li2S or Li2S complex. For example, the maximum charging voltage of Li / Li + It can be 3.0 V for. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1. The initial charge capacity (mAh) of the positive electrode active material layer (12) is obtained by multiplying the charge capacity density (charge specific 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). When several types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is 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) is also calculated in the same way. The initial charge capacity of the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (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). When several types of negative electrode active materials are used, the charge capacity density Х mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer (22). The charge capacity density of each of the positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell using lithium metal as a counter electrode. The initial charge capacity of each of the positive electrode active material layer (12) and the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass value of the negative electrode active material in the first negative electrode active material layer (22). 2can be directly measured using an all-solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, for example, 3.0 V (vs. Li / Li + ) can be performed for an operating voltage of up to 0.01 V for the cathode, for example, lithium metal, from the second open circuit voltage (OCV). For example, an all-solid-state half-cell having a cathode active material layer can measure a current of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The all-solid-state half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 The all-solid-state half-cell having the positive electrode active material layer can be charged from the first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0177] If the initial charge capacity of the first negative electrode active material layer (22) is too small, the thickness of the first negative electrode active material layer (22) becomes very thin, so that 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 collapse 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 the charge capacity of the first negative electrode active material layer (22) increases excessively, the energy density of the all-solid-state secondary battery (1) decreases and the internal resistance of the all-solid-state secondary battery (1) due to the first negative electrode active material layer (22) increases, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery (1).

[0178] The thickness of the first negative electrode active material layer (22) is, 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) is, for example, 1 to 50%, 1 to 40%, 1 to 30%, 1 to 20%, 1 to 10%, or 1 to 5% of the thickness of the positive electrode active material layer (12). The thickness of the first negative electrode active material layer (22) is, for example, 1 µm to 20 µm, 2 µm to 15 µm, or 3 µm to 10 µm. If the thickness of the first negative electrode active material layer (22) is too thin, lithium dendrites formed between the first negative electrode active material layer (22) and the negative electrode current collector (21) collapse 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 the thickness of the first negative electrode active material layer (22) increases excessively, the energy density of the all-solid-state secondary battery (1) decreases and the internal resistance of the all-solid-state secondary battery (1) due to the first negative electrode active material layer (22) increases, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery (1). If the thickness of the first negative electrode active material layer (22) decreases, for example, the initial charge capacity of the first negative electrode active material layer (22) also decreases.

[0179] [Cathode: Second negative electrode active material layer]

[0180] Referring to FIG. 3, the all-solid-state secondary battery (1) further includes, after being charged, a second negative electrode active material layer (24) disposed, for example, between the negative electrode current collector (21) and the first negative electrode active material layer (22). The second negative electrode active material layer (24) is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer (24) is a metal layer containing lithium, it functions as, for example, a lithium reservoir. The lithium alloy is, 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, a Li-Si alloy, etc., but is not limited thereto, and any lithium alloy used in the art may be used. The second negative electrode active material layer (24) may be made of one of these alloys or lithium, or may be made of several types of alloys. The second negative electrode active material layer (24) is, for example, a plated layer. The second negative electrode active material layer (24) is deposited between the first negative electrode active material layer (22) and the negative electrode current collector (21), for example, during the charging process of an all-solid-state secondary battery (1).

[0181] The thickness of the second negative electrode active material layer (24) is not particularly limited, but is, for example, 1 ㎛ to 500 ㎛, 1 ㎛ to 200 ㎛, 1 ㎛ to 150 ㎛, 1 ㎛ to 100 ㎛, or 1 ㎛ to 50 ㎛. If the thickness of the second negative electrode active material layer (24) is too thin, it is difficult for the second negative electrode active material layer (24) to perform the role of a lithium reservoir. If the thickness of the second negative electrode active material layer (24) is too thick, the mass and volume of the all-solid-state secondary battery (1) may increase, and the cycle characteristics of the all-solid-state secondary battery (1) may rather deteriorate.

[0182] Alternatively, in the all-solid-state secondary battery (1), the 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), for example, before assembling the all-solid-state secondary battery (1). 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) acts as a lithium reservoir because it is a metal layer containing lithium. 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).

[0183] When the second negative electrode active material layer (24) is precipitated by charging after assembling the all-solid-state secondary battery (1), the energy density of the all-solid-state secondary battery (1) increases because the second negative electrode active material layer (24) is not included when assembling the all-solid-state secondary battery (1). When charging the all-solid-state secondary battery (1), the charging is performed in excess of the charging capacity of the first negative electrode active material layer (22). That is, the first negative electrode active material layer (22) is overcharged. At the initial stage of charging, lithium is absorbed into the first negative electrode active material layer (22). The negative electrode active material included in the first negative electrode active material layer (22) forms an alloy or compound with the lithium ions that have moved from the positive electrode (10). When charging exceeds the capacity of the first negative electrode active material layer (22), for example, lithium is deposited on the back surface of the first negative electrode active material layer (22), that is, 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) is formed by the deposited lithium. The second negative electrode active material layer (24) is a metal layer mainly composed of lithium (i.e., metallic lithium). This result is obtained, for example, by the negative electrode active material included in the first negative electrode active material layer (22) including a material that forms an alloy or compound with lithium. During discharge, lithium in the first negative electrode active material layer (22) and the second negative electrode active material layer (24), that is, the metal layer, is ionized and moves toward the positive electrode (10). Therefore, it is possible to use lithium as the negative electrode active material in an all-solid-state secondary battery (1). In addition, since the first negative electrode active material layer (22) covers the second negative electrode active material layer (24), it acts as a protective layer for the second negative electrode active material layer (24), i.e., the metal layer, and at the same time, it suppresses the precipitation and growth of lithium dendrites. Accordingly, it suppresses short circuits and capacity reduction of the all-solid-state secondary battery (1), and consequently improves the cycle characteristics of the all-solid-state secondary battery (1).In addition, when the second negative electrode active material layer (24) is placed by charging after assembling the all-solid-state secondary battery (1), the negative electrode (20), i.e., the negative electrode current collector (21) and the first negative electrode active material layer (22) and the region between them are Li-free regions that do not contain lithium (Li) in the initial state or the state after complete discharge of the all-solid-state secondary battery (1).

[0184] [Cathode: Negative current collector]

[0185] The negative electrode current collector (21) is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative electrode current collector (21) is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, and any material that can be used as an electrode current collector in the relevant technical field can be used. The negative electrode current collector (21) may be composed of one type of the above-described metal, or may be composed of an alloy or a coating material of two or more types of metals. The negative electrode current collector (21) is, for example, in the form of a plate or foil.

[0186] Referring to FIG. 2, the all-solid-state secondary battery (1) may further include a thin film (23) containing an element capable of forming an alloy with lithium on one surface of the negative electrode collector (21). The thin film (23) is disposed between the negative electrode collector (21) and the first negative electrode active material layer (22). The thin film (23) contains, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film (23) is composed of one of these metals or an alloy of several types of metals. By placing the thin film (23) on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (24) deposited between the thin film (23) and the first negative electrode active material layer (22) becomes flatter, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0187] The thickness of the thin film (23) is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (23) is less than 1 nm, it may be difficult for the function of the thin film (23) to be exerted. If the thickness of the thin film (23) is excessively thick, the thin film (23) itself absorbs lithium, which reduces the amount of lithium precipitated from the negative electrode, thereby lowering the energy density of the all-solid-state battery and deteriorating the cycle characteristics of the all-solid-state secondary battery (1). The thin film (23) may be disposed on the negative electrode current collector (21) by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to these methods, and any method capable of forming the thin film (23) in the relevant technical field may be used.

[0188] Although not shown in the drawing, the negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base 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 a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and 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 an alloy thereof. The negative electrode current collector (21) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode collector (21), refer to the positive electrode collector (11) described above. By having this structure, the negative electrode collector (21) can reduce the weight of the negative electrode, and consequently, improve the energy density of the negative electrode and lithium battery.

[0189] [Cathode layer: second inert member]

[0190] Referring to FIGS. 6 to 7, the all-solid-state secondary battery (1) further includes a second inactive member (50) disposed on the other surface of the negative electrode collector (21).

[0191] The second inert member (50) is distinguished from the first inert member (40) in that it has conductivity by additionally including a conductive material. The second inert member (50) is, for example, a conductive flame-retardant inert member.

[0192] The conductive material is, for example, graphite, carbon black, acetylene black, Ketjen black, Denka black, carbon fiber, carbon nanotube (CNT), graphene, metal fiber, metal powder, etc. The 25°C electronic conductivity of the second inert member (50) is, for example, 100 times or more, 1000 times or more, or 10000 times or more, of the 25°C electronic conductivity of the first inert member (40).

[0193] The second inert member (50) includes, for example, a matrix, a filler, and a conductive material. The matrix includes, for example, a substrate and a reinforcing material. The second inert member (50) may further include a filler, a binder, etc. The content of the conductive material included in the second inert member (50) is, for example, 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 15 parts by weight, 1 to 10 parts by weight, 5 to 40 parts by weight, 5 to 30 parts by weight, or 5 to 35 parts by weight, based on 100 parts by weight of the second inert member (50).

[0194] The Young's modulus of the second inert member (50) is, for example, smaller than the elastic modulus of the negative electrode collector (21). The Young's modulus of the second inert member (50) is, for example, 50% or less, 30% or less, 10% or less, or 5% or less of the elastic modulus of the negative electrode collector (21). The Young's modulus of the second inert member (50) is, for example, 0.01% to 50%, 0.1 to 30%, 0.1 to 10%, or 1 to 5% of the elastic modulus of the negative electrode collector (21). The Young's modulus of the second inert member (50) is, for example, 100 MPa or less, 50 MPa or less, 30 MPa or less, 10 MPa or less, or 5 MPa or less. The elastic modulus of the second inert member (50) is, for example, 0.01 to 100 MPa, 0.1 to 50 MPa, 0.1 to 30 MPa, 0.1 to 10 MPa, or 1 to 5 MPa.

[0195] Since the second inert member (50, 50a, 50b) is conductive, it can function as a negative electrode current collector (50). In addition, since the second inert member (50) has a lower elastic coefficient than the negative electrode current collector (50), it can more effectively accommodate the volume change of the negative electrode layer (20) during charging and discharging of the all-solid-state secondary battery (1). As a result, the second inert member (50) can effectively alleviate the internal stress caused by the volume change of the all-solid-state secondary battery (1) during charging and discharging of the all-solid-state secondary battery (1), thereby improving the cycle characteristics of the all-solid-state secondary battery (1).

[0196] The thickness of the second inert member (50) is, for example, greater than the thickness of the first negative electrode active material layer (22). Since the second inert member (50) has a greater thickness than the first negative electrode active material layer (22), the volume change of the negative electrode layer (20) can be more effectively accommodated during charge and discharge. The thickness of the first negative electrode active material layer (22) is 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the second inert member (50). The thickness of the first negative electrode active material layer (22) is, for example, 1% to 50%, 1% to 40%, 1% to 30%, 1% to 20%, or 1% to 10% of the thickness of the second inert member (50). The thickness of the second inert member (50) is, for example, 1 ㎛ to 300 ㎛, 10 ㎛ to 300 ㎛, 50 ㎛ to 300 ㎛, or 100 ㎛ to 200 ㎛. If the thickness of the second inert member (50) is too thin, it may be difficult to provide the intended effect, and if the thickness of the second inert member (50) is too thick, the energy density of the all-solid-state secondary battery (1) may be reduced. The shape of the second inert member (50) is not particularly limited and may be selected according to the shape of the all-solid-state secondary battery (1). The second inert member (50) may be, for example, in the shape of a sheet, a rod, or a gasket. The second inert member (50) may be, for example, disposed on one side or both sides of one all-solid-state secondary battery (1). The second inert member (50) may be disposed, for example, between a plurality of stacked all-solid-state secondary batteries (1). The second inert member (50) may be disposed, for example, between each of the plurality of stacked all-solid-state secondary batteries (1), on the uppermost surface and / or the lowermost surface.

[0197] [Electrolyte layer]

[0198] [Electrolyte layer: electrolyte]

[0199] Referring to FIGS. 3 to 7, the electrolyte layer (30) includes 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.

[0200] The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0201] The solid electrolyte is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte refers to the dry positive electrode film described above.

[0202] Oxide solid electrolytes include, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La yTiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. The oxide-based solid electrolyte is manufactured, for example, by a sintering method.

[0203] Oxide-based solid electrolytes include, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M doped LLZO, M=Ga, W, Nb, Ta, or Al, 0 <a<2, 0≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체전해질이다.

[0204] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or may comprise a polymer having an ion-conducting functional group. The polymer solid electrolyte may, for example, be a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may, for example, not comprise a liquid.The polymer solid electrolyte comprises a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), Polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, 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) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0205] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0206] A polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atm. The polymer gel electrolyte may, for example, have a gel state without containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature, is composed solely of ions, and is liquid at room temperature or a molten salt at room temperature. The ionic liquid comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , SO4 2- , CF3SO3 - , (FSO2)2N - , (C2F2SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N -It may include at least one selected from compounds containing at least one anion selected from. The polymer solid electrolyte may form a polymer gel electrolyte by being impregnated in a liquid electrolyte, for example, in a secondary battery. The polymer gel electrolyte may further include inorganic particles. The polymer included in the polymer gel electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0207] [Electrolyte layer: binder]

[0208] The electrolyte layer (30) may include, for example, a binder. The binder included in the electrolyte layer (30) is not limited to, but may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., and any binder used in the relevant technical field may be used. The binder of the electrolyte layer (30) may be the same as or different from the binder included in the positive electrode active material layer (12) and the negative electrode active material layer (22). The binder may be omitted.

[0209] The binder content included in the electrolyte layer (30) is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the electrolyte layer (30).

[0210] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0211] (Manufacturing of positive electrode active materials)

[0212] Manufacturing Example 1: Li2S-LiI-CNF composite

[0213] (Stage 1)

[0214] Li2S and LiI were mixed in a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 28 G.

[0215] (Stage 2)

[0216] Li2S-LiI composite and carbon nanofiber (CNF) were mixed at a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNF composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 28 G. The Li2S-LiI-CNF composite was used as the cathode active material.

[0217] The Mohs hardness of Li2S was 0.6, the Mohs hardness of LiI was 2.0, and the Mohs hardness of carbon nanofiber (CNF) was 1.5.

[0218] Comparative Manufacturing Example 1: S-CNT-Li6PS5Cl composite

[0219] (Stage 1)

[0220] Sulfur (S) and carbon nanotubes (CNT) were mixed at a weight ratio of 25:25. The mixture was mechanically milled using a ball mill to produce an S-CNT composite. The milling conditions were 25°C, 600 rpm, and 10 h.

[0221] (Stage 2)

[0222] The S-CNT composite and Li6PS5Cl were mixed at a weight ratio of 50:50. The mixture was mechanically milled using a ball mill to prepare the S-CNT-Li6PS5Cl composite. The milling conditions were 25°C, 600 rpm, and 10 h.

[0223] The S-CNT-Li6PS5Cl composite was used as the cathode active material.

[0224]

[0225] (Manufacture of dry cathode films, dry cathodes, and all-solid-state secondary batteries)

[0226] Example 1: Dry, Li2S-LiI-CNF:SE:PTFE=60:39:1

[0227] (Dry cathode film manufacturing)

[0228] The Li2S-LiI-CNF composite manufactured in Manufacturing Example 1 was prepared as a dry cathode active material. Li6PS5Cl (D50=3.0 μm, crystalline), an argyrodite-type crystal, was prepared as a dry solid electrolyte. PTFE was prepared as a dry binder.

[0229] After preparing the dry cathode active material and the dry solid electrolyte at a weight ratio of 60:39, they were placed in a blade mixer and mixed for 2 minutes to prepare the first mixture.

[0230] The first mixture and the dry binder were prepared at a weight ratio of 99:1, placed in a blade mixer, and mixed for 20 seconds to prepare the second mixture.

[0231] The second mixture was further mixed using a kneader and then passed between calender rolls to prepare a self-standing dry positive electrode film in the form of a sheet with a thickness of approximately 100 μm.

[0232] The dry cathode film had a weight ratio of cathode active material: solid electrolyte: binder = 60: 39: 1. The binder was fiberized during the additional mixing and calendering process using a kneader.

[0233] (Dry anode manufacturing)

[0234] A dry cathode was manufactured by placing a dry cathode film on one side of a cathode current collector made of aluminum foil coated with carbon on one side. The thickness of the carbon-coated aluminum foil was approximately 20 μm. The thickness of the carbon coating layer was approximately 1 μm.

[0235] The area of ​​the positive electrode active material layer (dry positive electrode film) and the positive electrode current collector were the same.

[0236] (Cathode manufacturing)

[0237] A 10 ㎛ thick SUS foil was prepared as a negative electrode collector. Carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials.

[0238] A mixed powder of 4 g of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of N-methyl pyrrolidone (NMP) solution containing 7 wt% of PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum-dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold roll pressed to flatten the surface, thereby preparing a negative electrode having a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0239] (Manufacturing of solid electrolyte layer)

[0240] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50 =3.0 mm, crystalline), a mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of the solid electrolyte. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied onto 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 prepare a laminate. The prepared laminate was vacuum-dried at 80 ° C. for 2 hours, and then the solid electrolyte layer was separated from the PET substrate to prepare a solid electrolyte layer.

[0241] (First inert member)

[0242] A flame-retardant inert member was manufactured by forming a slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0243] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder was 20:8:70:2. The thickness of the inert material was 120 ㎛.

[0244] Before placing the manufactured flame-retardant inert material on the solid electrolyte layer, moisture, etc. of the flame-retardant inert material was removed by vacuum heat treatment at 80°C for 5 hours.

[0245] (second inert member)

[0246] A second inert member was prepared in the same manner as the first inert member, except that a slurry containing cellulose fiber, glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent was formed into a sheet.

[0247] The second inert member can act as an elastic sheet.

[0248] (Manufacturing of all-solid-state secondary batteries)

[0249] Referring to Fig. 3, a solid electrolyte layer was placed on the negative electrode such that the first negative electrode active material layer was in contact with the solid electrolyte layer, and an anode was placed on the solid electrolyte layer. A laminate was prepared by placing a gasket surrounding the positive electrode and in contact with the solid electrolyte layer. The thickness of the gasket was approximately 120 μm. The above-described flame-retardant inert member was used as the gasket. The gasket was placed so as to be in contact with the side surface of the positive electrode and the solid electrolyte layer. The positive electrode was placed at the center of the solid electrolyte layer, and the gasket was placed so as to surround the positive electrode and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed over the entire remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode was not placed. The gasket is the first inert member.

[0250] 85 prepared laminates o The solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 ㎛. The density of the Li6PS5Cl solid electrolyte, which was an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc. The area of ​​the solid electrolyte layer was the same as that of the negative electrode.

[0251] A second inert member having the same area and shape as the laminate was additionally placed on the outer surface of the negative electrode collector of the pressurized laminate.

[0252] A laminate with a second inert material added was placed in a pouch and vacuum-sealed to manufacture an all-solid-state secondary battery. Portions of the positive and negative current collectors were extended outside the sealed battery to serve as positive and negative terminals.

[0253] Example 2: Dry, Li2S-LiI-CNF:SE:PTFE=70:29:1

[0254] A dry cathode film, a dry cathode, and an all-solid-state secondary battery were manufactured in the same manner as in Example 1, except that the weight ratio of cathode active material: solid electrolyte: binder in the dry cathode film was changed to 70: 29: 1.

[0255] Example 3: Dry, Li2S-LiI-CNF:SE:PTFE=80:19:1

[0256] A dry cathode film, a dry cathode, and an all-solid-state secondary battery were manufactured in the same manner as in Example 1, except that the weight ratio of cathode active material: solid electrolyte: binder in the dry cathode film was changed to 80: 19: 1.

[0257] Example 4: Dry, Li2S-LiI-CNF:SE:PTFE=60:38:2

[0258] A dry cathode film, a dry cathode, and an all-solid-state secondary battery were manufactured in the same manner as in Example 1, except that the weight ratio of cathode active material: solid electrolyte: binder in the dry cathode film was changed to 60: 38: 2.

[0259] Reference Example 1

[0260] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the first inactive element was omitted.

[0261] Reference Example 2

[0262] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the second inert material was omitted.

[0263] Comparative Example 1: Wet, Li2S-LiI-CNF:SE:PVDF-HFP=60:39:1

[0264] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a wet positive electrode was manufactured in the following manner.

[0265] (Wet anode manufacturing)

[0266] As a cathode active material, the Li2S-LiI-CNF composite manufactured in Manufacturing Example 1 was prepared. As a solid electrolyte, Li6PS5Cl (D50=3.0 ㎛, crystalline) which is an argyrodite type crystal was prepared. A PVDF-HFP solution was prepared as a binder. These materials were mixed in a weight ratio of cathode active material: solid electrolyte: binder = 60:39:1, and octyl acetate was added to the mixture and stirred to prepare a cathode active material slurry.

[0267] A slurry of positive electrode active material was coated on one side of a 20 ㎛ thick aluminum foil positive electrode collector, dried, and then dried in a vacuum oven at 80° C. for 4 hours to prepare a laminate in which a layer of positive electrode active material was arranged on the positive electrode collector.

[0268] The areas of the positive electrode active material layer and the positive electrode current collector were the same.

[0269] Comparative Example 2: Dry, S-CNT-Li6PS5Cl:PTFE=99:1

[0270] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that a dry positive electrode was manufactured in the following manner.

[0271] (Dry anode manufacturing)

[0272] The S-CNT-Li6PS5Cl composite manufactured in Comparative Manufacturing Example 1 was prepared as a dry cathode active material. PTFE was prepared as a dry binder.

[0273] After preparing the dry cathode active material and dry binder at a weight ratio of 99:1, the mixture was placed in a blade mixer and mixed for 5 minutes.

[0274] The mixture was placed on one side of a stainless steel (SUS) substrate and rolled to produce a dry anode.

[0275] Comparative Example 3: Dry, binder-free

[0276] A dry cathode film was manufactured in the same manner as in Example 1, except that no binder was used.

[0277]

[0278] Evaluation Example 1: XRD Analysis and Scanning Electron Microscopy Analysis

[0279] XRD spectra were measured using Cu Kα radiation for the raw material (bare) Li2S used in Manufacturing Example 1, the pulverized Li2S, and the Li2S-LiI-CNF composite manufactured in Example 1. The measurement results are shown in Table 1 below. The Li2S crystallite size and lattice constant were derived from the first peak for the (111) crystal plane appearing at a diffraction angle of 2θ = 27° ± 2.0° in the XRD spectrum.

[0280] Crushed Li2S was prepared by milling under the same conditions as in the first step of Manufacturing Example 1, except that the 30:20 weight ratio mixture of Li2S and LiI was changed to 50 parts by weight of Li2S. The second step was not performed.

[0281] The particle size (i.e., D50 particle size) of the composite and the Li2S particle size of the composite were measured using a laser-assisted particle size analyzer (PSA) and a scanning electron microscope for the raw material Li2S used in Manufacturing Example 1, the pulverized Li2S, and the Li2S-LiI-CNF composite manufactured in Example 1. The measurement results are shown in Table 1 below.

[0282] Li2S crystallite size [nm]Li2S particle size [㎛]bare Li2S64.678Crushed Li2S15.42-Preparation example 1 (Li2S-LiI-CNF composite)9.861Less

[0283] As shown in Table 1, the Li2S particle size and crystallite size of the Li2S-LiI-CNF composite of Preparation Example 1 were significantly reduced compared to bare Li2S.

[0284] Although not shown in Table 1, the lattice constant of the Li2S-LiI-CNF composite of Preparation Example 1 was larger than that of bare Li2S.

[0285] The increase in the lattice constant of the Li2S-LiI-CNF composite compared to that of bare Li2S was attributed to the dissolution of LiI within the Li2S crystal. Therefore, it was confirmed that Li2S and LiI formed a solid solution in the Li2S-LiI-CNF composite.

[0286] Although not shown in Table 1, the particle size of the composite of Manufacturing Example 1 was approximately 5 μm.

[0287]

[0288] Evaluation Example 2: Measurement of tensile breaking strength

[0289] The tensile strength at break of the dry positive electrode films manufactured in Example 1 and Comparative Example 3 was measured according to ASTM D412, and the results are shown in Table 2 below.

[0290] The wet anode manufactured in Comparative Example 1 did not form a self-supporting film, so the tensile breaking strength could not be measured.

[0291] From the manufactured dry positive electrode film, a strip specimen with a width of 15 mm and a length of 50 mm was manufactured, and the longitudinal ends of the specimen were grasped in a tensile testing device so that the distance between chucks was 10 mm. Then, the tensile strength was measured under the conditions of a temperature of 23°C and a testing speed of 5 mm / min. The tensile strength at the point of fracture was defined as the tensile breaking strength [kPa]. The measurement results are shown in Table 2 below.

[0292] Tensile breaking strength [kPa] Example 1 (PTFE 1 wt%) 923 Comparative Example 3 (PTFE 0 wt%) Not measurable

[0293] As shown in Table 2, the dry positive electrode film of Example 1 exhibited excellent tensile strength.

[0294] In the dry positive electrode film of Example 1, the dispersibility of the dry binder was improved and the uniformity of the bonding between the positive electrode active material and the dry binder was improved. Consequently, the uniformity of the overall mechanical strength of the positive electrode film of Example 1 was improved.

[0295] The dry positive electrode film of Comparative Example 3 had a significant decrease in mechanical strength due to not including a binder, making it impossible to measure the mechanical strength.

[0296]

[0297] Evaluation Example 3: Surface resistivity measurement

[0298] The surface resistivity of the dry positive electrode films manufactured in Example 1 and Comparative Example 2 was measured using the 4-probe method according to ASTM D257, and the results are shown in Table 3 below.

[0299] Surface resistance [Ω / sq] Example 1 (dry, Li2S-LiI-CNF:SE:PTFE=60:39:1) 32 Comparative Example 2 (S-CNT-Li6PS5Cl:PTFE=99:1) 81.3

[0300] As shown in Table 3, the surface resistance of the dry positive electrode film of Example 1 was reduced compared to the surface resistance of the dry positive electrode film of Comparative Example 2.

[0301] It was determined that the dry positive electrode film of Comparative Example 2 had an increased surface resistance compared to the dry positive electrode film of Example 1 by using a composite of Li2S-lithium salt-carbon material as the positive electrode active material by using sulfur (S) as the positive electrode active material.

[0302] The electronic conductivity of sulfur (S) is ~10 -30 The electronic conductivity of Li2S is ~10 S / cm -13 It is lower than S / cm.

[0303]

[0304] Evaluation Example 4: Charge / Discharge Test

[0305] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 2 were evaluated by the following charge / discharge test. The charge / discharge test was performed by placing the all-solid-state secondary batteries in a constant temperature bath at 45°C.

[0306] The first cycle involved charging for 20 hours at a constant current of 0.05 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 20 hours at a constant current of 0.05 C until the battery voltage reached 1.0 V.

[0307] The second cycle was performed by charging for 20 hours at a constant current of 0.05 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 20 hours at a constant current of 0.05 C until the battery voltage reached 1.0 V.

[0308] The third cycle was performed by charging for 10 hours at a constant current of 0.1 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 10 hours at a constant current of 0.1 C until the battery voltage reached 1.0 V.

[0309] After the fourth cycle, 20 additional charge and discharge cycles were performed under the same conditions as the third cycle. The measurement results are shown in Table 2 below. The capacity retention rate is expressed by the following mathematical equation 1.

[0310] <Mathematical Formula 1>

[0311] Capacity retention rate [%] = [23rd cycle discharge capacity / 3rd cycle discharge capacity] × 100

[0312] 2nd cycle (0.05 C) discharge capacity [mAh / g] Capacity retention [%] Example 1 (dry, Li2S-LiI-CNF:SE:PTFE=60:39:1) 91586.5 Example 2 (dry, Li2S-LiI-CNF:SE:PTFE=70:29:1) 93980.7 Example 3 (dry, Li2S-LiI-CNF:SE:PTFE=80:19:1) 86884.2 Example 4 (dry, Li2S-LiI-CNF:SE:PTFE=60:38:2) 80585.2 Comparative Example 1 (wet, Li2S-LiI-CNF:SE:PVDF-HFP=60:39:1) 75874.0 Comparative Example 2 (dry, S-CNT-Li6PS5Cl:PTFE=99:1)67072.2

[0313] As shown in Table 4, the all-solid-state secondary batteries of Examples 1 to 4 using a dry positive electrode showed improved discharge capacity and life characteristics compared to the all-solid-state secondary battery of Comparative Example 1 using a wet positive electrode.

[0314] Therefore, it was confirmed that the dry anode provides improved reversibility of electrode reaction by having reduced internal resistance compared to the wet anode.

[0315] The all-solid-state secondary batteries of Examples 1 to 4 using the Li2S-LiI-CNF composite cathode active material showed improved discharge capacity and life characteristics compared to the all-solid-state secondary battery of Comparative Example 2 using the S-CNT-Li6PS5Cl composite cathode active material.

[0316] Therefore, it was confirmed that the Li2S-lithium salt-carbon material composite provides improved charge-discharge characteristics compared to the S-solid electrolyte-carbon material composite.

[0317] Although not shown in Table 2, the all-solid-state secondary battery of Reference Example 1, which omitted the first inert member, and the all-solid-state secondary battery of Reference Example 2, which omitted the second inert member, each had relatively poor life characteristics compared to the all-solid-state secondary battery of Example 1.

[0318] Although not shown in the drawing, it was confirmed that a second negative electrode active material layer (a lithium metal layer) was formed between the first negative electrode active material layer and the negative electrode current collector after initial charging in the all-solid-state secondary batteries of Examples 1 to 4. The formation of the second negative electrode active material layer was confirmed through a cross-sectional scanning electron microscope image of the all-solid-state secondary battery.

[0319] [Explanation of symbols]

[0320] 1 All-solid-state secondary battery 10 Cathode

[0321] 11. Cathode current collector 12. Cathode active material layer

[0322] 20 Cathode 21 Cathode current collector

[0323] 22 First negative electrode active material layer 23 Thin film

[0324] 24 Second negative electrode active material layer 30 Electrolyte layer

[0325] 40 First inert member 50 Second inert member

[0326] According to one aspect, it is possible to provide a dry cathode film having improved mechanical properties and reduced resistivity by including a composite of Li2S-lithium salt-carbon material and a dry binder binding them.

[0327] By providing such a dry cathode film, it is possible to provide an all-solid-state secondary battery with increased specific capacity and cycle characteristics.

Claims

1. Dry cathode active material, Dry sulfide solid electrolyte and Contains dry binder, The above dry cathode active material Li2S and lithium salt (Li a X b ) and a composite of carbon-based material (C), The above complex is Li2S-Li a X b -C (1≤a≤5, 1≤b≤5) is expressed as A dry cathode film wherein 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. In the first paragraph, the size of Li2S crystallite obtained from the X-ray diffraction (XRD) spectrum of the complex is 20 nm or less, A dry cathode film, wherein the above complex further comprises a solid solution of Li2S and a lithium salt.

3. In the first paragraph, the lithium salt is a binary compound or a ternary compound, The above binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3 or a combination thereof, A dry cathode film, wherein 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. A dry positive electrode film in the first paragraph, wherein the molar ratio of Li2S and lithium salt in the complex is 50:50 to 95:

5.

5. In the first paragraph, the Mohs hardness of the lithium salt and carbon-based material is greater than that of the Li2S, respectively. A dry positive electrode film, wherein the Mohs hardness of the lithium salt and carbon-based material is each 0.7 or higher.

6. In the first paragraph, the carbon-based material includes a fibrous carbon-based material, The above fibrous carbon material includes a carbon nanostructure, and the carbon nanostructure includes carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof. A dry cathode film, wherein the content of the carbon-based material is 1 to 20 wt% of the total weight of the composite.

7. A dry positive electrode film comprising 50 to 80 parts by weight of Li2S, 1 to 40 parts by weight of a lithium salt, and 1 to 20 parts by weight of a carbon-based material, per 100 parts by weight of the complex in the first paragraph.

8. In the first paragraph, the size of the composite particles is 10 μm or less, A dry cathode film, wherein the above complex content is 50 to 80 wt% of the total weight of the dry cathode film.

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

10. In the first paragraph, the dry binder comprises a fibrillized binder, The above dry binder includes a fluorine-based binder, The glass transition temperature (T) of the above dry binder g ) is 15 to 130 ℃, A dry cathode film, wherein the dry binder content is 0.1 to 5 wt% based on the total weight of the dry cathode film.

11. In the first paragraph, the dry positive electrode film is a self-standing film, The above dry cathode film is free of residual processing solvent, A dry positive electrode film having a thickness of 50 to 500 ㎛.

12. In the first paragraph, the tensile strength of the dry positive electrode film is 500 kPa to 5000 kPa, A dry positive electrode film having a surface resistivity of 70 Ω / sq or less.

13. Anode current collector; and A dry cathode comprising a dry cathode film according to any one of claims 1 to 12, which is disposed on one or both sides of the cathode current collector.

14. In the 13th paragraph, the positive electrode collector includes a base film and a metal layer disposed on one or both sides of the base film, The above 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, The above 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, It further includes an interlayer disposed between the positive electrode collector and the dry positive electrode film, A dry anode, wherein the intermediate layer comprises a carbon-based conductive material.

15. A positive electrode; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, The above positive electrode is a dry positive electrode according to claim 13, An all-solid-state secondary battery, wherein the negative electrode comprises a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

16. An all-solid-state secondary battery in claim 15, wherein the first negative electrode active material layer includes a negative electrode active material and a binder, the negative electrode active material has a particle form, and the average particle diameter of the negative electrode active material is 4 ㎛ or less.

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

18. In the 15th paragraph, a second negative electrode active material layer is further included, which is disposed between the negative electrode current collector and the first negative electrode active material layer and between the negative electrode current collector and the electrolyte layer. An all-solid-state secondary battery, wherein the second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

19. In the 15th paragraph, the electrolyte layer further includes a solid electrolyte, a gel electrolyte, or a combination thereof, The above solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof, An all-solid-state secondary battery, wherein the gel electrolyte comprises a polymer gel electrolyte.

20. In the first paragraph, at least one of a first inert member disposed on one side of the positive electrode and a second inert member disposed on the other side of the negative electrode collector is further included. An all-solid-state secondary battery, wherein the first inert member and the second inert member include a conductive flame-retardant inert member.

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