All-solid-state secondary battery

Abstract

The all-solid-state secondary battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, in which: the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector; at least one of the positive electrode active material layer and the solid electrolyte layer includes a first two-dimensional sulfide-based solid electrolyte; the negative electrode layer comprises a negative electrode current collector and a first negative electrode active material layer arranged on at least one surface of the negative electrode current collector; and an initial charge capacity (B) of the first negative electrode active material layer is less than about 50% of an initial charge capacity (A) of the positive electrode active material layer.

Description

Technical Field

[0001] The embodiments described herein relate to all-solid-state secondary batteries. Background Technology

[0002] Recently, batteries offering increased energy density and safety have been actively developed and / or researched. For example, lithium-ion batteries are used in information devices, communication devices, and vehicles. Since vehicles are related to user health, their safety is also crucial.

[0003] Lithium-ion batteries containing liquid electrolytes contain flammable organic solvents. Lithium-ion batteries containing liquid electrolytes pose a high risk of overheating and fire in the event of a short circuit.

[0004] Compared to liquid electrolytes, solid electrolytes offer a reduced risk of overheating and fire in the event of a short circuit. Lithium-ion batteries incorporating solid electrolytes provide improved safety compared to those using liquid electrolytes. Summary of the Invention

[0005] Technical issues Lithium-ion batteries may include a positive electrode active material layer, and this layer may include a conductive material to improve charge / discharge characteristics. The conductive material may be, for example, a carbon-based conductive material. Carbon-based conductive materials may have high electronic (e.g., electronic) conductivity, but low ionic (e.g., ionic) conductivity. Solid electrolytes can be used to improve the ionic conductivity of the positive electrode active material layer. According to the prior art, solid electrolytes may have a particle form, for example, having an aspect ratio of less than about 2. Prior art solid electrolyte particles with an aspect ratio of less than about 2 are difficult to form long-distance ion conduction paths. In lithium-ion batteries including prior art solid electrolyte particles with an aspect ratio of less than about 2, there is a high probability that ion conduction paths will be broken during charging or discharging of the lithium-ion battery. For example, lithium-ion batteries may include sulfide-based positive electrode active materials, and sulfide-based positive electrode active materials undergo significant volume changes during charging or discharging. During the charging or discharging of lithium-ion batteries, solid electrolyte particles with an aspect ratio of less than about 2 in the prior art struggle to suppress or reduce the disruption of ion conduction pathways and the increase in internal resistance caused by volume changes in sulfide-based positive electrode active materials. In some embodiments, a method is needed or desired that can suppress the disruption of ion conduction pathways in the positive electrode active material layer and suppress the increase in internal resistance of the lithium-ion battery due to volume changes in the positive electrode active material during charging or discharging.

[0006] Compared to lithium batteries that include a liquid electrolyte, lithium batteries that include a solid electrolyte can have relatively increased interfacial resistance and decreased ionic conductivity. In some embodiments, lithium batteries that include a solid electrolyte can have relatively low high-rate characteristics and output characteristics compared to lithium batteries that include a liquid electrolyte. In other embodiments, there is a need or a desire to improve the high-rate characteristics and output characteristics of lithium batteries that include a solid electrolyte by reducing interfacial resistance and increasing ionic conductivity.

[0007] A lithium battery may include a solid electrolyte layer, and the solid electrolyte layer may include, for example, solid electrolyte particles having an aspect ratio of less than about 2. Because the solid electrolyte layer may include solid electrolyte particles with an aspect ratio of less than about 2, the length of the interface path between the solid electrolyte particles formed in the thickness direction of the solid electrolyte layer will be similar to the thickness of the solid electrolyte layer. In some embodiments, the path of lithium dendrites deposited during the charging / discharging process of the lithium battery through the solid electrolyte layer is shortened, thus increasing the likelihood of a short circuit in the lithium battery due to the lithium dendrites. In some embodiments, a method for more effectively suppressing the growth of lithium dendrites and short circuits in the lithium battery is needed or desired.

[0008] An aspect according to one or more embodiments relates to a novel all-solid-state secondary battery.

[0009] Solution to the problem According to one or more embodiments, the all-solid-state secondary battery includes: A positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein, The positive electrode layer includes a positive electrode current collector and a layer of positive electrode active material disposed on at least one surface (e.g., one surface or two (e.g., opposite) surfaces) of the positive electrode current collector. At least one of the positive electrode active material layer and the solid electrolyte layer includes a first two-dimensional sulfide solid electrolyte, and The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on at least one surface (e.g., a surface or a layer of surfaces) of the negative electrode current collector, wherein, The initial charging capacity (B) of the first negative electrode active material layer is less than about 50% of the initial charging capacity (A) of the positive electrode active material layer.

[0010] According to one or more embodiments, the all-solid-state secondary battery includes: A positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein, The positive electrode layer includes a positive electrode current collector and a layer of positive electrode active material disposed on at least one surface (e.g., one surface or two (e.g., opposite) surfaces) of the positive electrode current collector. At least one of the positive electrode active material layer and the solid electrolyte layer includes a first two-dimensional sulfide solid electrolyte, and The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on at least one surface (e.g., a surface or a single surface) of the negative electrode current collector.

[0011] According to one or more embodiments, the all-solid-state secondary battery includes: A positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein, The positive electrode layer includes a positive electrode current collector and a layer of positive electrode active material disposed on at least one surface (e.g., one surface or two (e.g., opposite) surfaces) of the positive electrode current collector. At least one of the positive electrode active material layer and the solid electrolyte layer includes a first two-dimensional sulfide solid electrolyte.

[0012] Beneficial effects of the invention According to one aspect, according to an all-solid-state secondary battery with a novel structure, an all-solid-state secondary battery in which short circuits are suppressed or reduced and cycle characteristics are improved can be provided. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a two-dimensional sulfide-based solid electrolyte according to an embodiment.

[0014] Figure 2 This is a schematic diagram of a two-dimensional sulfide solid electrolyte with a core / shell structure according to an embodiment.

[0015] Figure 3 This is a cross-sectional view of a two-dimensional sulfide solid electrolyte with a core / shell structure according to an embodiment.

[0016] Figure 4 This is a cross-sectional view of a two-dimensional sulfide-based solid electrolyte having a core / intermediate layer / shell structure according to an embodiment.

[0017] Figures 5a to 5c This is a cross-sectional view of the positive electrode active material layer of a two-dimensional sulfide-based solid electrolyte according to an embodiment.

[0018] Figure 6 This is a cross-sectional view of a solid electrolyte layer including a two-dimensional sulfide-based solid electrolyte according to an embodiment.

[0019] Figure 7 This is a cross-sectional view of a solid electrolyte layer including an irregularly shaped sulfide-based solid electrolyte according to an embodiment.

[0020] Figure 8 This is a schematic diagram of a solid electrolyte layer including a two-dimensional sulfide-based solid electrolyte according to an embodiment.

[0021] Figure 9 This is a schematic diagram of a solid electrolyte layer including an irregularly shaped sulfide-based solid electrolyte according to an embodiment.

[0022] Figure 10 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0023] Figure 11 This is a cross-sectional view of a dual-cell all-solid-state secondary battery according to an embodiment.

[0024] Figure 12 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0025] Figure 13 This is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0026] Figure 14 This is a cross-sectional view of a dual-cell all-solid-state secondary battery according to an embodiment. Detailed Implementation

[0027] Various embodiments are illustrated in the accompanying drawings. However, this disclosure may be implemented in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art. The same reference numerals denote the same elements.

[0028] When an element is described as being "on" another element, it will be understood that the element may be directly disposed on the other element, or that one (or more) elements (intermediate elements) may be placed therebetween. On the other hand, when an element is described as being "directly on" another element, one (or more) elements may not be placed therebetween.

[0029] It will be understood that while the terms “first,” “second,” and “third” may be used herein to describe one or more suitable elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or portion from another. Therefore, without departing from the teachings of this specification, a first element, component, region, layer, or portion described herein may be designated as a second element, component, region, layer, or portion.

[0030] The terminology used herein is intended to describe particular embodiments only and is not intended to limit this disclosure. As used herein, unless explicitly stated otherwise, the singular forms “a,” “an,” and “the” are intended to include the plural forms that include “at least one.” “At least one” should not be construed as limited to the singular. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. When used in a detailed description, the terms “comprising,” “including,” and / or variations thereof indicate the presence of the stated features, regions, integrals, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, integrals, steps, operations, elements, components, and / or groups thereof.

[0031] Spatial relative terms such as “below,” “under,” “down,” “above,” and “above” are used herein to simply describe the relationship of one element or feature to other elements or features. It will be understood that spatial relative terms are intended to cover different orientations of the device in use or operation other than those depicted in the figures. For example, when the device in the figures is flipped, an element described as “below” or “under” other elements or features will subsequently be “above” or “above” said other elements or features. In some embodiments, the example term “below” may (e.g., simultaneously) cover both above and below orientations. The device may be otherwise positioned (rotated 90 degrees or in other orientations), and the spatial relative terms used herein may be interpreted accordingly.

[0032] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. For example, it will also be understood that terms (such as those defined in a general dictionary) shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field and in this disclosure, and shall not be interpreted in an idealized or overly formalized sense unless so explicitly defined herein.

[0033] The embodiments described herein are illustrated with reference to cross-sectional views, which are schematic representations of idealized embodiments. Thus, variations in the shapes illustrated will be expected due to factors such as manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shape regions shown herein, but may include shape deviations due to factors such as manufacturing processes. For example, areas shown or described as flat may generally be rough and / or have non-linear characteristics. Furthermore, sharp corners may be rounded. In some embodiments, the regions shown in the figures are schematic in nature, and their shapes are not intended to show the actual shapes of the regions, nor are they intended to limit the scope of the claims.

[0034] "Group" refers to the group of elements in the periodic table according to the classification system of Groups 1 to 18 of the International Union of Pure and Applied Chemistry (IUPAC).

[0035] As used herein, the term "aspect ratio" can be measured, for example, by using scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, or atomic force microscope (AFM) images.

[0036] As used herein, the “shape,” “structure,” “length,” “surface area,” and / or “thickness” of a two-dimensional sulfide solid electrolyte can be measured, for example, by using scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, or atomic force microscope (AFM) images.

[0037] As used herein, the “thickness” and / or “diameter” of the core and shell of the positive electrode active material can be measured, for example, by using scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, or atomic force microscope (AFM) images.

[0038] As used herein, the term "particle size" refers to the average diameter when the particle is spherical, and the average major axis length when the particle is non-spherical. Particle size can be measured using a particle size analyzer (PSA). "Particle size" is, for example, the average particle size. "Average particle size" refers to, for example, the median particle size (D50).

[0039] D50 refers to the particle size corresponding to 50% of the cumulative volume when calculating the particle size distribution (measured by laser diffraction) starting from particles with smaller particle sizes.

[0040] D90 refers to the particle size corresponding to 90% of the cumulative volume when calculating the particle size distribution (measured by laser diffraction) starting from particles with smaller particle sizes.

[0041] D10 refers to the particle size corresponding to 10% of the cumulative volume when calculating the particle size distribution (measured by laser diffraction) starting from particles with smaller particle sizes.

[0042] As used herein, the term "metal" includes all metals and metalloids, such as silicon and germanium in elemental or ionic states.

[0043] As used herein, the term "alloy" refers to a mixture of two or more metals.

[0044] As used herein, the term "electrode active material" refers to an electrode material that can undergo lithiation and delithiation.

[0045] As used herein, “positive electrode active material” refers to a positive electrode material that can undergo lithiation and delithiation.

[0046] As used herein, the term "negative electrode active material" refers to a negative electrode material that can undergo lithiation and delithiation.

[0047] As used herein, the term "lithiation" and its variations refer to the process of adding lithium to an electrode active material.

[0048] As used herein, the term "delithiation" and its variations refer to the process of removing lithium from the active material of an electrode.

[0049] As used herein, the term "charging" and its variations refer to the process of providing electrochemical energy to a battery.

[0050] As used herein, the term "discharge" and its variants refer to the process of removing electrochemical energy from a battery.

[0051] As used herein, the terms "positive electrode" and "positive electrode" refer to the electrode at which electrochemical reduction and lithiation occur during the discharge process.

[0052] As used herein, the terms “negative electrode” and “positive electrode” refer to the electrode at which electrochemical oxidation and delithiation occur during the discharge process.

[0053] While specific embodiments have been described, applicants or those skilled in the art will conceive of alternatives, modifications, variations, improvements, and substantial equivalents that are currently unforeseeable or may be unforeseeable. In some embodiments, the appended claims, both submitted and potentially modified, are intended to cover all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0054] The all-solid-state secondary battery according to the example embodiment will be described in more detail below.

[0055] [All-solid-state rechargeable battery] The all-solid-state secondary battery according to an embodiment may include a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface (e.g., one surface or two (e.g., opposite) surfaces) of the positive electrode current collector. At least one of the positive electrode active material layer and the solid electrolyte layer includes a first two-dimensional (2D) sulfide-based solid electrolyte. The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on at least one surface (e.g., one surface or one surface) of the negative electrode current collector. The initial charging capacity B of the first negative electrode active material layer is less than about 50% of the initial charging capacity A of the positive electrode active material layer.

[0056] All-solid-state secondary batteries may include a positive electrode active material layer, and the positive electrode active material layer may include a first 2D sulfide-based solid electrolyte, thereby ensuring a longer ion conduction path within the positive electrode active material layer. In some embodiments, during charging or discharging of the all-solid-state secondary battery, the interruption of ion conduction paths due to volume changes of the positive electrode active material in the positive electrode active material layer can be more effectively prevented or reduced. In some embodiments, the initial efficiency, discharge capacity, high-rate characteristics, and / or lifetime characteristics of the all-solid-state secondary battery can be improved.

[0057] All-solid-state secondary batteries may include a positive electrode active material layer, and the positive electrode active material layer may include a first 2D sulfide-based solid electrolyte, thereby ensuring the uniformity of ion conduction paths within the positive electrode active material layer. In some embodiments, the pressure required to manufacture all-solid-state secondary batteries can be reduced. For example, all-solid-state secondary batteries with excellent or suitable ion conduction paths can be achieved even under reduced pressure. In other embodiments, the occurrence of localized overvoltages in the positive electrode active material layer can be effectively prevented or reduced during the charging / discharging process of the all-solid-state secondary battery.

[0058] All-solid-state secondary batteries may include a positive electrode active material layer, and the positive electrode active material layer may include a first 2D sulfide-based solid electrolyte with a reduced specific surface area, thereby increasing moisture stability, reducing side reactions between the positive electrode active material and the sulfide-based solid electrolyte, reducing the interfacial resistance of the positive electrode active material layer, and suppressing the decrease in ionic conductivity. In some embodiments, the high-rate characteristics and output characteristics of all-solid-state secondary batteries can be improved.

[0059] An all-solid-state secondary battery may include a positive electrode active material layer, and the positive electrode active material layer may include a first 2D sulfide-based solid electrolyte to more effectively accommodate volume changes of the positive electrode active material during charging or discharging. In the positive electrode active material layer, the 2D sulfide-based solid electrolyte may be disposed around the positive electrode active material. During charging or discharging, the 2D sulfide-based solid electrolyte can appropriately disperse the volume changes of the positive electrode active material over its entire area to accommodate these changes, thereby accommodating volume changes of the positive electrode active material more effectively than sulfide-based solid electrolytes having a spherical particle form. In some embodiments, the disconnection between the positive electrode active material and the solid electrolyte due to volume changes of the positive electrode active material in the positive electrode active material layer can be suppressed or reduced, and the uniformity of the composition in the positive electrode active material layer can be improved. In other embodiments, the cycle characteristics of the all-solid-state secondary battery can be improved.

[0060] All-solid-state secondary batteries may include a solid electrolyte layer, and the solid electrolyte layer may include a first 2D sulfide-based solid electrolyte, thereby more effectively suppressing or reducing the growth of lithium dendrites in the thickness direction of the solid electrolyte layer. In some embodiments, the occurrence of short circuits, etc., due to lithium dendrite growth during charging or discharging of the all-solid-state secondary battery can be more effectively suppressed or reduced. For example, the lifetime characteristics of the all-solid-state secondary battery can be improved.

[0061] All-solid-state secondary batteries may include a solid electrolyte layer, and the solid electrolyte layer may include a first 2D sulfide-based solid electrolyte with an increased surface area, thereby reducing the likelihood of pinhole formation on the surface of the solid electrolyte layer during its fabrication. In some embodiments, the growth of lithium dendrites due to pinholes can be more effectively suppressed or reduced during the charging or discharging of the all-solid-state secondary battery. For example, the lifetime characteristics of the all-solid-state secondary battery can be improved.

[0062] Reference Figures 1 to 13 The all-solid-state secondary battery 1 may include a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20. The positive electrode layer 10 may include a positive current collector 11 and a positive active material layer 12 disposed on at least one surface (e.g., one surface or two (e.g., opposite) surfaces) of the positive current collector 11. The positive active material layer 12, the solid electrolyte layer 30, or a combination thereof may include a first 2D sulfide-based solid electrolyte 100. The negative electrode layer 20 may include a negative current collector 21 and a first negative active material layer 22 disposed on at least one surface of the negative current collector 21. The initial charge capacity B of the first negative active material layer 22 may be less than about 50% of the initial charge capacity A of the positive active material layer 12.

[0063] [Positive electrode layer] [Positive electrode layer: solid electrolyte] The positive electrode active material layer 12 may include a first 2D sulfide solid electrolyte 100.

[0064] Reference Figures 1 to 4The first 2D sulfide-based solid electrolyte 100 may be defined by a length L and a thickness T. The length L of the first 2D sulfide-based solid electrolyte 100 may correspond to the maximum value of the distance between the ends (e.g., two ends or opposite ends) of the first 2D sulfide-based solid electrolyte 100 in a direction perpendicular or orthogonal to the thickness direction (Y direction) of the first 2D sulfide-based solid electrolyte 100. The thickness T of the first 2D sulfide-based solid electrolyte 100 may correspond to the maximum value of the distance between the ends (e.g., two ends or opposite ends) of the first 2D sulfide-based solid electrolyte 100 in the thickness direction (Y direction). In other embodiments, the first 2D sulfide-based solid electrolyte 100 may include a first surface (e.g., a top surface) S1, a second surface (e.g., a bottom surface) S2 opposite to the first surface S1, and side surfaces S3a, S3b, S3c, and S3d for connecting the first surface S1 and the second surface S2, and may be defined by the area of ​​the first surface S1 or the area of ​​the second surface S2, and the heights of the side surfaces S3a, S3b, S3c, and S3d. The area of ​​the first surface S1 or the area of ​​the second surface S2 may correspond to, for example, the product of the maximum and minimum values ​​of the distance between the ends (e.g., two ends or opposite ends) of the perimeter of the first surface S1 or the perimeter of the second surface S2. The heights of the side surfaces S3a, S3b, S3c, and S3d may correspond to the maximum value of the distance between the first surface S1 and the second surface S2. In other embodiments, the area of ​​the first surface S1 or the second surface S2 may correspond to the integral value of the area read from a planar image (e.g., a planar view) of the first 2D sulfide-based solid electrolyte 100 in the thickness direction (Y direction). The heights of the side surfaces S3a, S3b, S3c, and S3d may correspond to the maximum values ​​read from a side view image of the SEM in the longitudinal direction (X direction or Z direction) of the first 2D sulfide-based solid electrolyte 100.

[0065] The aspect ratio of the length L to the thickness T of the first 2D sulfide-based solid electrolyte 100 can be, for example, about 3 or greater, about 4 or greater, about 5 or greater, about 10 or greater, or about 20 or greater. The aspect ratio of the length L to the thickness T of the first 2D sulfide-based solid electrolyte 100 can, for example, be in the range of about 3 to about 500, about 3 to about 400, about 4 to about 300, about 5 to about 200, or about 10 to about 200. The aspect ratio of the first 2D sulfide-based solid electrolyte 100 can be within such a range that the ion conduction pathway can be extended in the lithium battery including the first 2D sulfide-based solid electrolyte 100, which can more effectively accommodate volume changes of the positive electrode active material during charging or discharging of the lithium battery, and maintain the ion conduction pathway in the lithium battery despite the volume changes of the positive electrode active material. In some embodiments, lithium battery degradation can be suppressed or reduced, and the cycle characteristics of the lithium battery can be improved.

[0066] The length L of the first 2D sulfide-based solid electrolyte 100 can, for example, be in the range of about 0.1 μm to about 50 μm, about 0.5 μm to about 50 μm, about 1 μm to about 50 μm, about 1 μm to about 30 μm, about 1 μm to about 20 μm, or about 1 μm to about 10 μm. The thickness T of the first 2D sulfide-based solid electrolyte 100 can, for example, be in the range of about 10 nm to about 30 μm, about 10 nm to about 20 μm, about 10 nm to about 10 μm, about 10 nm to about 5 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 300 nm, or about 10 nm to about 100 nm. The length and / or thickness of the first 2D sulfide-based solid electrolyte 100 can be within a range that allows ion conduction pathways to extend within the lithium battery including the first 2D sulfide-based solid electrolyte 100, enabling more effective adaptation to volume changes in the positive electrode active material during charging or discharging of the lithium battery, and maintaining ion conduction pathways in the lithium battery despite volume changes in the positive electrode active material. In some embodiments, lithium battery degradation can be suppressed or reduced, and the cycle characteristics of the lithium battery can be improved.

[0067] The first 2D sulfide-based solid electrolyte 100 may have, for example, a plate structure, a flake (or “sheet”) structure, a sheet structure, or a combination thereof, but one or more embodiments are not necessarily limited to such forms. Any form can be used as long as it can have a 2D structure. The first 2D sulfide-based solid electrolyte 100 may have a plate structure, a flake structure, a sheet structure, etc., such that ion conduction pathways can be extended in a lithium battery including the first 2D sulfide-based solid electrolyte 100, more effectively accommodating volume changes of the positive electrode active material during charging or discharging of the lithium battery, and maintaining ion conduction pathways in the lithium battery despite volume changes of the positive electrode active material. In some embodiments, lithium battery degradation can be suppressed or reduced, and the cycle characteristics of the lithium battery can be improved.

[0068] The surface S1 or S2 of the first 2D sulfide-based solid electrolyte 100 may have, for example, an irregular shape, a circular shape, or a polygonal shape. The shape of the surface S1 or S2 of the first 2D sulfide-based solid electrolyte 100 may be, for example, a shape defined in a planar view along the thickness direction (Y direction) of the first 2D sulfide-based solid electrolyte 100. Polygonal shapes may include, for example, triangular, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, or decagonal shapes, but one or more embodiments are not necessarily limited to these. Any shape may be used, as long as the shape is a polygonal shape as used in the art.

[0069] Reference Figures 2 to 4The first 2D sulfide-based solid electrolyte 100 may have a core 110 / shell 120 structure, for example, including a core 110 and a shell 120 disposed on the core 110. The first 2D sulfide-based solid electrolyte 100 may have a core 110 / shell 120 structure, allowing ion conduction pathways to be extended in a lithium battery including the first 2D sulfide-based solid electrolyte 100. This allows for more efficient adaptation to volume changes in the positive electrode active material during charging or discharging of the lithium battery, and maintains the ion conduction pathways in the lithium battery despite volume changes in the positive electrode active material. In some embodiments, this can suppress or reduce lithium battery degradation and improve the cycle characteristics of the lithium battery. Conversely, a simple mixture of the materials of the core 110 and the shell 120 may easily lead to agglomeration of the materials of the core 110 and / or the shell 120, resulting in an inability to provide extended ion conduction pathways in the lithium battery, an inability to more effectively adapt to volume changes in the positive electrode active material during charging or discharging of the lithium battery, and a break in the ion conduction pathways in the lithium battery due to volume changes in the positive electrode active material. In the case of a simple mixture of the materials of the core 110 and the shell 120, the degradation of the lithium battery may increase, and the cycle characteristics of the lithium battery may deteriorate. For example, the first 2D sulfide-based solid electrolyte 100 having a core 110 / shell 120 structure can be a composite in which the core 110 is covered by the shell 120, and thus can be distinguished from a simple mixture of the materials of the core 110 and the shell 120.

[0070] The core 110 may include, for example, carbon-based materials, polymeric materials, metal-containing inorganic materials, sulfide-based solid electrolytes, oxide-based solid electrolytes, or combinations thereof. The core 110 may include any material (e.g., composed of any material), as long as the material can form a 2D structure.

[0071] Examples of carbon-based materials may include synthetic graphite, natural graphite, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, graphene oxide, reduced graphene oxide, carbon nanoribbons, carbon nanosheets, etc., but one or more embodiments are not limited thereto. Any material may be used, provided that it can be used in the art as a carbon-based material having a 2D structure.

[0072] Polymer materials may include (for example, are) at least one selected from the following (for example, one): poly(2-vinylpyridine); polytetrafluoroethylene (PTFE); tetrafluoroethylene-hexafluoropropylene copolymer; polychlorotrifluoroethylene; perfluoroalkoxy copolymer; fluorinated cyclic ether; polyethylene oxide diacrylate; polyethylene oxide dimethacrylate; polypropylene oxide diacrylate; polypropylene oxide dimethacrylate; polymethylene oxide diacrylate; polymethylene oxide dimethacrylate Polyalkyl glycol diacrylate; polyalkyl glycol dimethacrylate; polydivinylbenzene; polyether; polycarbonate; polyamide; polyester; polyvinyl chloride; polyimide (PI); polycarboxylic acid; polysulfonic acid; polyvinyl alcohol; polysulfone; polystyrene; polyethylene (PE); polypropylene (PP); poly(p-phenylene); polyacetylene; poly(p-phenylenevinylene); polyaniline; polypyrrole; polythiophene; poly(2,5-ethylenevinylene); polyaromatics; poly(naphthalene-2,6-dimethyl); polyethylene oxide (PE) O); polypropylene oxide; polyvinylidene fluoride (PVDF); copolymers of vinylidene fluoride and hexafluoropropylene; polyvinyl acetate; poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate); poly(methyl methacrylate-co-ethyl acrylate); polyacrylonitrile; polyvinyl chloride-co-vinyl acetate; poly(1-vinylpyrrolidone-co-vinyl acetate); polyvinylpyrrolidone; polyacrylate; polymethyl methacrylate; polyurethane; polyvinyl ether; acrylonitrile-butadiene rubber; styrene-butadiene rubber (SBR); acrylonitrile-butadiene-styrene rubber; sulfonated styrene / ethylene-butene triblock copolymer; polymers obtained from at least one acrylate monomer selected from ethoxylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated aliphatic urethane acrylate, ethoxylated alkylphenol acrylate and alkyl acrylate; polyvinyl alcohol; epoxy resin; acrylic resin; and combinations thereof; however, one or more embodiments are not necessarily limited thereto. Any polymer can be used, as long as it can form a 2D structure in the art. The polymer material may additionally include a lithium salt. The polymer material can have a 2D structure.

[0073] Metal-containing inorganic materials may include, for example, SiO2, TiO2, Al2O3, AlN, SiC, BaTiO3, metal-organic frameworks (MOFs), polyhedral oligomeric silsesquioxanes (POSS), Li2CO3, Li3PO4, Li3N, Li3S4, Li2O, montmorillonite, or combinations thereof, but one or more embodiments are not limited thereto. Any metal-containing inorganic material can be used, provided that the metal-containing inorganic material can form a 2D structure in the art. Metal-containing inorganic materials can have 2D structures. Metal-containing inorganic materials can have 2D nanostructures.

[0074] Sulfide solid electrolytes may include, for example, those selected from 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, and Li₂S-P₂S₅-Z. m S n (Where m and n are both positive numbers, and Z is one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (Where p and q are both positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 7-x PS 6-x Cl x (where 0≤x≤2), Li 7-x PS 6-x Br x (where 0 ≤ x ≤ 2) and Li 7-x PS 6-x I x At least one of (where 0 ≤ x ≤ 2). For example, sulfide solid electrolytes can be prepared by treating starting materials such as Li2S or P2S5 by melt quenching or mechanical grinding. For example, after such treatment, heat treatment can be performed. Sulfide solid electrolytes can be in an amorphous, crystalline, or mixed state of amorphous and crystalline states. In some embodiments, sulfide solid electrolytes may include, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements in the aforementioned sulfide solid electrolyte material. For example, sulfide solid electrolytes may be materials comprising Li2S-P2S5. If, for example, a material comprising Li2S-P2S5 is used as the sulfide solid electrolyte material, the molar ratio of Li2S to P2S5 (e.g., Li2S:P2S5) can be in the range of about 50:50 to about 90:10. Sulfide solid electrolytes may be compounds of the sulfide-germanium type or similar (e.g., sulfide-germanium) selected from at least one of the following: Li 7-x PS 6-x Cl x (where 0≤x≤2), Li 7-x PS 6-x Br x (where 0 ≤ x ≤ 2) and Li 7-xPS 6-x I x (Where 0 ≤ x ≤ 2). The sulfide solid electrolyte may include at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. The sulfide solid electrolyte may have a 2D structure.

[0075] The oxide solid electrolyte may include, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (Where 0 < x < 2 and 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (where 0 ≤ x < 1 and 0 ≤ y < 1), PB(Mg3Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO, Li3PO4, Li x Ti y (PO4)3 (where 0 < x < 2 and 0 < y < 3), Li x Al y [[ID=3%]]Ti z (PO4)3 (where 0 < x < 2, 0 < y < 1, and 0 < z < 3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (where 0 ≤ x ≤ 1 and 0 ≤ y ≤ )), Li x La y TiO3 (where 0 < x < 2 and 0 < y < 3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2, Li 3+x La3M2O 12 (where Me = Te, Nb, or Zr or a combination thereof, and 0 ≤ x ≤ 10). The oxide solid electrolyte can be prepared, for example, by sintering. The oxide solid electrolyte can be, for example, selected from Li7La3Zr2O 12 (LLZO) and Li 3+ x La3Zr It should be noted that there seems to be an incomplete or incorrect expression in the original text, such as "Li x y x y z 1+x+y x 2-x y 3-y 12 x y 3+x 12 12 3+ x " which may need to be further clarified or corrected in the source material for a more accurate translation.2-a M a O 12 A garnet-type (or similar) solid electrode of (LLZO doped with M), where M = Ga, W, Nb, Ta, or Al, 0 < a < 2, and 0 ≤ x ≤ 10. The oxide-based solid electrolyte may have a 2D structure.

[0076] The core 110 can be used as a template for the first 2D sulfide-based solid electrolyte 100. The core 110 may have an excellent or suitable elastic modulus. The elastic modulus of the core 110 can be, for example, 1 MPa or greater, 10 MPa or greater, or 100 MPa or greater. The elastic modulus of the core 110 can be, for example, in the range of about 1 MPa to about 1 GPa, about 10 MPa to about 1 GPa, or about 100 MPa to about 1 GPa. The core 110 can have an elastic modulus within such a range, and thus can further improve the mechanical properties of the first 2D sulfide-based solid electrolyte 100.

[0077] The shell 120 can include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a coating material, or a combination thereof. The coating material can be provided on a part or all of the core 110. For example, the coating material can provide water resistance, bonding strength, etc. to the core 110.

[0078] The sulfide-based solid electrolyte and the oxide-based solid electrolyte can be selected from the solid electrolytes included in the core 110.

[0079] The coating material is not limited and can be any material as long as it can provide the physical properties (such as water resistance and binding force) required for a lithium battery to the first 2D sulfide-based solid electrolyte 100. The coating material can be, for example, a sulfide-based solid electrolyte that substantially does not include cross-linked sulfur and Li2S. The coating material can be, for example, a composition that only includes Li2S and a compound containing elements such as P, Si, Ge in Group 14 and Group 15 of the periodic table. In a composition that only includes Li2S and P2S5, the content (e.g., amount) of Li2S can be in the range of about 70% to about 85%. In a composition that only includes Li2S and SiS2, the content (e.g., amount) of Li2S can be in the range of about 50% to about 80%. In a composition that only includes Li2S and GeS2, the content (e.g., amount) of Li2S can be in the range of about 50% to about 80%. In the aforementioned compositions, a cross-linked sulfur peak cannot be observed in the Raman spectrum, and a Li2S peak cannot be observed in the X-ray diffraction (XRD) spectrum. The sulfide-based solid electrolyte can have such a molar fraction that the amount of hydrogen sulfide generated can be reduced. The sulfide-based solid electrolyte can not include (e.g., can exclude) cross-linked sulfur and can not include (e.g., can exclude) Li2S, so the amount of hydrogen sulfide generated can be reduced. The sulfide-based solid electrolyte can be a sulfide glass.

[0080] The coating material can be, for example, a sulfide-based solid electrolyte including a crystalline glass having a composition of yLi2S-(100-x-y)P2S5.xP2O5, where 0 < x < 25 and <67 < y < 80>. Such a crystalline glass can have a prototypical composition to have improved stability against water, so that the amount of hydrogen sulfide generated can be reduced. The term "prototypical" generally can refer to the product having the highest degree of hydration among oxyacids obtained by hydrating the same oxides. In the Li2S-P2S5-based sulfide-based solid electrolyte, the maximum addition of Li2S to the crystal composition of P2S5 (e.g., Li3PS4) can correspond to the prototypical composition. The molar fraction of Li2S in 75Li2S-25P2S5 having the prototypical composition can be about 75%, so it can substantially not include cross-linked sulfur. The cross-linked sulfur can be, for example, sulfur that cross-links two phosphorus atoms in S3P-S-PS3 formed by the reaction between Li2S and P2S5. Such cross-linked sulfur can easily react with water and can easily generate hydrogen sulfide. The fact that the sulfide-based solid electrolyte substantially does not contain cross-linked sulfur can be confirmed, for example, by measuring the Raman spectrum. In the Raman spectrum, the peak of S^3P-S-PS^3 generally appears at about 402 cm -1 ^-1^. In the Raman spectrum of the sulfide-based solid electrolyte, the peak at about 402 cm -1The peak at that location. In the Raman spectrum of sulfide solid electrolytes, this indicates the presence of PS4. 3- The peak (approximately 417cm) -1 (Location).

[0081] The coating material may include, for example, an adhesive. The adhesive may include, for example, polyethylene (PE), polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, or combinations thereof, but one or more embodiments are not necessarily limited thereto. Any material may be used, provided that it is suitable as an adhesive in the art.

[0082] At least one of the core 110 and the shell 120 may include a sulfide-based solid electrolyte. At least one of the core 110 and the shell 120 may include a sulfide-based solid electrolyte, thereby providing excellent or suitable ionic conductivity and mechanical properties simultaneously (e.g., concurrently).

[0083] The core 110 may include, for example, a 2D nanostructure. Since the core 110 may include a 2D nanostructure, the shell 120 disposed on the core 110 can easily have a 2D structure.

[0084] 2D nanostructures may include, for example, graphene, graphene oxide, reduced graphene oxide, carbon nanoribbons, carbon nanosheets, carbon nanoplates, carbon nanofibers, SiO2, TiO2, Al2O3, AlN, SiC, BaTiO3, or combinations thereof, but one or more embodiments are not necessarily limited thereto. Any material may be used as long as it can have a 2D nanostructure and is usable in the art.

[0085] The first 2D sulfide-based solid electrolyte 100 may include a 2D nanostructure as a core, allowing ion conduction pathways to extend within the lithium battery including the first 2D sulfide-based solid electrolyte 100. This enables more efficient adaptation to volume changes in the positive electrode active material during charging or discharging of the lithium battery, and maintains the ion conduction pathways within the lithium battery despite volume changes in the positive electrode active material. In some embodiments, lithium battery degradation can be further suppressed or reduced, and the cycle characteristics of the lithium battery can be further improved.

[0086] Reference Figures 2 to 4The ratio of the first thickness T1 of the core 110 to the second thickness T2 of the shell 120 can, for example, be in the range of about 1:0.01 to about 1:1,000, about 1:0.1 to about 1:1,000, about 1:0.1 to about 1:100, about 1:0.1 to about 1:10, about 1:0.5 to about 1:5, about 1:1 to about 1:4, about 1:1 to about 1:3, or about 1:1 to about 1:2.

[0087] The ratio of the first length L1 of the core 110 to the second length L2 of the shell 120 can be in the range of about 1:1 to about 1:10, about 1:1.01 to about 1:1.5, about 1:1.01 to about 1:2, about 1:1.03 to about 1:1.5, about 1:1.05 to about 1:1.3, and about 1:1.05 to about 1:1.1.

[0088] In the first 2D sulfide-based solid electrolyte 100, the core 110 and shell 120 may have a thickness ratio and / or length ratio within a range such that ion conduction pathways can extend within the lithium battery including the first 2D sulfide-based solid electrolyte 100, more effectively accommodating volume changes of the positive electrode active material during charging or discharging of the lithium battery, and maintaining ion conduction pathways in the lithium battery despite volume changes of the positive electrode active material. In some embodiments, lithium battery degradation can be further suppressed or reduced, and the cycle characteristics of the lithium battery can be further improved.

[0089] In some embodiments, the core 110 may have a multilayer structure. The multilayer structure of the core 110 allows for greater variation in its shape, physical properties, etc. The core 110 may have, for example, a two-layer, three-layer, or four-layer structure. The individual layers of the multilayer core 110 may comprise the same or different materials.

[0090] In some embodiments, the shell 120 may have a multi-layered structure. The shell 120 can have a multi-layered structure, thus allowing for greater variety in its shape, physical properties, etc. The shell 120 may have, for example, a two-layered, three-layered, or four-layered structure. The individual layers of the shell 120 with a multi-layered structure may comprise the same or different materials.

[0091] Reference Figure 4 An intermediate layer 130 may be included between the core 110 and the shell 120. The first 2D sulfide solid electrolyte 100 may also include an intermediate layer 130, which can improve the bonding force between the core 110 and the shell 120, and improve the structural stability of the core 110 and the shell 120. Alternatively, the intermediate layer 130 may not be provided.

[0092] The intermediate layer 130 may have a third thickness T3 and a third length L3. For example, the third length L3 of the intermediate layer 130 may be greater than the first length L1 of the core 110 and less than the second length L2 of the shell 120. For example, the third length L3 of the intermediate layer 130 may be in the range of about 101% to about 150%, about 101% to about 120%, or about 101% to about 110% of the first length L1 of the core 110. The third thickness T3 of the intermediate layer 130 may, for example, be in the range of about 1% to about 50%, about 1% to about 20%, or about 1% to about 10% of the first thickness T1 of the core 110. The material of the intermediate layer 130 may be selected from the materials used in the core 110 and the materials used in the shell 120. The material of the intermediate layer 130 may be, for example, a polymer.

[0093] Reference Figure 5a The positive electrode layer 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12, and the positive electrode active material layer 12 may include a first region 12A adjacent to the positive electrode current collector 11 and a second region 12B adjacent to the solid electrolyte layer 30. For example, a first 2D sulfide-based solid electrolyte 100 may be disposed in the first region 12A and may not be present in the second region 12B. The thickness of the first region 12A may be 50% or less, 40% or less, 30% or less, or 20% or less of the total thickness of the positive electrode active material layer 12. The first 2D sulfide-based solid electrolyte 100 may be uniformly distributed, for example, in the first region 12A. In other embodiments, the first 2D sulfide-based solid electrolyte 100 may have a concentration gradient decreasing in the first region 12A (e.g., in the direction from the positive electrode current collector 11 to the solid electrolyte layer 30). The first 2D sulfide-based solid electrolyte 100 can be disposed in the first region 12A and may not be present in the second region 12B. Therefore, it is easier to form long-distance ion conduction paths in the first region 12A, which has an increased separation distance from the solid electrolyte layer 30. This allows lithium ions to be more easily conducted to the positive electrode active material layer 12. In some embodiments, the increase in internal resistance of the lithium battery during charging or discharging can be suppressed or reduced, and the cycle characteristics of the lithium battery can be further improved.

[0094] Reference Figure 5bThe positive electrode layer 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12, and the positive electrode active material layer 12 may include a first region 12A adjacent to the positive electrode current collector 11 and a second region 12B adjacent to the solid electrolyte layer 30. For example, a first 2D sulfide-based solid electrolyte 100 may be disposed in the second region 12B and may not be present in the first region 12A. The thickness of the second region 12B may be about 50% or less, about 40% or less, about 30% or less, or about 20% or less of the total thickness of the positive electrode active material layer 12. The first 2D sulfide-based solid electrolyte 100 may be uniformly distributed, for example, in the second region 12B. In other embodiments, the first 2D sulfide-based solid electrolyte 100 may have a concentration gradient in the second region 12B (e.g., in the direction from the solid electrolyte layer 30 to the positive electrode current collector 11). The first 2D sulfide-based solid electrolyte 100 can be disposed in the second region 12B adjacent to the solid electrolyte layer 30, thereby more effectively reducing the interfacial resistance between the solid electrolyte layer 30 and the positive electrode active material layer 12, and allowing lithium ions to be more easily conducted from the solid electrolyte layer 30 to the positive electrode active material layer 12. In some embodiments, the increase in the internal resistance of the lithium battery during charging or discharging can be suppressed or reduced, and the cycle characteristics of the lithium battery can be further improved.

[0095] Reference Figure 5c The positive electrode layer 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12, and the positive electrode active material layer 12 may include a first region 12A adjacent to the positive electrode current collector 11 and a second region 12B adjacent to the solid electrolyte layer 30. For example, a first 2D sulfide-based solid electrolyte 100 may be disposed in the first region 12A and the second region 12B. The first 2D sulfide-based solid electrolyte 100 may be disposed in both the first region 12A and the second region 12B (e.g., simultaneously), thereby improving the overall ionic conductivity of the positive electrode active material layer 12.

[0096] Reference Figures 5a to 5c and Figures 10 to 13The content (e.g., amount) of the first 2D sulfide-based solid electrolyte 100 may, for example, be in the range of about 1 wt% to about 50 wt%, about 1 wt% to about 40 wt%, about 5 wt% to about 40 wt%, about 10 wt% to about 40 wt%, about 15 wt% to about 40 wt%, about 20 wt% to about 40 wt%, or about 25 wt% to about 40 wt% of the total weight of the positive electrode active material layer 12. The positive electrode active material layer 12 may have a content (e.g., amount) of the first 2D sulfide-based solid electrolyte 100 within a range such that ion conduction pathways can extend within the positive electrode active material layer 12 including the first 2D sulfide-based solid electrolyte 100, more effectively accommodating volume changes of the positive electrode active material during charging or discharging of the lithium battery, and maintaining ion conduction pathways in the lithium battery despite volume changes of the positive electrode active material. In some embodiments, lithium battery degradation can be further suppressed or reduced, and the cycle characteristics of the lithium battery can be further improved. If (e.g., when) the content (e.g., amount) of the first 2D sulfide-based solid electrolyte 100 is too high, the interfacial resistance may increase due to incomplete filling between the first two-dimensional sulfide-based solid electrolytes 100 in the positive electrode active material layer 12.

[0097] The positive electrode active material layer 12 may also include an irregularly shaped sulfide-based solid electrolyte, different from the first 2D sulfide-based solid electrolyte 100. The aspect ratio of the irregularly shaped sulfide-based solid electrolyte may be less than about 2, less than about 1.5, or less than about 1.3. The particle size of the irregularly shaped sulfide-based solid electrolyte may, for example, be in the range of about 0.1 μm to about 50 μm, about 0.1 μm to about 50 μm, about 0.1 μm to about 30 μm, about 0.1 μm to about 20 μm, about 0.1 μm to about 10 μm, about 0.1 μm to about 5 μm, or about 0.1 μm to about 3 μm. The weight ratio of the first 2D sulfide-based solid electrolyte 100 to the irregularly shaped sulfide-based solid electrolyte can, for example, be in the range of about 1:99 to about 99:1, about 5:95 to about 95:5, about 10:90 to about 90:10, about 20:80 to about 80:20, or about 30:70 to about 70:30. The weight ratio of the first 2D sulfide-based solid electrolyte 100 to the irregularly shaped sulfide-based solid electrolyte can, for example, be in the range of about 1:99 to about 50:50, about 3:97 to about 40:60, about 5:95 to about 30:70, about 5:95 to about 25:75, or about 5:95 to about 20:80. Such a weight ratio allows for further suppression or reduction of lithium battery degradation and further improvement of the lithium battery's cycle characteristics.

[0098] The size of the solid electrolyte included in the positive electrode active material layer 12 can be smaller than the size of the solid electrolyte included in the solid electrolyte layer 30. For example, the D50 average particle size of the solid electrolyte included in the positive electrode active material layer 12 can be about 90% or less, about 80% or less, about 70% or less, about 60% or less, about 50% or less, about 40% or less, about 30% or less, or about 20% or less of the D50 average particle size of the solid electrolyte included in the solid electrolyte layer 30. The D50 average particle size can be, for example, the median particle size (D50). If (for example, when) the particle size distribution measured by laser diffraction is calculated from particles with smaller particle sizes, the median particle size (D50) can be the particle size corresponding to about 50% of the cumulative volume. The particle size of sulfide-based solid electrolytes can be measured using a measuring device that uses, for example, laser diffraction or dynamic light scattering. For example, particle size can be measured using a laser scattering particle size analyzer (e.g., the LA-920 manufactured by Horiba), and can be a value for the median particle size (D50) if (e.g., when) metal oxide particles accumulate to approximately 50% by volume from smaller particles. In other embodiments, the particle size of sulfide-based solid electrolytes can be measured from SEM images or optical microscopes.

[0099] [Positive electrode layer: Positive electrode active material] Reference Figures 10 to 14 The positive electrode active material layer 12 may include, for example, a positive electrode active material.

[0100] The positive electrode active material included in the positive electrode active material layer 12 can be a positive electrode active material capable of reversibly adsorbing and desorbing lithium ions. The positive electrode active material can include, for example, oxide-based positive electrode active materials, sulfide-based positive electrode active materials, or combinations thereof.

[0101] Oxide-based positive electrode active materials may include, for example, lithium transition metal oxides, metal oxides, or combinations thereof. Lithium transition metal oxides may include, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron phosphate, or combinations thereof. Metal oxides may include, for example, iron oxides, vanadium oxides, or combinations thereof.

[0102] Sulfide-based positive electrode active materials may include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes or combinations thereof.

[0103] Oxide-based positive electrode active materials may include, for example, a composite oxide of lithium and at least one metal selected from cobalt, manganese, nickel, and combinations thereof. Oxide-based positive electrode active materials may include, for example, compounds represented by at least one of the following formulas: Li a A 1-b B' b D2 (where 0.90≤a≤1 and 0≤b≤0.5); Li a E 1-b B' b O 2-c D c (Where, 0.90≤a≤1, 0≤b≤0.5 and 0≤c≤0.05); LiE 2-b B' b O 4-c D c (Where, 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05 and 0<α≤2); Li a Ni 1-b-c Co b B' c O 2-α F' α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2); Li a Ni1-b-c Co b B' c O 2-α F' α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2); Li a Ni 1-b-c Mn b B' c D α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05 and 0<α≤2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2); Li a Ni b E c G d O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5 and 0.001≤d≤0.1); Li a Ni b Co c Mn d G e O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5 and 0.001≤e≤0.1); Li a NiG b O2 (where 0.90≤a≤1 and 0.001≤b≤0.1); Li a CoG b O2 (where 0.90≤a≤1 and 0.001≤b≤0.1); Li a MnG b O2 (where 0.90≤a≤1 and 0.001≤b≤0.1); Li a Mn2G b O4 (where 0.90≤a≤1 and 0.001≤b≤0.1); LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3 (where 0≤f≤2); Li(3-f) Fe2(PO4)3 (where 0≤f≤2); and LiFePO4.

[0104] In the formula representing the aforementioned compounds, A can be Ni, Co, Mn, or a combination thereof; B' can be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D can be O, F, S, P, or a combination thereof; E can be Co, Mn, or a combination thereof; F' can be F, S, P, or a combination thereof; G can be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; I' can be Cr, V, Fe, Sc, Y, or a combination thereof; and J can be V, Cr, Mn, Co, Ni, Cu, or a combination thereof. Compounds for adding a coating to the surface of the aforementioned compounds can also be used, as well as mixtures of the aforementioned compounds and the compounds to which a coating is added. The coating added to the surface of the aforementioned compounds can include, for example, oxides or hydroxides of the coating element, hydroxyoxides of the coating element, oxycarbonates of the coating element, or hydroxycarbonates of the coating element. The compounds constituting the coating can be amorphous or crystalline. The coating elements included in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The method of forming the coating may be selected within a range that will not adversely affect the physical properties of the positive electrode active material. Coating methods may include, for example, spraying, dipping, etc. Specific coating methods will be well understood by those skilled in the art, and therefore will not be described in detail.

[0105] Oxide-based positive electrode active materials may include at least one of lithium transition metal oxides represented by Formulas 1 to 8: <Formula 1> Li a Ni x Co y M z O 2-b A b In Equation 1, 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3,x+y+z=1, M can be manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and A can be F, S, Cl, Br, or a combination thereof; <Formula 2> LiNix Co y Mn z O2 <Formula 3> LiNi x Co y Al z O2 In Formulas 2 and 3, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1; <Formula 4> LiNi x Co y Mn z Al[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ <Formula 7> Li a M1 x M2 y PO 4-b X b In Equation 7, 0.90 ≤ a ≤ 1.1, 0 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.5, 0.9 <x+y<1.1,0≤b≤2, M1 can be chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof. M2 can be magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y), or combinations thereof, and X can be O, F, S, P, or combinations thereof; and <Formula 8> Li a M3 z PO4 In Equation 8, 0.90 ≤ a ≤ 1.1, 0.9 ≤ z ≤ 1.1, and M3 can be chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0106] Oxide-based positive electrode active materials can be coated. Any coating can be used as the coating, as long as it is suitable for use as a positive electrode active material in all-solid-state secondary batteries. The coating may include, for example, Li₂O-ZrO₂ (LZO).

[0107] The size (e.g., diameter) of the oxide-based positive electrode active material can, for example, range from about 0.1 μm to about 30 μm, from about 0.5 μm to about 20 μm, or from about 1 μm to about 15 μm. The oxide-based positive electrode active material can include, for example, single-crystal particles or polycrystalline particles (e.g., it can be in the form of single-crystal particles or polycrystalline particles).

[0108] Sulfide-based cathode active materials may include, for example, Li₂S-containing complexes. Li₂S-containing complexes may include, for example: complexes of Li₂S and carbon; complexes of Li₂S, carbon, and solid electrolytes; complexes of Li₂S and solid electrolytes; complexes of Li₂S and lithium salts; complexes of Li₂S, lithium salts, and carbon; complexes of Li₂S and metal carbides; complexes of Li₂S, carbon, and metal carbides; complexes of Li₂S and metal nitrides; complexes of Li₂S, carbon, and metal nitrides; or combinations thereof.

[0109] The Li2S and carbon complex can include carbon. As carbon, for example, any material can be used, as long as it is a material comprising carbon atoms and can be used as a conductive material in the art. Carbon can be, for example, crystalline carbon, amorphous carbon, or a combination thereof. Carbon can be, for example, a sintered product of a carbon precursor. Carbon can include, for example, carbon nanostructures. Carbon nanostructures can include, for example, one-dimensional carbon nanostructures, 2D carbon nanostructures, three-dimensional carbon nanostructures, or a combination thereof. Carbon nanostructures can include, for example, carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon nanoribbons, carbon nanorods, graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene spheres (GB), or a combination thereof. Carbon can be, for example, porous carbon or non-porous carbon. Porous carbon can include, for example, periodic and regular 2D or three-dimensional pores. Porous carbon can include, for example, CB, KB, AB, electrochemical acetylene black, thermally cracked carbon black, or channel black; graphite; activated carbon; or a combination thereof. The form of carbon can be, for example, particulate, sheet, and / or shaving form, etc., but one or more embodiments are not limited thereto. Any material can be used, as long as it is usable as carbon in the art. The method for preparing the Li₂S and carbon composite can be dry, wet, or a combination thereof, but is not limited thereto. Methods for preparing the Li₂S and carbon composite in the art can include, for example, grinding, heat treatment, deposition, etc., but one or more embodiments are not limited thereto. Any method can be used, as long as it is usable in the art.

[0110] The complex of Li₂S, carbon, and solid electrolyte may include carbon and a solid electrolyte. Carbon may be defined as in the previously described complex of Li₂S and carbon. The solid electrolyte may be, for example, an amorphous solid electrolyte, and any material may be used, provided that the material is suitable for use as an ion-conducting material in the art. The solid electrolyte may be, for example, an inorganic solid electrolyte. The solid electrolyte may be, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte may be, for example, a sulfide solid electrolyte, an oxide solid electrolyte, or a combination thereof. Sulfide solid electrolytes may include, for example, Li, S, and P, and may optionally further include halogen elements. The sulfide solid electrolyte may be selected from sulfide solid electrolytes used in solid electrolyte layers. For example, a sulfide solid electrolyte may have a density of about 1 × 10⁻⁶ at room temperature. -5An ionic conductivity of S / cm or greater. Sulfide solid electrolytes may include, for example, at least one selected from the following: Li3PO4-Li2SO4; Li2S-P2S5; Li2S-P2S5-LiX (where X is a halogen element); Li2S-P2S5-Li2O; Li2S-P2S5-Li2O-LiI; Li2S-SiS2; Li2S-SiS2-LiI; Li2S-SiS2-LiBr; Li2S-SiS2-LiCl; Li2S-SiS2-B2S3-LiI; Li2S-SiS2-P2S5-LiI; Li2S-B2S3; Li2S-P2S5-Z m S n (Where m and n are each positive numbers and Z is one of Ge, Zn, and Ga); Li2S-GeS2; Li2S-SiS2-Li3PO4; Li2S-SiS2-Li p MO q (Where p and q are each positive numbers and M is one of P, Si, Ge, B, Al, Ga, and In); Li 7-x PS 6-x Cl x (where 0 ≤ x ≤ 2); Li 7-x PS 6-x Br x (where 0 ≤ x ≤ 2); and Li 7-x PS 6-x I x (Where 0 ≤ x ≤ 2). Oxide-based solid electrolytes may include, for example, Li, O, and transition metal elements, and may optionally further include other elements. For example, oxide-based solid electrolytes may have a content of about 1 × 10⁻⁶ at room temperature. -5 Solid electrolytes with an ionic conductivity of S / cm or greater. Oxide-based solid electrolytes can be selected from those used in solid electrolyte layers. Solid electrolytes can be, for example, mixtures of sulfide-based solid electrolytes and lithium salts. For example, solid electrolytes may include mixtures of Li3PO4-Li2SO4 and binary lithium salts or mixtures of Li3PO4-Li2SO4 and ternary lithium salts.

[0111] Complexes of Li₂S and solid electrolytes may include solid electrolytes. Solid electrolytes can be defined as previously described as complexes of Li₂S, carbon, and solid electrolytes.

[0112] Complexes of Li₂S and lithium salts may include lithium salt compounds. Lithium salt compounds may not include (e.g., may exclude) sulfur (S) atoms. Lithium salt compounds may be binary compounds, for example, comprising lithium and one or more elements selected from groups 13 to 17 of the periodic table. Binary compounds may include, for example, at least one selected from LiF, LiCl, LiBr, LiI, LiH, Li₂S, Li₂O, Li₂Se, Li₂Te, Li₃N, Li₃P, Li₃As, Li₃Sb, LiI₃, and LiB₃. Lithium salt compounds may be ternary compounds, for example, comprising lithium and two types (classes) of elements selected from groups 13 to 17 of the periodic table. Ternary compounds may include, for example, at least one selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. Lithium salt compounds may include at least one lithium halide compound selected from LiF, LiCl, LiBr, and LiI. Complexes of Li2S and solid electrolytes may include solid electrolytes. Solid electrolytes may be defined as those previously described for use in complexes of Li2S, carbon, and solid electrolytes. Complexes of Li2S and solid electrolytes may include, for example, complexes of Li2S with at least one lithium salt selected from: LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3.

[0113] Complexes of Li₂S, lithium salts, and carbon can include lithium salt compounds and carbon. Carbon can be defined as previously described for complexes of Li₂S and carbon.

[0114] The complex of Li2S and metal carbides can include metal carbides. The metal carbide can be, for example, a 2D metal carbide. The 2D metal carbide can be, for example, MXene. The 2D metal carbide can be made from, for example, M... n+1 C n T x In this representation, M is a transition metal, T is an end group (O, OH, and / or F), n = 1, 2, or 3, and x is the number of end groups. 2D metal carbides can be, for example, Ti₂CT. x 、(Ti 0.5 , Nb 0.5 )2CT x Nb2CT x V2CT x Ti3C2Tx 、(V 0.5 , Cr 0.5 3C2T x Ti3CNT x Ta4C3T x Nb4C3T x Or a combination thereof. The surface of 2D metal carbides can be terminated with O, OH and / or F.

[0115] Complexes of Li₂S, carbon, and metal carbides may include both carbon and metal carbides. Carbon can be defined as previously described for complexes of Li₂S and carbon. Metal carbides can be defined as previously described for complexes of Li₂S and metal carbides.

[0116] Complexes of Li₂S and metal nitrides can include metal nitrides. The metal nitride can be, for example, a 2D metal nitride. A 2D metal nitride can be, for example, composed of M… n+1 N n T x The expression is represented as follows: where M is a transition metal, T is an end group (O, OH, and / or F), n = 1, 2, or 3, and x is the number of end groups. The surface of a 2D metal nitride can be terminated with O, OH, and / or F.

[0117] Complexes of Li₂S, carbon, and metal nitrides may include carbon and metal nitrides. Carbon can be defined as previously described for complexes of Li₂S and carbon. Metal nitrides can be defined as previously described for complexes of Li₂S and metal nitrides.

[0118] The Li2S-containing complex may also include, for example, a second 2D sulfide solid electrolyte. The Li2S-containing complex can be a complex of Li2S and a second 2D sulfide solid electrolyte, or a complex of Li2S, a second 2D sulfide solid electrolyte, and the aforementioned carbon, solid electrolyte, lithium salt, metal carbide, or metal nitride.

[0119] The Li₂S-containing composite may further include a second 2D sulfide-based solid electrolyte, which can further suppress or reduce lithium battery degradation and further improve the cycle characteristics of the lithium battery. The size of the second 2D sulfide-based solid electrolyte may be smaller than the size of the first 2D sulfide-based solid electrolyte 100. The length and / or thickness of the second 2D sulfide-based solid electrolyte may be about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less, respectively, of the length and / or thickness of the first 2D sulfide-based solid electrolyte 100. The length and / or thickness of the second 2D sulfide-based solid electrolyte may be in the range of about 0.1% to about 50%, about 0.5% to about 40%, about 1% to about 30%, about 1% to about 20%, or about 1% to about 10%, respectively, of the length and / or thickness of the first 2D sulfide-based solid electrolyte 100. For example, the second 2D sulfide-based solid electrolyte can have the same shape as the first 2D sulfide-based solid electrolyte 100, but can have a smaller size than the first 2D sulfide-based solid electrolyte 100. This reduced length and / or thickness of the second 2D sulfide-based solid electrolyte allows for easier distribution within Li₂S-containing complexes. This reduced length and / or thickness further suppresses or reduces lithium battery degradation and further improves the cycle characteristics of the lithium battery.

[0120] The size of sulfide-based positive electrode active materials can, for example, range from about 0.1 μm to about 50 μm, about 0.5 μm to about 30 μm, about 0.5 μm to about 20 μm, or about 1 μm to about 10 μm. The size of Li₂S can, for example, range from about 1 nm to about 10 μm, about 10 nm to about 5 μm, about 10 nm to about 3 μm, or about 10 nm to about 1 μm. The size of Li₂S-containing complexes can, for example, range from about 0.1 μm to about 50 μm, about 0.5 μm to about 30 μm, about 0.5 μm to about 20 μm, or about 1 μm to about 10 μm.

[0121] For example, the positive electrode active material can be a composite positive electrode active material comprising a core that adsorbs or desorbs lithium and a shell disposed on the core.

[0122] Composite positive electrode active materials may include, for example, a core for adsorbing and desorbing lithium and a shell disposed along the surface of the core, wherein the shell comprises at least one type or class of material of formula M a O b(where 0 < a ≤ 3, 0 < b < 4, and when a is 1, 2, or 3, b is not an integer) the first metal oxide and graphene, the first metal oxide is disposed in the graphene matrix, and M is at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table. The core for adsorbing or desorbing lithium may include, for example, the previously described Li₂S-containing composite. The Li₂S-containing composite may include, for example: a composite of Li₂S and carbon; a composite of Li₂S, carbon, and a solid electrolyte; a composite of Li₂S and a solid electrolyte; a composite of Li₂S and a lithium salt; a composite of Li₂S, a lithium salt, and carbon; a composite of Li₂S and a metal carbide; a composite of Li₂S, carbon, and a metal carbide; a composite of Li₂S and a metal nitride; a composite of Li₂S, carbon, and a metal nitride; or a combination thereof. The core for adsorbing or desorbing lithium may include, for example, at least one of the lithium transition metal oxides represented by Formulas 1 to 8. The core for adsorbing or desorbing lithium may include, for example, a lithium transition metal oxide having a Ni content (e.g., amount) of about 80 mol% or more. A shell including, for example, the first metal oxide and graphene may be disposed on the core for adsorbing or desorbing lithium. Graphene according to the prior art may be difficult to uniformly apply on the core due to agglomeration. In other embodiments, in the composite positive electrode active material, a composite including a plurality of first metal oxides disposed in the graphene matrix may be used, so that agglomeration of graphene can be prevented or reduced, and a substantially uniform shell can also be disposed on the core. In some embodiments, contact between the core and the electrolyte can be effectively blocked, thereby preventing or reducing side reactions caused by contact between the core and the electrolyte. The shell including graphene may be flexible, so that it can easily adapt to volume changes of the composite positive electrode active material during charging or discharging, thereby suppressing the occurrence of cracks inside the composite positive electrode active material. Graphene may have high electronic conductivity, so that the interfacial resistance between the composite positive electrode active material and the electrolyte can be reduced. In some embodiments, although a shell including graphene is introduced, the internal resistance of the lithium battery can be maintained or reduced. In other embodiments, the first metal oxide may have voltage resistance, so that deterioration of the Li₂S-containing composite and lithium transition metal oxide included in the core during charging or discharging at high voltage can be prevented or reduced. For example, the cycle characteristics and high-temperature stability of a lithium battery including the composite positive electrode active material can be improved. The shell may include, for example, at least one type or kind of the first metal oxide or two or more different types (kinds) of the first metal oxide. The metal included in the first metal oxide may include, for example, at least one selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se. The first metal oxide may include, for example, at least one selected from the following: Al₂O z(where 0 < z < 3); NbO x (where 0 < x < 2.5); MgO x (where 0 < x < 1); Sc2O z (where 0 < z < 3); TiO y (where 0 < y < 2); ZrO y (where 0 < y < 2); V2O z (where 0 < z < 3); WO y (where 0 < y < 2); MnO y (where 0 < y < 2); Fe2O z (where 0 < z < 3); Co3O w (where 0 < w < 4); PdO x (where 0 < x < 1); CuO x (where 0 < x < 1); AgO x (where 0 < x < 1); ZnO x (where 0 < x < 1); Sb2O z (where 0 < z < 3); and SeO y (where 0 < y < 2). The first metal oxide can be disposed in the graphene matrix to improve the uniformity of the shell disposed on the core and further improve the voltage resistance of the composite positive electrode active material. For example, the shell can include Al2O x , where 0 < x < 3. The shell can also include at least one type or species of a second metal compound represented by the formula M a O c (where 0 < a ≤ 3, 0 < c ≤ 4, and if (for example, when) a is 1, 2, or 3 (then), c is an integer). M can be at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table. For example, the second metal oxide can include the same metal as the first metal oxide, and the ratio c / a of c to a as the second metal oxide can have a value greater than the ratio b / a of b to a as the first metal oxide. For example, c / a > b / a. The second metal oxide can be selected from, for example, Al2O3, NbO, NbO2, Nb2O5, MgO, Scs2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2. The first metal oxide can be a reduction product of the second metal oxide. A part or all of the second metal oxide can be reduced to obtain the first metal oxide. In some embodiments, the first metal oxide has a lower oxygen content (for example, amount) and a lower metal oxidation number than the second metal oxide. For example, the shell can include Al2O x(where 0 < x < 3) and Al2O3 as the second metal oxide. The thickness of the shell can be, for example, in the range of about 1 nm to about 5 μm, about 1 nm to about 1 μm, about 1 nm to about 500 nm, about 1 nm to about 200 nm, about 1 nm to about 100 nm, about 1 nm to about 90 nm, about 1 nm to about 80 nm, about 1 nm to about 70 nm, about 1 nm to about 60 nm, about 1 nm to about 50 nm, about 1 nm to about 40 nm, about 1 nm to about 30 nm, about 1 nm to about 20 nm, or about 1 nm to about 10 nm. The shell can have a thickness within such a range, and thus an increase in the internal resistance of a lithium battery including the composite positive electrode active material can be suppressed or reduced. The average particle size of at least one selected from the first metal oxide and the second metal oxide included in the composite can be in the range of about 1 nm to about 1 μm, about 1 nm to about 500 nm, about 1 nm to about 200 nm, about 1 nm to about 100 nm, about 1 nm to about 70 nm, about 1 nm to about 50 nm, about 1 nm to about 30 nm, about 3 nm to about 30 nm, about 3 nm to about 25 nm, about 5 nm to about 25 nm, about 5 nm to about 20 nm, or about 7 nm to about 20 nm. The first metal oxide and / or the second metal oxide can have a particle size within such a nanoscale range, and thus can be more uniformly distributed in the graphene matrix of the composite. In some embodiments, such a composite can be uniformly applied to the core without agglomeration to form a shell. For example, the first metal oxide and / or the second metal oxide can have a particle size within such a range, and thus can be more uniformly disposed on the core. In some embodiments, the first metal oxide and / or the second metal oxide can be uniformly disposed on the core, so as to more effectively exhibit the withstand voltage characteristics. The average particle size of each of the first metal oxide and the second metal oxide can be measured, for example, by a measuring device using a laser diffraction method or a dynamic light scattering method. In other embodiments, the particle size of each of the first metal oxide and the second metal oxide can be measured by SEM and a transmission electron microscope.

[0123] The positive electrode active material can have, for example, a particulate shape (such as a spherical shape or an elliptical shape). The particle size of the positive electrode active material is not limited and can be within the range applicable to the positive electrode active material of a all-solid-state secondary battery according to the prior art. The content (e.g., amount) of the positive electrode active material in the positive electrode layer 10 is also not limited and can be within the range applicable to the positive electrode layer of a all-solid-state secondary battery according to the prior art. With respect to the total weight of the positive electrode active material layer 12, the content (e.g., amount) of the positive electrode active material included in the positive electrode active material layer 12 can be, for example, in the range of about 10 wt% to about 99 wt%, about 10 wt% to about 90 wt%, about 10 wt% to about 80 wt%, about 10 wt% to about 70 wt%, or about 10 wt% to about 50 wt%.

[0124] [Positive electrode layer: conductive material] The positive electrode active material layer 12 may also include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metallic conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, CB, AB, KB, carbon fiber, or a combination thereof, but one or more embodiments are not limited thereto. Any material may be used, as long as it is usable as a carbon-based conductive material in the art. The metallic conductive material may be metal powder, metal fiber, or a combination thereof, but one or more embodiments are not limited thereto. Any material may be used, as long as it is usable as a metallic conductive material in the art. The content (e.g., amount) of the conductive material included in the positive electrode active material layer 12 may, for example, range from about 1 wt% to about 30 wt%, from about 1 wt% to about 20 wt%, or from about 1 wt% to about 10 wt% of the total weight of the positive electrode active material layer 12.

[0125] [Positive electrode layer: binder] The positive electrode active material layer 12 may also include a binder. The binder may include, for example, SBR, PTFE, PVDF, PE, etc., but one or more embodiments are not limited thereto. Any material can be used, provided that it is usable as a binder in the art. The content (e.g., amount) of the binder included in the positive electrode active material layer 12 may, for example, range from about 1 wt% to about 10 wt% of the total weight of the positive electrode active material layer 12. No binder may be provided.

[0126] [Positive electrode layer: other additives] In addition to the aforementioned positive electrode active material, solid electrolyte, binder and conductive material, the positive electrode active material layer 12 may also include additives such as fillers, coatings, dispersants and ionic conductive agents.

[0127] As fillers, coatings, dispersants, ion-conducting additives, etc., which can be included in the positive electrode active material layer 12, suitable materials commonly used in electrodes for all-solid-state secondary batteries can be used.

[0128] [Positive electrode layer: Positive electrode current collector] The positive current collector 11 can be a plate or foil composed 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 alloys thereof. The positive current collector 11 may not be provided. The thickness of the positive current collector 11 can be, for example, in the range of about 1 μm to about 100 μm, about 1 μm to about 50 μm, about 5 μm to about 25 μm, or about 10 μm to about 20 μm.

[0129] The positive current collector 11 may include, for example, a substrate film and a metal layer disposed on at least one surface (e.g., one surface or two (e.g., opposite) surfaces) of the substrate film. The substrate film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), PI, or combinations thereof. The substrate film may be, for example, an insulator. The substrate film may include an insulating thermoplastic polymer, so that if (e.g., when) a short circuit occurs, the substrate film can soften or liquefy to interrupt battery operation, thereby suppressing a rapid increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or alloys thereof. The metal layer may serve as an electrochemical fuse that can be interrupted if (e.g., when) an overcurrent occurs, thereby performing a short-circuit prevention function. The thickness of the metal layer can be adjusted to regulate the limiting current and maximum current. The metal layer can be plated or deposited on the substrate film. If (e.g., when) the thickness of the metal layer is reduced, the limiting current and / or maximum current of the positive current collector 11 can be reduced, thus improving the stability of the lithium battery during short circuits. Lead tabs can be added to the metal layer for external connections. The lead tabs can be welded to the metal layer or the metal layer / substrate film stack by ultrasonic welding, laser welding, spot welding, etc. When the substrate film and / or metal layer melts during welding, the metal layer can be electrically connected to the lead tabs. To more firmly weld the metal layer and lead tabs, a metal sheet can be added between the metal layer and the lead tabs. The metal sheet can be shavings comprising the same material as the metal layer (e.g., composed of the same material as the metal layer). The metal sheet can be, for example, metal foil or metal mesh. The metal sheet can be, for example, aluminum foil, copper foil, or SUS foil. Metal sheets can be disposed on a metal layer and then soldered to lead terminals, thus allowing the lead terminals to be soldered to a metal sheet / metal layer stack or a metal sheet / metal layer / substrate film stack. During soldering, the metal layer or metal layer / metal sheet stack can be electrically connected to the lead terminals while the substrate film, metal layer, and / or metal sheet melt. Metal sheets and / or lead terminals can be added to a portion of the metal layer. The thickness of the substrate film can, for example, be in the range of about 1 μm to about 50 μm, about 1.5 μm to about 50 μm, about 1.5 μm to about 40 μm, or about 1 μm to about 30 μm. The substrate film can have a thickness within such a range, thus allowing for a more effective reduction in the weight of the electrode assembly. The melting point of the substrate film can, for example, be in the range of about 100°C to about 300°C, about 100°C to about 250°C, or about 100°C to about 200°C.The substrate film can have a melting point within a certain range, so that it can melt and easily bond to the lead patch during the bonding process. To improve the adhesion strength between the substrate film and the metal layer, the substrate film can be subjected to surface treatments such as corona treatment. The thickness of the metal layer can, for example, be in the range of about 0.01 μm to about 3 μm, about 0.1 μm to about 3 μm, about 0.1 μm to about 2 μm, or about 0.1 μm to about 1 μm. The metal layer can have a thickness within this range, thus ensuring the stability of the electrode assembly while maintaining conductivity. The thickness of the metal sheet can, for example, be in the range of about 2 μm to about 10 μm, about 2 μm to about 7 μm, or about 4 μm to about 6 μm. The metal sheet can have a thickness within this range, thus making it easier to connect the metal layer and the lead patch. The positive current collector 11 can have such a structure that the weight of the positive electrode layer 10 can be reduced, thereby improving the energy density of the positive electrode layer 10 and the lithium battery.

[0130] [Positive electrode layer: Inactive component] Reference Figures 12 to 14 The positive electrode layer 10 may include a positive electrode current collector 11, a positive electrode active material layer 12 disposed on at least one surface of the positive electrode current collector 11, and may also include an inactive member 40 (40a or 40b) disposed on at least one side surface of the positive electrode layer 10.

[0131] The inactive component 40 can be provided to prevent or reduce cracking of the solid electrolyte layer 30 during the manufacture and / or charging / discharging of the all-solid-state secondary battery 1, thereby improving the cycle characteristics of the all-solid-state secondary battery 1. In an all-solid-state secondary battery 1 without the inactive component 40, uneven pressure may be applied to the solid electrolyte layer 30 in contact with the positive electrode layer 10 during the manufacture and / or charging / discharging of the all-solid-state secondary battery 1, resulting in cracks in the solid electrolyte layer 30, and lithium metal may grow through the cracks, thereby increasing the possibility of a short circuit.

[0132] The inactive component 40 may be disposed along the side surface of the positive electrode layer 10 to surround the positive electrode layer 10. The inactive component 40 may surround, for example, a portion or all of the side surface of the positive electrode layer 10 and may be in contact with the solid electrolyte layer 30. The inactive component 40's ability to surround the side surface of the positive electrode layer 10 and be in contact with the solid electrolyte layer 30 effectively suppresses cracking of the solid electrolyte layer 30, which is caused during the pressing process in the portion of the solid electrolyte layer 30 not in contact with the positive electrode layer 10 due to pressure differential. The inactive component 40 may surround the side surface of the positive electrode layer 10 and may be separated from the negative electrode layer 20 (e.g., the first negative electrode active material layer 22 (22a or 22b)). The inactive component 40 may surround the side surface of the positive electrode layer 10, may be in contact with the solid electrolyte layer 30, and may be separated from the negative electrode layer 20. In some embodiments, the possibility of a short circuit due to physical contact between the positive electrode layer 10 and the first negative electrode active material layer 22 or due to overcharging of lithium may be suppressed or reduced. (Refer to...) Figure 12 The inactive component 40 can be disposed on at least one side surface of the positive electrode active material layer 12, and concurrently (e.g., simultaneously) on at least one side surface of the positive electrode current collector 11, thereby more effectively suppressing the possibility of a short circuit due to contact between the positive electrode current collector 11 and the negative electrode layer 20. In other embodiments, refer to Figure 13 The inactive component 40 may be disposed on at least one side surface of the positive electrode active material layer 12, and may be disposed between the solid electrolyte layer 30 and the positive electrode current collector 11 opposite to the solid electrolyte layer 30. The inactive component 40 may not be disposed on at least one side surface of the positive electrode current collector 11. The inactive component 40 may be disposed between the positive electrode current collector 11 and the solid electrolyte layer 30, thereby effectively preventing or reducing short circuits caused by contact between the positive electrode current collector 11 and the negative electrode layer 20.

[0133] In some embodiments, a portion of the entire inactive component 40 (40a or 40b) may be spaced apart from the side surface of the positive electrode layer 10. The partial or complete separation of the inactive component 40 (40a or 40b) from the side surface of the positive electrode layer 10 simplifies the manufacturing process of the all-solid-state secondary battery 1 and increases its manufacturing speed. Furthermore, the separation of the inactive component 40 (40a or 40b) from the side surface of the positive electrode layer 10 allows for more effective adaptation to lateral volume changes in the positive electrode layer 10 during charging or discharging, thereby further improving the lifespan characteristics of the all-solid-state secondary battery 1. The distance between the inactive components 40 (40a and 40b) and the side surface of the positive electrode layer 10 can each be independently within the range of, for example, about 0.1 μm to about 10 mm, about 1 μm to about 1 mm, about 1 μm to about 500 μm, about 1 μm to about 100 μm, about 1 μm to about 50 μm, or about 1 μm to about 10 μm.

[0134] The inactive component 40 may further include a positioning unit configured to determine the position of the inactive component 40 on the solid electrolyte layer 30. The inactive component 40 may include a positioning unit, thus making it easy to determine the position of the inactive component 40 disposed on the solid electrolyte layer 30. In some embodiments, this can increase the manufacturing speed of the all-solid-state secondary battery 1 and improve its ease of manufacture.

[0135] Reference Figure 13 and Figure 14 The inactive member 40 can extend from one side surface of the positive electrode layer 10 to the end of the solid electrolyte layer 30. The inactive member 40 extending to the end of the solid electrolyte layer 30 can suppress or reduce cracking at the end of the solid electrolyte layer 30. The end of the solid electrolyte layer 30 can be the outermost point in contact with the side surface of the solid electrolyte layer 30. The inactive member 40 can extend to the outermost point in contact with the side surface of the solid electrolyte layer 30. The inactive member 40 can be separate from the negative electrode layer 20 (e.g., the first negative electrode active material layer 22 (22a or 22b)). The inactive member 40 can extend to the end of the solid electrolyte layer 30 but not in contact with the negative electrode layer 20. For example, the inactive member 40 can fill the space extending from one side surface of the positive electrode layer 10 to the end of the solid electrolyte layer 30.

[0136] The inactive component 40 can be, for example, a gasket. By using a gasket as the inactive component 40, cracks in the solid electrolyte layer 30 caused by pressure differences during the pressing process can be effectively suppressed or reduced.

[0137] The inactive component 40 may have, for example, a single-layer structure. In other embodiments, the inactive component 40 may have a multi-layer structure. In an inactive component 40 with a multi-layer structure, the individual layers may have different compositions. The inactive component 40 with 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 inactive component 40 with a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers. For example, the adhesive layer can effectively prevent or reduce separation between the positive electrode layer 10 and the solid electrolyte layer 30 due to volume changes of the positive electrode layer 10 during the charging / discharging process of the all-solid-state secondary battery 1, and can provide bonding forces between the support layer and other layers to improve the film strength of the inactive component 40. The support layer can provide support forces to the inactive component 40, can prevent or reduce non-uniformity of pressure applied to the solid electrolyte layer 30 during the pressing process or the charging / discharging process, and can prevent or reduce shape deformation of the all-solid-state secondary battery 1 to be manufactured.

[0138] Reference Figure 14The all-solid-state secondary battery 1 may include a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 (30a or 30b) disposed therebetween. The positive electrode layer 10 includes a positive current collector 11 and each of a first positive active material layer 12a and a second positive active material layer 12b disposed on two surfaces of the positive current collector 11. The solid electrolyte layer 30 includes each of a first solid electrolyte layer 30a in contact with the first positive active material layer 12a and a second solid electrolyte layer 30b in contact with the second positive active material layer 12b. The negative electrode layer 20 includes each of a first negative electrode layer 20a in contact with the first solid electrolyte layer 30a and a second negative electrode layer 20b in contact with the second solid electrolyte layer 30b. An inactive member 40 is disposed between the first solid electrolyte layer 30a and the second solid electrolyte layer 30b, which are opposite to each other, to surround the side surface of the positive electrode layer 10. The inactive component 40 may include, for example, a first inactive component 40a in contact with the first solid electrolyte layer 30a and a second inactive component 40b in contact with the second solid electrolyte layer 30b. In some embodiments, the all-solid-state secondary battery 1 may have a dual-cell structure. The all-solid-state secondary battery 1 may have such a dual-cell structure that the solid electrolyte layer 30 and the negative electrode layer 20 can each be disposed relative to the positive electrode layer 10, thereby more effectively suppressing structural deformation due to pressure applied during the manufacturing of the all-solid-state secondary battery 1. In some embodiments, cracks in the solid electrolyte layer 30 can be suppressed or reduced during the manufacturing process and / or charging / discharging process of the all-solid-state secondary battery 1, thereby preventing or reducing short circuits in the all-solid-state secondary battery 1 and further improving the cycle characteristics of the all-solid-state secondary battery 1. In other embodiments, only one positive electrode current collector 11 can be used for multiple positive electrode active material layers 12a and 12b, thus increasing the energy density of the all-solid-state secondary battery 1.

[0139] Reference Figures 12 to 14 The inactive component 40 can be, for example, a flame-retardant inactive component. The flame-retardant inactive component can provide flame retardancy to prevent or reduce the possibility of thermal runaway and ignition in the all-solid-state secondary battery 1. In some embodiments, the safety of the all-solid-state secondary battery 1 can be further improved. The flame-retardant inactive component can be configured to adsorb residual moisture in the all-solid-state secondary battery 1, thereby preventing or reducing the degradation of the all-solid-state secondary battery 1 and improving its lifespan characteristics.

[0140] The flame-retardant inactive component may include, for example, a matrix and a filler. The matrix may include, for example, a substrate and a reinforcing material. The matrix may include, for example, a fiber substrate and a fiber reinforcing material. The matrix may include a substrate to be elastic. In some embodiments, the matrix can effectively accommodate volume changes in the all-solid-state secondary battery 1 during charging or discharging and may be disposed at any of one or more suitable locations. The substrate included in the matrix may include, for example, a first fiber material. By including the first fiber material, the substrate can effectively accommodate volume changes in the positive electrode layer 10 that occur during the charging / discharging process of the all-solid-state secondary battery 1 and can effectively suppress or reduce deformation of the inactive component 40 due to volume changes in the positive electrode layer 10. The first fiber material may be, for example, a material with an aspect ratio of about 5 or greater, about 20 or greater, or about 50 or greater. The first fiber material may be, for example, a material with an aspect ratio of about 5 to about 1,000, about 20 to about 1,000, or about 50 to about 1,000. The first fiber material may be, for example, an insulating material. The first fiber material can be an insulating material, thus effectively preventing or reducing short circuits between the positive electrode layer 10 and the negative electrode layer 20 due to lithium dendrites or the like during charging or discharging of the all-solid-state secondary battery 1. The first fiber material can include, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conducting polymer fibers. The matrix can include a reinforcing material, thus improving the strength of the matrix. In some embodiments, the matrix can prevent or reduce excessive volume changes of the all-solid-state secondary battery 1 during charging / discharging and can prevent or reduce deformation of the all-solid-state secondary battery 1. The reinforcing material included in the matrix can include, for example, a second fiber material. The reinforcing material can include a second fiber material, thus the strength of the matrix can be improved more uniformly. The second fiber material can be, for example, a material with an aspect ratio of about 3 or greater, about 5 or greater, or about 10 or greater. The second fiber material can be, for example, a material with an aspect ratio of about 3 to about 100, about 5 to about 100, or about 10 to about 100. The second fiber material can be, for example, a flame-retardant material. The second fiber material can be a flame-retardant material, thus effectively suppressing or reducing ignition caused by thermal runaway or external impact during the charging / discharging process of the all-solid-state secondary battery 1. The second fiber material may include, for example, glass fiber, metal oxide fiber, or ceramic fiber.

[0141] In addition to the matrix, the flame-retardant inactive component may also include a filler. The filler may be disposed in the matrix, on the surface of the matrix, or (e.g., simultaneously) in the matrix and on the surface. The filler may include, for example, an inorganic material. The filler included in the flame-retardant inactive component may be, for example, a hygroscopic agent, a flame retardant, or a lithium fixative. For example, a hygroscopic agent may adsorb moisture at a temperature below about 100°C to remove residual moisture in the all-solid-state secondary battery 1, thereby preventing or reducing the degradation of the all-solid-state secondary battery 1. In some embodiments, if (e.g., when) the temperature of the all-solid-state secondary battery 1 increases to about 150°C or higher due to thermal runaway or external shock occurring during the charging / discharging process of the all-solid-state secondary battery 1, the hygroscopic agent may release the adsorbed moisture to effectively suppress or reduce ignition of the all-solid-state secondary battery 1. The hygroscopic agent may include, for example, a metal hydroxide having moisture adsorption properties. The metal hydroxide included in the filler may be, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, Ti(OH)3, Zr(OH)4, Al(OH)3, or combinations thereof. The flame retardant may include, for example, at least one selected from zinc borate, calcium-zinc molybdate complex, MoO3, (NH4)2Mo2O7, Sb2O3, and Sb3O5. The lithium fixative may be a compound that fixes lithium, for example, by reacting with liquid lithium at a temperature of about 180°C or higher, which is the melting temperature of lithium. The lithium fixative may react with, for example, liquid lithium to convert lithium into other insoluble compounds. The lithium fixative may be, for example, a metal oxide that reacts with liquid lithium. The metal oxide included in the filler may be, for example, TiO2, ZrO2, HfO2, ThO2, or combinations thereof. The metal oxide may react with, for example, liquid lithium to produce Li2O and metal. The reaction may be, for example, 4Li + MO2 → M + 2Li2O. Liquid lithium may be fixed by reacting with the metal oxide to generate lithium oxide. Leakage of molten liquid lithium to the positive electrode layer 10 at high temperatures can be suppressed or reduced. In some embodiments, the safety of the all-solid-state secondary battery 1 can be improved.

[0142] The content (e.g., amount) of filler included in the flame-retardant inactive component relative to 100 parts by weight can, for example, range from about 1 part by weight to about 80 parts by weight, from about 5 parts by weight to about 80 parts by weight, from about 10 parts by weight to about 80 parts by weight, from about 20 parts by weight to about 80 parts by weight, from about 30 parts by weight to about 80 parts by weight, from about 40 parts by weight to about 80 parts by weight, from about 50 parts by weight to about 80 parts by weight, from about 60 parts by weight to about 80 parts by weight, or from about 65 parts by weight to about 80 parts by weight.

[0143] Flame-retardant inactive components may also include, for example, adhesives. Adhesives may include, for example, curable polymers or non-curable polymers. Curable polymers may be polymers that are cured by heat and / or pressure. Curable polymers may be, for example, solids at room temperature. Flame-retardant inactive components may include, for example, hot-pressed curable films and / or their cured products. Hot-pressed curable polymers may be, for example, Toray's TSA-66.

[0144] In addition to the aforementioned substrate, reinforcing material, filler, and binder, the flame-retardant inactive component may also include other materials. The flame-retardant inactive component may also include at least one material selected from, for example, paper, insulating polymers, ionically conductive polymers, insulating inorganic materials, oxide solid electrolytes, and sulfide solid electrolytes. The insulating polymer may be, for example, an olefin polymer, such as PP or PE.

[0145] The density of the substrate or reinforcing material included in the flame-retardant inactive component may, for example, be in the range of about 10% to about 300%, about 10% to about 150%, about 10% to about 140%, about 10% to about 130%, or about 10% to about 120% of the density of the positive active material included in the positive active material layer 12.

[0146] The inactive component 40 may be a component that does not include an electrochemically active material (e.g., an electrode active material). The electrode active material may be a material that adsorbs / desorbs lithium. The inactive component 40 may be a component that includes materials other than electrode active materials used in the art (e.g., composed of materials other than electrode active materials used in the art).

[0147] [Solid electrolyte layer] [Solid electrolyte layer: solid electrolyte] Reference Figures 6 to 14 The solid electrolyte layer 30 may include a solid electrolyte disposed between the positive electrode layer 10 and the negative electrode layer 20.

[0148] Reference Figure 6 and Figure 8 The solid electrolyte layer 30 may include, for example, a first 2D sulfide-based solid electrolyte 100 arranged in one direction. The first 2D sulfide-based solid electrolyte 100 can be arranged in one direction, thus further improving the density of the solid electrolyte layer 30. In some embodiments, the energy density of the lithium battery can be further improved.

[0149] For example, the direction along which the first 2D sulfide-based solid electrolyte 100 is arranged may be different from the thickness direction (Y direction) of the solid electrolyte layer 30. The angle formed between the direction along which the first 2D sulfide-based solid electrolyte 100 is arranged and the thickness direction of the solid electrolyte layer 30 may, for example, be in the range of about 10° to about 170°, about 20° to about 160°, about 30° to about 150°, about 14° to about 135°, about 60° to about 120°, or about 75° to about 105°.

[0150] For example, the first 2D sulfide-based solid electrolyte 100 may be arranged in a direction substantially perpendicular to the thickness direction of the solid electrolyte layer 30 (Z direction or X direction). For example, the first 2D sulfide-based solid electrolyte 100 may be arranged such that the first surface S1 and / or the second surface S2 of the first 2D sulfide-based solid electrolyte 100 are disposed in a direction parallel to the surface of the solid electrolyte layer 30.

[0151] The solid electrolyte layer 30 may include a first 2D sulfide-based solid electrolyte disposed in a direction different from the thickness direction of the solid electrolyte layer 30, thereby suppressing or reducing the growth of lithium dendrites in the thickness direction of the solid electrolyte layer 30, and suppressing or reducing short circuits, etc. In some embodiments, the degradation of the all-solid-state secondary battery 1 can be suppressed or reduced, and its lifetime characteristics can be improved.

[0152] The direction along which the first 2D sulfide-based solid electrolyte 100 is stacked can be, for example, similar to the thickness direction of the solid electrolyte layer 30. The angle formed between the direction along which the first 2D sulfide-based solid electrolyte 100 is stacked and the thickness direction of the solid electrolyte layer 30 can be, for example, in the range of about -30° to about 30° or about -20° to about 20°. For example, the first 2D sulfide-based solid electrolyte 100 can be stacked in the thickness direction of the solid electrolyte layer 30 such that the first surface S1 and / or the second surface S2 of the first 2D sulfide-based solid electrolyte 100 are arranged in a direction parallel to the surface of the solid electrolyte layer 30.

[0153] The first 2D sulfide-based solid electrolyte 100 may be stacked, for example, in the thickness direction of the solid electrolyte layer 30. The solid electrolyte layer 30 may include a stack of first 2D sulfide-based solid electrolytes 200. The solid electrolyte layer 30 may include a plurality of first 2D sulfide-based solid electrolyte stacks 200. The number of first 2D sulfide-based solid electrolytes 100 included in a first 2D sulfide-based solid electrolyte stack 200 may be about 2 or more, about 5 or more, about 10 or more, about 50 or more, about 100 or more, or about 200 or more. The number of first 2D sulfide-based solid electrolytes 100 included in a first 2D sulfide-based solid electrolyte stack 200 may be in the range of about 2 to about 1,000, about 5 to about 1,000, about 10 to about 1,000, about 50 to about 1,000, about 100 to about 1,000, or about 200 to about 1,000. The solid electrolyte layer 30 may include a first 2D sulfide-based solid electrolyte 100 stacked in a direction similar to the thickness direction of the solid electrolyte layer 30, thereby suppressing or reducing the growth of lithium dendrites in the thickness direction of the solid electrolyte layer 30, and suppressing or reducing short circuits, etc. In some embodiments, the degradation of the all-solid-state secondary battery 1 can be suppressed or reduced, and its lifetime characteristics can be improved.

[0154] The content (e.g., amount) of the first 2D sulfide-based solid electrolyte 100 can be, for example, about 50 wt% or more, about 60 wt% or more, about 70 wt% or more, about 80 wt% or more, about 90 wt% or more, or about 95 wt% or more of the total weight of the solid electrolyte layer 30. The content (e.g., amount) of the first 2D sulfide-based solid electrolyte 100 can be, for example, in the range of about 50 wt% to about 100 wt%, about 60 wt% to about 100 wt%, about 70 wt% to about 100 wt%, about 80 wt% to about 100 wt%, about 90 wt% to about 99.99 wt%, or about 95 wt% to about 99 wt% of the total weight of the solid electrolyte layer 30. The solid electrolyte layer 30 can include the first 2D sulfide-based solid electrolyte 100 having such a high content (e.g., amount), thus further reducing the possibility of pinholes P forming on the surface of the solid electrolyte layer 30 during its preparation. For example, the growth of lithium dendrites due to pinholes can be more effectively suppressed or reduced during the charging or discharging of the all-solid-state secondary battery 1. In some embodiments, the lifetime characteristics of the all-solid-state secondary battery 1 can be further improved.

[0155] Conversely, refer to Figure 7 and Figure 9In a solid electrolyte layer 30 comprising an irregularly shaped sulfide-based solid electrolyte 100A with an aspect ratio less than about 2, grain boundaries between the irregularly shaped sulfide-based solid electrolyte 100A particles connect in the thickness direction of the solid electrolyte layer 30, thus lithium dendrites readily grow in the thickness direction of the solid electrolyte layer 30. For example, pinholes P readily form on the surface of the solid electrolyte layer 30 between the irregularly shaped sulfide-based solid electrolyte 100A particles, thus lithium dendrites more easily grow through the pinholes. In some embodiments, the likelihood of short circuits in a lithium battery including the solid electrolyte layer 30 increases, and its cycle characteristics deteriorate.

[0156] The first 2D sulfide-based solid electrolyte 100 may be selected from sulfide-based solid electrolytes included in the positive electrode active material layer 12. In other embodiments, the solid electrolyte layer 30 may include an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0157] The oxide-based solid electrolyte can be selected from the oxide-based solid electrolytes used in the positive electrode active material layer 12.

[0158] Polymer solid electrolytes may include, for example, dry polymer electrolytes, gel polymer electrolytes, or combinations thereof.

[0159] Dry polymer electrolytes can be electrolytes comprising, for example, a mixture of lithium salts and polymers. Dry polymer electrolytes can be, for example, polymer electrolytes that do not include a liquid electrolyte. Polymers included in dry polymer electrolytes can include, for example, PEO, PVDF, vinylidene fluoride-hexafluoropropylene (PVDF-HFP), poly(styrene)-b-(ethylene oxide) (PS-PEO) block or reduction copolymers, poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block or reduction copolymers, poly(styrene-ethylene oxide-styrene) block or reduction copolymers, or combinations thereof. As lithium salts, any material can be used, provided that the material is usable as a lithium salt in the art. For example, lithium salts can include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are each in the range of 1 to 20), LiCl, LiI, or mixtures thereof.

[0160] Gel polymer electrolytes can be electrolytes comprising a liquid electrolyte and a polymer. The liquid electrolyte may include, for example, a mixture of a lithium salt and an organic solvent. The polymer included in the gel polymer electrolyte may be selected from polymers included in dry polymer electrolytes. The lithium salt may be selected from lithium salts used in dry polymer electrolytes.

[0161] The solid electrolyte layer 30 may be impermeable to lithium polysulfides. In some embodiments, this can prevent side reactions between the negative electrode layer and lithium polysulfides that occur during charging or discharging of the sulfide-based positive electrode active material. In some embodiments, the cycle characteristics of the all-solid-state secondary battery 1 including the solid electrolyte layer 30 can be improved.

[0162] [Solid electrolyte layer: binder] The solid electrolyte layer 30 may include, for example, a binder. The binder included in the solid electrolyte layer 30 may include, for example, SBR, PTFE, PVDF, PE, etc., but one or more embodiments are not limited thereto. Any material may be used, as long as it is applicable as a binder in the art. The binder of the solid electrolyte layer 30 may be the same as or different from the binder included in the positive electrode active material layer 12 and the first negative electrode active material layer 22. No binder may be provided.

[0163] The amount (e.g., quantity) of the binder included in the solid electrolyte layer 30 relative to the total weight of the solid electrolyte layer 30 can be in the range of about 0.1 wt% to about 10 wt%, about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 1 wt%, about 0 wt% to about 0.5 wt%, or about 0 wt% to about 0.1 wt%.

[0164] [Negative electrode layer] [Negative electrode layer: Negative electrode active material] Reference Figures 4 to 10 The negative electrode layer 20 may include a first negative electrode active material layer 22. The first negative electrode active material layer 22 may include, for example, a negative electrode active material and a binder.

[0165] The negative electrode active material included in the first negative electrode active material layer 22 can be, for example, a negative electrode material that can form an alloy or compound with lithium.

[0166] The negative electrode active material included in the first negative electrode active material layer 22 can be, for example, in particulate form. The average particle size of the negative electrode active material in particulate form can be, for example, about 4 μm or less, about 3 μm or less, about 2 μm or less, about 1 μm or less, about 500 nm or less, about 300 nm or less, or about 100 nm or less. The average particle size of the negative electrode active material in particulate form can, for example, be in the range of about 10 nm to about 4 μm, about 10 nm to about 3 μm, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 300 nm, or about 10 nm to about 100 nm. The negative electrode active material can have an average particle size within such a range, thus making reversible adsorption and / or desorption of lithium during charging or discharging easier. The average particle size of the negative electrode active material can be, for example, the median particle size (D50) measured using a laser-type or laser-like particle size analyzer.

[0167] The negative electrode active material included in the first negative electrode active material layer 22 may include at least one selected from, for example, carbon-based negative electrode active materials and metal or quasi-metal negative electrode active materials.

[0168] Carbon-based anode active materials may include, for example, amorphous carbon, crystalline carbon, porous carbon, or combinations thereof.

[0169] The carbon-based negative electrode active material can be, for example, amorphous carbon. Examples of amorphous carbon may include CB, AB, FB, KB, graphene, etc., but one or more embodiments are not necessarily limited to this. Any material can be used, as long as it can be classified as amorphous carbon in the art. Amorphous carbon can be carbon that is non-crystalline or has very low crystallinity, and can be distinguished from crystalline carbon or graphitic carbon.

[0170] Carbon-based anode active materials can be, for example, porous carbon. The pore volume of porous carbon can, for example, range from about 0.1 cc / g to about 10.0 cc / g, from about 0.5 cc / g to about 5 cc / g, or from about 0.1 cc / g to about 1 cc / g. The average pore size of porous carbon can, for example, range from about 1 nm to about 50 nm, from about 1 nm to about 30 nm, or from about 1 nm to about 10 nm. The Brunauer-Emmett-Teller (BET) specific surface area of ​​porous carbon can, for example, be about 100 m². 2 / g to approximately 3,000m 2 Within the range of / g.

[0171] Metallic or quasi-metallic anode active materials may include at least one selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but one or more embodiments are not necessarily limited thereto. Any material may be used, provided that it is applicable in the art as a metallic or quasi-metallic anode active material to form an alloy or compound with lithium. For example, nickel (Ni) cannot form an alloy with lithium and therefore may not be a metallic anode active material.

[0172] The first negative electrode active material layer 22 may comprise one type or variety of negative electrode active material or a mixture of multiple different negative electrode active materials. For example, the first negative electrode active material layer 22 may comprise only amorphous carbon, or may comprise at least one selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). In other embodiments, the first negative electrode active material layer 22 may comprise amorphous carbon and a mixture of at least one selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the amorphous carbon to the gold, etc., may be, for example, a weight ratio in the range of about 99:1 to about 1:99, about 10:1 to about 1:2, about 5:1 to about 1:1, or about 4:1 to about 2:1, but one or more embodiments are not necessarily limited to such ranges. The mixing ratio can be selected based on the desired characteristics of the all-solid-state secondary battery 1. The negative electrode active material can have such a composition, thus further improving the cycle characteristics of the all-solid-state secondary battery 1.

[0173] The negative electrode active material included in the first negative electrode active material layer 22 may include, for example, a mixture of first particles composed of amorphous carbon and second particles composed of metal or metalloid. Examples of metal or metalloid may include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), etc. In other embodiments, the metalloid may be a semiconductor. The content (e.g., amount) of the second particles relative to the total weight of the mixture may range from about 1 wt% to about 99 wt%, from about 1 wt% to about 60 wt%, from about 8 wt% to about 60 wt%, from about 10 wt% to about 50 wt%, from about 15 wt% to about 40 wt%, or from about 20 wt% to about 30 wt%. The second particles may have a content (e.g., amount) within such a range, thus, for example, further improving the cycle characteristics of the all-solid-state secondary battery 1.

[0174] In other embodiments, the first negative electrode active material layer 22 may include a composite negative electrode active material. The composite negative electrode active material may include, for example, a carbon-based carrier and a metal-based negative electrode active material loaded on the carbon-based carrier. The composite negative electrode active material may have such a structure that it can prevent or reduce the localization of the metal-based negative electrode active material in the first negative electrode active material layer 22 and obtain its substantially uniform distribution. In some embodiments, the cycle characteristics of the all-solid-state secondary battery 1 including the first negative electrode active material layer 22 may be further improved.

[0175] The metal-based negative electrode active material loaded on the carbon-based carrier may include, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. Examples of the metal may include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), etc. Examples of the metal oxide may include gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, zinc (Zn) oxide, etc. The metal oxide may include, for example, Au x O y (where 0 < x ≤ 2 and 0 < y ≤ 3), Pt x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), Pd x O y (where 0 < x ≤ 1 and 0 < y ≤ 1), Si x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), Ag x O y (where 0 < x ≤ 2 and 0 < y ≤ 1), Al x O y (where 0 < x ≤ 2 and 0 < y ≤ 3), Bi x O y (where 0 < x ≤ 2 and 0 < y ≤ 3), Sn x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), Zn x O y (where 0 < x ≤ 1 and 0 < y ≤ 1) or a combination thereof. The composite of a metal and a metal oxide may include, for example, a composite of Au and Au x O y (where 0 < x ≤ 2 and 0 < y ≤ 3), a composite of Pt and Pt x O y (where 0 < x ≤ 1 and 0 < y ≤ 2), a composite of Pd and Pd x O yComplexes where (0 < x ≤ 1 and 0 < y ≤ 1), Si and Si x O y Complexes where (0 < x ≤ 1 and 0 < y ≤ 2), Ag and Ag x O y Complexes where (0 < x ≤ 2 and 0 < y ≤ 1), Al and Al x O y Complexes where (0 < x ≤ 2 and 0 < y ≤ 3), Bi and Bi x O y Complexes where (0 < x ≤ 2 and 0 < y ≤ 3), Sn and Sn x O y Complexes where (0 < x ≤ 1 and 0 < y ≤ 2), Zn and Zn x O y Complexes where (0 < x ≤ 1 and 0 < y ≤ 1) or combinations thereof.

[0176] The carbonaceous support may include, for example, amorphous carbon. Examples of amorphous carbon may include CB, AB, FB, KB, graphene, activated carbon, CNF, CNT, etc., but one or more embodiments are not necessarily limited thereto. Any material may be used as long as it can be classified as amorphous carbon in the art. Amorphous carbon may be carbon that does not have crystallinity or has very low crystallinity and may be distinguishable from crystalline carbon or graphite-like carbon. The carbonaceous material may be, for example, a carbonaceous negative electrode active material.

[0177] Composite anode active materials can be, for example, in particulate form. The particle size of composite anode active materials in particulate form can, for example, be in the range of about 10 nm to about 4 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. Composite anode active materials can have particle sizes within such ranges, thus facilitating reversible adsorption and / or desorption of lithium during charging or discharging. Metallic anode active materials supported on carbon-based supports can, for example, be in particulate form. The particle size of metallic anode active materials can, for example, be in the range of about 1 nm to about 200 nm, about 1 nm to about 150 nm, about 5 nm to about 100 nm, or about 10 nm to about 50 nm. Carbon-based supports can, for example, be in particulate form. The particle size of the carbon-based support can, for example, be in the range of about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. The carbon-based support can have a particle size within such a range, and therefore can be disposed more uniformly in the first negative electrode active material layer 22. The carbon-based support can include, for example, nanoparticles having a particle size of about 500 nm or smaller. The particle size of the composite negative electrode active material, the particle size of the metal-based negative electrode active material, and the particle size of the carbon-based support can each be, for example, an average particle size. The average particle size can be, for example, the median particle size (D50) measured using a laser-type or laser-based particle size analyzer. In other embodiments, the average particle size can be determined automatically using software, for example, from an electron microscope image, or manually according to a manual.

[0178] [Negative electrode layer: binder] The binder included in the first negative electrode active material layer 22 can be, for example, SBR, PTFE, PVDF, PE, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but one or more embodiments are not necessarily limited to this. Any material can be used, as long as it is applicable as a binder in the art. The binder can be provided as a single binder or as a combination of different binders.

[0179] The first negative electrode active material layer 22 may include a binder, thus stabilizing it on the negative electrode current collector 21. In some embodiments, cracking of the first negative electrode active material layer 22 can be suppressed or reduced despite changes in volume and / or relative position of the first negative electrode active material layer 22 during the charging / discharging process. For example, if (e.g., when) the first negative electrode active material layer 22 does not include a binder, it will easily separate from the negative electrode current collector 21. At the portion of the negative electrode current collector 21 exposed due to the separation of the first negative electrode active material layer 22 from the negative electrode current collector 21, the negative electrode current collector 21 will come into contact with the solid electrolyte layer 30, which will increase the likelihood of a short circuit. The first negative electrode active material layer 22 can be formed, for example, by applying a slurry in which materials constituting the first negative electrode active material layer 22 are dispersed onto the negative electrode current collector 21 and drying the slurry. The first negative electrode active material layer 22 may include a binder, thus allowing the negative electrode active material to be stably distributed in the slurry. For example, if (e.g., when) the paste is applied to the negative electrode current collector 21 by screen printing, screen clogging (e.g., clogging by aggregates of negative electrode active material) can be suppressed or reduced.

[0180] [Negative electrode layer: Other additives] The first negative electrode active material layer 22 may also include additives used in the all-solid-state secondary battery 1 according to the prior art, such as fillers, coating agents, dispersants and / or conductive aids.

[0181] [Negative electrode layer: solid electrolyte] The first negative electrode active material layer 22 may also include a solid electrolyte. The solid electrolyte may be, for example, a material selected from solid electrolytes included in the solid electrolyte layer 30. The solid electrolyte included in the first negative electrode active material layer 22 can serve as a reaction site for the initiation of lithium metal formation in the first negative electrode active material layer 22, can serve as a space for storing the formed lithium metal, or can serve as a pathway for lithium ions to transfer therethrough. Alternatively, a solid electrolyte may not be provided.

[0182] In the first negative electrode active material layer 22, for example, the content (e.g., amount) of solid electrolyte may be high in the region adjacent to the solid electrolyte layer 30 and low in the region adjacent to the negative electrode current collector 21. The solid electrolyte in the first negative electrode active material layer 22 may have, for example, a concentration gradient that decreases from the region adjacent to the solid electrolyte layer 30 to the region adjacent to the negative electrode current collector 21.

[0183] [Negative electrode layer: First negative electrode active material layer] The initial charge capacity B of the first negative electrode active material layer 22 can be less than about 50%, about 45% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less of the initial charge capacity A of the positive electrode active material layer 12. For example, the ratio B / A of the initial charge capacity B of the first negative electrode active material layer 22 to the initial charge capacity A of the positive electrode active material layer 12 can be in the range of about 0.005 to about 0.45. The initial charge capacity of the positive electrode active material layer 12 can be determined by the first open-circuit voltage (OCV) relative to Li / Li + The initial charging capacity of the first negative electrode active material layer 22 can be determined at the maximum charging voltage relative to Li / Li. + Measured at approximately 0.01V.

[0184] The maximum charging voltage can be determined based on the type (variety) of the positive electrode active material. The maximum charging voltage can be, for example, approximately 1.5V, approximately 2.0V, approximately 2.5V, approximately 3.0V, approximately 3.5V, approximately 4.0V, approximately 4.2V, or approximately 4.3V. For example, the maximum charging voltage of Li₂S or a Li₂S complex can be relative to Li / Li + Approximately 2.5V. For example, the maximum charging voltage of Li₂S or Li₂S complexes can be relative to Li / Li + Approximately 3.0V. The ratio B / A of the initial charge capacity B of the first negative electrode active material layer 22 to the initial charge capacity A of the positive electrode active material layer 12 can, for example, be in the range of approximately 0.01 to approximately 0.4, approximately 0.01 to approximately 0.3, approximately 0.01 to approximately 0.2, or approximately 0.05 to approximately 0.1.

[0185] The initial charge capacity (mAh) of the positive electrode active material layer 12 can be obtained by multiplying the specific charge capacity (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer 12. If (for example, when) one or more suitable types (species) of positive electrode active material are used, the specific charge capacity × mass value can be calculated for each positive electrode active material, and the sum of these values ​​can be the initial charge capacity of the positive electrode active material layer 12. The initial charge capacity of the first negative electrode active material layer 22 can also be calculated in substantially the same way. The initial charge capacity of the first negative electrode active material layer 22 can be obtained by multiplying the specific charge capacity (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer 22. If (for example, when) one or more suitable types (species) of negative electrode active material are used, the specific charge capacity × mass value can be calculated for each negative electrode active material, and the sum of these values ​​can be the initial charge capacity of the first negative electrode active material layer 22. The specific charge capacity of the positive and negative active materials can be measured using a solid-state half-cell with lithium metal as the counter electrode. The initial charge capacity of the positive active material layer 12 and the first negative active material layer 22 can be measured using an all-solid-state half-cell at a constant current density (e.g., approximately 0.1 mA / cm²). 2 Direct measurement is possible from the first OCV up to, for example, about 3.0V (relative to Li / Li). + The positive electrode is measured at its maximum charging voltage. For the negative electrode (e.g., lithium metal), measurements can be taken at operating voltages from the 200V up to approximately 0.01V. For example, an all-solid-state half-cell including the positive electrode active material layer 12 can be measured at approximately 0.1mA / cm. 2 A constant current is applied from the first OCV until approximately 3.0V, and the all-solid-state half-cell, including the first negative electrode active material layer 22, can be charged at approximately 0.1mA / cm. 2 A constant current is applied from the second OCV until approximately 0.01V is reached. The current density during constant current charging can be, for example, approximately 0.2 mA / cm². 2 Or approximately 0.5 mA / cm 2 The all-solid-state half-cell, including the positive electrode active material layer 12, can be charged, for example, from the first OCV up to approximately 2.5V, approximately 2.0V, approximately 3.5V, or approximately 4.0V. The maximum charging voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that meets the safety conditions according to JISC8712:2015 of the Japanese Standards Institute.

[0186] If, for example, the initial charge capacity of the first negative electrode active material layer 22 is too low, the first negative electrode active material layer 22 will become very thin. Therefore, during repeated charge / discharge processes, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 will cause the first negative electrode active material layer 22 to collapse, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If, for example, the charge capacity of the first negative electrode active material layer 22 is excessively increased, the energy density of the all-solid-state secondary battery 1 will decrease, and the internal resistance of the all-solid-state secondary battery 1 due to the first negative electrode active material layer 22 will increase, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0187] The thickness of the first negative electrode active material layer 22 can be, for example, about 50% or less, about 40% or less, about 30% or less, about 20% or less, about 10% or less, or about 5% or less of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 can, for example, be in the range of about 1% to about 50%, about 1% to about 40%, about 1% to about 30%, about 1% to about 20%, about 1% to about 10%, or about 1% to about 5% of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 can, for example, be in the range of about 1 μm to about 20 μm, about 2 μm to about 15 μm, or about 3 μm to about 10 μm. If (for example, when) the first negative electrode active material layer 22 is too thin, the lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 will cause the first negative electrode active material layer 22 to collapse, which will make it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If, for example, the thickness of the first negative electrode active material layer 22 is excessively increased, the energy density of the all-solid-state secondary battery 1 will decrease, and the internal resistance of the all-solid-state secondary battery 1 due to the first negative electrode active material layer 22 will increase, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. For example, if, for example, the thickness of the first negative electrode active material layer 22 is decreased, the initial charging capacity of the first negative electrode active material layer 22 will also decrease.

[0188] [Negative electrode layer: Second negative electrode active material layer] In some embodiments, the all-solid-state secondary battery 1 may further include a second negative electrode active material layer disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 after charging. The second negative electrode active material layer may be a metal layer comprising lithium or a lithium alloy. The metal layer may comprise lithium or a lithium alloy. In some embodiments, the second negative electrode active material layer may be a lithium-containing metal layer and thus can be used, for example, as a lithium storage device. Examples of lithium alloys may include Li-Al alloys, Li-Sn alloys, Li-In alloys, Li-Ag alloys, Li-Au alloys, Li-Zn alloys, Li-Ge alloys, Li-Si alloys, etc., but one or more embodiments are not limited thereto. Any material may be used, as long as it is usable as a lithium alloy in the art. The second negative electrode active material layer may comprise one of such alloys or lithium (e.g., composed of one of such alloys or lithium), or may comprise one or more suitable types (types) of alloys (e.g., composed of one or more suitable types (types) of alloys). The second negative electrode active material layer may be, for example, a plating. For example, the second negative electrode active material layer can be deposited between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charging process of the all-solid-state secondary battery 1.

[0189] There is no limitation on the thickness of the second negative electrode active material layer, but it can be, for example, in the range of about 1 μm to about 500 μm, about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 1 μm to about 100 μm, or about 1 μm to about 50 μm. If (for example) the second negative electrode active material layer is too thin, it is difficult for the second negative electrode active material layer to function as a lithium storage device. If (for example) the second negative electrode active material layer is too thick, the mass and volume of the all-solid-state secondary battery 1 will increase, and the cycle characteristics of the all-solid-state secondary battery 1 will actually deteriorate.

[0190] In other embodiments, in the all-solid-state secondary battery 1, for example, a second negative electrode active material layer may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembling the all-solid-state secondary battery 1. If (for example, when) the second negative electrode active material layer 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 may be a metal layer including lithium and thus may act as a lithium storage device. For example, a lithium foil may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembling the all-solid-state secondary battery 1.

[0191] If (for example, when) the second negative electrode active material layer is deposited by charging the all-solid-state secondary battery 1 after assembly, the all-solid-state secondary battery 1 may not include (e.g., may exclude) the second negative electrode active material layer during assembly, thus increasing the energy density of the all-solid-state secondary battery. During charging of the all-solid-state secondary battery 1, the first negative electrode active material layer 22 may be charged beyond its charging capacity. For example, the first negative electrode active material layer 22 may be overcharged. At the start of charging, lithium may be adsorbed into the first negative electrode active material layer 22. The negative electrode active material included in the first negative electrode active material layer 22 may form an alloy or compound together with lithium ions moving from the positive electrode layer 10. If (for example, when) a charge exceeding the capacity of the first negative electrode active material layer 22 is performed, lithium may, for example, be deposited on the rear surface of the first negative electrode active material layer 22 (e.g., 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 may be formed by the deposited lithium. The second negative electrode active material layer can be a metal layer mainly composed of lithium (e.g., metallic lithium). This is achieved, for example, because the negative electrode active material included in the first negative electrode active material layer 22 comprises a material that forms an alloy or compound with lithium. During discharge, lithium (e.g., lithium in the metal layer) in the first negative electrode active material layer 22 and the second negative electrode active material layer can be ionized to move toward the positive electrode layer 10. In some embodiments, lithium can be used as the negative electrode active material in the all-solid-state secondary battery 1. In some embodiments, the first negative electrode active material layer 22 can cover the second negative electrode active material layer, thereby serving as a protective layer for the second negative electrode active material layer (e.g., the metal layer) and simultaneously (e.g., simultaneously) suppressing or reducing the precipitation and growth of lithium dendrites. In some embodiments, short-circuiting and capacity reduction in the all-solid-state secondary battery 1 can be suppressed or reduced, thereby improving the cycle characteristics of the all-solid-state secondary battery 1. In other embodiments, if (for example, when) the second negative electrode active material layer is provided by charging the all-solid-state secondary battery 1 after assembly, the negative electrode layer 20 (e.g., the negative electrode current collector 21, the first negative electrode active material layer 22, and the region therebetween) can be a Li-free region that does not contain lithium (Li) in the initial state of the all-solid-state secondary battery 1 or in the state after it is fully discharged.

[0192] [Negative electrode layer: Negative electrode current collector] The negative electrode current collector 21 may comprise a material that does not react with lithium (e.g., a material that does not form both an alloy and a compound with lithium). Examples of materials constituting the negative electrode current collector 21 may include copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but one or more embodiments are not necessarily limited thereto. Any material may be used, provided that it is suitable for use as an electrode current collector in the art. The negative electrode current collector 21 may comprise one type or class of the aforementioned metals, an alloy of two or more types (classes) of metals, or a coating material (e.g., composed of one type or class of the aforementioned metals, an alloy of two or more types (classes) of metals, or a coating material). The negative electrode current collector 21 may be in the form of, for example, a plate or foil.

[0193] For example, in some embodiments, the all-solid-state secondary battery 1 may further include a thin film comprising elements capable of forming an alloy with lithium on at least one surface of the negative electrode current collector 21. The thin film may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The thin film may include, for example, elements capable of forming an alloy with lithium. Examples of elements capable of forming an alloy with lithium may include gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but one or more embodiments are not necessarily limited to this. Any material may be used, as long as it can form an alloy with lithium in the art. The thin film may include an alloy of one or more suitable types (types) of such metals (e.g., composed of an alloy of one or more suitable types (types) of such metals). The thin film may be disposed on at least one surface of the negative electrode current collector 21 such that, for example, the plating of a second negative electrode active material layer deposited between the thin film and the first negative electrode active material layer 22 can be further planarized, and the cycle characteristics of the all-solid-state secondary battery 1 can be further improved.

[0194] The thickness of the thin film can, for example, be in the range of about 1 nm to about 800 nm, about 10 nm to about 700 nm, about 50 nm to about 600 nm, or about 100 nm to about 500 nm. If the thickness of the thin film is less than about 1 nm, the thin film may be difficult to function. If the film is too thick, the film itself will adsorb lithium, thus reducing the amount of lithium deposited on the negative electrode layer 20, resulting in a decrease in the energy density and cycle characteristics of the all-solid-state secondary battery 1. The thin film can be deposited on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, coating, etc., but one or more embodiments are not limited to such methods. Any method in the art capable of forming a thin film can be used.

[0195] In some embodiments, the negative current collector 21 may include, for example, a substrate film and a metal layer disposed on at least one surface (e.g., one surface or two (e.g., opposite) surfaces) of the substrate film. The substrate film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, PET, polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or combinations thereof. The polymer may be an insulating polymer. The substrate film may include an insulating thermoplastic polymer, so that if (e.g., when) a short circuit occurs, the substrate film may soften or liquefy to interrupt the operation of the battery, thereby suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The negative current collector 21 may additionally include a metal sheet and / or lead terminals. The substrate film, metal layer, metal sheet, and lead terminals of the negative current collector 21 may be defined as in the previously described positive current collector 11. The negative electrode current collector 21 can have such a structure that the weight of the negative electrode layer 20 can be reduced, thereby improving the energy density of the negative electrode layer 20 and the lithium battery.

[0196] Invention patterns This disclosure will be described in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only, and the scope of this disclosure is not limited by the examples.

[0197] (2D sulfide solid electrolyte) Preparation Example 1: First 2D Sulfide Solid Electrolyte As the first 2D sulfide-based solid electrolyte, an rGO-Li6PS5Cl composite was prepared. The rGO-Li6PS5Cl composite was prepared according to the method disclosed in Materials Today Energy 23 (2022) 100913, except that the weight ratio of rGO (reduced graphene oxide) to Li6PS5Cl was changed to approximately 1:60. The rGO-Li6PS5Cl composite was obtained by coating the rGO core with a Li6PS5Cl shell, which is a sulfogermanite-type (or quasi-)crystal. The rGO-Li6PS5Cl composite was in sheet form with a thickness of approximately 1 μm, a length of 3 μm, and an aspect ratio of approximately 3. The rGO-Li6PS5Cl composite had a polygonal shape in the planar image. The thickness and length of the rGO-Li6PS5Cl composite were each averaged calculated from multiple composite particles read from SEM images.

[0198] (All-solid-state rechargeable battery) Example 1: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material (Li2S-C-LiI complex), flake solid electrolyte: particulate solid electrolyte weight ratio = approximately 10:40, including first 2D sulfide-based solid electrolyte. (Preparation of the negative electrode layer) Prepare a stainless steel (SUS) foil with a thickness of approximately 10 μm as the negative electrode current collector. For example, prepare CB particles with a primary particle size of approximately 30 nm and silver (Ag) particles with an average particle size of approximately 60 nm as the negative electrode active material.

[0199] Approximately 4 g of a mixed powder obtained by mixing CB particles and silver (Ag) particles in a weight ratio of approximately 3:1 was placed in a container, and approximately 4 g of an N-methyl-2-pyrrolidone (NMP) solution including approximately 7 wt% PVDF binder (Kureha #9300) was added to prepare a mixed solution. The mixed solution was stirred while NMP was added little by little to prepare a slurry. The prepared slurry was applied to an SUS sheet using a bar coater and dried in air at approximately 80°C for approximately 10 minutes to prepare a stack. The prepared stack was vacuum dried at approximately 40°C for approximately 10 hours. The dried stack was cold-rolled to planarize the surface of the first negative electrode active material layer to prepare a negative electrode layer. The thickness of the first negative electrode active material layer was approximately 15 μm. The area of ​​the first negative electrode active material layer was equal to the area of ​​the negative electrode current collector. The initial charge capacity of the negative electrode (i.e., the first negative electrode active material layer) was measured using a half-cell as described previously.

[0200] (Preparation of the positive electrode layer) A Li₂S-C-LiI composite was prepared as the positive electrode active material. The Li₂S-C-LiI composite was prepared according to the method disclosed in Nano Lett. 2016, 16, 7, pp4521-4527, except that Li₆PS₅Cl was replaced with LiI. The rGO-Li₆PS₅Cl composite prepared in Preparation Example 1 was prepared as the first 2D sulfide-type solid electrolyte. Li₆PS₅Cl (D₅₀ = approximately 3.0 μm, crystalline) as a sulfargillite-type or sulfargillite-like (e.g., sulfargillite) crystal was prepared as an irregularly shaped particulate solid electrolyte. KB was prepared as the conductive material. The aspect ratio of the irregularly shaped particulate solid electrolyte was less than approximately 2.

[0201] These materials are mixed such that the positive electrode active material, the first 2D sulfide-based solid electrolyte, the irregularly shaped particulate solid electrolyte, and the conductive agent have a weight ratio of approximately 40:10:40:10, thereby preparing a positive electrode mixture. The positive electrode mixture is obtained by dry mixing using a ball mill. The positive electrode mixture obtained by ball milling forms an ionic and electronic conductive network.

[0202] A positive electrode mixture is placed on at least one surface of a positive electrode current collector made of aluminum foil, one surface of which is coated with carbon, and pressed at a pressure of about 200 MPa for about 10 minutes to prepare a positive electrode layer. The thickness of the positive electrode layer is about 120 μm. The thickness of the positive electrode active material layer is about 100 μm, and the thickness of the carbon-coated aluminum foil is about 20 μm. The area of ​​the positive electrode active material layer is equal to the area of ​​the positive electrode current collector. The initial charge capacity of the positive electrode (i.e., the positive electrode active material layer) is measured using the above half-cell. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer is less than 0.5. The initial charge capacity of the positive electrode active material layer is obtained by charging from a first open-circuit voltage to about 2.8V (relative to Li / Li). + The initial charge capacity of the first negative electrode active material layer is determined by charging from the second open-circuit voltage to approximately 0.01V (relative to Li / Li). + The ratio (B / A) is measured using the method described above. Furthermore, in each of Examples 2 through 10 and Example 12, the ratio (B / A) is also less than 0.5.

[0203] (Preparation of solid electrolyte layer) The mixture was prepared as follows: Approximately 1.5 parts by weight of an acrylic binder was added to a Li6PS5Cl solid electrolyte (D50 = approximately 3.0 μm, crystalline) as a sulforaphite-type or sulforaphite-type (e.g., sulforaphite) crystal, relative to approximately 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 to a nonwoven fabric of approximately 15 μm thickness placed on a PET substrate of approximately 75 μm thickness using a bar coater and dried in air at approximately 80°C for approximately 10 minutes to obtain a stack. The obtained stack was then vacuum dried at approximately 80°C for approximately 2 hours. The solid electrolyte layer was prepared through this process.

[0204] (Flame-retardant non-active components) The pulp obtained by mixing pulp fibers (cellulose fibers), glass fibers, aluminum hydroxide (Al(OH)3), acrylic binders and solvents is molded into gasket shapes, and then the solvent is removed to prepare flame-retardant inactive components.

[0205] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder is approximately 20:8:70:2. The thickness of the inactive component is approximately 120 μm.

[0206] Before placing the prepared flame-retardant inactive component on the solid electrolyte layer, it is subjected to vacuum heat treatment at a temperature of about 80°C for about 5 hours to remove moisture and other substances from the flame-retardant inactive component.

[0207] (Manufacturing of all-solid-state secondary batteries) Reference Figure 10 A solid electrolyte layer is placed on the negative electrode layer, so that the first negative electrode active material layer is in contact with the solid electrolyte layer. A flame-retardant inactive component is hot-pressed and placed on the solid electrolyte layer to prepare a negative electrode layer / solid electrolyte layer / inactive component stack.

[0208] A negative electrode layer / solid electrolyte layer / inactive component stack is disposed on at least one surface of a positive electrode layer, such that the inactive component is opposite to the positive electrode active material layer, thereby fabricating a negative electrode layer / solid electrolyte layer / positive electrode layer electrode assembly. The inactive component is disposed around the positive electrode layer to surround the side surface of the positive electrode layer and to contact the solid electrolyte layer. The inactive component serves as a gasket. The positive electrode layer is disposed in the central portion of the solid electrolyte layer, and the gasket is configured to surround the positive electrode layer and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode layer is approximately 90% of the area of ​​the solid electrolyte layer, and the gasket is disposed in the remaining 10% of the total area of ​​the solid electrolyte layer where the positive electrode layer is not disposed.

[0209] The prepared negative electrode / solid electrolyte / positive electrode assembly is plate-pressed. This pressing allows the solid electrolyte layer to be sintered to improve battery characteristics. The thickness of the sintered solid electrolyte layer is approximately 45 μm. The sintered electrode assembly is then placed in a bag and sealed to prepare a sealed electrode assembly. The portions of the positive and negative current collectors extend to the outside of the sealed electrode assembly and serve as positive and negative electrode layer terminals.

[0210] An electrode assembly is placed between two pressure plates, which are then bolted together to apply pressure to the two surfaces of the electrode assembly, thereby manufacturing an all-solid-state secondary battery.

[0211] Example 2: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI composite, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 5:45, including first 2D sulfide-based solid electrolyte. Except for changing the weight ratio of sheet solid electrolyte to particulate solid electrolyte to about 5:45, the all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1.

[0212] Example 3: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI composite, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 20:20, including first 2D sulfide-based solid electrolyte. Except for changing the weight ratio of sheet solid electrolyte to particulate solid electrolyte to about 20:20, the all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1.

[0213] Example 4: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI composite, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 30:20, including first 2D sulfide-based solid electrolyte. Except for changing the weight ratio of sheet solid electrolyte to particulate solid electrolyte to about 30:20, the all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1.

[0214] Example 5: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI composite, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 40:10, including first 2D sulfide-based solid electrolyte. Except for changing the weight ratio of sheet solid electrolyte to particulate solid electrolyte to about 40:10, the all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1.

[0215] Example 6: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI-2D sulfide-based solid electrolyte complex, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 10:40, first 2D sulfide-based solid electrolyte and second 2D sulfide-based solid electrolyte The all-solid-state secondary battery was manufactured in essentially the same manner as in Example 1, except that a Li2S-C-LiI-2D sulfide-based solid electrolyte complex was used instead of the Li2S-C-LiI complex as the positive electrode active material.

[0216] The Li2S-C-LiI-2D sulfide solid electrolyte complex was prepared by the following method.

[0217] The Li2S-C-LiI complex was prepared in essentially the same manner as in Example 1. The Li2S-C-LiF complex and the rGO-Li6PS5Cl complex prepared in Example 1 were mixed at a low speed in a weight ratio of approximately 4:1 using a mixer to form a mixture. This mixture was then further mixed using a mixer at a speed of approximately 100 rpm to approximately 2,000 rpm for approximately 0.1 hours to approximately 20 hours to form a complex, thus preparing the Li2S-C-LiI-2D sulfide solid electrolyte complex.

[0218] Example 7: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI-2D sulfide-based solid electrolyte complex, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 0:50, second 2D sulfide-based solid electrolyte The all-solid-state secondary battery was manufactured in essentially the same manner as in Example 1, except that: the Li2S-C-LiI-2D sulfide-based solid electrolyte complex used in Example 6 was used instead of the Li2S-C-LiI complex as the positive electrode active material, and the weight ratio of sheet solid electrolyte to particulate solid electrolyte in the positive electrode mixture was changed to about 0:50, and the sheet solid electrolyte was not used.

[0219] Example 8: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI composite, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 10:40, two layers of positive electrode active material, sheet-like solid electrolyte disposed on the top layer. A first positive electrode mixture was prepared in substantially the same manner as in Example 1.

[0220] The second positive electrode mixture was prepared in essentially the same manner as in Example 1, except that the sheet solid electrolyte was not used, but the weight ratio of the sheet solid electrolyte to the particulate solid electrolyte was changed to about 0:50.

[0221] The all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1, except that a first positive electrode mixture (containing a sheet-like solid electrolyte) and a second positive electrode mixture (excluding a sheet-like solid electrolyte) are sequentially disposed on the positive electrode current collector to prepare a positive electrode layer.

[0222] The positive electrode active material layer includes a first positive electrode active material layer derived from a first positive electrode mixture and a second positive electrode active material layer derived from a second positive electrode mixture, and each of the first positive electrode active material layer and the second positive electrode active material layer has a thickness of approximately 50 μm.

[0223] The first positive electrode active material layer adjacent to the positive electrode current collector includes a sheet-like solid electrolyte, and the second positive electrode active material layer adjacent to the solid electrolyte layer does not contain a sheet-like solid electrolyte.

[0224] Example 9: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI composite, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 10:40, two layers of positive electrode active material, sheet-like solid electrolyte set at the bottom layer. The all-solid-state secondary battery is manufactured in essentially the same manner as in Example 8, except that the positions of the first and second positive electrode active material layers are reversed, with the second positive electrode active material layer arranged adjacent to the positive electrode current collector and the first positive electrode active material layer arranged adjacent to the solid electrolyte layer. The second positive electrode active material layer adjacent to the positive electrode current collector does not contain sheet-like solid electrolyte, and the first positive electrode active material layer adjacent to the solid electrolyte layer includes sheet-like solid electrolyte.

[0225] Example 10: Single-cell all-solid-state secondary battery, oxide-based positive electrode active material NCA, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 10:40 (Preparation of the positive electrode layer) Prepare LiNi0.8Co0 coated with LZO. 15 Mn0. 05 O2 (NCM) was used as the positive electrode active material. A positive electrode active material coated with LZO was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. The rGO-Li6PS5Cl composite prepared in Preparation Example 1 was prepared as the first 2D sulfide-based solid electrolyte. Li6PS5Cl (D50 = approximately 0.5 μm, crystalline) as an irregularly shaped particulate solid electrolyte was prepared as a sulfarginite-type or sulfarginite-based (e.g., sulfarginite) crystal. PTFE binder was prepared as a binder. CNF was prepared as a conductive agent. A slurry comprising the positive electrode active material, the first 2D sulfide-based solid electrolyte, the irregularly shaped particulate solid electrolyte, the conductive agent, and the binder in a weight ratio of approximately 84:2:9.5:3:1.5 was mixed with xylene solvent to prepare a slurry, which was then formed into a sheet and vacuum dried at approximately 40°C for approximately 8 hours to prepare the positive electrode sheet. The prepared positive electrode sheet is disposed on a carbon layer comprising an aluminum foil (e.g., composed of aluminum foil) and a positive electrode current collector having a carbon layer coated on at least one surface, and heated and rolled at a temperature of about 85°C to prepare the positive electrode layer. The total thickness of the positive electrode layer is about 120 μm. The thickness of the positive electrode active material layer is about 95 μm, and the thickness of the carbon-coated aluminum foil is about 25 μm.

[0226] (Manufacturing of all-solid-state secondary batteries) The all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1, except that the previously described positive electrode layer is used.

[0227] Example 11: Single-cell all-solid-state secondary battery, oxide-based positive electrode active material NCA, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 0:50, first 2D sulfide-based solid electrolyte, solid electrolyte layer is a stack of first 2D sulfide-based solid electrolytes. (Preparation of the positive electrode layer) A novel cathode active material coated with LZO was prepared. The LZO-coated cathode active material was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. Li6PS5Cl (D50 = approximately 0.5 μm, crystalline) as a sulfargillite-type or sulfargillite-like (e.g., sulfargillite) crystal was prepared as a solid electrolyte. A PTFE binder was prepared as a binder. CNF was prepared as a conductive agent. A slurry comprising the cathode active material, a first 2D sulfide-type solid electrolyte, irregularly shaped particulate solid electrolyte, a conductive agent, and a binder in a weight ratio of approximately 84:0:11.5:3:1.5 was mixed with xylene solvent to prepare a slurry. The slurry was formed into a sheet and then vacuum-dried at approximately 40°C for approximately 8 hours to prepare a cathode sheet. The prepared positive electrode sheet is disposed on a carbon layer comprising an aluminum foil (e.g., composed of aluminum foil) and a positive electrode current collector having a carbon layer coated on at least one surface thereon, and heated and rolled at a temperature of approximately 85°C to prepare the positive electrode layer. The total thickness of the positive electrode layer is approximately 120 μm. The thickness of the positive electrode active material layer is approximately 95 μm, and the thickness of the carbon-coated aluminum foil is approximately 25 μm. The initial charge capacity of the positive electrode (i.e., the positive electrode active material layer) is measured using the above half-cell. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer is less than 0.5. The initial charge capacity of the positive electrode active material layer is obtained by charging from a first open-circuit voltage to approximately 4.25V (relative to Li / Li). + The initial charge capacity of the first negative electrode active material layer is determined by charging from the second open-circuit voltage to approximately 0.01V (relative to Li / Li). + (To measure)

[0228] (Preparation of solid electrolyte layer) A mixture was prepared by adding approximately 1.5 parts by weight of an acrylic binder to approximately 98.5 parts by weight of the rGO-Li6PS5Cl composite, which was prepared as the first 2D sulfide-based solid electrolyte in Preparation Example 1. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied to a nonwoven fabric of approximately 15 μm thickness placed on a PET substrate of approximately 75 μm thickness using a bar coater and dried in air at approximately 80°C for approximately 10 minutes to obtain a stack. The obtained stack was then vacuum dried at approximately 80°C for approximately 2 hours. A solid electrolyte layer was prepared through this process.

[0229] (Manufacturing of all-solid-state secondary batteries) The all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1, except that the previously described positive electrode layer and solid electrolyte are used.

[0230] Comparison Example 1: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI composite, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 0:50 The all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1, except that the sheet solid electrolyte is not used, but rather the weight ratio of sheet solid electrolyte to particulate solid electrolyte is changed to approximately 0:50.

[0231] Comparison Example 2: Single-cell all-solid-state secondary battery, oxide-based positive electrode active material NCA, sheet-like solid electrolyte: particulate solid electrolyte weight ratio = 0:50 The all-solid-state secondary battery is manufactured in essentially the same manner as in Example 10, except that the sheet solid electrolyte is not used by changing the weight ratio of sheet solid electrolyte to particulate solid electrolyte to about 0:50.

[0232] Comparative Example 3: Single-cell all-solid-state secondary battery, sulfide-based positive electrode active material Li2S-C-LiI complex, and sheet-like solid electrolyte complex using a simple mixture of rGO and Li6PS5Cl instead of rGO and Li6PS5Cl. The all-solid-state secondary battery is used in essentially the same manner as in Example 1, except that a mixture of rGO and Li6PS5Cl with a weight ratio of about 1:60 is used instead of the sheet solid electrolyte (a composite of rGO and Li6PS5Cl).

[0233] Comparative Example 4: Single-cell all-solid-state secondary battery, oxide-based positive electrode active material NCA, and sheet-like solid electrolyte complex using a simple mixture of rGO and Li6PS5Cl instead of rGO and Li6PS5Cl. The all-solid-state secondary battery is used in essentially the same manner as in Example 10, except that a mixture of rGO and Li6PS5Cl with a weight ratio of about 1:60 is used instead of the sheet solid electrolyte (a composite of rGO and Li6PS5Cl).

[0234] Reference Example 1: Sulfide-based positive electrode active materials, without the use of inactive components. The all-solid-state secondary battery is manufactured in essentially the same manner as in Example 1, except that flame-retardant inactive components (e.g., gaskets) are not used during the manufacture of the all-solid-state secondary battery.

[0235] Reference Example 2: Oxide-based positive electrode active material, without using inactive components The all-solid-state secondary battery is manufactured in substantially the same manner as in Example 10, except that flame-retardant inactive components (e.g., gaskets) are not used during the manufacture of the all-solid-state secondary battery.

[0236] Example 12: A dual-cell all-solid-state secondary battery, a sulfide-based positive electrode active material Li2S-C-LiI composite, a sheet-like solid electrolyte to particulate solid electrolyte weight ratio of 10:40, and a first 2D sulfide-based solid electrolyte. Manufacturing of dual-cell all-solid-state secondary batteries Except that the positive electrode active material layer is prepared as disposed on the two surfaces of the positive electrode current collector, the positive electrode layer is prepared in essentially the same manner as in Example 1.

[0237] The total thickness of the positive electrode layer is approximately 220 μm. The thickness of each positive electrode active material layer is approximately 100 μm, and the thickness of the carbon-coated aluminum foil is approximately 20 μm.

[0238] Two negative electrode layers, two solid electrolyte layers, and two flame-retardant inactive components were prepared in essentially the same manner as in Example 1.

[0239] Reference Figure 3 A solid electrolyte layer is disposed on the negative electrode layer, such that the first negative electrode active material layer is in contact with the solid electrolyte layer, and a positive electrode layer is disposed on the solid electrolyte layer. The positive electrode layer has a structure in which the positive electrode active material layer is disposed on each of the two surfaces of the positive electrode current collector. A gasket is disposed around the positive electrode layer to surround the positive electrode layer and to contact the solid electrolyte layer. The thickness of the gasket is approximately 220 μm. For example, the gasket can have a structure of two gaskets stacked together with a thickness of approximately 110 μm, or it can be configured as a single gasket with a thickness of approximately 220 μm. The aforementioned flame-retardant inactive component is used as the gasket.

[0240] A gasket is positioned to contact the side surface of the positive electrode layer and the solid electrolyte layer. The positive electrode layer is disposed in the central portion of the solid electrolyte layer, and the gasket is positioned to surround the positive electrode layer and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode layer is approximately 90% of the area of ​​the solid electrolyte layer, and the gasket is disposed in the remaining approximately 10% of the total area of ​​the solid electrolyte layer where the positive electrode layer is not disposed. A solid electrolyte layer is disposed on the positive electrode layer and the gasket, and a negative electrode layer is disposed on the solid electrolyte layer to fabricate a stack.

[0241] The prepared stack is pressed at approximately 85°C. This pressing allows the solid electrolyte layer to be sintered to improve battery characteristics. The thickness of a sintered solid electrolyte layer is approximately 45 μm. The area of ​​the solid electrolyte layer is equal to the area of ​​the negative electrode layer. The pressed stack is placed in a bag and vacuum-sealed to manufacture an all-solid-state secondary battery. The portions of the positive and negative current collectors extend to the outside of the sealed battery and serve as positive and negative electrode layer terminals.

[0242] Evaluation Example 1: High-Temperature Lifetime Characteristic Test The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 9, Example 12, Comparative Example 1, Comparative Example 3, and Reference Example 1 were evaluated by the following charge / discharge tests. The all-solid-state secondary batteries were placed in a thermostatic bath at approximately 45°C for the charge / discharge tests.

[0243] In the first cycle, the all-solid-state secondary battery was operated at approximately 0.6 mA / cm². 2 The battery was charged with a constant current for approximately 12.5 hours until the battery voltage reached approximately 2.5V to approximately 2.8V. Subsequently, the all-solid-state secondary battery was charged at approximately 0.6mA / cm². 2 The constant current discharge lasts for about 12.5 hours until the battery voltage reaches about 0.5V.

[0244] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 10, 11, Comparative Example 4, and Reference Example 2 were evaluated by the following charge / discharge tests. The all-solid-state secondary batteries were placed in a thermostatic bath at approximately 45°C for the charge / discharge tests.

[0245] In the first cycle, the all-solid-state secondary battery was operated at approximately 0.6 mA / cm². 2 The battery was charged with a constant current for approximately 12.5 hours until the battery voltage reached approximately 3.9V to approximately 4.25V. Subsequently, the all-solid-state secondary battery was charged at approximately 0.6mA / cm². 2 The constant current discharge lasts for about 12.5 hours until the battery voltage reaches about 2.5V.

[0246] The discharge capacity of the first cycle was used as the standard capacity. Starting from the second cycle, charging and discharging were performed under the same conditions as the first cycle until the 150th cycle. The measurement results are shown in Table 2.

[0247] It is believed that the lifetime characteristics improve as the number of cycles required for the discharge capacity to decrease to about 95% of the standard capacity after the second cycle increases.

[0248] In the all-solid-state secondary batteries of Reference Example 1 and Reference Example 2, a short circuit occurs before the completion of the first cycle, making it impossible to measure lifetime characteristics.

[0249] Table 1

[0250] As shown in Table 1, the lifetime characteristics of the all-solid-state secondary batteries including the sulfide-based positive electrode active materials of Examples 1 to 9 and Example 12 are improved compared with the all-solid-state secondary batteries of Comparative Examples 1 and 3.

[0251] It is determined that the all-solid-state secondary batteries of Examples 1 to 9 include a sheet-like solid electrolyte to have an increased ion conduction path and to more effectively accommodate volume changes in the positive electrode active material during charging or discharging, thereby improving lifetime characteristics.

[0252] In the all-solid-state secondary batteries of Examples 1 to 5, the lifetime characteristics vary depending on the weight ratio of sheet-like solid electrolyte to particulate solid electrolyte.

[0253] Compared to the all-solid-state secondary battery of Comparative Example 3, which includes a simple mixture of graphene and a solid electrolyte, the all-solid-state secondary battery including the sheet-like solid electrolyte of Example 1 exhibits improved lifetime characteristics. It is determined that the performance of the all-solid-state secondary battery is degraded by the simple mixture of graphene and solid electrolyte due to increased side reactions caused by inhomogeneous mixing.

[0254] Compared with the all-solid-state secondary batteries of Comparative Examples 2 and 4, the all-solid-state secondary batteries including the oxide-based positive electrode active materials of Examples 10 and 11 have improved lifetime characteristics.

[0255] It is determined that placing the sheet-like solid electrolyte in the positive electrode active material layer gives the all-solid-state secondary battery of Example 10 an increased ion conduction path and allows it to more effectively adapt to volume changes in the positive electrode active material during charging or discharging to improve lifetime characteristics.

[0256] It is confirmed that in the all-solid-state secondary battery of Example 11, a sheet-like solid electrolyte is disposed in the solid electrolyte layer to reduce the formation of pinholes on the surface of the solid electrolyte layer, thereby suppressing or reducing cracks in the solid electrolyte layer and short circuits caused by cracks, so as to improve lifetime characteristics.

[0257] Compared to the all-solid-state secondary battery of Comparative Example 4, which comprises a simple mixture of graphene and a solid electrolyte, the all-solid-state secondary battery of Example 10, comprising a sheet-like solid electrolyte, exhibits improved lifetime characteristics. It is determined that the performance of the all-solid-state secondary battery is degraded by the simple mixture of graphene and solid electrolyte due to the increase in side reactions caused by inhomogeneous mixing.

[0258] It is certain that, due to the symmetrical arrangement of the dual-cell structure of each component, the volume change during charging or discharging is effectively reduced, and therefore the all-solid-state secondary battery of Example 12 has improved life characteristics compared with the all-solid-state secondary batteries of Examples 1 to 5 which have a single-cell structure.

[0259] After the first charge cycle was completed in the all-solid-state secondary batteries of Examples 1 to 12, SEM images of the cross-section of each battery were measured to confirm the formation of a lithium metal plating corresponding to the second negative electrode active material layer between the solid electrolyte layer and the negative electrode current collector.

[0260] As described above, the all-solid-state secondary battery according to the embodiments can be applied to one or more suitable portable devices, vehicles, etc.

[0261] Although embodiments have been described in more detail with reference to the accompanying drawings, this disclosure is not limited to these embodiments. It will be apparent to those skilled in the art to which this disclosure pertains that one or more suitable changes and modifications may occur within the scope of the technical concept described in the claims, and those are to be understood to naturally fall within the technical scope of this disclosure.

[0262] List of reference numerals for key components 1 all-solid-state secondary battery; 10 positive electrode layers 11 Positive current collector; 12 Positive active material layer 20 Negative electrode layer; 21 Negative electrode current collector 22 First negative electrode active material layer; 30 Solid electrolyte layer 40 Inactive Components 100 First 2D sulfide solid electrolyte 110 cores; 120 shells 130 intermediate layer 200 First 2D sulfide-based solid electrolyte stack.

[0263] Industrial applicability According to one aspect, according to an all-solid-state secondary battery with a novel structure, an all-solid-state secondary battery in which short circuits are suppressed or reduced and cycle characteristics are improved can be provided.

Claims

1. An all-solid-state secondary battery, the all-solid-state secondary battery comprising: Positive electrode layer; Negative electrode layer; as well as A solid electrolyte layer is located between the positive electrode layer and the negative electrode layer. in, The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on at least one surface of the positive electrode current collector. At least one of the positive electrode active material layer and the solid electrolyte layer includes a first two-dimensional sulfide solid electrolyte, and The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on at least one surface of the negative electrode current collector, and Wherein, the initial charging capacity B of the first negative electrode active material layer is less than 50% of the initial charging capacity A of the positive electrode active material layer.

2. The all-solid-state secondary battery according to claim 1, wherein, The first two-dimensional sulfide solid electrolyte is defined by its length and thickness. The aspect ratio of the length to the thickness is 3 or greater. The first two-dimensional sulfide-based solid electrolyte has a length of 1 μm to 50 μm and a thickness of 10 nm to 30 μm, and The first two-dimensional sulfide solid electrolyte includes plate structure, chip structure, sheet structure or combination thereof.

3. The all-solid-state secondary battery according to claim 1, wherein, The surface of the first two-dimensional sulfide-based solid electrolyte has an irregular shape, a circular shape, or a polygonal shape, and The polygonal shapes include triangular, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, or decagonal shapes.

4. The all-solid-state secondary battery according to claim 1, wherein, The first two-dimensional sulfide-based solid electrolyte comprises a core and a shell on the core, and in, The core includes carbon-based materials, polymers, metal-containing inorganic materials, sulfide solid electrolytes, oxide solid electrolytes, or combinations thereof. The shell may comprise a sulfide solid electrolyte, an oxide solid electrolyte, a coating material, or a combination thereof. At least one of the core and the shell comprises a sulfide-based solid electrolyte, and The core comprises a two-dimensional nanostructure, and The two-dimensional nanostructures include graphene, graphene oxide, reduced graphene oxide, carbon nanoribbons, carbon nanosheets, carbon nanoplates, carbon nanofibers, SiO2, TiO2, Al2O3, AlN, SiC, BaTiO3, or combinations thereof.

5. The all-solid-state secondary battery according to claim 4, wherein, The ratio of the first thickness of the core to the second thickness of the shell is in the range of 1:0.01 to 1:1,000, and The ratio of the first length of the core to the second length of the shell is in the range of 1:1 to 1:

100.

6. The all-solid-state secondary battery according to claim 1, wherein, The positive electrode active material layer includes a first region adjacent to the positive electrode current collector and a second region adjacent to the solid electrolyte layer, and in: The first two-dimensional sulfide solid electrolyte is located in the first region and is not present in the second region; The first two-dimensional sulfide solid electrolyte is located in the second region and is not present in the first region; or The first two-dimensional sulfide solid electrolyte is located in each of the first and second regions.

7. The all-solid-state secondary battery according to claim 1, wherein, The content of the first two-dimensional sulfide solid electrolyte is in the range of 1 wt% to 50 wt% of the total weight of the positive electrode active material layer. The positive electrode active material layer also includes an irregularly shaped sulfide solid electrolyte, which is different from the first two-dimensional sulfide solid electrolyte, and The weight ratio of the first two-dimensional sulfide solid electrolyte to the irregular sulfide solid electrolyte is in the range of 1:99 to 99:

1.

8. The all-solid-state secondary battery according to claim 1, wherein, The positive electrode active material layer includes a positive electrode active material. The positive electrode active material includes oxide-based positive electrode active materials, sulfide-based positive electrode active materials, or combinations thereof. The oxide-based positive electrode active material includes lithium transition metal oxides, metal oxides, or combinations thereof. The lithium transition metal oxides include lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron phosphate, or combinations thereof. The metal oxides include iron oxides, vanadium oxides, or combinations thereof. The sulfide-based positive electrode active materials include nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof.

9. The all-solid-state secondary battery according to claim 8, wherein, The Li2S-containing complexes include: complexes of Li2S and carbon; complexes of Li2S, carbon, and solid electrolytes; complexes of Li2S and solid electrolytes; complexes of Li2S and lithium salts; complexes of Li2S, lithium salts, and carbon; complexes of Li2S and metal carbides; complexes of Li2S, carbon, and metal carbides; complexes of Li2S and metal nitrides; complexes of Li2S, carbon, and metal nitrides; or combinations thereof.

10. The all-solid-state secondary battery according to claim 8, wherein, The Li2S-containing complex also includes a second two-dimensional sulfide solid electrolyte, and The size of the second two-dimensional sulfide solid electrolyte is smaller than that of the first two-dimensional sulfide solid electrolyte.

11. The all-solid-state secondary battery according to claim 1, wherein, The positive electrode active material layer further includes at least one selected from conductive materials and binders, and The conductive material includes carbon-based conductive materials.

12. The all-solid-state secondary battery according to claim 1, further comprising an inactive component on at least one side surface of the positive electrode layer. in, The inactive component extends along the side surface of the positive electrode layer to surround the positive electrode layer and includes a positioning portion configured to determine the position of the inactive component on the solid electrolyte layer.

13. The all-solid-state secondary battery according to claim 1, wherein, The solid electrolyte layer includes a first two-dimensional sulfide-type solid electrolyte arranged in one direction.

14. The all-solid-state secondary battery according to claim 13, wherein, The first two-dimensional sulfide-based solid electrolyte is arranged in a direction perpendicular to the thickness direction of the solid electrolyte layer, and is stacked in the thickness direction of the solid electrolyte layer. The content of the first two-dimensional sulfide solid electrolyte is 50 wt% or more of the total weight of the solid electrolyte layer.

15. The all-solid-state secondary battery according to claim 1, wherein, The first negative electrode active material layer includes a negative electrode active material and a binder, and The negative electrode active material has a particulate form and an average particle size of 4 μm or smaller.

16. The all-solid-state secondary battery according to claim 15, wherein, The negative electrode active material includes at least one selected from carbon-based negative electrode active materials and metal-based negative electrode active materials, and in, The carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or combinations thereof, and The metallic anode active material includes gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or combinations thereof.

17. The all-solid-state secondary battery according to claim 15, wherein, The negative electrode active material comprises a mixture of first particles and second particles. The first particle comprises amorphous carbon, and the second particle comprises a metal or a metalloid. The content of the second particle is in the range of 8 wt% to 60 wt% relative to the total weight of the mixture.

18. The all-solid-state secondary battery according to claim 15, wherein, The negative electrode active material includes a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support, and in, The metal-based negative electrode active material includes metals, metal oxides, complexes of metals and metal oxides, or combinations thereof. The metal-based negative electrode active material has a particulate form and a particle size of 1 nm to 200 nm, and The carbon-based support has particulate form and a particle size of 10 nm to 2 μm.

19. The all-solid-state secondary battery according to claim 1, further comprising a second negative electrode active material layer between the solid electrolyte layer and the negative electrode current collector. in, The second negative electrode active material layer is located between the first negative electrode active material layer and the negative electrode current collector and / or between the first negative electrode active material layer and the solid electrolyte layer, and The second negative electrode active material layer is a metal layer comprising lithium metal or lithium alloy.

20. The all-solid-state secondary battery according to claim 1, wherein, At least one of the positive electrode current collector and the negative electrode current collector includes a substrate film and a metal layer on at least one surface of the substrate film, and in, The substrate film comprises a polymer, including polyethylene terephthalate, polyethylene, polypropylene, polybutylene terephthalate, polyimide, or combinations thereof, and The metal layer includes indium, copper, magnesium, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, lithium, or alloys thereof.

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