All-solid-state secondary battery

Abstract

An all-solid-state secondary battery is provided, comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The positive electrode layer comprises a positive current collector and a positive active material layer on one side of the positive current collector. The negative electrode layer comprises a negative current collector and a first negative active material layer on one side of the negative current collector. The first negative active material layer comprises a first negative active material and a carbon-based material, and the first negative active material comprises an alloy phase.

Description

Technical Field

[0001] This disclosure relates to all-solid-state secondary batteries. Background Technology

[0002] Recently, batteries with high energy density and high safety have been actively developed to meet industrial needs. For example, lithium batteries are used in various applications, including information devices, communication devices, and vehicles. Because vehicles significantly impact people's lives, safety is also crucial.

[0003] Short circuits in lithium-ion batteries using liquid electrolytes can increase the likelihood of fire and / or explosion. All-solid-state secondary batteries using solid electrolytes instead of liquid electrolytes have been proposed. Solid electrolytes are less likely to catch fire than liquid electrolytes.

[0004] Because all-solid-state secondary batteries use a solid electrolyte instead of a liquid electrolyte, the possibility of fire or explosion is reduced. All-solid-state batteries offer improved safety. Summary of the Invention

[0005] Technical issues

[0006] On the one hand, it provides an all-solid-state secondary battery, wherein the negative electrode active material layer includes a first negative electrode active material having an alloy phase, thereby suppressing volume changes during charging and discharging and improving charging and discharging characteristics.

[0007] Problem Solution

[0008] According to an embodiment, an all-solid-state secondary battery is provided, the all-solid-state secondary battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive current collector and a positive active material layer on one side of the positive current collector, the negative electrode layer includes a negative current collector and a first negative active material layer on one side of the negative current collector, the first negative active material layer includes a first negative active material and a carbon-based material, and the first negative active material includes an alloy phase.

[0009] Beneficial effects of the invention

[0010] According to one aspect, an all-solid-state secondary battery is provided, wherein the negative electrode active material layer includes a first negative electrode active material having an alloy phase, thereby suppressing the reduction of volumetric energy density, suppressing volume changes during charging and discharging, and improving lifespan and high-rate characteristics. Attached Figure Description

[0011] Figure 1 To ~ Figure 12 This is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0012] <List of reference numerals for key components>

[0013] 1: All-solid-state secondary battery; 10: Positive electrode

[0014] 11: Positive electrode current collector; 12: Positive electrode active material layer

[0015] 20: Negative electrode 21: Negative electrode current collector

[0016] 22: First negative electrode active material layer 23: Thin film

[0017] 24: Second negative electrode active material layer; 30: Solid electrolyte layer

[0018] 40 (40a or 40b): First inactive component; 50: Second inactive component Detailed Implementation

[0019] Unless otherwise specified, all terms used in this disclosure (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. Furthermore, terms (such as those defined in common dictionaries) shall be interpreted as having the same meaning as they have in the relevant field and in the context of this disclosure, and shall not be interpreted in an idealized or overly formal sense.

[0020] This disclosure illustrates exemplary embodiments with reference to cross-sectional views, which are schematic diagrams of ideal embodiments. Therefore, deviations in the illustrated shapes are expected due to factors such as manufacturing techniques and / or tolerances. Accordingly, the embodiments described in this disclosure should not be construed as limited to the specific shapes of the regions illustrated herein, but rather include deviations in shape, for example, due to manufacturing processes. For instance, regions illustrated or described as flat may generally have rough and / or non-linear characteristics. Furthermore, corners illustrated as sharp angles may be rounded. Thus, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0021] The inventive concept can be embodied in many different forms and should not be construed as limited to the embodiments set forth in this disclosure. The provision of embodiments makes this disclosure thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. The same reference numerals refer to the same elements.

[0022] When a component is described as being "on" another component, it will be understood that the component may be directly placed on the other component or that another component may be inserted between them. On the other hand, when a component is described as being "directly on" another component, no other component is inserted between them.

[0023] It should be understood that although the terms "first," "second," and "third" may be used in this disclosure to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this disclosure, the first element, component, area, layer, or portion described below may be referred to as the second element, component, area, layer, or portion.

[0024] The terminology used herein is intended to describe particular embodiments only and is not intended to limit the inventive concept. The singular forms (including "at least one") used herein are intended to include the plural forms unless otherwise clearly indicated. "At least one" should not be construed as limited to the singular. The terms "and / or" as used in this disclosure include any and all combinations of one or more of the associated enumerated items. The terms "comprising" and / or "comprising" as used in the detailed description indicate the presence of the described features, areas, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, areas, integers, steps, operations, elements, components, and / or groups thereof.

[0025] Spatial relative terms such as "below," "below," "down," "above," "above," and "top" may be used herein to readily describe the relationship of one element or feature to another. It will be understood that, in addition to the orientations depicted in the figures, spatial relative terms are intended to also cover different orientations of the device in use or operation. For example, when the device in the figures is flipped, an element described as "below" or "below" to other elements or features will be oriented "above" or "above" to those elements or features. Thus, the exemplary term "below" can encompass both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or otherwise), and the spatial relative descriptors used in this disclosure may be interpreted accordingly.

[0026] "Group" refers to the group of elements in the periodic table according to the classification system of Groups 1-18 of the International Union of Pure and Applied Chemistry ("IUPAC").

[0027] As used herein, the terms "particle size" or "size" refer to the average diameter when the particles are spherical, and the average major axis length when the particles are non-spherical. Particle size or size can be measured using a particle size analyzer (PSA) or a scanning electron microscope. "Particle size" is, for example, the average particle size. "Average particle size" refers to, for example, the median particle size (D). 50 ).

[0028] D 50This refers to the particle size distribution measured by laser diffraction, calculated from particles with smaller particle sizes, corresponding to the particle size at 50% of the cumulative volume.

[0029] D 90 This refers to the particle size distribution measured by laser diffraction, calculated from particles with smaller particle sizes, corresponding to the particle size at 90% of the cumulative volume.

[0030] D 10 This refers to the particle size distribution measured by laser diffraction, calculated from particles with smaller particle sizes, corresponding to the particle size at 10% of the cumulative volume.

[0031] As used herein, the term "metal" includes all metals and metalloids in their elemental or ionic states, such as silicon and germanium, and the term "alloy" refers to a mixture of two or more metals.

[0032] As used herein, the term "electrode active material" refers to an electrode material capable of lithiation and delithiation. The term "positive electrode active material" refers to a positive electrode material capable of lithiation and delithiation, and the term "negative electrode active material" refers to a negative electrode material capable of lithiation and delithiation.

[0033] As used herein, the terms "lithiate" and "lithiating" refer to the process of adding lithium to an electrode active material, while "delithiate" and "delithiating" refer to the process of removing lithium from an electrode active material.

[0034] As used herein, the terms "charge" and "charging" refer to the process of providing electrochemical energy to a battery, and the terms "discharge" and "discharging" refer to the process of removing electrochemical energy from a battery.

[0035] As used herein, the terms "positive electrode" and "negative electrode" refer to an electrode that undergoes electrochemical reduction and lithiation during the discharge process, and the terms "negative electrode" and "negative electrode" refer to an electrode that undergoes electrochemical oxidation and delithiation during the discharge process.

[0036] As used herein, the term "thickness" refers to average thickness, and the term "length" refers to average length.

[0037] As used herein, the term "aspect ratio" refers to the ratio (L / D) of the length of the major axis (e.g., length L) to the length of the minor axis (e.g., diameter D). In this disclosure, aspect ratio, length of the major axis, length of the minor axis, length, and diameter are all average values.

[0038] Although specific implementations have been described, applicants or those skilled in the art may conceive of alternatives, modifications, variations, improvements, and substantially equivalents that are not currently foreseen or unforeseen. Accordingly, the appended claims, and possibly modified thereof, are intended to cover all such alternatives, modifications, variations, improvements, and substantially equivalents.

[0039] The all-solid-state secondary battery according to an exemplary embodiment will be described in more detail below.

[0040] [All-solid-state rechargeable battery]

[0041] The all-solid-state secondary battery according to the embodiments includes: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive current collector and a positive active material layer on one side of the positive current collector, the negative electrode layer includes a negative current collector and a first negative active material layer on one side of the negative current collector, the first negative active material layer includes a first negative active material and a carbon-based material, and the first negative active material includes an alloy phase.

[0042] Because the first negative electrode active material layer includes a first negative electrode active material with an alloy phase, the initial charge and discharge efficiency of the all-solid-state secondary battery can be improved during charging and discharging. Since the all-solid-state secondary battery has improved initial charge and discharge efficiency, its irreversible capacity can be reduced. As a result, the specific capacity of the all-solid-state secondary battery can be increased, and its energy density can be improved.

[0043] Because the first negative electrode active material layer includes a first negative electrode active material with an alloy phase, the volume change of the first negative electrode active material layer can be mitigated during charging and discharging of the all-solid-state secondary battery. As a result, since the volume change of the negative electrode layer is mitigated during charging and discharging of the all-solid-state secondary battery, the high-rate characteristics and / or lifetime characteristics of the all-solid-state secondary battery can be improved. Furthermore, since the volume change of the negative electrode layer is mitigated during charging and discharging of the all-solid-state secondary battery, the thickness of the buffer member used to accommodate the volume change of the negative electrode layer can be reduced, or the buffer member can be omitted. As a result, the energy density of the all-solid-state secondary battery can be improved.

[0044] The first negative electrode active material layer comprises a carbon-based material, which provides conductive pathways between the first negative electrode active materials. Accordingly, the carbon-based material can more easily suppress the increase in internal resistance of the first negative electrode active material layer during charging and discharging in the all-solid-state secondary battery. As a result, the increase in internal resistance of the all-solid-state secondary battery can be suppressed.

[0045] The carbon-based material in the first negative electrode active material layer serves as a support / buffer between the first negative electrode active materials. Accordingly, the carbon-based material can more easily mitigate the volume change of the first negative electrode active material layer during charging and discharging in the all-solid-state secondary battery. As a result, volume change during charging and discharging of the all-solid-state secondary battery can be reduced.

[0046] The content of carbon-based materials in the first negative electrode active material layer ranges from 1 to 50 wt%, 1 to 40 wt%, 1 to 30 wt%, 1 to 20 wt%, or 1 to 10 wt%, relative to the total weight of the first negative electrode active material and carbon-based materials. When the content of carbon-based materials is within this range, the charging and discharging characteristics of the all-solid-state secondary battery can be improved.

[0047] refer to Figure 1 To ~ Figure 12 The all-solid-state secondary battery 1 includes a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 between the positive electrode layer 10 and the negative electrode layer 20. The positive electrode layer 10 includes a positive current collector 11 and a positive active material layer 12 on one side of the positive current collector 11. The negative electrode layer 20 includes a negative current collector 21 and a first negative active material layer 22 on one side of the negative current collector 21. The first negative active material layer 22 includes a first negative active material and a fibrous carbon-based material. The first negative active material includes an alloy phase.

[0048] [Negative electrode layer]

[0049] [First negative electrode active material layer: First negative electrode active material]

[0050] refer to Figure 1 To ~ Figure 12 The negative electrode layer 20 includes a first negative electrode active material layer 22. The first negative electrode active material layer 22 includes a first negative electrode active material.

[0051] The first negative electrode active material includes an alloy phase. The first negative electrode active material is, for example, an alloy-type negative electrode active material. Because the first negative electrode active material includes an alloy phase, it can provide increased initial charge and discharge efficiency and / or increased discharge capacity. The first negative electrode active material may include, for example, an alloy phase composed of metals other than lithium.

[0052] The first negative electrode active material may include, for example, silicon (Si), iron (Fe), and a first metal. The first negative electrode active material may include, for example, an alloy phase comprising two or more metals selected from silicon (Si), iron (Fe), and the first metal. Because the first negative electrode active material includes silicon, its capacity can be improved. One silicon atom may be bonded to 4.4 lithium atoms. Because the first negative electrode active material includes iron and / or the first metal, the rapid volume change of the first negative electrode active material can be mitigated, thereby improving the lifetime characteristics of the all-solid-state secondary battery 1 including the first negative electrode active material. The first metal may include, for example, copper (Cu), aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), zirconium (Zr), niobium (Nb), molybdenum (Mo), tin (Sn), cerium (Ce), or combinations thereof.

[0053] Relative to 100 at% of the total amount of the first negative electrode active material, the first negative electrode active material may include, for example, 60-90 at%, 65-90 at%, or 70-90 at% of silicon (Si). Because the first negative electrode active material includes silicon (Si) within this range, it can provide a high discharge capacity. Relative to 100 at% of the total amount of the first negative electrode active material, the first negative electrode active material may include, for example, greater than 0 to 30 at%, 1 to 25 at%, 1 to 20 at%, 1 to 15 at%, or 1 to 10 at% of iron (Fe).

[0054] The first negative electrode active material may include, for example, a first metal in an amount greater than 0 to 30 at%, 1 to 25 at%, 1 to 20 at%, 1 to 15 at%, or 1 to 10 at%, relative to 100 at% of the total amount of the first negative electrode active material.

[0055] The first negative electrode active material may include, for example, an amount of copper (Cu) greater than 0 to 20 at%, 1 to 15 at%, or 1 to 10 at%, relative to 100 at% of the total amount of the first negative electrode active material.

[0056] The first negative electrode active material may include, for example, 0-10 at%, 0-7 at%, or 0-5 at% of the total amount of aluminum (Al) relative to 100 at% of the total amount of the first negative electrode active material.

[0057] Because the first negative electrode active material includes iron, the first metal, copper and / or aluminum within the above content range, excessive volume change of the first negative electrode active material can be effectively suppressed.

[0058] The first negative electrode active material may include, for example, 60 to 90 at% of silicon (Si), greater than 0 to 30 at% of iron (Fe), and greater than 0 to 10 at% of a first metal. Alternatively, the first negative electrode active material may include, for example, 60 to 90 at% of silicon (Si), greater than 0 to 30 at% of iron (Fe), and greater than 0 to 10 at% of copper (Cu).

[0059] The first negative electrode active material may include, for example, 60 to 90 at% of silicon (Si), more than 0 to 30 at% of iron (Fe), more than 0 to 10 at% of copper (Cu), and 0 to 10 at% of aluminum (Al). Because the first negative electrode active material has the above composition, the cycle characteristics of the all-solid-state secondary battery 1 including the first negative electrode active material can be further improved.

[0060] The first negative electrode active material may, for example, form an alloy with lithium or form a compound with lithium. The first negative electrode active material may include, for example, a single silicon phase, an alloy phase of silicon and iron, an alloy phase of silicon and a first metal, an alloy phase of iron and a first metal, an alloy phase of multiple first metals, or a combination thereof. The first negative electrode active material may further include, for example, a single iron phase, a single first metal phase, or a combination thereof. For example, the single silicon phase may undergo a significant volume change by forming an alloy with lithium or a compound with lithium. The first negative electrode active material may include an alloy phase of silicon and iron, an alloy phase of silicon and a first metal, an alloy phase of iron and a first metal, an alloy phase of multiple first metals, or a combination thereof, and some or all of these alloy phases may, for example, form an alloy with lithium or form a compound with lithium. Alternatively, at least one of the alloy phases of silicon and iron, the alloy phases of silicon and a first metal, the alloy phases of iron and a first metal, the single iron phase, the single first metal phase, and the alloy phases of multiple first metals may suppress the volume change of the first negative electrode active material by, for example, suppressing the volume change of the single silicon phase without bonding with lithium. At least one of the following alloy phases—a silicon-iron alloy phase, a silicon-first metal alloy phase, an iron-first metal alloy phase, an iron single phase, a first metal single phase, and an alloy phase of multiple first metals—may, for example, surround part or all of the silicon single phase. The silicon single phase may, for example, be uniformly and / or non-uniformly distributed within at least one of the following alloy phases: the silicon-iron alloy phase, the silicon-first metal alloy phase, the iron-first metal alloy phase, and the alloy phase of multiple first metals. Because the first negative electrode active material has this structure, the volume change of the first negative electrode active material during charging and discharging can be more effectively suppressed. The silicon-iron alloy phase may be composed of, for example, Fe. a Si b (where a and b are each an independent natural number from 1 to 100). The alloy phase of silicon and the first metal can be represented by, for example, M1. c Si d(c and d are each natural numbers from 1 to 100). The alloy phase of iron and the first metal can be represented by, for example, Fe. e M1 f (e and f are each a natural number from 1 to 100). The alloy phases of various first metals can be represented by, for example, M1'. g M1" h (g and h are each natural numbers from 1 to 100, and M1' and M1" are each metals selected from M1) indicates. The alloy phase of silicon and iron may include, for example, FeSi2, Fe2Si5, FeSi, or combinations thereof. The alloy phase of various first metals may be, for example, an alloy phase of copper and aluminum.

[0061] The first negative electrode active material may further include, for example, boron (B), carbon (C), phosphorus (P), or combinations thereof. The first negative electrode active material may further include boron (B), carbon (C), phosphorus (P), or combinations thereof, thereby more effectively mitigating the volume change of the first negative electrode active material. Alternatively, the first negative electrode active material may not include, for example, boron (B), carbon (C), phosphorus (P), or combinations thereof. Because the first negative electrode active material does not include boron (B), carbon (C), phosphorus (P), or combinations thereof, the first negative electrode active material can be prepared more simply and easily.

[0062] The first negative electrode active material can be, for example, a lithiated negative electrode active material. The lithiated negative electrode active material is, for example, an alloy-type negative electrode active material having the aforementioned alloy phase in which lithium is further substituted. Methods for lithium substitution may include sputtering, electrochemical charging, grinding, etc., but one or more embodiments are not limited thereto. Any method can be used, as long as it is a method known in the art for substituting lithium into an alloy-type negative electrode active material. The first negative electrode active material may include, for example, lithium (Li), silicon (Si), iron (Fe), and a first metal. The first negative electrode active material may include, for example, a lithium-silicon alloy phase. The first negative electrode active material may include, for example, lithium (Li), silicon (Si), iron (Fe), and a first metal, and may include a lithium-silicon alloy phase. Because the first negative electrode active material is a lithiated negative electrode active material, the initial charge and discharge efficiency of the all-solid-state secondary battery 1 including the first negative electrode active material can be further improved. As a result, due to the reduction in the irreversible capacity of the all-solid-state secondary battery 1, the specific capacity of the all-solid-state secondary battery 1 can be increased, and its energy density can be increased.

[0063] The first negative electrode active material layer 22 includes a first negative electrode active material, and the first negative electrode active material is, for example, in particulate form. The size of the first negative electrode active material in particulate form is, for example, 20 μm or less, 15 μm or less, 10 μm, or 7 μm or less. The size range of the first negative electrode active material in particulate form is, for example, 0.1~20 μm, 0.5~20 μm, 1~20 μm, 1~15 μm, 1~10 μm, or 3~7 μm. Because the first negative electrode active material has a size within this range, it can more easily undergo reversible absorption and / or desorption of lithium during charging and discharging. The size of the first negative electrode active material is, for example, the average particle size of the first negative electrode active material. The average particle size of the first negative electrode active material is, for example, the median diameter (D) measured using a laser diffraction particle size analyzer. 50 The size of the first negative electrode active material can be measured, for example, by using a laser diffraction particle size analyzer, a scanning electron microscope, etc.

[0064] The aspect ratio of the first negative electrode active material is, for example, 5 or less, 4 or less, 3 or less, or 2 or less. The range of the aspect ratio of the first negative electrode active material is, for example, 1–5, 1–4, 1–3, or 1–2. Because the first negative electrode active material has an aspect ratio within this range, it can be more uniformly distributed within the first negative electrode active material layer 22. As a result, non-uniformity in the volume change of the first negative electrode active material during charging and discharging can be suppressed. The aspect ratio of the first negative electrode active material can be measured, for example, using a scanning electron microscope.

[0065] In this disclosure, the average particle size is, for example, the median diameter (D) measured using a laser diffraction particle size analyzer. 50 Alternatively, the average particle size can be determined automatically using software (e.g., from electron microscope images) or manually using manual methods.

[0066] The first negative electrode active material layer 22 includes a first negative electrode active material. Because the first negative electrode active material has a weight ratio within this range, the cycle characteristics of the all-solid-state secondary battery 1 can be further improved.

[0067] [First negative electrode active material layer: carbon material]

[0068] In addition to the first negative electrode active material, the first negative electrode active material layer 22 also includes carbon-based materials. These carbon-based materials may include, for example, fibrous carbon materials.

[0069] The first negative electrode active material layer 22 may comprise, for example, a mixture of fibrous carbon material and a first negative electrode active material comprising an alloy phase. The first negative electrode active material layer 22 may comprise, for example, a mixture of fibrous carbon material and at least one first negative electrode active material selected from the group consisting of silicon (Si), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture containing the fibrous carbon material and the first negative electrode active material (e.g., silicon) may, by weight, be in the range of, for example, 99:1 to 1:99, 10:1 to 1:10, 1:1 to 1:9, 1:1 to 1:8, 1:1 to 1:7, 1:1 to 1:6, 1:1 to 1:5, 1:1 to 1:4, or 1:1 to 1:3, but is not necessarily limited to this range, and may be selected according to the desired characteristics of the all-solid-state secondary battery 1. Because the fibrous carbon materials and negative electrode active materials have this composition, the cycle characteristics of the all-solid-state secondary battery 1 can be further improved.

[0070] The first negative electrode active material layer 22 may comprise, for example, a mixture of first particles composed of a first negative electrode active material and second particles composed of fibrous carbonaceous material. The first particles may be, for example, particles comprising silicon (Si), iron (Fe), and a first metal, and including an alloy phase comprising two or more elements selected therefrom. The first metal may include, for example, copper (Cu), titanium (Ti), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), tin (Sn), cerium (Ce), or combinations thereof. The content of the second particles relative to the total weight of the mixture ranges, for example, 1~50 wt%, 1~40 wt%, 1~30 wt%, 1~25 wt%, 1~20 wt%, 1~15 wt%, or 1~10 wt%. Because the fibrous carbonaceous material has a content within this range, the cycle characteristics of the all-solid-state secondary battery 1 may be further improved, for example.

[0071] The fibrous carbon material can be, for example, a conductive carbon material. Because the fibrous carbon material is conductive, it can provide a conductive path within the first negative electrode active material layer 22. The fibrous carbon material can more effectively reduce the internal resistance of the first negative electrode active material layer 22. As a result, the cycle characteristics of the all-solid-state secondary battery 1 are improved. The first negative electrode active material layer 22 may not include any other carbon-based conductive material besides the fibrous carbon material. Because the first negative electrode active material layer 22 does not include any other carbon-based conductive material besides the fibrous carbon material, the energy density of the first negative electrode active material layer 22 can be further improved.

[0072] The aspect ratio of fibrous carbon materials can be, for example, 10 or greater, 20 or greater, 30 or greater, or 50 or greater. The aspect ratio of fibrous carbon materials can be, for example, 2,000 or less, 1,000 or less, 500 or less, 200 or less, or 100 or less. The aspect ratio of fibrous carbon materials can be, for example, in the range of 10~2,000, 20~2,000, 30~2,000, or 50~2,000. The aspect ratio of fibrous carbon materials can be, for example, in the range of 10~2,000, 10~1,000, 10~500, 10~200, 10~100, 10~50, or 10~20. The aspect ratio of fibrous carbon materials is, for example, the ratio of the length of the major axis of the fibrous carbon material (i.e., the length of the fibrous carbon material) to the length of the minor axis perpendicular to the major axis (i.e., the diameter of the fibrous carbon material). Because fibrous carbon materials have an aspect ratio within this range, they can provide longer conductive paths within the first negative electrode active material layer 22. The fibrous carbon materials can form a three-dimensional conductive network within the first negative electrode active material layer 22, thereby more effectively reducing the internal resistance of the first negative electrode active material layer 22. As a result, the internal resistance of the all-solid-state secondary battery 1 is reduced. For example, the high-rate characteristics of the all-solid-state secondary battery 1 can be improved.

[0073] Fibrous carbon materials may include, for example, amorphous fibrous carbon materials, crystalline fibrous carbon materials, or combinations thereof. Because fibrous carbon materials include amorphous fibrous carbon materials, side reactions between lithium and fibrous carbon materials can be more effectively suppressed. Because the reversibility of electrode reactions during charging and discharging of the all-solid-state secondary battery 1 is improved, the cycle characteristics of the all-solid-state secondary battery 1 can be improved.

[0074] The diameter of the fibrous carbon material can be, for example, 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. The diameter of the fibrous carbon material can, for example, be in the range of 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. Because the fibrous carbon material has a diameter within such a range, the internal resistance of the first negative electrode active material layer 22 can be effectively reduced, and the fibrous carbon material can be easily dispersed in solvents and / or slurries during the preparation of the first negative electrode active material layer 22.

[0075] The length of fibrous carbon materials can be, for example, 1,000 μm or less, 100 μm or less, 50 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, or 300 nm or less. The length of fibrous carbon materials can also be, for example, in the range of 100 nm to 1,000 μm, 100 nm to 500 μm, 100 nm to 100 μm, 100 nm to 50 μm, 100 nm to 10 μm, 100 nm to 5 μm, 100 nm to 2 μm, 100 nm to 1 μm, 100 nm to 500 nm, or 100 nm to 300 nm. The length of the fibrous carbon material can be, for example, in the range of 500 nm to 1,000 μm, 500 nm to 500 μm, 500 nm to 100 μm, 500 nm to 50 μm, 500 nm to 10 μm, 1 μm to 10 μm, or 2 μm to 8 μm. As the length of the fibrous carbon material increases, the internal resistance of the electrode can be reduced.

[0076] Fibrous carbon materials may include, for example, fibrous carbon nanostructures. Fibrous carbon nanostructures may include, for example, carbon nanofibers, carbon nanotubes, carbon nanoribbons, or combinations thereof.

[0077] Carbon nanotubes may include, for example, primary carbon nanotube structures, secondary carbon nanotube structures formed by aggregating multiple primary carbon nanotube particles, or combinations thereof.

[0078] The primary structure of carbon nanotubes is a single carbon nanotube unit. Each carbon nanotube unit has a structure in which the graphite sheet is in the form of a cylinder with a diameter on the nanometer scale, and possesses sp... 2 Bonding structure. Depending on the bending angle and structure of the graphite sheet, carbon nanotube units can exhibit conductive or semiconductor properties. Based on the number of bonds forming the walls, carbon nanotube units can be classified as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), multi-walled carbon nanotubes (MWCNTs), etc. As the wall thickness of the carbon nanotube unit decreases, the electrical resistance decreases.

[0079] The primary structure of carbon nanotubes may include, for example, SWCNTs, DWCNTs, MWCNTs, or combinations thereof. The diameter of the primary structure of carbon nanotubes may be, for example, 1 nm or greater, or 2 nm or greater. The diameter of the primary structure of carbon nanotubes may be, for example, 20 nm or less, or 10 nm or less. The diameter of the primary structure of carbon nanotubes may be, for example, in the range of 1 nm to 20 nm, 1 nm to 15 nm, or 1 nm to 10 nm. The length of the primary structure of carbon nanotubes may be, for example, 100 nm or greater, or 200 nm or greater. The length of the primary structure of carbon nanotubes may be, for example, 2 μm or less, 1 μm or less, 500 nm or less, or 300 nm or less. The length of the primary structure of carbon nanotubes may be, for example, in the range of 100 nm to 2 μm, 100 nm to 1 μm, 100 nm to 500 nm, 100 nm to 400 nm, 100 nm to 300 nm, or 200 nm to 300 nm. The diameter and length of the primary structure of carbon nanotubes can be measured using scanning electron microscopy (SEM) or transmission electron microscopy (TEM) images. Alternatively, the diameter and / or length of the primary structure of carbon nanotubes can be measured using laser diffraction methods.

[0080] Carbon nanotube secondary structures are structures formed by aggregating all or part of the primary carbon nanotube structures to form bundled or rope-like nanotubes. Carbon nanotube secondary structures can include, for example, bundled carbon nanotubes, rope-like carbon nanotubes, or combinations thereof. The diameter of the carbon nanotube secondary structure can be, for example, 2 nm or greater, or 3 nm or greater. The diameter of the carbon nanotube secondary structure can be, for example, 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. The diameter of the carbon nanotube secondary structure can be, for example, in the range of 2 nm to 50 nm, 2 nm to 30 nm, or 2 nm to 20 nm. The length of the carbon nanotube secondary structure can be, for example, 500 nm or greater, 700 nm or greater, 1 μm or greater, or 10 μm or greater. The length of the carbon nanotube secondary structure can be, for example, 1,000 μm or less, 500 μm or less, or 100 μm or less. The lengths of carbon nanotube secondary structures can range, for example, from 500 nm to 1,000 μm, 500 nm to 500 μm, 500 nm to 200 μm, 500 nm to 100 μm, 500 nm to 50 μm, 500 nm to 10 μm, 1 μm to 10 μm, or 2 μm to 8 μm. The diameter and length of the carbon nanotube secondary structures can be measured from SEM images or optical microscopy. Alternatively, the diameter and / or length of the carbon nanotube secondary structures can be measured by laser diffraction methods.

[0081] The secondary carbon nanotube structure can be dispersed, for example, in a solvent to convert it into a primary carbon nanotube structure, which is then used to prepare the first negative electrode active material layer 22.

[0082] [First negative electrode active material layer: binder]

[0083] The first negative electrode active material layer 22 may further include a binder.

[0084] Because the binder bonds the first negative electrode active material and the fibrous carbon material, it can more effectively suppress the breakage of the conductive path between the first negative electrode active material and the fibrous carbon material caused by the volume change of the first negative electrode active material during lithium deposition and / or dissolution during charging and discharging. This can suppress the non-uniformity of the electrode reaction in the all-solid-state secondary battery 1.

[0085] The binder can improve the bonding strength between the first negative electrode active material layer 22 and the solid electrolyte layer 30, or between the first negative electrode active material layer 22 and the negative electrode current collector 21. For example, the binder can improve the wettability between the first negative electrode active material layer 22 and the solid electrolyte layer 30, or between the first negative electrode active material layer 22 and the negative electrode current collector 21. Accordingly, the binder can more effectively reduce the increase in interfacial resistance caused by, for example, the formation of voids between the first negative electrode active material layer 22 and the solid electrolyte layer 30, or between the first negative electrode active material layer 22 and the negative electrode current collector 21. This can improve the cycle characteristics of the all-solid-state secondary battery 1.

[0086] When a binder is not included in the first negative electrode active material layer, the surfaces of the solid electrolyte layer and / or the negative electrode current collector may be exposed because the first negative electrode active material layer detaches from the solid electrolyte layer and / or the negative electrode current collector. For example, the exposed negative electrode current collector may cause a short circuit. The cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0087] The binder is, for example, a polymer binder. The binder included in the first negative electrode active material layer 22 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these. Any material can be used, as long as that material is used as a binder in the art. The binder can be provided as a single binder or in the form of multiple different binders. The binder may include, for example, a fluorinated binder.

[0088] Because the first negative electrode active material layer 22 includes a binder, it is stable on the negative electrode current collector 21. Furthermore, even with volume changes and / or relative positional shifts in the first negative electrode active material layer 22 during charging and discharging processes, breakage of the first negative electrode active material layer 22 is suppressed. For example, when the first negative electrode active material layer 22 does not include a binder, it can 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 comes into contact with the solid electrolyte layer 30, which increases the likelihood of a short circuit. For example, the first negative electrode active material layer 22 can be prepared by applying a slurry containing materials constituting the first negative electrode active material layer 22 to the negative electrode current collector 21 and drying the slurry. Because the first negative electrode active material layer 22 includes a binder, the negative electrode active material and fibrous carbon materials can be stably dispersed in the slurry. For example, when the paste is applied to the negative electrode current collector 21 by screen printing, screen clogging (e.g., clogging caused by the aggregation of negative electrode active material) can be suppressed.

[0089] The binder content relative to 100 parts by weight of the first negative electrode active material can be in the range of 0.1 to 20 parts by weight, 0.1 to 15 parts by weight, 1 to 10 parts by weight, or 5 to 10 parts by weight. Because the binder content is within such a range, the cycle characteristics of the all-solid-state secondary battery 1 can be further improved.

[0090] [First negative electrode active material layer: other additives]

[0091] The first negative electrode active material layer 22 may further include additives used in the all-solid-state secondary battery 1 according to the prior art, such as fillers, coating agents, dispersants, ion-conducting agents, etc.

[0092] [Negative electrode layer: First negative electrode active material layer]

[0093] refer to Figure 1 To ~ Figure 12 The positive electrode layer 10 includes a positive electrode active material layer 12, and the negative electrode layer 20 includes a first negative electrode active material layer 22.

[0094] The initial charge capacity (B) of the first negative electrode active material layer 22 is, for example, 75% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the initial charge capacity (A) of the positive electrode active material layer 12.

[0095] The ratio (B / A) of the initial charging capacity (B) of the first negative electrode active material layer 22 to the initial charging capacity (A) of the positive electrode active material layer 12 is, for example, in the range of 0.01~0.75, 0.01~0.7, 0.01~0.6, 0.01~0.5, 0.01~0.6, 0.01~0.5, 0.01~0.4, 0.01~0.3, 0.01~0.2, or 0.01~0.1. The ratio (B / A) of the initial charging capacity (B) of the first negative electrode active material layer 22 to the initial charging capacity (A) of the positive electrode active material layer 12 is, for example, in the range of 0.05 to 0.75, 0.1~0.7, 0.1~0.6, 0.2~0.6, 0.2~0.5, or 0.2~0.45. The initial charge capacity of the positive electrode active material layer 12 is achieved by charging from the first open-circuit voltage to a value relative to Li / Li. + The initial charging capacity of the first negative electrode active material layer 22 is determined by charging from the second open-circuit voltage to 0.01 V (relative to Li / Li). + The maximum charging voltage is determined by the type of positive electrode active material. The maximum charging voltage can be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charging voltage for Li₂S or Li₂S complexes can be determined to be between 2.5 and 3.0 V (relative to Li / Li). + Within the constant current range. For example, the maximum charging voltage of lithium transition metal oxides can be determined to be 3.0~4.5 V (relative to Li / Li). + Within the range of ).

[0096] The initial charge capacity (mAh) of the positive electrode active material layer 12 is 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. When using various types of positive electrode active materials, the specific charge capacity × mass value of each positive electrode active material is calculated, and the sum of these values ​​is the initial charge capacity of the positive electrode active material layer 12. The initial charge capacity of the first negative electrode active material layer 22 is also calculated in the same manner. The initial charge capacity of the first negative electrode active material layer 22 is 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. When using various types of negative electrode active materials, the specific charge capacity × mass value of each negative electrode active material is calculated, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer 22. The specific charge capacity of each of the positive and negative electrode active materials can be measured using an all-solid-state half-cell with lithium metal as the counter electrode. The initial charge capacity of each of the positive electrode active material layer 12 and the first negative electrode active material layer 22 can be achieved by using an all-solid-state half-cell at a constant current density (e.g., 0.1 mA / cm²). 2 Direct measurement is possible from the first open-circuit voltage (OCV) to the maximum charging voltage (e.g., 3.0 V relative to Li / Li). + The operating voltage of the positive electrode can be measured. The negative electrode can be measured at operating voltages ranging from the 2nd OCV to 0.01 V (for the negative electrode, e.g., lithium metal). For example, an all-solid-state half-cell with a positive electrode active material layer can be measured at 0.1 mA / cm². 2 The constant current is applied from the 10V to 3.0V. The all-solid-state half-cell with the first negative electrode active material layer can be charged at 0.1 mA / cm². 2 The constant current charging is applied from the second OCV to 0.01 V. The current density during constant current charging can be, for example, 0.2 mA / cm². 2 or 0.5 mA / cm 2 All-solid-state half-cells with a positive electrode active material layer can be charged, for example, from the first OCV to 2.5 V, 2.0 V, 3.5 V, 4.0 V, or 4.5 V. 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 JIS C 8712:2015 of the Japanese Standards Institute.

[0097] When the initial charge capacity of the first negative electrode active material layer 22 is too small, the first negative electrode active material layer 22 becomes very thin. Therefore, during repeated charge and discharge processes, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 may cause the first negative electrode active material layer 22 to collapse, which may make it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. When 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 may decrease, and the internal resistance of the all-solid-state secondary battery 1 may increase due to the first negative electrode active material layer 22, which may also make it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0098] The thickness of the first negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, in the range of 1-50%, 1-40%, 1-30%, 1-20%, or 1-10% of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, in the range of 1-50 μm, 2-40 μm, 3-30 μm, 4-20 μm, or 5 μm-20 μm. The thickness of the first negative electrode active material layer 22 is, for example, in the range of 5-50 μm, 10-50 μm, 15-50 μm, 20-50 μm, or 25 μm-50 μm. When the first negative electrode active material layer 22 is too thin, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 may cause the first negative electrode active material layer 22 to collapse, which may make it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. When 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 may decrease, and the internal resistance of the all-solid-state secondary battery 1 may increase due to the first negative electrode active material layer 22, which may make it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. When the thickness of the first negative electrode active material layer 22 is reduced, for example, the initial charging capacity of the first negative electrode active material layer 22 also decreases.

[0099] [Negative electrode layer: Second negative electrode active material layer]

[0100] refer to Figure 3After charging, the all-solid-state secondary battery 1 may further include, for example, a second negative electrode active material layer 24 disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The second negative electrode active material layer 24 is a metal layer comprising lithium or a lithium alloy. The metal layer comprises lithium or a lithium alloy. Therefore, the second negative electrode active material layer 24 is a lithium-containing metal layer, and thus serves as, for example, a lithium storage tank. The lithium alloy may be, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., but is not limited thereto. Any material can be used, as long as that material is used as a lithium alloy in the art. The second negative electrode active material layer 24 may be composed of one of these alloys or lithium, or may be composed of various types of alloys. The second negative electrode active material layer 24 may be, for example, a plating layer. For example, the second negative electrode active material layer 24 is deposited between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charging process of the all-solid-state secondary battery 1.

[0101] The thickness of the second negative electrode active material layer 24 is not particularly limited, but can be in the range of, for example, 1~200 μm, 1~150 μm, 1~100 μm, 1~50 μm, 1~30 μm, 1~22 μm, or 1 μm~10 μm. If the second negative electrode active material layer 24 is too thin, it is difficult to use it as a lithium storage tank. If the second negative electrode active material layer 24 is too thick, the mass and volume of the all-solid-state secondary battery 1 may increase, and the cycle characteristics of the all-solid-state secondary battery 1 may deteriorate.

[0102] The thickness of the second negative electrode active material layer 24 can, for example, be less than the thickness of the first negative electrode active material layer 22. The thickness of the second negative electrode active material layer 24 can, for example, be in the range of 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less of the thickness of the first negative electrode active material layer 22. The thickness of the second negative electrode active material layer 24 can be, for example, 1-70%, 1-60%, 1-50%, 1-40%, or 1-30% of the thickness of the first negative electrode active material layer 22. Since the thickness of the second negative electrode active material layer 24 is less than the thickness of the first negative electrode active material layer 22, volume changes in the all-solid-state secondary battery during charging and discharging can be suppressed. As a result, degradation of the all-solid-state secondary battery due to volume changes can be suppressed.

[0103] Alternatively, in the all-solid-state secondary battery 1, for example, before assembly of the all-solid-state secondary battery 1, a second negative electrode active material layer 24 may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. When the second negative electrode active material layer 24 is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembly of the all-solid-state secondary battery 1, the second negative electrode active material layer 24 is a lithium-containing metal layer and thus serves as a lithium storage tank. 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 assembly of the all-solid-state secondary battery 1.

[0104] When the second negative electrode active material layer 24 is deposited by charging after the assembly of the all-solid-state secondary battery 1, the energy density of the all-solid-state secondary battery 1 increases because the all-solid-state secondary battery 1 did not include the second negative electrode active material layer 24 during assembly. During the charging of the all-solid-state secondary battery 1, the first negative electrode active material layer 22 is charged beyond its charging capacity. That is, the first negative electrode active material layer 22 is overcharged. At the start of charging, lithium is absorbed into the first negative electrode active material layer 22. The negative electrode active material included in the first negative electrode active material layer 22 forms an alloy or compound with lithium ions moving from the positive electrode layer 10. When charging exceeds the capacity of the first negative electrode active material layer 22, for example, lithium is deposited on the back side 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 24 is formed by the deposition of lithium. The second negative electrode active material layer 24 is a metal layer mainly composed of lithium (e.g., metallic lithium). For example, this result is achieved 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 24 is ionized and moves toward the positive electrode layer 10. Therefore, lithium can be used as the negative electrode active material in the all-solid-state secondary battery 1. In addition, since the first negative electrode active material layer 22 covers the second negative electrode active material layer 24, the first negative electrode active material layer 22 serves as a protective layer for the second negative electrode active material layer 24 (i.e., the metal layer) and simultaneously suppresses the precipitation and growth of lithium dendrites. Accordingly, short circuits and capacity reduction in the all-solid-state secondary battery 1 are suppressed, thereby improving the cycle characteristics of the all-solid-state secondary battery 1. Furthermore, when the second negative electrode active material layer 24 is provided by charging after the assembly of the all-solid-state secondary battery 1, the negative electrode 20 (i.e., the negative electrode current collector 21, the first negative electrode active material layer 22 and the region therebetween) is a lithium-free region that does not contain lithium in the initial state of the all-solid-state secondary battery 1 or in the state after it is fully discharged.

[0105] [Negative electrode: Negative electrode current collector]

[0106] The negative electrode current collector 21 is composed of, for example, a material that does not react with lithium (i.e., a material that neither forms an alloy with lithium nor a compound with lithium). Materials constituting the negative electrode current collector 21 include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), etc., but are not necessarily limited to these. Any material can be used, provided that it is used as an electrode current collector in the art. The negative electrode current collector 21 may be composed of one type of the aforementioned metals, or may be composed of an alloy or coating material of two or more types of metals. The negative electrode current collector 21 is in the form of, for example, a plate or foil.

[0107] refer to Figure 2 The all-solid-state secondary battery 1 may further include a thin film 23 comprising elements capable of forming an alloy with lithium on one side of the negative electrode current collector 21. The thin film 23 is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The thin film 23 comprises, for example, elements capable of forming an alloy with lithium. Elements capable of forming an alloy with lithium include, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but are not necessarily limited to these. Any material can be used, as long as it is capable of forming an alloy with lithium in the art. The thin film 23 is composed of one of these metals, or an alloy of various types of metals. Because the thin film 23 is disposed on one side of the negative electrode current collector 21, for example, the deposition form of the second negative electrode active material layer 24 deposited between the thin film 23 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.

[0108] The thickness of the thin film 23 is, for example, in the range of 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. When the thickness of the thin film 23 is less than 1 nm, the thin film 23 may be difficult to function. When the thin film 23 is too thick, the thin film 23 itself can absorb lithium, thus reducing the amount of lithium deposited in the negative electrode, resulting in a decrease in the energy density of the all-solid-state battery 1 and a deterioration in the cycle characteristics of the all-solid-state secondary battery 1. The thin film 23 can be deposited on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, electroplating, etc., but one or more embodiments are not necessarily limited to this method. Any method can be used, as long as the method can form the thin film 23 in the art.

[0109] Although not shown in the accompanying drawings, the negative electrode current collector 21 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or combinations thereof. The polymer may be an insulating polymer. Because the base film includes an insulating thermoplastic polymer, it may soften or liquefy to interrupt battery operation when a short circuit occurs, 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 electrode current collector 21 may additionally include a metal sheet and / or lead terminals. For specific details regarding the base film, metal layer, metal sheet, and lead terminals of the negative electrode current collector 21, refer to the positive electrode current collector 11 described above. Because the negative electrode current collector 21 has this structure, the weight of the negative electrode can be reduced, thereby improving the energy density of the negative electrode and the all-solid-state secondary battery.

[0110] [Negative electrode layer: First inactive component]

[0111] refer to Figure 4 and Figure 5 as well as Figures 8-12 The all-solid-state secondary battery 1 may further include a first inactive member 40 (40a or 40b) disposed on at least one of the negative current collector 21 and the positive current collector 11.

[0112] The first inactive component 40 (40a or 40b) may not include electrode active material. The first inactive component 40 (40a or 40b) may be, for example, an insulating component.

[0113] The first inactive component 40 (40a or 40b) further includes a conductive material to be conductive. The first inactive component 40 (40a or 40b) may further include a flame-retardant material to make it, for example, a flame-retardant inactive component.

[0114] The first inactive member 40 (40a or 40b) may be, for example, an elastic member. The first inactive member 40 (40a or 40b) may be, for example, a porous elastic member. The first inactive member 40 (40a or 40b) may be, for example, an elastic member having at least one of porosity, electrical conductivity and flame retardancy.

[0115] The first inactive component 40 (40a or 40b) provides a buffering function for the all-solid-state secondary battery 1. The first inactive component 40 (40a or 40b) provides, for example, stress relaxation and restoring force. The first inactive component 40 (40a or 40b) can effectively accommodate volume changes in the all-solid-state secondary battery 1 and apply a constant pressure to the all-solid-state secondary battery 1.

[0116] The first inactive component 40 (40a or 40b) may have an elastic modulus, for example, lower than that of the negative electrode current collector 21. Because the first inactive component 40 (40a or 40b) has an elastic modulus lower than that of the negative electrode current collector 21, the first inactive component 40 (40a or 40b) can more effectively accommodate the volume changes of the negative electrode layer 20 during charging and discharging of the all-solid-state secondary battery 1. The first inactive component 50 can effectively alleviate the internal stress caused by the volume changes of the all-solid-state secondary battery 1 during charging and discharging, thereby improving the cycle characteristics of the all-solid-state secondary battery 1.

[0117] A first inactive component 40 (40a or 40b) may be disposed on, for example, the negative electrode layer 20 of an all-solid-state secondary battery 1. When the volume change of the negative electrode layer 20 during charging and discharging of the all-solid-state secondary battery 1 is relatively greater than the volume change of the positive electrode layer 10 and the solid electrolyte layer 30, the first inactive component 40 (40a or 40b) can more effectively accommodate the volume change of the negative electrode layer 20 because it is disposed adjacent to the negative electrode layer 20. In addition, the first inactive component 40 (40a or 40b) can apply a constant pressure to the negative electrode layer 20, thereby inducing, for example, uniform deposition of lithium metal in the negative electrode layer 20. Accordingly, the formation of defects in the all-solid-state secondary battery 1 due to uneven lithium metal deposition can be more effectively prevented.

[0118] Alternatively, a first inactive component 40 (40a or 40b) may be disposed on, for example, the positive electrode layer 10 of the all-solid-state secondary battery 1. Because the first inactive component 40 (40a or 40b) is disposed adjacent to the positive electrode layer 10, it can more effectively accommodate volume changes in the all-solid-state secondary battery 1. Furthermore, the first inactive component 40 (40a or 40b) can apply a constant pressure to the all-solid-state secondary battery 1, thereby inducing, for example, uniform deposition of lithium metal in the negative electrode layer 20. Accordingly, the formation of defects in the all-solid-state secondary battery 1 due to uneven lithium metal deposition can be more effectively prevented.

[0119] The first inactive component 40 (40a or 40b) may comprise a polymer material, a rubber material, or a combination thereof. Because the first inactive component 40 (40a or 40b) comprises a polymer material, a rubber material, or a combination thereof, the first inactive component 40 (40a or 40b) may possess stress relaxation and restoring forces. The polymer material may include, for example, polyurethane polymers, polyacrylic polymers, polystyrene polymers, polyester polymers, polyamide polymers, polyolefin polymers, or combinations thereof. The polymer material may be, for example, a polymer resin. The polymer material may be, for example, an adhesive resin. Rubber materials may include, for example, natural rubber (NR), butadiene rubber (BR), nitrile rubber, silicone rubber, isoprene rubber (IR), SBR, isoprene-butadiene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber, halogenated butyl rubber, chloroprene (CR), halogenated isoprene rubber, halogenated isobutylene copolymer, chloroprene rubber, butyl rubber (IIR), halogenated isobutylene-p-methylstyrene rubber, or combinations thereof. Polyurethane polymers may include, for example, polyester polyurethanes, polyether polyurethanes, or combinations thereof. Polyacrylic polymers may include, for example, polyacrylates, polymethyl methacrylates, polymethyl methacrylates, or combinations thereof. Polystyrene polymers may include, for example, styrene-ethylene-butene copolymer (SEB), styrene-butadiene-styrene copolymer (SBS), hydrogenated products of SBS (styrene-ethylene-butene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), hydrogenated products of SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), styrene-isobutylene-styrene copolymer (SIBS), styrene-butadiene-styrene-butadiene (SBSB), styrene-butadiene-styrene-butadiene-styrene (SBSBS), polystyrene (PS), acrylonitrile-styrene copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS), or combinations thereof. Polyester polymers may include, for example, PET, PBT, or combinations thereof. Polyamide polymers may include, for example, polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, or combinations thereof.Polyolefin polymers may include, for example, PE, PP, ethylene-propylene copolymers, propylene-1-hexene copolymers, propylene-4-methyl-1-pentene copolymers, propylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-4-methyl-pentene copolymers, ethylene-1-butene copolymers, 1-butene-1-hexene copolymers, 1-butene-4-methyl-pentene, ethylene-methacrylic acid copolymers, ethylene-ethyl methacrylate copolymers, ethylene-ethyl methacrylate copolymers, ethylene-butyl methacrylate copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-butyl acrylate copolymers, propylene-methacrylic acid copolymers, propylene-methyl methacrylate copolymers, propylene-ethyl methacrylate copolymers, propylene-butyl methacrylate copolymers, propylene-methyl acrylate copolymers, propylene-ethyl acrylate copolymers, propylene-butyl acrylate copolymers, ethylene-vinyl acetate copolymers (EVA), and polyolefins or combinations thereof.

[0120] The first inactive component 40 (40a or 40b) may include, for example, porous foam, porous sponge, or a combination thereof. The first inactive component 40 (40a or 40b) may include, for example, porous foam sheets, porous sponge sheets, or a combination thereof. The first inactive component 40 (40a or 40b) may have this form, thus providing both porosity and cushioning function simultaneously. Porous foam may include, for example, closed-cell, open-cell, or a combination thereof. Porous sponge may include, for example, closed-cell, open-cell, or a combination thereof. Closed-cell refers to, for example, a pore or pore that is closed and does not communicate with the surrounding atmosphere. Open-cell refers to, for example, a pore or pore that communicates with the surrounding atmosphere. The first inactive component 40 (40a or 40b) may include, for example, closed-cell porous foam, open-cell porous foam, closed-cell porous sponge, open-cell porous sponge, or a combination thereof. Porous foam may include, for example, both closed-cell and open-cell. Porous sponge may include, for example, both closed-cell and open-cell.

[0121] The first inactive component 40 (40a or 40b) may include, for example, a conductive material. Conductive materials include, for example, graphite, carbon black, acetylene black, Ketjen black, superconducting acetylene black, carbon fiber, carbon nanotubes (CNTs), graphene, metal fibers, metal powder, etc. The content of the conductive material included in the first inactive component 40 (40a or 40b) relative to 100 parts by weight is, for example, in the range of 1-30 parts by weight, 1-20 parts by weight, 1-15 parts by weight, 1-10 parts by weight, 5-40 parts by weight, 5-30 parts by weight, or 5-35 parts by weight. The first inactive component 50 may be conductive, and therefore it can be used as a negative electrode current collector 50.

[0122] The first inactive component 40 (40a or 40b) includes, for example, a matrix and a filler. The matrix includes, for example, a substrate and a reinforcing material. The matrix includes, for example, a fiber substrate and a fiber reinforcing material. Because the matrix includes a fiber substrate, the matrix can be elastic. The fiber substrate includes, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conducting polymer fibers. The matrix includes a reinforcing material, thus improving the strength of the matrix. The fiber reinforcing material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc. The fiber reinforcing material is, for example, a flame-retardant material. The filler is, for example, a hygroscopic agent and / or a flame retardant. The filler is, for example, a metal hydroxide with hygroscopic properties. The metal hydroxide included in the filler is, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, Ti(OH)3, Zr(OH)4, Al(OH)3, or combinations thereof.

[0123] The thickness of the first inactive component 40 (40a or 40b) is, for example, in the range of 1 μm to 300 μm, 10 μm to 200 μm, 10 μm to 100 μm, or 10 μm to 50 μm. When the first inactive component 40 (40a or 40b) is too thin, it may be difficult to provide the desired effect, and when the first inactive component 40 (40a or 40b) is too thick, the energy density of the all-solid-state secondary battery 1 may decrease. The form of the first inactive component 40 (40a or 40b) is not particularly limited and can be selected according to the form of the all-solid-state secondary battery 1. The first inactive component 40 (40a or 40b) may be, for example, in the form of a sheet, a rod, or a spacer. The first inactive component 40 (40a or 40b) may, for example, be omitted.

[0124] [Positive electrode layer]

[0125] [Positive electrode active material layer: positive electrode active material]

[0126] refer to Figures 1-12 The positive electrode layer 10 includes a positive electrode active material layer 12. The positive electrode active material layer 12 includes a positive electrode active material.

[0127] The positive electrode active material included in the positive electrode active material layer 12 is a positive electrode active material capable of reversibly absorbing and desorbing lithium ions. Positive electrode active materials include, for example, oxide-based positive electrode active materials, sulfide-based positive electrode active materials, or combinations thereof.

[0128] Oxide-based positive electrode active materials include, for example, lithium transition metal oxides, metal oxides, or combinations thereof. Lithium transition metal oxides 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. Lithium oxides include, for example, iron oxide, vanadium oxide, or combinations thereof.

[0129] Sulfide-based positive electrode active materials include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof.

[0130] Oxide-based positive electrode active materials may include, for example, a complex oxide of at least one lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. Lithium-containing oxide-based positive electrode active materials may include compounds represented by any one of the following formulas, for example, Li... a A 1-b B' b D2 (0.90≤a≤1 and 0≤b≤0.5); Li a E 1-b B' b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, and 0≤c≤0.05); LiE 2-b B' b O 4-c D c (0≤b≤0.5 and 0≤c≤0.05); Li a Ni 1-b-c Co b B' c D α (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 (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 (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 (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 (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); Li a Ni1-b-c Mn b B' c O 2-α F' α (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 (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 (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 (0.90≤a≤1 and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1 and 0.001≤b≤0.1); Li a MnG b O2 (0.90≤a≤1 and 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1 and 0.001≤b≤0.1); LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3 (0≤f≤2); Li (3-f) Fe2(PO4)3 (0≤f≤2); and LiFePO4.

[0131] In the formula representing the above compound, A is Ni, Co, Mn or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; F' is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; I' is Cr, V, Fe, Sc, Y or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu or a combination thereof. A compound for a coating added to the surface of the above compound may also be used, and a mixture of the above compound and a compound added to the coating may also be used. The coating added to the surface of the above compound includes, for example, a coating element compound which is an oxide or hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. The compound constituting the coating is amorphous or crystalline. The coating element included in the coating is Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The method for forming the coating is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spraying, dipping and the like. Specific coating methods can be well understood by those skilled in the art, and thus detailed descriptions thereof will be omitted.

[0132] The oxide-based positive electrode active material may include, for example, a lithium transition metal oxide represented by the following Formulas 1 to 8:

[0133] Formula 1

[0134] Li a Ni x Co y M z O 2-b A b

[0135] In Formula 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 is 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 is F, S, Cl, Br or a combination thereof,

[0136] Formula 2

[0137] LiNi x Co y Mn z O2

[0138] Formula 3

[0139] LiNi x Co y Al z O2

[0140] wherein, in Formula 2 and Formula 3, 0.8≤x≤0.95, 0≤y≤0.2, 0<z≤0.2, and x+y+z=1,

[0141] Formula 4

[0142] LiNi x Co y Mn z Al w O2

[0143] wherein, in Formula 4, 0.8≤x≤0.95, 0≤y≤0.2, 0<z≤0.2, 0<w≤0.2, and x+y+z+w=1,

[0144] Formula 5

[0145] Li a Co x M y O 2-b A b

[0146] wherein, in Formula 5, 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1, M is 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 is F, S, Cl, Br or a combination thereof,

[0147] Formula 6

[0148] Li a Ni x Mn y M' z O 2-b A b

[0149] wherein, in Formula 6, 1.0≤a≤1.2, 0≤b≤0.2, 0<x≤0.3, 0.5≤y<1, 0<z≤0.3, and x+y+z=1, M' is cobalt (Co), 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 is F, S, Cl, Br or a combination thereof; and

[0150] Formula 7

[0151] Li a M1 x M2 y PO 4-b X b

[0152] wherein, in Formula 7, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9<x+y<1.1, 0≤b≤2, M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof, M2 is 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 a combination thereof, and X is O, F, S, P or a combination thereof, and

[0153] Formula 8

[0154] Li a M3 z PO4, wherein, in Formula 8, 0.90≤a≤1.1, 0.9≤z≤1.1, and M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof.

[0155] The oxide-based positive active material may be covered with a coating. As the coating, any coating may be used as long as it is a known coating for positive active materials of all-solid secondary batteries. The coating includes, for example, Li2O-ZrO2 (LZO) and the like.

[0156] The size of the oxide-based positive active material may be, for example, in the range of 0.1 to 30 μm, 0.5 to 20 μm, or 1 to 15 μm. The oxide-based positive active material may be, for example, single-crystal particles or polycrystalline particles.

[0157] The sulfide-based positive active material may include, for example, a Li2S-containing composite. The Li2S-containing composite includes, 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.

[0158] The Li2S and carbon complex includes carbon. As carbon, any material can be used, for example, as long as it comprises carbon atoms and is used in the art as a conductive material. Carbon can be, for example, crystalline carbon, amorphous carbon, or a combination thereof. Carbon can be, for example, a calcined product of a carbon precursor. Carbon can be, for example, a carbon nanostructure. Carbon nanostructures can be, for example, one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, or a combination thereof. Carbon nanostructures can be, for example, CNTs, carbon nanofibers, 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 two-dimensional or three-dimensional pores. Porous carbon can be, for example, carbon black (such as Ketjen black, acetylene black, superconducting acetylene black, thermally cracked carbon black, or channel black); graphite, activated carbon, or a combination thereof. Carbon can be in, for example, particulate form, flake form, fibrous form, etc., but is not limited thereto. Any material can be used, provided that it is used as carbon in the art. Methods for preparing the Li₂S and carbon composite can be dry, wet, or a combination thereof, but are 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 necessarily limited thereto. Any method can be used, provided that the method is used in the art.

[0159] The complex of Li₂S, carbon, and solid electrolyte includes carbon and a solid electrolyte. For carbon, refer to the above description of the 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 used in the art as an ion-conducting material. 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. The sulfide solid electrolyte may include, for example, Li, S, and P, and may optionally further include halogen elements. The sulfide solid electrolyte may be selected from the sulfide solid electrolytes used in the solid electrolyte layer. For example, the sulfide solid electrolyte may have a density of 1 × 10⁻⁶ at room temperature. -5 Ionic conductivity of S / cm or greater. Sulfide solid electrolytes may include, for example, those selected from 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, 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 (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 (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) and Li 7-x PS 6- x I x At least one of (0 ≤ x ≤ 2). Oxide solid electrolytes may include, for example, Li, O, and transition metal elements, and may optionally further include other elements. For example, an oxide solid electrolyte may have a concentration of 1 × 10⁻⁶ at room temperature. -5 Solid electrolytes with ionic conductivity of S / cm or greater. Oxide-based solid electrolytes may be selected from those used in the solid electrolyte layer. The solid electrolyte may be, for example, a mixture of sulfide-based solid electrolytes and lithium salts. For example, the solid electrolyte may be a mixture of Li3PO4-Li2SO4 and binary lithium salts or a mixture of Li3PO4-Li2SO4 and ternary lithium salts.

[0160] Complexes of Li₂S and solid electrolytes include solid electrolytes. For solid electrolytes, refer to the above description of complexes of Li₂S, carbon, and solid electrolytes.

[0161] Complexes of Li₂S and lithium salts include lithium salt compounds. Lithium salt compounds do not include, for example, sulfur (S) atoms. Lithium salt compounds can be, for example, binary compounds comprising lithium and one of the elements selected from groups 13-17 of the periodic table. Binary compounds can 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 can be, for example, ternary compounds comprising lithium and two of the elements selected from groups 13-17 of the periodic table. Ternary compounds 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. The lithium salt compound is at least one lithium halide compound selected from LiF, LiCl, LiBr, and LiI. The complex of Li₂S and a solid electrolyte includes a solid electrolyte. For the solid electrolyte, refer to the solid electrolyte used in the above-described complex of Li₂S, carbon, and a solid electrolyte. The complex of Li₂S and a solid electrolyte includes, for example, a complex of Li₂S and at least one lithium salt selected from LiF, LiCl, LiBr, LiI, LiH, Li₂S, Li₂O, Li₂Se, Li₂Te, Li₃N, Li₃P, Li₃As, Li₃Sb, LiI₃, and LiB₃.

[0162] Complexes of Li₂S, lithium salts, and carbon include lithium salt compounds and carbon. For lithium salt compounds, refer to the above description of complexes of Li₂S and lithium salts. For carbon, refer to the above description of complexes of Li₂S and carbon.

[0163] Complexes of Li₂S and metal carbides include metal carbides. These metal carbides are, for example, two-dimensional metal carbides. Two-dimensional metal carbides are, for example, MXene. Two-dimensional metal carbides are, for example, composed of M... n+1 C n T x (M is a transition metal, T is an end group, T is O, OH and / or F, n = 1, 2 or 3, and x is the number of end groups) Two-dimensional metal carbides are, for example, Ti₂CT. x 、(Ti 0.5 ,Nb 0.5 )2CT x Nb2CT x V2CT x Ti3C2T x 、(V 0.5 ,Cr 0.53C2T x Ti3CNT x Ta4C3T x Nb4C3T x Or a combination thereof. The surface of two-dimensional metal carbides terminates with O, OH and / or F.

[0164] Complexes of Li₂S, carbon, and metal carbides include carbon and metal carbides. For carbon, refer to the above description of complexes of Li₂S and carbon. For metal carbides, refer to the above description of complexes of Li₂S and metal carbides.

[0165] Complexes of Li₂S and metal nitrides include metal nitrides. These metal nitrides are, for example, two-dimensional metal nitrides. Two-dimensional metal nitrides are, for example, composed of M… n+1 N n T x (M is a transition metal, T is an end group, T is O, OH and / or F, n=1, 2 or 3, and x is the number of end groups) represents the surface of two-dimensional metal nitrides terminated by O, OH and / or F.

[0166] Complexes of Li₂S, carbon, and metal nitrides include carbon and metal nitrides. For carbon, refer to the above description of complexes of Li₂S and carbon. For metal carbides, refer to the above description of complexes of Li₂S and metal nitrides.

[0167] The Li2S-containing complex may further include, for example, a second fibrous sulfide solid electrolyte (not shown). The Li2S-containing complex may be a complex of Li2S and a second fibrous sulfide solid electrolyte, or a complex of Li2S, a second fibrous sulfide solid electrolyte, and the aforementioned carbon, solid electrolyte, lithium salt, metal carbide, or metal nitride.

[0168] Because the Li2S-containing complex further includes a second fibrous sulfide-based solid electrolyte, degradation of the all-solid-state secondary battery can be further suppressed, and the cycle characteristics of the all-solid-state secondary battery can be further improved. The size of the second fibrous sulfide-based solid electrolyte can be smaller than the size of the first fibrous sulfide-based solid electrolyte 100. The length and / or thickness of the second fibrous sulfide-based solid electrolyte can be 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less, respectively, of the length and / or thickness of the first fibrous sulfide-based solid electrolyte 100. The length and / or thickness of the second fibrous sulfide-based solid electrolyte can be in the range of 0.1% to 50%, 0.5% to 40%, 1% to 30%, 1% to 20%, or 1% to 10%, respectively, of the length and / or thickness of the first fibrous sulfide-based solid electrolyte 100. For example, the second fibrous sulfide-based solid electrolyte can have the same shape as the first fibrous sulfide-based solid electrolyte 100 and can have a smaller size than the first fibrous sulfide-based solid electrolyte. The second fibrous sulfide-based solid electrolyte can have this reduced length and / or thickness, thereby facilitating its distribution within the Li₂S-containing complex. Because the second fibrous sulfide-based solid electrolyte has this reduced length and / or thickness, it can further suppress the degradation of the all-solid-state secondary battery and further improve its cycle characteristics.

[0169] The size of sulfide-based positive electrode active materials can be, for example, in the range of 0.1–50 μm, 0.5–30 μm, 0.5–20 μm, or 1–10 μm. The size of Li₂S can be, for example, in the range of 1 nm–10 μm, 10 nm–5 μm, 10 nm–3 μm, or 10 nm–1 μm. The size of Li₂S-containing complexes can be, for example, in the range of 0.1–50 μm, 0.5–30 μm, 0.5–20 μm, or 1–10 μm.

[0170] The shape of the positive electrode active material is, for example, particulate, such as a true sphere or an ellipsoidal sphere. The particle size of the positive electrode active material is not particularly limited and is within the range suitable for positive electrode active materials in all-solid-state secondary batteries according to the prior art. The content of the positive electrode active material in the positive electrode layer 10 is also not particularly limited and is within the range suitable for positive electrode layers in all-solid-state secondary batteries according to the prior art. The content of the positive electrode active material included in the positive electrode active material layer 12 relative to the total weight of the positive electrode active material layer 12 can, for example, be in the range of 10 wt% to 99 wt%, 10 wt% to 90 wt%, 10 wt% to 80 wt%, 10 wt% to 70 wt%, or 10 wt% to 50 wt%.

[0171] [Positive electrode active material layer: solid electrolyte]

[0172] The positive electrode active material layer 12 may further include, for example, a solid electrolyte. The solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode layer 10 may be the same as or different from the solid electrolyte included in the solid electrolyte layer 30. For details regarding the solid electrolyte, refer to the description of the solid electrolyte layer 30.

[0173] The solid electrolyte included in the positive electrode active material layer 12 may have a smaller D than the solid electrolyte included in the solid electrolyte layer 30. 50 Average particle size. For example, the D of the solid electrolyte included in the positive electrode active material layer 12. 50 The average particle size can be the D of the solid electrolyte included in the solid electrolyte layer 30. 50 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average particle size. D 50 The average particle size is, for example, the median particle size (D). 50 Median particle size (D) 50 The particle size distribution measured by laser diffraction is calculated from particles with smaller particle sizes, corresponding to the particle size of 50% of the cumulative volume.

[0174] The content of the solid electrolyte included in the positive electrode active material layer 12 may, for example, be in the range of 1 wt% to 40 wt%, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12.

[0175] [Positive electrode active material layer: conductive material]

[0176] The positive electrode active material layer 12 may further 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, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but one or more embodiments are not limited thereto. Any material may be used, provided that it is used in the art as a carbon-based conductive material. The metallic conductive material may be metal powder, metal fiber, or a combination thereof, but is not limited thereto. Any material may be used, provided that it is used in the art as a metallic conductive material. The content of the conductive material included in the positive electrode active material layer 12 may, for example, be in the range of 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12.

[0177] [Positive electrode active material layer: binder]

[0178] The positive electrode active material layer 12 may further include a binder. The binder may include, for example, SBR, polytetrafluoroethylene, polyvinylidene fluoride, PE, etc., but one or more embodiments are not limited thereto. Any material may be used, as long as it is used as a binder in the art. The content of the binder included in the positive electrode active material layer 12 may, for example, be in the range of 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12. The binder may be omitted.

[0179] [Positive electrode active material layer: other additives]

[0180] In addition to the above-mentioned positive electrode active material, solid electrolyte, binder and conductive material, the positive electrode active material layer 12 may further include, for example, additives (e.g., fillers, coating agents, dispersants and ion-conducting aids).

[0181] As fillers, coatings, dispersants, ion-conducting additives, etc., which may be included in the positive electrode active material layer 12, known materials commonly used in the electrodes of all-solid-state secondary batteries can be used.

[0182] [Positive electrode layer: Positive electrode current collector]

[0183] The positive current collector 11 is provided as a plate, foil, or the like, 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 be omitted. The thickness of the positive current collector 11 is, for example, in the range of 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0184] The positive electrode current collector 11 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, PET, PE, PP, PBT, PI, or combinations thereof. The base film may be, for example, an insulator. Because the base film includes an insulating thermoplastic polymer, it can soften or liquefy to interrupt battery operation when a short circuit occurs, 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 can function as an electrochemical fuse to be cut off when an overcurrent occurs, thereby preventing a short circuit. The thickness of the metal layer can be adjusted to regulate the limiting current and the maximum current. The metal layer may be electroplated or deposited on the base film. When the thickness of the metal layer is reduced, the limiting current and / or the maximum current of the positive electrode current collector 11 can be reduced, thereby improving the stability of the all-solid-state secondary battery during a short circuit. Lead terminals can be added to the metal layer for external connections. Lead terminals can be welded to the metal layer or metal layer / base film stack using ultrasonic welding, laser welding, spot welding, etc. When the base film and / or metal layer melts during welding, the metal layer can be electrically connected to the lead terminals. To more firmly weld the metal layer and lead terminals, a metal sheet can be added between the metal layer and the lead terminals. The metal sheet can be a thin sheet made of the same material as the metal of the metal layer. The metal sheet can be, for example, metal foil, metal mesh, etc. The metal sheet can be, for example, aluminum foil, copper foil, stainless steel (SUS) foil, etc. The metal sheet can be placed on the metal layer and then welded to the lead terminals, thereby welding the lead terminals to the metal sheet / metal layer stack or metal sheet / metal layer / base film stack. During welding, when the base film, metal layer, and / or metal sheet melt, the metal layer or metal layer / metal sheet stack becomes electrically connected to the lead terminals. Metal sheets and / or lead terminals can be added to a portion of the metal layer. The thickness of the base film can be, for example, in the range of 1~50 μm, 1.5~50 μm, 1.5~40 μm, or 1~30 μm. Because the base film has a thickness within this range, the weight of the electrode assembly can be reduced more effectively. The melting point of the base film can be, for example, in the range of 100~300°C, 100~250°C, or less, or 100~200°C. Because the base film has a melting point within this range, it can be melted and easily bonded to the lead pads during the soldering process. To improve the adhesion strength between the base film and the metal layer, surface treatments, such as corona treatment, can be applied to the base film. The thickness of the metal layer can be, for example, in the range of 0.01~3 μm, 0.1~3 μm, 0.1~2 μm, or 0.1~μm. Because the metal layer has a thickness within this range, the stability of the electrode assembly can be ensured while maintaining conductivity.The thickness of the metal sheet can be, for example, in the range of 2~10 μm, 2~7 μm, or 4~6 μm. Because the metal sheet has a thickness within such a range, the metal layer can be more easily connected to the lead terminals. Because the positive electrode current collector 11 has this structure, the weight of the positive electrode is reduced, thereby improving the energy density of the positive electrode and the all-solid-state secondary battery.

[0185] [Positive electrode layer: First inactive component]

[0186] refer to Figure 4 and Figure 5 as well as Figures 8-12 The all-solid-state secondary battery 1 may further include a first inactive member 40 (40a or 40b) disposed on at least one of the negative current collector 21 and the positive current collector 11.

[0187] For more specific details regarding the first inactive component 40a (40a or 40b), refer to the first inactive component 40 (40a or 40b) of the negative electrode layer described above.

[0188] [Positive electrode layer: Second inactive component]

[0189] refer to Figures 6-12 The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one side of the positive electrode current collector 11. A second inactive component 50 is disposed on one side of the positive electrode layer 10.

[0190] refer to Figure 7 , Figure 9 and Figure 11 The second inactive component 50 is disposed on one side of the positive electrode active material layer 12 and between the solid electrolyte layer 30 and the positive electrode current collector 11 facing the solid electrolyte layer 30. The second inactive component 50 is not disposed on the side of the positive electrode current collector 11. (See reference) Figure 6 , Figure 8 , Figure 10 and Figure 12 A second inactive component 50 is disposed on one side of the positive electrode active material layer 12 and the positive electrode current collector 11. The inclusion of the second inactive component 50 prevents the solid electrolyte layer 30 from cracking during the manufacture of the all-solid-state secondary battery 1 and / or during charging and discharging, thereby improving the cycle characteristics of the all-solid-state secondary battery 1. In an all-solid-state secondary battery 1 without the second inactive component 50, uneven pressure is applied to the solid electrolyte layer 30 in contact with the positive electrode layer 10 during the manufacture of the all-solid-state secondary battery 1 and / or during charging and discharging, causing cracking within the solid electrolyte layer 30, through which lithium metal grows, thereby increasing the likelihood of a short circuit.

[0191] refer to Figures 6-12In the all-solid-state secondary battery 1, the thickness of the second inactive component 50 is, for example, greater than the thickness of the first negative electrode active material layer 22. The thickness of the second inactive component 50 is, for example, greater than the thickness of the solid electrolyte layer 30.

[0192] refer to Figures 6-12 The second inactive component 50 surrounds the side of the positive electrode layer 10 and is in contact with the solid electrolyte layer 30. Because the second inactive component 50 surrounds the side of the positive electrode layer 10 and is in contact with the solid electrolyte layer 30, it effectively suppresses the cracking of the solid electrolyte layer 30, which occurs in the portion of the solid electrolyte layer 30 not in contact with the positive electrode layer 20 due to pressure differential during the pressing process. The second inactive component 50 surrounds the side of the positive electrode layer 10 and is separated from the negative electrode layer 20, more specifically, from the first negative electrode active material layer 22. The second inactive component 50 surrounds the side of the positive electrode layer 10, is in contact with the solid electrolyte layer 30, and is separated from the negative electrode layer 20. This suppresses 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 the possibility of a short circuit due to lithium overcharging. The second inactive component 50 is disposed on one side of the positive electrode active material layer 12 and on the other side of the positive electrode current collector 11, thereby more effectively suppressing the possibility of short circuit due to contact between the positive electrode current collector 11 and the negative electrode layer 20.

[0193] refer to Figures 6-12 A second inactive member 41 (41a or 41b) extends from one side of the positive electrode layer 30 to the end of the solid electrolyte layer 30. A second inactive member 50 may extend to the end of the solid electrolyte layer 30, thereby suppressing breakage at the end of the solid electrolyte layer 30. The end of the solid electrolyte layer 30 is the outermost portion in contact with the side surface of the solid electrolyte layer 30. The second inactive member 50 extends to the outermost portion in contact with the side surface of the solid electrolyte layer 30. The second inactive member 50 is separate from the negative electrode layer 20, and more specifically, from the first negative electrode active material layer 22. The second inactive member 50 extends to the end of the solid electrolyte layer 30 but does not contact the negative electrode layer 20. For example, the second inactive member 50 fills the space extending from one side of the positive electrode layer 30 to the end of the solid electrolyte layer 30.

[0194] The area of ​​the positive electrode active material layer 12 or the positive electrode layer 10 may be smaller than the area of ​​the first negative electrode active material layer 22 or the negative electrode layer 20. The area of ​​the positive electrode active material layer 12 or the positive electrode layer 10 may be smaller than the area of ​​the solid electrolyte layer 30.

[0195] The second inactive component 50 can be, for example, a gasket. By using a gasket as the second inactive component 50, the rupture of the solid electrolyte layer 30 caused by pressure differential during the pressing process can be effectively suppressed.

[0196] The second inactive member 50 has, for example, a single-layer structure. Alternatively, although not shown in the figures, the second inactive member 50 may have a multi-layer structure. The multi-layer structure may have, for example, two, three, or four layers, and the second inactive member 50 may have a multi-layer structure, allowing for more precise adjustment of the physical properties of the second inactive member 50.

[0197] Although not shown in the accompanying drawings, part or all of the second inactive member 50 may be spaced apart from the sides of the positive electrode active material layer 12. Because part or all of the second inactive member 50 is spaced apart from the sides of the positive electrode active material layer 12, the manufacturing process of the all-solid-state secondary battery 1 is simplified, and the manufacturing speed of the all-solid-state secondary battery 1 can be increased. Because part or all of the second inactive member 50 is spaced apart from the sides of the positive electrode active material layer 12, the second inactive member 50 can more effectively adapt to the lateral volume changes of the positive electrode active material layer 12 during charging and discharging, thereby further improving the lifetime characteristics of the all-solid-state secondary battery 1. The distance between the second inactive member 50 and the sides of the positive electrode active material layer 12 can each be independently, for example, within the range of 0.1 μm to 10 mm, 1 μm to 1 mm, 1 μm to 500 μm, 1 μm to 100 μm, 1 μm to 50 μm, or 1 μm to 10 μm.

[0198] refer to Figures 6-12 The second inactive component 50 may be, for example, a material selected from those used in the first inactive component 40 (40a or 40b) described above. The second inactive component 50 does not include, for example, an electrode active material. The second inactive component 50 may be, for example, a flame-retardant inactive component, an electronically insulating inactive component, an ionically insulating inactive component, or an elastic inactive component.

[0199] [Solid electrolyte layer]

[0200] [Solid electrolyte layer: solid electrolyte]

[0201] refer to Figures 1-12 The all-solid-state secondary battery 1 includes a solid electrolyte layer 30 disposed between a positive electrode layer 10 and a negative electrode layer 20. The solid electrolyte layer 30 includes, for example, a solid electrolyte, or a combination of a solid electrolyte and a gel electrolyte.

[0202] Solid electrolytes may include, for example, sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or combinations thereof.

[0203] Solid electrolytes are, for example, sulfide-based solid electrolytes. Sulfide-based solid electrolytes 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 (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 (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) and Li 7-x PS 6-x I x At least one of (0 ≤ x ≤ 2). For example, a sulfide-based solid electrolyte is prepared by treating the raw material (such as Li₂S or P₂S₅) with melt quenching or mechanical grinding. After such treatment, heat treatment may be performed. The solid electrolyte can be amorphous, crystalline, or a mixture thereof. Furthermore, the solid electrolyte can be a material that includes, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements in the aforementioned sulfide-based solid electrolyte material. For example, the solid electrolyte can be a material comprising Li₂S-P₂S₅. When a material comprising Li₂S-P₂S₅ is used as a sulfide-based solid electrolyte material for forming the solid electrolyte, the molar ratio of Li₂S to P₂S₅ (e.g., Li₂S:P₂S₅) is in the range of approximately 20:80~90:10, 25:75~90:10, 30:70~70:30, or 40:60~60:40.

[0204] Sulfide solid electrolytes may include, for example, sulfide-germanium ore type solid electrolytes represented by Formula 9 below:

[0205] <Form 9>

[0206] Li + 12-n-x A n+ X 2- 6-xY - x

[0207] wherein, in Formula 9, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, 1≤n≤5, and 0≤x≤2. The sulfide-based solid electrolyte may for example include a material selected from Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) and Li 7-x PS 6-x I x (0≤x≤2). The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I.

[0208] The argyrodite-type solid electrolyte may have a density of 1.5 to 2.0 g / cc. The argyrodite-type solid electrolyte may have a density of 1.5 g / cc or higher, such that the internal resistance of an all-solid secondary battery may be reduced, and penetration of Li into the solid electrolyte layer may be effectively suppressed.

[0209] The oxide-based solid electrolyte may be, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (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) (0≤x<1, and 0≤y<1), Pb(Mg3Nb 2 / 3 )O3-PbTiO3 (PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3 (0<x<2 and 0 <y<3), Li x Al y Ti z(PO4)3 (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 (0≤x≤1 and 0≤y≤1), Li x La y TiO3 (0<x<2 and 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M=Te, Nb or Zr, and 0≤x≤10) or a combination thereof. For example, the oxide-based solid electrolyte is prepared by sintering or the like.

[0210] The oxide-based solid electrolyte is, for example, a garnet-type solid electrolyte selected from Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M-doped LLZO, M=Ga, W, Nb, Ta or Al, 0<a<2, and 0≤x≤10).

[0211] For example, polymeric solid electrolytes may include mixtures of lithium salts and polymers, or may include polymers having ion-conducting functional groups. Polymeric solid electrolytes may be, for example, polymeric electrolytes that are solid at 25°C and 1 atm. Polymeric solid electrolytes may not include, for example, liquids. Polymeric solid electrolytes may include polymers, and polymers may include, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA), polyethylene glycol (PEG), and polypropylene. Acrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylene dioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, polyacetylene, NAFION, AQUIVION, FLEMION, GORE, ACIPLEX, MORGANE-ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(aryl ether ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazolidinebenzisoquinolinone)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylanthracene-2-sulfonate (DPASLi) + (or combinations thereof), but one or more embodiments are not limited thereto. Any material may be used, provided that it is usable in the art for polymer electrolytes. It may be used as a lithium salt, and any material may be used, provided that it is usable as a lithium salt in the art. Lithium salts are, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are each natural numbers from 1 to 20), LiCl, LiI, or mixtures thereof. The polymer included in the polymeric solid electrolyte may be, for example, a compound comprising 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight-average molecular weight of the polymer included in the polymeric solid electrolyte may be, for example, 1,000 Daltons or greater, 10,000 Daltons or greater, 100,000 Daltons or greater, or 1,000,000 Daltons or greater.

[0212] The gel electrolyte may be, for example, a polymer gel electrolyte. The gel electrolyte may have a gel state that does not include, for example, a polymer.

[0213] Polymer gel electrolytes may include, for example, a liquid electrolyte and a polymer, or may include an organic solvent and a polymer having ionicly conductive functional groups. Polymer gel electrolytes may be, for example, polymer electrolytes that are in a gel state at 25°C and 1 atm. Polymer gel electrolytes may have a gel state that does not, for example, exclude liquids. The liquid electrolyte used in polymer gel electrolytes may include, for example, a mixture of ionic liquids, lithium salts, and organic solvents; a mixture of ionic liquids and organic solvents; or a mixture of lithium salts, ionic liquids, and organic solvents. The polymer used in polymer gel electrolytes may be selected from the polymers used in solid polymer electrolytes. The organic solvent may be selected from the organic solvents used in liquid electrolytes. Organic solvents may be, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-ethylene glycol dimethyl ether, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof. Lithium salts may be selected from lithium salts used in polymeric solid electrolytes. Ionic liquids may refer to salts having a melting point at room temperature or lower, consisting solely of ions, and being liquid at room temperature, or salts that melt at room temperature. Ionic liquids may include, for example, at least one cation selected from the group consisting of: a) at least one cation selected from the group consisting of ammonium cations, pyrrolidine cations, pyridinium cations, pyrimidine cations, imidazolium cations, piperidinium cations, pyrazolium cations, oxazolium cations, pyridazine cations, phosphonium cations, thioonium cations, triazolium cations, and mixtures thereof; and b) at least one cation selected from the group consisting of BF4. - PF6 - AsF6 - SbF6 - AlCl4 - HSO4 - ClO4 - 、 CH3SO3 - 、 CF3CO2 - 、 Cl - ,Br - I - SO4 - CF3SO3 - (FSO2)2N- (C2F5SO2)2N - (C2F5SO2)(CF3SO2)N - and (CF3SO2)2N - At least one anion in the polymer. The polymer solid electrolyte may be impregnated with a liquid electrolyte, for example, in a secondary battery, to form a polymer gel electrolyte. The polymer gel electrolyte may further comprise inorganic particles. The polymer included in the polymer gel electrolyte may be, for example, a compound comprising 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight-average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Daltons or greater, 1,000 Daltons or greater, 10,000 Daltons or greater, 100,000 Daltons or greater, or 1,000,000 Daltons or greater.

[0214] [Solid electrolyte layer: binder]

[0215] 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 used as a binder in the art. The binder of the solid electrolyte layer 30 may be the same as or different from the binders included in the positive electrode active material layer 12 and the negative electrode active material layer 22. The binder may be omitted.

[0216] The content of the binder included in the solid electrolyte layer 30 relative to the total weight of the solid electrolyte layer 30 is in the range of 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt%.

[0217] The inventive concept will be described in more detail through the following embodiments and comparative examples. However, the embodiments are for illustrative purposes only, and the scope of the inventive concept is not limited by the embodiments.

[0218] (Preparation of positive electrode active material based on sulfide complex)

[0219] Preparation Example 1: Li2S-LiI-CNF Complex Positive Electrode Active Material

[0220] Li₂S and LiI were mixed at a weight ratio of 30:20. The resulting mixture was mechanically milled using a ball mill to prepare the Li₂S-LiI composite. The milling conditions were 25°C, 510 rpm, and 10 hours.

[0221] The Li₂S-LiI composite and CNF were mixed at a weight ratio of 50:10. The mixture was mechanically ground using a ball mill to prepare the Li₂S-LiI-CNF composite. The grinding conditions were 25°C, 510 rpm, and 10 hours. The Li₂S-LiI-CNF composite was used as the composite positive electrode active material.

[0222] (Manufacturing of all-solid-state secondary batteries)

[0223] Example 1: Elastic sheet (25 μm) / Positive electrode layer (112 μm, NCA) / Solid electrolyte layer (30 μm) / Negative electrode layer (37 μm, Si alloy particles: CNT = 9:1 + binder)

[0224] (Manufacturing of the positive electrode layer)

[0225] Preparation of LZO-coated LiNi0.8Co0. 15 Al0. 05 O2 (NCA) was used as the positive electrode active material. LZO-coated positive electrode active material was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942A. Li6PS5Cl (D) was prepared as a sulfogermanium sulfide-type crystal. 50 =0.5 μm, crystalline) as a solid electrolyte. PTFE binder was prepared as a binder. Carbon nanofibers (CNF) were prepared as a conductive agent. A slurry was prepared by mixing these materials with xylene solvent at a weight ratio of positive electrode active material: solid electrolyte: conductive agent: binder = 84:11:3:2, and then the sheet was vacuum dried at 40 °C for 8 hours to prepare a positive electrode sheet. The prepared positive electrode sheet was placed on the carbon layer of a positive electrode current collector consisting of an aluminum foil coated with a carbon layer on one side, and heated and rolled at 85 °C to prepare a positive electrode layer. The total thickness of the positive electrode layer was approximately 112 μm. The thickness of the positive electrode active material layer was approximately 92 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0226] The initial charge capacity of the positive electrode layer is measured using the aforementioned half-cell. The initial charge capacity of the positive electrode active material layer is measured using a half-cell.

[0227] (Preparation of the negative electrode layer)

[0228] A 10 μm thick SUS foil was prepared as the negative electrode current collector. D was prepared as the first negative electrode active material. 50 Silicon-iron-copper-aluminum alloy (Si) with a particle size of 4 μm 75 Fe 9.5 Cu 9.5Al6 particles (MK Electronics Co., Ltd.). Silicon-iron-copper-aluminum alloy (Si-Fe-Cu-Al) particles include single-phase silicon, silicon-iron alloy phase, and silicon-copper alloy phase. The silicon-iron-copper-aluminum alloy (Si-Fe-Cu-Al) particles have a structure in which the single-phase silicon is surrounded by silicon-iron alloy phase, silicon-copper alloy phase, etc.

[0229] CNTs were prepared as fibrous carbon materials. CNTs consist of a primary carbon nanotube structure and a secondary carbon nanotube structure. The primary carbon nanotube structure is composed of individual carbon nanotube units. The length of the carbon nanotube units ranges from 200 nm to 300 nm, for example, 250 nm, and the diameter of the carbon nanotube units ranges from 5 to 10 nm or 7.5 nm. The secondary carbon nanotube structure is formed by the aggregation of multiple carbon nanotube units. The secondary carbon nanotube structure has a length of approximately 5 μm and a diameter of approximately 40 nm.

[0230] A mixture of 4 g of silicon-iron-copper-aluminum (Si-Fe-Cu-Al) particles and CNTs was placed in a container at a weight ratio of 9:1, and 4 g of an N-methyl-2-pyrrolidone (NMP) solution including 7 wt% PVDF binder (#9300 manufactured by Kureha Corporation) was added to prepare a mixed solution. The mixed solution was stirred while NMP was gradually added to prepare a slurry. The prepared slurry was applied to an SUS substrate using a doctor blade coater, dried in air at 80°C for 10 minutes, and then vacuum dried at 40°C for 10 hours to prepare a stack. The prepared stack was cold-rolled to planarize its surface, thereby preparing a negative electrode with a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 27 μm.

[0231] The initial charge capacity of the negative electrode was measured using the aforementioned half-cell. The initial charge capacity of the first negative electrode active material layer was also measured using the half-cell.

[0232] 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 determined by charging from the first OCV to 4.25 V (relative to Li / Li). + The initial charge capacity of the first negative electrode active material layer is determined by charging from the second OCV to 0.01 V (relative to Li / Li). + 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, measured under the same conditions as in Example 1, was less than 0.5 in each case.

[0233] (Preparation of solid electrolyte layer)

[0234] By adding 1.5 parts by weight of acrylic binder relative to 98.5 parts by weight of solid electrolyte to Li6PS5Cl solid electrolyte (D, which is a sulforaphite-germanium type crystal)... 50 The mixture was prepared by means of a particle size of 3.0 μm (crystallized). Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied to a nonwoven fabric placed on a PET substrate using a doctor blade coater and dried in air at 80°C for 10 minutes to prepare a stack. The prepared stack was vacuum dried at 80°C for 2 hours to prepare a solid electrolyte layer.

[0235] (Non-active component: elastic sheet)

[0236] A porous polyurethane foam sheet with a thickness of 25 μm was prepared as an elastic sheet.

[0237] (Manufacturing of all-solid-state secondary batteries)

[0238] A solid electrolyte layer is placed on the negative electrode, so that the first negative electrode active material layer is in contact with the solid electrolyte layer, and a positive electrode is placed on the solid electrolyte layer, so that the positive electrode active material layer is in contact with the solid electrolyte layer, thereby preparing a stack.

[0239] The prepared stack was pressed at 85°C and 500 MPa for 30 minutes. This pressing sintered the solid electrolyte layer to improve battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 30 μm. The density of the Li6PS5Cl solid electrolyte, which consisted of silver sulfide-germanium ore-type crystals included in the sintered solid electrolyte layer, was 1.6 g / cc. The area of ​​the solid electrolyte layer was equal to the area of ​​the negative electrode. An elastic sheet was additionally disposed on the positive electrode current collector of the pressed stack.

[0240] The stack, including the elastic sheet, is further placed in a bag and vacuum-sealed to prepare an all-solid-state secondary battery. A portion of the positive and negative current collectors extends to the outside of the sealed battery and serves as the positive and negative terminals, respectively.

[0241] Example 2: Elastic sheet (25 μm) / Positive electrode layer (112 μm, NCA) / Solid electrolyte layer (30 μm) / Negative electrode layer (37 μm, lithium-ionized Si alloy particles: CNT = 9:1 + binder)

[0242] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that lithium-ionized silicon-iron-copper-aluminum alloy (Si-Fe-Cu-Al) particles (MK Electronics Ltd.) were used instead of silicon-iron-copper-aluminum alloy (Si-Fe-Cu-Al) particles (MK Electronics Ltd.).

[0243] Comparative Example 1: Elastic sheet (100 μm) / Positive electrode layer (112 μm, NCA) / Solid electrolyte layer (30 μm) / Negative electrode layer (17 μm, Ag-C + binder): (Ag-C at a weight ratio of 4)

[0244] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that a mixture of carbon black (CB) and silver (Ag) in a weight ratio of 3:1 (4 g) was used instead of a mixture of silicon-iron-copper-aluminum alloy particles and CNTs in a weight ratio of 9:1. The thickness of the negative electrode active material layer was changed to 7 μm, and the thickness of the elastic sheet was changed to 100 μm. The thickness of the negative electrode layer is the total thickness of the negative electrode current collector and the negative electrode active material layer.

[0245] Example 3: Positive electrode layer (113.8 μm, Li2S-LiI-CNF) / solid electrolyte layer (30 μm) / negative electrode layer (37 μm, Si alloy particles:CNT=9:1 + binder)

[0246] An all-solid-state secondary battery was prepared in the same manner as in Example 1, except that a positive electrode containing a sulfide-based positive electrode active material was used, and the elastic sheet was omitted.

[0247] (Preparation of the positive electrode)

[0248] The Li₂S-LiI-CNF complex prepared in Preparation Example 1 was used as the positive electrode active material. Li₆PS₅Cl(D) was prepared as a sulforaphite-germanium-type crystal. 50 =3.0 μm, crystalline) as the solid electrolyte. PTFE was prepared as the binder. These materials were mixed at a weight ratio of composite positive electrode active material: solid electrolyte: binder = 60:40:1.2 to prepare a positive electrode mixture. The positive electrode mixture was obtained by mixing using a ball mill.

[0249] The positive electrode mixture was placed on one side of a positive electrode current collector consisting of an aluminum foil coated with carbon on one side, and the plate was pressed at a pressure of 200 MPa for 10 minutes to prepare the positive electrode. The total thickness of the positive electrode layer was approximately 113.8 μm. The thickness of the positive electrode active material layer was approximately 93.8 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0250] The initial charge capacity of the positive electrode layer was measured using the aforementioned half-cell. The initial charge capacity of the positive electrode active material layer was measured using the half-cell. The initial charge capacity of the negative electrode was measured in the same manner as in Example 1.

[0251] 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 determined by charging from the first OCV to 2.8 V (relative to Li / Li). + To determine.

[0252] Example 4: Positive electrode layer (113.8 μm, Li2S-LiI-CNF) / solid electrolyte layer (30 μm) / negative electrode layer (37 μm, lithiated Si alloy particles:CNT=9:1 + binder)

[0253] The all-solid-state secondary battery was manufactured in the same manner as in Example 3, except that lithium-ionized silicon-iron-copper-aluminum alloy (Si-Fe-Cu-Al) particles (MK Electronics Ltd.) were used instead of silicon-iron-copper-aluminum alloy (Si-Fe-Cu-Al) particles (MK Electronics Ltd.). The elastic sheet was omitted.

[0254] Comparative Example 2: Elastic sheet (50 μm) / Positive electrode layer (113.8 μm, Li2S-LiI-CNF) / Solid electrolyte layer (30 μm) / Negative electrode layer (17 μm, Ag-C + binder): (Ag-C at a weight ratio of 4)

[0255] An all-solid-state secondary battery was manufactured in the same manner as in Example 3, except that the positive electrode of Example 3 was used, and instead of the mixture of silicon-iron-copper-aluminum alloy (Si-Fe-Cu-Al) particles and CNTs in a weight ratio of 9:1, 4 g of a 3:1 mixture of CB and silver (Ag) was used. The thickness of the negative electrode active material layer was changed to 7 μm, and the thickness of the elastic sheet was changed to 50 μm. The thickness of the negative electrode layer is the total thickness of the negative electrode current collector and the negative electrode active material layer.

[0256] Evaluation Example 3: Charge-Discharge Test

[0257] The charge and discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 and 2, as well as Comparative Example 1, were evaluated by the following charge-discharge tests. The all-solid-state secondary batteries were placed in a constant-temperature bath at 45°C for the charge-discharge tests.

[0258] In the first cycle, the all-solid-state secondary battery achieved 0.5 mA / cm². 2 The battery was charged at a constant current for 12.5 hours until the battery voltage reached 4.25 V. Subsequently, the all-solid-state secondary battery was charged at 0.5 mA / cm².2 Discharged under constant current for 12.5 hours until the battery voltage reaches 2.5 V.

[0259] Meanwhile, the charging and discharging characteristics of the all-solid-state secondary batteries manufactured in Examples 3 and 4, as well as Comparative Example 2, were evaluated through the following charge-discharge tests. The all-solid-state secondary batteries were placed in a constant-temperature bath at 45°C for the charge-discharge tests.

[0260] In the first cycle, the all-solid-state rechargeable battery was charged at a constant current of 0.1 C for 12.5 hours until the battery voltage reached 2.8 V. Subsequently, the all-solid-state rechargeable battery was discharged at a constant current of 0.1 C for 12.5 hours until the battery voltage reached 0.3 V.

[0261] The discharge capacity of the first cycle is defined as the standard capacity. After the first cycle, up to 850 charge and discharge cycles were performed under the same conditions as the first cycle. The measurement results are shown in Tables 1 and 2 below. Table 1 shows the results of Examples 1 and 2 and Comparative Example 1, and Table 2 shows the results of Examples 3 and 4 and Comparative Example 2.

[0262] Cycle count refers to the number of cycles required for the discharge capacity to drop to 80% of the standard capacity after the first cycle. It is believed that lifetime characteristics improve with increasing cycle count.

[0263] The initial efficiency of each solid secondary cell is represented by Equation 1 below, and its thickness change rate is represented by Equation 2 below.

[0264] Equation 1

[0265] Initial efficiency (%) = [Discharge capacity at the beginning of the first cycle / Charge capacity at the beginning of the first cycle] × 100

[0266] Equation 2

[0267] Thickness change rate (%) = [(cell thickness after charging - initial cell thickness) / initial cell thickness] × 100

[0268] [Table 1]

[0269]

[0270] As shown in Table 1, the all-solid-state secondary batteries of Examples 1 and 2 exhibit excellent initial efficiency and lifetime characteristics because thickness changes and increases in internal resistance are suppressed during charging and discharging.

[0271] The all-solid-state secondary batteries of Examples 1 and 2 include a first negative electrode active material having an alloy phase, and therefore have improved initial efficiency and lifetime characteristics compared to the all-solid-state secondary battery of Comparative Example 1.

[0272] [Table 2]

[0273]

[0274] As shown in Table 2, the all-solid-state secondary batteries of Examples 3 and 4 exhibit superior initial efficiency and lifetime characteristics because the first negative electrode active material containing an alloy phase suppresses thickness changes and increases in internal resistance during charging and discharging.

[0275] Evaluation Example 4: Evaluation of High-Rate Characteristics

[0276] The high-rate characteristics of the all-solid-state secondary batteries of Examples 1 and 2, as well as Comparative Example 1, were evaluated by the following charge-discharge tests. The all-solid-state secondary batteries were placed in a constant temperature bath at 45°C for charge-discharge testing.

[0277] The all-solid-state secondary batteries of Examples 1 and 2, as well as Comparative Example 1, were charged at 45°C with a constant current at a rate of 0.1 C until the voltage reached 3.9 V (relative to Li). Then, in constant voltage mode, charging was stopped at a current rate of 0.05 C while maintaining 3.9 V. Subsequently, during discharge, the all-solid-state secondary batteries were discharged at a constant current at a rate of 0.1 C until the voltage reached 2.5 V (relative to Li) (formation cycling).

[0278] The all-solid-state secondary battery undergoing formation cycling was charged at 45°C with a constant current at a rate of 0.2 C until the voltage reached 3.9 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current at a rate of 0.2 C until the voltage reached 2.5 V (relative to Li) (Cycle 1).

[0279] The all-solid-state secondary battery undergoing its first cycle was charged at a constant current rate of 0.2 C at 45°C until the voltage reached 3.9 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current rate of 0.33 C until the voltage reached 2.5 V (relative to Li) (second cycle).

[0280] The all-solid-state secondary battery undergoing its second cycle was charged at 45°C with a constant current at a rate of 0.2 C until the voltage reached 3.9 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current at a rate of 0.5 C until the voltage reached 2.5 V (relative to Li) (third cycle).

[0281] The all-solid-state secondary battery undergoing its third cycle was charged at 45°C with a constant current at a rate of 0.2 C until the voltage reached 3.9 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current at a rate of 1.0 C until the voltage reached 2.5 V (relative to Li) (fourth cycle).

[0282] In all charge / discharge cycles, the all-solid-state secondary battery was left to rest for 10 minutes after each charge / discharge cycle.

[0283] In addition, the high-rate characteristics of the all-solid-state secondary batteries of Examples 3 and 4 and Comparative Example 2 were evaluated by the following charge-discharge tests. The all-solid-state secondary batteries were placed in a constant temperature bath at 45°C for charge-discharge tests.

[0284] The all-solid-state secondary batteries of Examples 3 and 4, as well as Comparative Example 2, were charged at 45°C with a constant current at a rate of 0.1 C until the voltage reached 2.5 V (relative to Li). Then, in constant voltage mode, charging was stopped at a current rate of 0.05 C while maintaining 2.5 V. Subsequently, during discharge, the all-solid-state secondary batteries were discharged at a constant current at a rate of 0.1 C until the voltage reached 0.3 V (relative to Li) (formation cycling).

[0285] The all-solid-state secondary battery undergoing formation cycling was charged at a constant current rate of 0.2 C at 45°C until the voltage reached 2.5 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current rate of 0.2 C until the voltage reached 0.3 V (relative to Li) (Cycle 1).

[0286] The all-solid-state secondary battery undergoing its first cycle was charged at a constant current rate of 0.2 C at 45°C until the voltage reached 2.5 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current rate of 0.33 C until the voltage reached 0.3 V (relative to Li) (second cycle).

[0287] The all-solid-state secondary battery undergoing its second cycle was charged at a constant current rate of 0.2 C at 45°C until the voltage reached 2.5 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current rate of 0.5 C until the voltage reached 0.3 V (relative to Li) (third cycle).

[0288] The all-solid-state secondary battery undergoing its third cycle was charged at a constant current rate of 0.2 C at 45°C until the voltage reached 2.5 V (relative to Li). Subsequently, during discharge, the all-solid-state secondary battery was discharged at a constant current rate of 1.0 C until the voltage reached 0.3 V (relative to Li) (fourth cycle).

[0289] In all charge / discharge cycles, the all-solid-state secondary cells were left to rest for 10 minutes after each charge / discharge cycle. Some charge-discharge test results at room temperature are shown in Table 3 below. The high-rate characteristics of each solid-state secondary cell are defined by Equation 3 below.

[0290] Equation 3

[0291] High rate capability [%] = [Discharge capacity at 4th cycle / Discharge capacity at formation cycle] × 100

[0292] [Table 3]

[0293]

[0294] As shown in Table 3, the all-solid-state secondary batteries of Examples 1 and 2 include a first negative electrode active material with an alloy phase, and therefore have improved high-rate characteristics compared with the all-solid-state secondary battery of Comparative Example 1.

[0295] In addition, as shown in Table 3, the all-solid-state secondary batteries of Examples 3 and 4 include a first negative electrode active material having an alloy phase, and therefore have improved high-rate characteristics compared with the all-solid-state secondary battery of Comparative Example 2.

Claims

1. An all-solid-state secondary battery, comprising: Positive electrode layer; Negative electrode layer; and The solid electrolyte layer 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 on one side of the positive electrode current collector. The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one side of the negative electrode current collector. The first negative electrode active material layer includes a first negative electrode active material and a carbon-based material, and The first negative electrode active material includes an alloy phase.

2. The all-solid-state secondary battery as claimed in claim 1, wherein the first negative electrode active material comprises silicon (Si), iron (Fe) and a first metal, and The first metal includes copper (Cu), aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), zirconium (Zr), niobium (Nb), molybdenum (Mo), tin (Sn), cerium (Ce), or combinations thereof.

3. The all-solid-state secondary battery as claimed in claim 1, wherein the first negative electrode active material comprises 60 to 90 at% of silicon (Si) and more than 0 to 30 at% of iron (Fe) relative to 100 at% of the total amount of the first negative electrode active material.

4. The all-solid-state secondary battery as claimed in claim 1, wherein the first negative electrode active material comprises a single-phase silicon, an alloy phase of silicon and iron, an alloy phase of silicon and a first metal, an alloy phase of iron and a first metal, an alloy phase of multiple first metals, or a combination thereof, and The alloy phase of silicon and iron includes FeSi2, Fe2Si5, FeSi, or combinations thereof.

5. The all-solid-state secondary battery of claim 1, wherein the first negative electrode active material further comprises boron (B), carbon (C), phosphorus (P), or a combination thereof.

6. The all-solid-state secondary battery as described in claim 1, wherein the first negative electrode active material is a lithium-based negative electrode active material.

7. The all-solid-state secondary battery as claimed in claim 1, wherein the first negative electrode active material is in particulate form, and The size of the first negative electrode active material ranges from 0.1 to 20 μm.

8. The all-solid-state secondary battery of claim 1, wherein the carbon material includes fibrous carbon material. The aspect ratio of the fibrous carbon material is 10 or greater, and The fibrous carbon materials include amorphous fibrous carbon materials, crystalline fibrous carbon materials, or combinations thereof.

9. The all-solid-state secondary battery as claimed in claim 1, wherein the content of the carbon material is in the range of 1 to 50 wt% relative to the total weight of the first negative electrode active material and the carbon material.

10. The all-solid-state secondary battery of claim 1, wherein the carbon material comprises a fibrous carbon nanostructure, and The fibrous carbon nanostructures include carbon nanotubes, carbon nanofibers, carbon nanoribbons, carbon nanorods, or combinations thereof.

11. The all-solid-state secondary battery of claim 1, wherein the first negative electrode active material layer further comprises a binder.

12. The all-solid-state secondary battery of claim 11, wherein the binder comprises a polymer binder, and The adhesive includes fluorinated adhesives.

13. The all-solid-state secondary battery as claimed in claim 1, wherein the ratio (B / A) of the initial charging capacity (B) of the first negative electrode active material layer to the initial charging capacity (A) of the positive electrode active material layer is in the range of 0.01 to 0.

75.

14. The all-solid-state secondary battery of claim 1, further comprising a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer and / or between the negative electrode current collector and the electrolyte layer. The second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

15. The all-solid-state secondary battery as claimed in claim 1, wherein the positive electrode active material layer comprises a positive electrode active material; The positive electrode active material includes sulfide-based positive electrode active materials, oxide-based positive electrode active materials, or combinations thereof; The sulfide-based positive electrode active material includes nickel sulfide, copper sulfide, Li₂S, Li₂S-containing complexes, or combinations thereof; and The oxide-based positive electrode active material includes lithium transition metal oxides, metal oxides, or combinations thereof; wherein 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; and the lithium oxides include iron oxide, vanadium oxide, or combinations thereof.

16. The all-solid-state secondary battery of claim 1, wherein the positive electrode active material layer further comprises at least one selected from solid electrolyte, conductive material, and binder. The solid electrolyte includes sulfide solid electrolytes, and The conductive material includes carbon-based conductive materials.

17. The all-solid-state secondary battery of claim 1, wherein the solid electrolyte layer comprises a solid electrolyte or a combination of a solid electrolyte and a gel electrolyte. The solid electrolyte includes sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or combinations thereof, and The gel electrolyte includes a polymer gel electrolyte.

18. The all-solid-state secondary battery of claim 17, wherein the sulfide-based solid electrolyte comprises a subset 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 (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 (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) and Li 7-x PS 6-x I x At least one of (0≤x≤2), The sulfide solid electrolytes include silver-germanium sulfide-type solid electrolytes, and The sulfide-germanium ore type solid electrolyte includes at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I, and has a density of 1.5~2.0 g / cc.

19. The all-solid-state secondary battery of claim 1, wherein at least one of the positive electrode current collector and the negative electrode current collector comprises a substrate film and a metal layer disposed on one or both sides of the substrate film. The base film comprises a polymer, wherein the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof, and The metal layer includes 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.

20. The all-solid-state secondary battery of claim 1, further comprising a first inactive component disposed on at least one of the opposite sides of the positive electrode current collector and the negative electrode current collector. The first inactive component is an elastic component.

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