Negative electrode-solid electrolyte subassembly for all-solid secondary battery and all-solid secondary battery including same

Abstract

The present invention relates to a negative electrode-solid electrolyte subassembly for an all-solid-state secondary battery and an all-solid-state secondary battery including the same. The negative electrode-solid electrolyte subassembly includes a negative electrode current collector, a negative electrode active material layer disposed on the negative electrode current collector, and a solid electrolyte disposed on the negative electrode active material layer. The negative electrode active material layer includes a first negative electrode active material layer in contact with the solid electrolyte and a second negative electrode active material layer in contact with the negative electrode current collector. The first negative electrode active material layer includes a first negative electrode active material containing a mixture / composite of carbon and one or more first elements selected from metals and metalloids, and the second negative electrode active material layer includes a second negative electrode active material containing a mixture / composite of carbon and one or more first elements selected from metals and metalloids, and a first negative active material containing a mixture / complex of carbon and one or more second elements selected from metals and metalloids, the amount of the first element being greater than the amount of the second element, and the amount of the first element being from about 25 wt% to about 80 wt% relative to the total weight of the first negative active material.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application Nos. 10-2024-0002441, filed on January 5, 2024, and 10-2024-0197881, filed on December 27, 2024, with the Korean Intellectual Property Office, and all rights arising therefrom, the entire contents of which are hereby incorporated by reference herein. Technical field

[0003] The present disclosure relates to a negative electrode-solid electrolyte subassembly for an all-solid-state secondary battery and an all-solid-state secondary battery including the negative electrode-solid electrolyte subassembly. Background art

[0004] In accordance with recent requirements in the industry, batteries with high energy density and stability are being actively developed. For example, lithium-ion batteries can be used in industries related to information devices, communication devices, automobiles, etc. In the automotive industry, safety is particularly emphasized because it directly affects human life.

[0005] Currently commercially available lithium-ion batteries use a liquid electrolyte containing a flammable organic solvent, and thus, in the case of a short circuit, may overheat and catch fire. In this regard, all-solid-state secondary batteries using a solid electrolyte instead of a liquid electrolyte have been proposed.

[0006] By not using a flammable organic solvent, all-solid-state secondary batteries can significantly reduce the risk of fire or explosion even in the case of a short circuit. Thus, such all-solid-state secondary batteries can provide significantly higher safety compared to lithium-ion batteries using a liquid electrolyte. Summary of the invention

[0007] A new negative electrode-solid electrolyte subassembly for an all-solid-state secondary battery is provided.

[0008] An all-solid-state secondary battery is provided, which has improved battery performance by including the negative electrode-solid electrolyte subassembly.

[0009] Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0010] According to one aspect of the present disclosure, a negative electrode-solid electrolyte subassembly for an all-solid-state secondary battery includes:

[0011] A negative electrode current collector; a negative electrode active material layer provided on the negative electrode current collector; and a solid electrolyte provided on the negative electrode active material layer and opposite to the negative electrode current collector,

[0012] wherein the negative electrode active material layer includes a first negative electrode active material layer provided in contact with the solid electrolyte and a second negative electrode active material layer provided in contact with the negative electrode current collector,

[0013] wherein the first negative electrode active material layer includes a first negative electrode active material, and the first negative electrode active material contains: i) a first carbon negative electrode active material and ii) a mixture of one or more first elements selected from metals and metalloids; i) a first carbon negative electrode active material and ii) a complex of one or more first elements selected from metals and metalloids; or a combination thereof,

[0014] wherein the second negative electrode active material layer includes a second negative electrode active material, and the second negative electrode active material contains: i) a second carbon negative electrode active material and ii) a mixture of one or more second elements selected from metals and metalloids; i) a second carbon negative electrode active material and ii) a complex of one or more second elements selected from metals and metalloids; or a combination thereof, and

[0015] wherein the amount of the first element in the first negative electrode active material layer is greater than the amount of the second element in the second negative electrode active material layer, and the amount of the first element is about 25 wt% to about 80 wt% based on the total weight of the first negative electrode active material.

[0016] The total amount of the first and second elements in the negative electrode active material layer may be about 15 wt% to about 40 wt% based on the total weight of the negative electrode active material layer. The thickness of each of the first negative electrode active material layer and the second negative electrode active material layer may be about 1 µm to about 10 µm.

[0017] The first and second negative electrode active materials may each independently include a mixture of first particles and second particles, the first particles being composed of amorphous carbon and the second particles being composed of a metal or a metalloid.

[0018] According to another aspect of the present disclosure, a all-solid-state secondary battery includes: a positive electrode; and the negative electrode-solid electrolyte subassembly provided on the positive electrode, wherein the solid electrolyte of the negative electrode-solid electrolyte subassembly is provided between the positive electrode and the negative electrode active material layer.

[0019] The solid electrolyte of the negative electrode-solid electrolyte subassembly may include a sulfide solid electrolyte. The sulfide solid electrolyte may include a thiogermanate-type solid electrolyte, the thiogermanate-type solid electrolyte may include one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I, and the thiogermanate-type solid electrolyte may have a density of about 1.5 g / cc to about 2.0 g / cc.

[0020] The first negative electrode active material may include a mixture of first particles composed of amorphous carbon and second particles composed of a metal or a metalloid.

[0021] When the all-solid-state secondary battery is in an initial state or a state after discharge, the negative electrode current collector, the first negative electrode active material layer, and the region therebetween may be a lithium (Li)-metal-free region without Li metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other aspects, features, and advantages of some embodiments of the present disclosure will become clearer from the following description when considered in conjunction with the accompanying drawings, where:

[0023] Figure 1A and 1B Schematically show the structures of the negative electrodes for embodiments of all-solid-state secondary batteries after charging and after discharging, respectively;

[0024] Figure 2A and 2B Schematically show the structures of the negative electrodes for all-solid-state secondary batteries after charging and after discharging, respectively, for comparison with Figure 1A and 1B Show the changes in the discharge capacities (milliamperes-hour / gram, mAh / g) of the all-solid-state secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 6 during high-temperature (45 °C) and 1 C discharge;

[0025] Figure 3A Show the changes in the discharge capacities (milliamperes-hour / gram, mAh / g) of the all-solid-state secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 6 during high-temperature (45 °C) and 2 C discharge;

[0026] Figure 3B Show the changes in the average voltages (volts, V) of the all-solid-state secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 6 during high-temperature (45 °C) and 1 C discharge;

[0027] Figure 3C Show the changes in the average voltages (volts, V) of the all-solid-state secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 6 during high-temperature (45 °C) and 2 C discharge;

[0028] Figure 3DShows the change in the average voltage (volts, V) of the all-solid-state secondary batteries of Example 1 and Example 2 and Comparative Examples 1 to 6 during high temperature (45 °C) and 2 C discharge;

[0029] Figure 4A Shows the change in the discharge capacity (milliamps-hour / gram, mAh / g) of the all-solid-state secondary batteries of Example 1 and Example 2 and Comparative Examples 1 to 6 during low temperature (0 °C) and 0.1 C discharge;

[0030] Figure 4B Shows the voltage characteristics (V, relative to Li / Li + ) of the all-solid-state secondary batteries of Example 2 and Comparative Example 2 when the charging rate is increased to 0.1 C, 0.2 C, and 0.33 C while fixing the discharge rate at 0.1 C;

[0031] Figure 4C Is a graph showing the change in the voltage characteristics (V, relative to Li / Li + ) of the all-solid-state secondary batteries of Example 3 and Comparative Example 2 when the charging rate is increased to 0.1 C and 0.2 C while fixing the discharge rate at 0.1 C;

[0032] Figure 5 Is a schematic diagram of one embodiment of the structure of the all-solid-state secondary battery;

[0033] Figure 6 Is a schematic diagram of another embodiment of the structure of the all-solid-state secondary battery; and

[0034] Figure 7 Is a schematic diagram of another embodiment of the structure of the all-solid-state secondary battery. Detailed Embodiments

[0035] The embodiments will now be described in detail, with examples illustrated in the accompanying drawings, where like reference numerals always refer to like elements. In this regard, the present embodiments may have different forms and should not be construed as limited to the descriptions set forth herein. Accordingly, the embodiments are described below only by reference to the accompanying drawings to illustrate aspects. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one (kind) of..." when before or after a list of elements modify the entire list of elements and not the individual elements of the list.

[0036] The inventive concept, which will be described more fully hereinafter, may have various variations and various embodiments, and specific embodiments will be shown in the drawings and described in more detail. However, the inventive concept should not be construed as being limited to the specific embodiments set forth herein. On the contrary, these embodiments will be construed to cover all variations, equivalents, or alternatives included within the scope of the inventive concept.

[0037] Unless otherwise explicitly stated in this specification, when an element such as a layer, film, region, and plate is referred to as being "on" or "above" another element, it can be directly on the other element or there can also be intervening elements.

[0038] Unless otherwise explicitly stated in this specification, any term expressed in the singular form can also include the plural form. Additionally, unless explicitly stated otherwise, "including A or B" can mean "including A, including B, or including A and B".

[0039] As used herein, the term "a combination thereof" can mean a mixture, laminate, composite, copolymer, alloy, reaction product, etc. of the indicated substances.

[0040] Unless otherwise defined herein, the particle diameter can be the average particle diameter. Additionally, the particle diameter can mean the average particle diameter (D50), which refers to the diameter of the particles at the cumulative 50 volume % in the particle size distribution. The average particle size (D50) can be measured by methods well-known to those skilled in the art. For example, the average particle size (D50) can be measured by a particle size analyzer, or can be measured by using a transmission electron microscopy image, or a scanning electron microscopy image. Alternatively, such measurement can be performed by a measuring device using dynamic light scattering technology, and the number of particles within a given particle size range can be counted through data analysis, and the average particle diameter (D50) value can be calculated therefrom. Alternatively, the average particle diameter (D50) can be measured using a laser diffraction method. If the laser diffraction method is used for the measurement, for example, the particles to be measured can be dispersed in a dispersion medium and subjected to ultrasonic radiation at a power output of about 28 kHz and 60 watts, and the average particle diameter (D50) can be calculated based on 50% in the particle size distribution according to the measuring device.

[0041] The terms used hereinafter are for the purpose of describing specific embodiments only and are not intended to limit the inventive concept. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. As used herein, the term "comprising" or "including" indicates the presence of the stated features, regions, wholes, steps, operations, elements, components, ingredients, materials, or combinations thereof, but does not preclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, ingredients, materials, or combinations thereof. As used herein, " / " can be interpreted as "and" or "or" depending on the context.

[0042] In the drawings, for clarity of description, the thicknesses of layers and regions may be exaggerated. The same reference numerals throughout the specification denote the same elements. Throughout the specification, when a component such as a layer, film, region, or plate is described as being "on" or "above" another component, the component may be directly on the other component or there may also be another component therebetween. It will be understood that although the terms "first", "second", etc. may be used herein to describe different elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0043] For ease of description, spatial relative terms such as "top", "bottom", "below", "beneath", "lower", "above", "upper", etc. may be used herein to describe the relationship of one element or feature to another element or feature as shown in the figures. It will be understood that, in addition to the directions shown in the figures, the spatial relative terms are also intended to cover different orientations of the device in use or operation. For example, if the device in one of the figures is flipped, an element described as "below" or "beneath" another element or feature will then be oriented "above" the other element or feature. Thus, the term "below" can cover both an orientation above and below. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in this disclosure are to be interpreted accordingly.

[0044] As used herein, "about" or "approximately" includes the stated value and means within an acceptable deviation range for a particular value as determined by one of ordinary skill in the art in view of the measurements discussed and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated value, or within ±15%, 10%, or 5%.

[0045] As used herein, the term "metal" refers to both metals and metalloids in elemental or ionic states such as silicon and germanium.

[0046] As used herein, the term "positive electrode active material" refers to a positive electrode material capable of undergoing lithiation and delithiation, and the term "negative electrode active material" refers to a negative electrode material capable of undergoing lithiation and delithiation.

[0047] As used herein, the term "lithiation" refers to the process of adding lithium to a positive electrode active material or a negative electrode active material, and the term "delithiation" refers to the process of removing lithium from a positive electrode active material or a negative electrode active material.

[0048] As used herein, the term "charging" refers to the process of supplying electrochemical energy to a battery, and the term "discharging" refers to the process of removing electrochemical energy from a battery.

[0049] As used herein, the terms "positive electrode" and "positive pole" refer to the electrode at which electrochemical reduction and lithiation occur during the discharging process, and the terms "negative electrode" and "negative pole" refer to the electrode at which electrochemical oxidation and delithiation occur during the discharging process.

[0050] As used herein, the "particle diameter" of a particle, if the particle is spherical, refers to the average diameter, and if the particle is non-spherical, refers to the average major axis length. The particle diameter of a particle can be measured using a particle size analyzer (PSA). As used herein, the "particle diameter" of a particle refers to, for example, the average particle diameter. Unless otherwise explicitly specified, the average particle diameter refers to the median particle diameter (D50). The median particle diameter (D50) refers to the size of the particle on the particle size distribution curve where the particles in the sample are cumulated from the smallest particle size to the largest particle size and which corresponds to the 50% cumulative value when counted from the smallest particle size. The cumulative value can be, for example, the cumulative volume. The median particle diameter (D50) can be measured, for example, by a laser diffraction method.

[0051] If measured using a scanning electron microscope, the size of the particle can be determined as follows: the average of the particle diameters of 30 or more randomly selected particles with a diameter of 1 µm or greater, excluding fine particles.

[0052] The average particle diameter of the positive electrode active material can be measured using a laser diffraction method. More particularly, the positive electrode active material can be dispersed in a solution and introduced into a commercial laser diffraction particle size measuring device (e.g., Microtrac MT3000) to undergo ultrasonic radiation at a power output of about 28 kilohertz (kHz) and 60 watts, and the average particle diameter (D50) can be calculated based on 50% in the particle size distribution of the measuring device.

[0053] As used herein, the term "D10" may refer to the diameter of the particles corresponding to 10 volume % cumulative in the particle size distribution, and the term "D90" as used herein may refer to the diameter of the particles corresponding to 90 volume % cumulative in the particle size distribution.

[0054] In the present specification, "a composite of a carbon negative electrode active material and one or more elements selected from metals and metalloids" refers to a material in which the carbon negative electrode active material and the one or more elements selected from metals and metalloids are complexated, and conceptually, refers to a material in which two or more materials are complexed and which exhibits improved properties compared to when each constituent material is used alone, while each material physically and chemically retains its original phase. The composite is distinguished from a mixture of the carbon negative electrode active material and the one or more elements selected from metals and metalloids.

[0055] Hereinafter, a negative electrode-solid electrolyte subassembly for an all-solid-state secondary battery, an all-solid-state secondary battery including the same, and a method for preparing the same according to embodiments will be described in more detail.

[0056] The all-solid-state secondary battery may include an intermediate layer containing silver (Ag) and carbon-based carbon particles to suppress the formation of lithium dendrites that may occur during charging and discharging, and to increase the energy density. Use of such an intermediate layer promotes the diffusion and deposition of lithium on the current collector, where silver (Ag) is used to reduce the nucleation overpotential for lithium deposition, which can result in a lower battery resistance. If such an intermediate layer is applied, the process of lithium diffusing into the intermediate layer can be greatly affected by the operating temperature and pressure. Additionally, if a discharge current of up to 1 C or greater flows, the reversible capacity can decrease.

[0057] If an intermediate layer containing silver and carbon particles is applied, as charging proceeds, silver (Ag) may migrate to the current collector and remain as a solid solution with lithium metal, and a large number of particles may remain closer to the current collector when discharging. As a result, due to the insufficient Ag content at the interface between the solid electrolyte layer and the intermediate layer, there may be an increase in overvoltage, which can lead to an increase in battery resistance.

[0058] To solve some of the foregoing problems, there is provided a negative electrode-solid electrolyte subassembly for an all-solid-state secondary battery that can improve high-rate performance and low-temperature operating performance, and an all-solid-state secondary battery containing the negative electrode-solid electrolyte subassembly.

[0059] The negative electrode-solid electrolyte subassembly according to the embodiment includes: a negative electrode current collector; a negative electrode active material layer disposed on the negative electrode current collector; and a solid electrolyte disposed on the negative electrode active material layer and opposite to the negative electrode current collector, wherein the negative electrode active material layer includes a first negative electrode active material layer disposed in contact with the solid electrolyte and a second negative electrode active material layer disposed in contact with the negative electrode current collector, wherein the first negative electrode active material layer includes a first negative electrode active material, and the first negative electrode active material contains: i) a first carbon negative electrode active material and ii) a mixture of one or more first elements selected from metals and metalloids; a complex of i) a first carbon negative electrode active material and ii) one or more first elements selected from metals and metalloids; or a combination thereof, wherein the second negative electrode active material layer includes a second negative electrode active material, and the second negative electrode active material contains: i) a second carbon negative electrode active material and ii) a mixture of one or more second elements selected from metals and metalloids; a complex of i) a second carbon negative electrode active material and ii) one or more second elements selected from metals and metalloids; or a combination thereof.

[0060] In the initial state of the battery, the amount of the first element in the first negative electrode active material layer may be greater than the amount of the second element in the second negative electrode active material layer, and the amount of the first element may be about 25% by weight to about 80% by weight relative to the total weight of the first negative electrode active material. All-solid-state secondary battery

[0061] The amount of one or more first elements selected from metals and metalloids in the first negative electrode active material layer adjacent to the solid electrolyte may be, for example, about 25 wt% to about 70 wt%, about 25 wt% to about 60 wt%, or about 25 wt% to about 40 wt% relative to the total weight of the first negative electrode active material. If the amount of the first element in the first negative electrode active material layer is within the foregoing range, after discharging of the all-solid-state secondary battery, the amount of the first element at the interface between the solid electrolyte and the first negative electrode active material layer may increase, so that the nucleation overpotential during the process of lithium diffusion and deposition may be reduced, and as a result, it may be possible to manufacture an all-solid-state secondary battery having improved high-rate performance and low-temperature operating performance. The amount of one or more second elements selected from metals and metalloids in the second negative electrode active material layer adjacent to the negative electrode current collector may be, for example, about 10 wt% to about 25 wt%, about 10 wt% to about 20 wt%, about 10 wt% to about 18 wt%, or about 10 wt% to about 15 wt% relative to the total weight of the second negative electrode active material. If the amount of the second element in the second negative electrode active material layer is within the foregoing range, after discharging of the all-solid-state secondary battery, due to insufficient content of the second element, such as insufficient silver (Ag) content, at the interface between the solid electrolyte layer and the intermediate layer, the overpotential may increase, and as a result, it may be possible to manufacture an all-solid-state secondary battery having improved high-rate performance and low-temperature operating performance without an increase in battery resistance.

[0062] In the present disclosure, silver is adopted as a non-limiting example of the first element and the second element.

[0063] By the high silver concentration at the interface between the solid electrolyte and the first negative electrode active material layer, the nucleation overpotential during lithium diffusion and deposition can be reduced. In addition, it may be possible to solve the problem of an increase in battery resistance during charging because, after charging and discharging, silver moves toward the current collector, resulting in a reduced silver concentration at the interface between the solid electrolyte and the first negative electrode active material layer. Thus, since the lithium diffusion resistance (resistance) within the negative electrode can be minimized, it may be possible to realize an all-solid-state secondary battery capable of high output and having improved low-temperature charge-discharge characteristics.

[0064] The total amount of the first element and the second element in the negative electrode active material layer may be, for example, about 1 wt% to about 65 wt%, about 10 wt% to about 55 wt%, about 15 wt% to about 55 wt%, or about 15 wt% to about 45 wt% relative to the total weight of the first and second negative electrode active materials (collectively, the negative electrode active material) in the negative electrode active material layer. Here, the negative electrode active material layer means the combined first and second negative electrode active material layers. If the total amount of the first element and the second element is within the foregoing range, the lithium diffusion resistance in the negative electrode can be minimized, so that a all-solid-state secondary battery having improved high output and low-temperature charge-discharge characteristics can be achieved.

[0065] According to an embodiment, the difference between the amount of the first element in the first negative electrode active material layer and the amount of the second element in the second negative electrode active material layer may be about 10 wt% to about 70 wt%, about 15 wt% to about 30 wt%, or about 15 wt% to about 25 wt%. If the difference between the amount of the first element in the first negative electrode active material layer and the amount of the second element in the second negative electrode active material layer is within the foregoing range, it may be possible to effectively prevent one or more selected from metals and metalloids from locally concentrating in the negative electrode active material layer adjacent to the negative electrode current collector after discharge.

[0066] According to another embodiment, the difference between the amount of the first element in the first negative electrode active material layer and the amount of the second element in the second negative electrode active material layer may be, for example, about 10 wt% to about 50 wt%, or about 10 wt% to about 24 wt%.

[0067] Figure 1A Shows a negative electrode of an all-solid-state secondary battery according to an embodiment, and shows the structure of the negative electrode after charging. Figure 1B Shows after discharge Figure 1A the structure of the negative electrode.

[0068] The negative electrode according to an embodiment may include: a negative electrode current collector 21; a lithium metal layer 23 provided on the negative electrode current collector 21; and a negative electrode active material layer 22 provided on the lithium metal layer 23. The lithium metal layer 23 may exist during battery assembly, or may be formed after charging. After charging, silver 2 may be uniformly present in the negative electrode active material layer 22.

[0069] As Figure 1B shown, the negative electrode active material layer 22 may include silver 2 and a carbon negative electrode active material 3. In addition, after discharge, the negative electrode may have an increased amount of silver 2 in the region of the negative electrode active material layer 22 in contact with the negative electrode current collector 21.

[0070] Figure 2A and 2B shows the state of a normal negative electrode after charging and discharging. After charging, silver (Ag) 2 in the negative electrode may be distributed in the negative electrode active material layer 22, as shown in Figure 2A . In contrast, after discharging Figure 2B the negative electrode in has a higher amount of silver (3) in the region adjacent to the negative electrode current collector in the negative electrode active material layer 22. In a all-solid-state secondary battery having such a negative electrode, since silver (Ag) moves toward the current collector after charging and discharging, when charging, the concentration of silver (Ag) at the interface between the solid electrolyte and the negative electrode active material layer, and as a result the battery resistance, may increase, and the battery performance may deteriorate.

[0071] In the negative electrode according to the embodiment, after charging, as shown in Figure 1A , the amount of silver in the first negative electrode active material layer 22a may remain higher than the amount of silver in the second negative electrode active material layer 22b provided on the lithium metal layer 23 containing lithium 23a. In addition, after discharging, compared with the case shown in Figure 2B , as shown in Figure 1B , the difference in silver content between the first region (top) of the negative electrode active material layer 22 in contact with the solid electrolyte layer and the second region (bottom) of the negative electrode active material layer close to the lithium plating layer and the negative electrode current collector may be relatively reduced. Therefore, since an increase in the Ag concentration in the negative electrode active material layer adjacent to the solid electrolyte layer is suppressed, an increase in the battery resistance when charging can be effectively prevented. As shown in Figure 1A , the first negative electrode active material layer 22a and the second negative electrode active material layer 22b may contain carbon or a carbon-based negative electrode active material 3 and a metal such as silver 2. In addition, although shown as having the same thickness in Figure 1A , the first negative electrode active material layer 22a and the second negative electrode active material layer 22b may have different thicknesses from each other.

[0072] According to the embodiment, in the negative electrode active material layer shown in Figure 1B , the difference in the amount of an element such as silver between the first region (top) of the negative electrode active material layer in contact with the solid electrolyte layer and the second region (bottom) of the negative electrode active material layer may be 25 wt% or less, or about 15 wt% to about 25 wt%, and such a difference can be confirmed by SEM-EDX analysis.

[0073] In the present disclosure, with respect to the total distance from the contact point with the negative electrode current collector to the contact point of the negative electrode active material layer with the solid electrolyte, the first region (top) of the negative electrode active material layer refers to a region of about 50 length % to about 80 length % starting from the contact point with the solid electrolyte. Additionally, with respect to the total distance from the contact point with the negative electrode current collector to the contact point with the solid electrolyte, the second region (bottom) of the negative electrode active material layer refers to a region of about 20 length % to about 50 length % starting from the contact point with the negative electrode current collector. According to an embodiment, with respect to the total distance from the contact point with the negative electrode current collector to the contact point with the solid electrolyte, the first region refers to a region of about 50 length % starting from the contact point with the solid electrolyte, and with respect to the total distance from the contact point with the negative electrode current collector to the contact point with the solid electrolyte, the second region refers to a region of about 50 length % starting from the contact point with the negative electrode current collector.

[0074] In the discharged state of the all-solid-state secondary battery after the formation process, the difference between the amount of one or more selected from metals and metalloids in the first region and the amount of one or more selected from metals and metalloids in the second region may be 25 wt% or less. The amount of one or more selected from metals and metalloids in the second region may be greater than the amount of one or more selected from metals and metalloids in the first region, where the difference therebetween may be about 1 wt% to about 25 wt%.

[0075] The first negative electrode active material layer and the second negative electrode active material layer, as described above, may utilize a carbon negative electrode active material having one or more selected from metals and metalloids supported thereon.

[0076] According to an embodiment, the first negative electrode active material layer may include a material having a first element supported on a first carbon negative electrode active material, and the second negative electrode active material layer may include a material having a second element supported on a second carbon negative electrode active material. For example, the first element and the second element may be fixed on the respective first and second carbon negative electrode active materials.

[0077] For example, if the first negative electrode active material layer uses a first carbon negative electrode active material on which one or more selected from metals and metalloids are supported, compared with when using a mixture of the first carbon negative electrode active material and one or more selected from metals and metalloids, one or more selected from metals and metalloids, such as Ag, can be fixed on the first carbon negative electrode active material, so that the migration of silver toward the current collector during charging and discharging can be effectively suppressed, thereby allowing the concentration of silver (Ag) at the solid electrolyte interface to remain high. That is, if the first negative electrode active material layer includes one or more selected from metals and metalloids supported on the first carbon negative electrode active material, the lithium diffusion resistance in the negative electrode can be minimized, so that a all-solid-state battery with improved high-output and low-temperature operation characteristics can be achieved.

[0078] In this specification, the term "size" refers to the particle diameter or the average particle diameter if the particles are spherical, and refers to the major axis length or the average major axis length if the particles are non-spherical. The size of the particles can be measured using a scanning electron microscope or a particle size analyzer. For example, the particle size analyzer can be the LA-950 laser particle size analyzer of HORIBA. When measuring the size of the particles using a particle size analyzer, the average particle diameter refers to D50. D50 means the diameter or the average diameter of the particles corresponding to 50 volume% of the cumulative volume, and on the distribution curve of the particles accumulated from the smallest particle size to the largest particle size, when the total number of particles is 100%, it means the value of the particle diameter corresponding to 50% starting from the smallest particle. In this disclosure, "particle size" and "particle diameter" can be used interchangeably.

[0079] The size of the positive electrode active material in this specification can be, for example, the median particle diameter D50 measured by a laser-type particle size distribution analyzer.

[0080] The average particle diameter of the solid electrolyte can be measured using a laser diffraction method. More specifically, the positive electrode active material or the solid electrolyte can be dispersed in a solution and introduced into a commercial laser diffraction particle size measuring device (for example, Microtrac MT 3000) to undergo ultrasonic radiation at a power output of about 28 kHz and 60 watts, and the average particle diameter (D50) can be calculated based on 50% in the particle size distribution according to the measuring device.

[0081] The average particle diameter in this specification can be the median particle diameter measured by a laser-type particle size distribution analyzer.

[0082] As used herein, the term "D10" may refer to the diameter of the particles corresponding to 10 volume % cumulative in the particle size distribution, and the term "D90" as used herein may refer to the diameter of the particles corresponding to 90 volume % cumulative in the particle size distribution.

[0083] According to an embodiment, each of the first negative electrode active material layer and the second negative electrode active material layer may have a thickness of about 1 µm to about 10 µm, about 1 µm to about 9 µm, about 1 µm to about 8 µm, such as about 2 µm to about 8 µm, or about 3 µm to about 5 µm.

[0084] In the present disclosure, the thickness of the second negative electrode active material layer may be the same as the thickness of the first negative electrode active material layer, or the thickness of the second negative electrode active material layer may be greater than the thickness of the first negative electrode active material layer. The ratio of the thickness of the second negative electrode active material layer to the thickness of the first negative electrode active material layer may be about 1:0.25 to about 1:1. The thickness of the first negative electrode active material layer may be about 2 µm to about 5 µm, and the thickness of the second negative electrode active material layer may be about 5 µm to about 8 µm. If the first and second negative electrode active material layers have a thickness ratio within the foregoing ranges, then after discharging, the first element and / or the second element may be uniformly present in the negative electrode active material layer, such that the discharge capacity and the average voltage characteristics may be improved, and an all-solid-state secondary battery having improved high-rate performance and low-temperature charge-discharge characteristics may be fabricated.

[0085] In the present disclosure, the solid electrolyte may include a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, a gel electrolyte, or a combination thereof, wherein the gel electrolyte may include a polymer gel electrolyte.

[0086] The sulfide solid electrolyte may be, for example, one or more selected from the following: Li2S-P2S5 and Li2S-P2S5-LiX where X may be 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 where m and n are each positive numbers and Z may be Ge, Zn or Ga m S n ; Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li where p and q are each positive numbers and M may be P, Si, Ge, B, Al, Ga or Inp MO q ; wherein Li with 0 ≤ x ≤ 2 7-x PS 6-x Cl x ; wherein Li with 0 ≤ x ≤ 2 7-x PS 6-x Br x ; wherein Li with 0 ≤ x ≤ 2 7-x PS 6-x I x ; and Li a PS b (Cl) d (5 ≤ a < 7, 4 ≤ b ≤ 6, and 0 < d ≤ 2).

[0087] The sulfide solid electrolyte may be, for example, a thiogermanate compound including one or more selected from the following: Li6PS5Cl, Li6PS5Br, Li6PS5I, and Li a PS b (Cl) d (5 ≤ a < 7, 4 ≤ b ≤ 6, and 0 < d ≤ 2).

[0088] The sulfide solid electrolyte may be prepared by treating starting materials such as Li2S and P2S5 through methods such as melt quenching, mechanical grinding, etc. Additionally, after such treatment, heat treatment may be carried out. The sulfide solid electrolyte may be amorphous, crystalline, or may be in a mixed state between amorphous and crystalline. Additionally, among the sulfide solid electrolyte materials described herein, the solid electrolyte may be a material containing at least sulfur (S), phosphorus (P), and lithium (Li) as its constituent elements. For example, the solid electrolyte may be a material including Li2S - P2S5. If the sulfide solid electrolyte material used to form the solid electrolyte contains Li2S - P2S5, the mixed molar ratio of Li2S:P2S5 may be in the range of, for example, about 20:80 to about 90:10, about 25:75 to about 90:10, about 30:70 to about 70:30, or about 40:60 to about 60:40.

[0089] For example, the sulfide solid electrolyte may include a thiogermanate solid electrolyte represented by Formula 1:

[0090] Formula 1

[0091] Li + 12-n-x A n+ X 2- 6-x Y - x

[0092] In Formula 1, A can be P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; X can be S, Se, or Te; Y can be Cl, Br, I, F, CN, OCN, SCN, or N3; and 1 ≤ n ≤ 5 and 0 ≤ x ≤ 2. For example, the sulfide solid electrolyte can be a thiogermanate compound including one or more selected from the following: Li 7-x PS 6-x Cl x , where 0 ≤ x ≤ 2; Li 7-x PS 6- x Br x , where 0 ≤ x ≤ 2; and Li 7-x PS 6-x I x , where 0 ≤ x ≤ 2. The sulfide solid electrolyte can be, for example, a thiogermanate compound including one or more selected from the following: Li6PS5Cl, Li6PS5Br, Li6PS5I, and Li a PS b (Cl) d (5 ≤ a < 7, 4 ≤ b ≤ 6, and 0 < d ≤ 2).

[0093] The thiogermanate solid electrolyte can have a density of about 1.5 g / cc to about 2.0 g / cc. By using a thiogermanate solid electrolyte having a density of 1.5 g / cc or greater, the internal resistance of the all-solid secondary battery can be reduced, and Li penetration into the solid electrolyte layer can be more effectively suppressed. The sulfide solid electrolyte can have excellent ionic conductivity and chemical stability. Therefore, the sulfide solid electrolyte can provide improved stability against air and electrochemical stability against lithium metal.

[0094] The sulfide solid electrolyte can include a thiogermanate solid electrolyte, which can include one or more selected from the following: Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 5.75 PS 4.75 Cl 1.25 , Li 6.25 PS5Cl 1.25 , and Li6PS 4.875 Cl 1.25 , and the thiogermanate solid electrolyte can have a density of about 1.5 g / cc to about 2.0 g / cc.

[0095] The sulfide solid electrolyte can have an ionic conductivity at 25°C of about 1 mS / cm to about 7 mS / cm, or about 1 mS / cm to about 6 mS / cm.

[0096] The oxide 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(Mg 1 / 3 Nb 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. The oxide solid electrolyte can be manufactured, for example, by a sintering method or the like.

[0097] For example, the oxide solid electrolyte may be a garnet - type solid electrolyte selected from the following: Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12(M-doped LLZO, where M = Ga, W, Nb, Ta, or Al, and 0 < a < 2 and 0 ≤ x ≤ 10).

[0098] For example, the polymer solid electrolyte may include a mixture of a lithium salt and a polymer, or may include a polymer having an ion-conducting functional group. For example, the polymer solid electrolyte may be a polymer electrolyte that is solid at 25°C and 1 atmosphere (atm). For example, the polymer solid electrolyte may not contain a liquid. The polymer solid electrolyte may include a polymer. For example, the polymer may be polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), 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, polysulfonated styrene (PSS), polyvinyl fluoride (PVF), poly(methyl methacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazole benzoisoquinolinone)] (SPBIBI), or a combination thereof. However, the polymer is not limited to the foregoing examples and may be any material available in the art for use in a polymer electrolyte. The lithium salt may be any lithium salt available in the art. The lithium salt may be, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1(SO2) (where x and y are each integers from 1 to 20), LiCl, LiI, or a mixture thereof. For example, the polymer included in the polymer solid electrolyte may be a compound containing 10 or more repeating units, 20 or more repeating units, 50 or more repeating units, or 100 or more repeating units. For example, the polymer included in the polymer solid electrolyte may have a weight-average molecular weight of 1,000 daltons or greater, 10,000 daltons or greater, 100,000 daltons or greater, or 1,000,000 daltons or greater.

[0099] The gel electrolyte may be, for example, a polymer gel electrolyte. For example, the gel electrolyte may have a gel state.

[0100] For example, the polymer gel electrolyte may include a liquid electrolyte and a polymer, or may include an organic solvent and a polymer having an ion-conducting functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atmosphere. For example, the polymer gel electrolyte may have a gel state while not containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, a mixture of an ionic liquid, a lithium salt, and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt and an ionic liquid. The polymer used in the polymer gel electrolyte is selected from the polymers used in the solid polymer electrolyte. The organic solvent is selected from the organic solvents used in the liquid electrolyte. The lithium salt is selected from the lithium salts used in the polymer solid electrolyte. An ionic liquid may refer to a room-temperature molten salt or a salt that is in a liquid state at room temperature, which is composed of individual ions and has a melting point at room temperature or lower. For example, the ionic liquid may be at least one selected from compounds containing the following: a) at least one cation selected from the following: ammonium, pyrrolidine , pyridine , pyrimidine , imidazole , piperidine , pyrazole , azole , pyridazine , , sulfonium, triazole , and mixtures thereof; and b) at least one anion selected from the following: BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3- , CF3CO2 - , Cl - , Br - , I - , SO4 2- , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - . For example, the polymer solid electrolyte can be formed into a polymer gel electrolyte by impregnating a liquid electrolyte in a secondary battery. The polymer gel electrolyte may further include inorganic particles. For example, the polymer included in the polymer gel electrolyte may be a compound containing 10 or more repeating units, 20 or more repeating units, 50 or more repeating units, or 100 or more repeating units. For example, the polymer included in the polymer gel electrolyte may have a weight-average molecular weight of 500 Dalton or greater, 1,000 Dalton or greater, 10,000 Dalton or greater, 100,000 Dalton or greater, or 1,000,000 Dalton or greater.

[0101] The negative electrode may further include a binder. The binder may contain one or more selected from the following: styrene-butadiene-styrene copolymer, acrylic resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0102] According to another aspect, there is provided a all-solid-state secondary battery including: a positive electrode; and a negative electrode-solid electrolyte subassembly according to an embodiment disposed on the positive electrode, wherein the solid electrolyte of the negative electrode-solid electrolyte subassembly is disposed between the positive electrode and the negative electrode.

[0103] Hereinafter, with reference to the drawings, the all-solid-state secondary battery according to an embodiment will be described in more detail.

[0104] Reference Figure 5 and 6 , the all-solid-state secondary battery 1 may contain: a negative electrode 20 including a negative electrode current collector 21 and a negative electrode active material layer 22; a positive electrode 10 including a positive electrode current collector 11 and a positive electrode active material layer 12; and a solid electrolyte 30 disposed between the negative electrode 20 and the positive electrode 10. The all-solid-state secondary battery may contain a negative electrode-solid electrolyte subassembly according to an embodiment. The negative electrode active material layer 22 may contain a first negative electrode active material layer 22a and a second negative electrode active material layer 22b.

[0105] The positive electrode 10 may contain a conductive material. The positive electrode 10 may contain a binder.

[0106] Negative electrode

[0107] The negative electrode 20 may include a negative electrode current collector 21 and a negative electrode active material layer 22, and the negative electrode active material layer 22 may include a negative electrode active material. The negative electrode active material layer 22 may contain a first negative electrode active material layer 22a and a second negative electrode active material layer 22b disposed in contact with the solid electrolyte layer 30.

[0108] The negative electrode active material included in the first negative electrode active material layer 22a and the second negative electrode active material layer 22b may have, for example, a particulate form. The negative electrode active material having a particulate form may have an average particle diameter of, for example, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less. The average particle diameter of the negative electrode active material having a particulate form may be, for example, from about 10 nm to about 4 μm, from about 10 nm to about 3 μm, from about 10 nm to about 2 μm, from about 10 nm to about 1 μm, or from about 10 nm to 900 nm. By using a negative electrode active material having an average particle diameter within the above range, reversible absorption and / or desorption of lithium during charge / discharge can be promoted. The average particle diameter of the negative electrode active material may be, for example, the median particle diameter (D50) measured by a laser-type particle size distribution analyzer.

[0109] The negative electrode active material may include carbon or a carbon-based negative electrode active material and one or more selected from metal or metalloid negative electrode active materials, and the carbon or carbon-based negative electrode active material may include one or more selected from amorphous carbon and crystalline carbon. The metal or metalloid negative electrode active material may be silver (Ag), indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0110] The negative electrode active material layer may include i) a composite of a first particle composed of amorphous carbon and a second particle composed of a metal or metalloid, or ii) a mixture of a first particle composed of amorphous carbon and a second particle composed of a metal or metalloid.

[0111] The solid electrolyte of the negative electrode-solid electrolyte subassembly may include a solid electrolyte, or a combination of a solid electrolyte and a gel electrolyte, wherein the solid electrolyte may include a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a combination thereof, and the gel electrolyte may include a polymer gel electrolyte.

[0112] When the all-solid-state secondary battery 1 is in an initial state or a state after discharge, the negative electrode current collector, the negative electrode active material layer, and the region therebetween may be a lithium (Li)-metal-free region without Li metal.

[0113] A third negative electrode active material layer 23 may be further included at least between the negative electrode current collector and the negative electrode active material layer 22, or between the solid electrolyte layer 30 and the negative electrode active material layer 22, wherein the third negative electrode active material layer 23 may be a metal layer including lithium or a lithium alloy.

[0114] Examples of the amorphous carbon may include carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, etc.; however, the carbon or carbon-based negative electrode active material is not limited to the foregoing examples and may be any material classified as amorphous carbon in the art. Amorphous carbon is carbon that does not have a crystalline structure or has a very low crystallinity, and thus, can be distinguished from crystalline carbon or graphite carbon.

[0115] Among these negative electrode active materials, the negative electrode active material layer 22 may include a mixture of a variety of different negative electrode active materials. For example, the first and second negative electrode active material layers 22a and 22b may each independently include a mixture of amorphous carbon and one or more selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of amorphous carbon to a metal such as gold (Au) in the mixture may be, for example, about 10:1 to about 1:2, about 5:1 to about 1:1, or about 4:1 to about 2:1 by weight ratio. However, the mixing ratio is not limited to the foregoing range and may be selected according to the required characteristics of the all-solid-state secondary battery 1. If the negative electrode active material has the above composition, the cycle performance of the all-solid-state secondary battery 1 can be further improved.

[0116] The negative electrode active material included in the negative electrode active material layer 22 may include, for example, a mixture of first particles and second particles, the first particles being composed of amorphous carbon, and the second particles being composed of a metal or a metalloid. Examples of the metal or metalloid may include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), etc. In another embodiment, the metalloid may be a semiconductor.

[0117] The negative electrode active material layer 22 may include, for example, a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or the like. However, the binder is not limited to the foregoing examples and may be any material that can be used as a binder in the art. The binder may be composed of a single type of binder or a plurality of different types of binders.

[0118] Since the negative electrode active material layer 22 includes a binder, the negative electrode active material layer 22 can be stably held on the negative electrode current collector 21. In addition, the formation of cracks in the negative electrode active material layer 22 can be suppressed despite the volume change and / or displacement of the negative electrode active material layer 22 during charging and discharging. For example, if the negative electrode active material layer 22 does not contain any binder, the negative electrode active material layer 22 may be easily delaminated from the negative electrode current collector 21. At the portion where the negative electrode active material layer 22 is separated from the negative electrode current collector 21, the negative electrode current collector 21 may be exposed and come into contact with the solid electrolyte layer 30, increasing the possibility of a short circuit. For example, the negative electrode active material layer 22 may be prepared by applying and drying a slurry in which materials forming the negative electrode active material layer 22 are dispersed on the negative electrode current collector 21. By including a binder in the negative electrode active material layer 22, stable dispersion of the negative electrode active material in the slurry can be achieved. For example, if the slurry is to be applied to the negative electrode current collector 21 by a screen printing method, it may be possible to prevent clogging of the screen (e.g., clogging by aggregates of the negative electrode active material).

[0119] For example, the negative electrode active material layer may have a thickness of 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less relative to the thickness of the positive electrode active material layer. The negative electrode active material layer may have, for example, a thickness of about 1 µm to about 20 µm, about 2 µm to about 10 µm, or about 3 µm to about 7 µm. If the negative electrode active material layer is too thin, lithium dendrites formed between the negative electrode active material layer 22 and the negative electrode current collector 21 may cause disintegration of the negative electrode active material layer 22, making it difficult to achieve improved cycle performance of the all-solid-state secondary battery 1. If the thickness of the negative electrode active material layer is excessively increased, the energy density of the all-solid-state secondary battery 1 decreases, while the internal resistance of the all-solid-state secondary battery 1 through the negative electrode active material layer 22 increases, and thus, it may be difficult to achieve improved cycle performance of the all-solid-state secondary battery 1.

[0120] The amount of the binder included in the negative electrode active material layer may be, for example, about 0.1% by weight to about 10% by weight, or about 0.1% by weight to about 5% by weight, relative to the total weight of the negative electrode active material layer. The negative electrode active material layer may include a conductive material. The amount of the conductive material included in the negative electrode active material layer may be, for example, about 0.1% by weight to about 10% by weight, or about 0.1% by weight to about 5% by weight, relative to the total weight of the negative electrode active material layer. The amount of the negative electrode active material included in the negative electrode active material layer may be, for example, about 90% by weight to about 99% by weight, or about 95% by weight to about 99% by weight, relative to the total weight of the negative electrode active material layer.

[0121] The negative electrode current collector may be formed of a material that does not react with lithium, for example, does not form an alloy or a compound with lithium. Examples of the material for forming the negative electrode current collector may include copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), etc. However, the material for forming the negative electrode current collector 21 is not necessarily limited to the foregoing materials, but may be any material that can be used as an electrode current collector in the art. The negative electrode current collector may be formed of one type of the foregoing metals, an alloy of two or more types of the metals, or a coated material. The negative electrode current collector may be, for example, in a plate type or a foil type.

[0122] The negative electrode current collector may include, for example, a base film and a metal layer provided on one or both sides of the base film. For example, the base film may include a polymer. For example, the polymer may include polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. For example, the metal layer may include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. By using the negative electrode current collector having the foregoing structure, the weight of the electrode can be reduced, and as a result, the energy density of the lithium battery can be improved.

[0123] The negative electrode active material layer 22 may further include other additives used in a conventional all-solid secondary battery, such as a filler, a dispersant, an ion conductor, etc.

[0124] Reference Figure 7, the all-solid-state secondary battery 1 may further include a thin film 24 containing an element capable of forming an alloy with lithium, for example, on the negative electrode current collector 21. The thin film 24 may be located between the negative electrode current collector 21 and the negative electrode active material layer 22. The thin film 24 may include, for example, an element capable of alloying with lithium. Examples of the element capable of forming an alloy with lithium may include gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but are not limited thereto, and any element available in the art capable of forming an alloy with lithium may be used. The thin film 24 may be composed of one of the aforementioned metals or may be composed of an alloy of different types of metals. If the thin film 24 is provided on the negative electrode current collector 21, the third negative electrode active material layer 23 plated between the thin film 24 and the second negative electrode active material layer 22b may have a further flattened form, and the all-solid-state secondary battery 1 may have further improved cycle performance.

[0125] For example, the thin film may have a thickness of about 1 nm to about 800 nm, about 10 nm to about 700 nm, about 50 nm to about 600 nm, or about 100 nm to about 500 nm. If the thickness of the thin film 24 is less than 1 nm, it may be difficult to achieve the functions attributable to the thin film 24. If the thickness of the thin film 24 is too large, the amount of lithium plated at the negative electrode decreases, and as a result, the all-solid-state secondary battery 1 may have a reduced energy density and deteriorated cycle performance. The thin film 24 may be disposed on the negative electrode current collector 21 by a vacuum deposition method, a sputtering method, a plating method, etc., but is not limited to the aforementioned methods, and may be any method available in the art capable of forming the thin film 24.

[0126] The all-solid-state secondary battery 1 may further include a third negative electrode active material layer 23, which is disposed, for example, between the negative electrode current collector 21 and the solid electrolyte layer 30 by charging. The all-solid-state secondary battery 1 may further include a third negative electrode active material layer 23, which is disposed, for example, between the negative electrode current collector 21 and the negative electrode active material layer 22 by charging. Although not shown in the drawings, the all-solid-state secondary battery 1 may further include a third negative electrode active material layer 23, which is disposed, for example, between the solid electrolyte layer 30 and the negative electrode active material layer 22 by charging. Although not shown in the drawings, the all-solid-state secondary battery 1 may further include a third negative electrode active material layer 23, which is disposed, for example, within the negative electrode active material layer 22 by charging.

[0127] The third negative electrode active material layer 23 may be, for example, a lithium metal layer containing lithium or a lithium alloy. The lithium metal layer may include lithium or a lithium alloy. Thus, since it is a metal layer containing lithium, the third negative electrode active material layer 23 can be used as a lithium reservoir, for example. The lithium alloy may include, 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, and may be any material that can be used as a lithium alloy in the art. The third negative electrode active material layer 23 may be composed of one of such alloys or lithium, or may be composed of multiple types of alloys.

[0128] The third negative electrode active material layer 23 is not limited to any specific thickness, but may have, for example, a thickness of about 1 µm to about 1,000 µm, about 1 µm to about 500 µm, about 1 µm to about 200 µm, about 1 µm to about 150 µm, about 1 µm to about 100 µm, or about 1 µm to about 50 µm. If the third negative electrode active material layer is too thin, the third negative electrode active material layer 23 may fail to function as a lithium reservoir. If the third negative electrode active material layer is too thick, the mass and volume of the all-solid-state secondary battery 1 may increase, while the cycling performance deteriorates considerably. The third negative electrode active material layer 23 may be, for example, a metal foil having a thickness within the foregoing range.

[0129] In the all-solid-state secondary battery 1, the third negative electrode active material layer 23 may be disposed, for example, between the negative electrode current collector 21 and the negative electrode active material layer 22 before the assembly of the all-solid-state secondary battery 1, or the third negative electrode active material layer 23 may be plated between the negative electrode current collector 21 and the negative electrode active material layer 22 after the assembly of the all-solid-state secondary battery 1.

[0130] If the third negative electrode active material layer 23 is disposed between the negative electrode current collector 21 and the negative electrode active material layer 22 before the assembly of the all-solid-state secondary battery 1, then since it is a metal layer containing lithium, the third negative electrode active material layer 23 can act as a lithium reservoir. The all-solid-state secondary battery 1 including the third negative electrode active material layer 23 may have further improved cycling performance. For example, before the assembly of the all-solid-state secondary battery 1, a lithium foil may be placed between the negative electrode current collector 21 and the negative electrode active material layer 22.

[0131] If the third negative electrode active material layer 23 is provided by charging after the assembly of the all-solid-state secondary battery 1, since the third negative electrode active material layer 23 is not included during the assembly of the all-solid-state secondary battery 1, the all-solid-state secondary battery 1 can have an increased energy density. For example, when the all-solid-state secondary battery 1 is charged, it can be charged beyond the charging capacity of the negative electrode active material layer 22. Then the negative electrode active material layer 22 can be overcharged. At the start of the charging, lithium can be absorbed into the negative electrode active material layer 22. The negative electrode active material included in the negative electrode active material layer 22 can form an alloy or a compound with the lithium ions moving from the positive electrode 10. If the charging is carried out beyond the capacity of the negative electrode active material layer 22, lithium can be plated, for example, on the back surface of the negative electrode active material layer 22, for example, between the negative electrode current collector 21 and the negative electrode active material layer 22, and the plated lithium can then form a metal layer corresponding to the third negative electrode active material layer 23. The third negative electrode active material layer 23 can be a metal layer mainly composed of lithium (i.e., metallic lithium). This result can be obtained from the fact that the negative electrode active material included in the negative electrode active material layer 22 is composed of a material that forms an alloy or a compound with lithium. During discharging, the lithium in the metal layer, for example, in the negative electrode active material layer 22 and the third negative electrode active material layer 23, can be ionized and migrate toward the positive electrode 10. In some embodiments, lithium can be used as the negative electrode active material in the all-solid-state secondary battery 1. In addition, since the negative electrode active material layer 22 covers the third negative electrode active material layer 23, the negative electrode active material layer 22 can act as a protective layer for the third negative electrode active material layer 23, i.e., the metal layer, while suppressing the precipitation and growth of lithium dendrites. In some embodiments, short circuits and capacity fade in the all-solid-state secondary battery 1 can be suppressed, and thus, the cycle performance of the all-solid-state secondary battery 1 can be improved. Furthermore, if the third negative electrode active material layer 23 is provided by charging after the assembly of the all-solid-state secondary battery 1, the negative electrode current collector 21, the negative electrode active material layer 22, and the region therebetween can be, for example, a Li-free region that does not include lithium (Li) metal or a lithium (Li) alloy when the all-solid-state secondary battery 1 is in an initial state or in a state after discharging.

[0132] The all-solid-state secondary battery 1 can have a structure in which the third negative electrode active material layer 23 is provided on the negative electrode current collector 21, and the solid electrolyte layer 30 is directly provided on the third negative electrode active material layer 23. The third negative electrode active material layer 23 can be, for example, a lithium metal layer or a lithium alloy layer.

[0133] Since the aforementioned sulfide solid electrolyte included in the solid electrolyte layer 30 suppresses side reactions between the third negative electrode active material layer 23, which is a lithium metal layer, and the solid electrolyte layer 30, the cycle performance of the all-solid-state secondary battery 1 can be improved.

[0134] Solid electrolyte layer

[0135] The solid electrolyte layer 30 may contain an oxide solid electrolyte, a sulfide solid electrolyte, a polymer electrolyte, or a combination thereof.

[0136] The solid electrolyte layer 30 may further include, for example, a binder. The binder included in the solid electrolyte layer 30 may include, for example, one or more selected from the following: styrene-butadiene-styrene copolymer, acrylic resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate; however, it is not limited to the aforementioned examples, and any material that can be used as a binder in the art can be used. The binder in the solid electrolyte layer 30 may be the same binder as the binder contained in the positive active material layer 12 and the negative active material layer 22, or a different binder.

[0137] According to an embodiment, the solid electrolyte layer 30 may use styrene-butadiene-styrene copolymer, (meth)acrylic resin, or a combination thereof as a binder.

[0138] An amount of the binder in the solid electrolyte layer may be about 0.5 parts by weight to about 2.0 parts by weight relative to 100 parts by weight of the total weight of the solid electrolyte and the binder.

[0139] In the composition forming the solid electrolyte, a dispersant may be further added. The dispersant may include Croda's KD14, KD9, and KD13, and BYK's DISPERBYK, etc., and such a dispersant is an example of a nonionic polymer dispersant. Examples of BYK's DISPERBYK may include DISPERBYK-180 and DISPERBYK-192.

[0140] positive electrode

[0141] The positive electrode 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12 .

[0142] For example, the positive electrode current collector 11 may be made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or a plate or foil formed of an alloy thereof. The positive electrode current collector 11 may be omitted.

[0143] The positive electrode active material layer 12 may include a bimodal (bimodal) positive electrode active material and a solid electrolyte. The solid electrolyte included in the positive electrode 10 may be similar (same) or different from the solid electrolyte included in the solid electrolyte 30. According to an embodiment, the solid electrolyte may contain a sulfide solid electrolyte according to an embodiment.

[0144] The positive electrode may contain a positive electrode active material.

[0145] The positive electrode active material may include, for example, an oxide-based positive electrode active material, a sulfide-based positive electrode active material, or a combination thereof.

[0146] The oxide-based positive electrode active material may include, for example, a lithium transition metal oxide, a metal oxide, or a combination thereof. The lithium transition metal oxide may include, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron phosphate, or a combination thereof. The metal oxide may include, for example, iron oxide, vanadium oxide, or a combination thereof.

[0147] The sulfide-based positive electrode active material may include, for example, nickel sulfide, copper sulfide, Li2S, a complex containing Li2S, or a combination thereof.

[0148] The oxide-based positive electrode active material may include, for example, one or more complex oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. For example, the oxide-based positive electrode active material containing lithium may include a compound represented by any of the following formulas: Li a A 1-b B’ b D2 (in this formula, 0.90 ≤ a ≤ 1 and 0 ≤ b ≤ 0.5); Li a E 1- b B’ b O 2-c D c (in this formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B’ b O 4-c D c (in this formula, 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B’ c D α (in this formula, 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 (in this formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni 1-b-c Cob B’ c O 2-α F’2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni 1-b-c Mn b B’ c D α (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α ≤ 2); Li a Ni 1-b-c Mn b B’ c O 2-α F’ α (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni 1-b-c Mn b B’ c O 2-α F’2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni b E c G d O2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (where 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (where 0.90 ≤ a ≤ 1 and 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (where 0.90 ≤ a ≤ 1 and 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (where 0.90 ≤ a ≤ 1 and 0.001 ≤ b ≤ 0.1); LiV2O5; LiI’O2; LiNiVO4; Li (3-f) J2(PO4)3 (0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3 (0≤f≤2); and LiFePO4.

[0149] In the formulae representing the foregoing compounds, A may be nickel (Ni), cobalt (Co), manganese (Mn), or a combination thereof; B' may be aluminum (Al), Ni, Co, Mn, chromium (Cr), iron (Fe), magnesium (Mg), strontium (Sr), vanadium (V), rare earth elements, or a combination thereof; D' may be oxygen (O), fluorine (F), sulfur (S), phosphorus (P), or a combination thereof; E may be Co, Mn, or a combination thereof; F' may be F, S, P, or a combination thereof; G may be Al, Cr, Mn, Fe, Mg, lanthanum (La), cerium (Ce), Sr, V, or a combination thereof; Q may be titanium (Ti), molybdenum (Mo), Mn, or a combination thereof; I' may be Cr, V, Fe, Sc, yttrium (Y), or a combination thereof; and J may be V, Cr, Mn, Co, Ni, copper (Cu), or a combination thereof. Compounds with a coating layer added on the surface of the above compounds may also be used. In addition, mixtures of the above compounds and compounds with a coating layer added thereon may also be used. The coating layer added on the surface of the foregoing compounds may include, for example, compounds of coating elements such as oxides and hydroxides of coating elements, hydroxyoxides of coating elements, carbonate oxides of coating elements, and hydroxycarbonates of coating elements. The compounds forming the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may be 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 layer may be selected within a range that does not adversely affect the physical properties of the positive electrode active material. Examples of coating methods may include spraying, dip coating, etc. Specific coating methods are well known to those of ordinary skill in the art, and therefore, detailed descriptions thereof will be omitted herein.

[0150] The oxide-based positive electrode active material may include, for example, lithium transition metal oxides represented by the following formulae 2 to 9:

[0151] Formula 2

[0152] Li a Ni x Co y M z O 2-b A b

[0153] In Formula 2, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.8 ≤ x < 1, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1, M can be manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and A can be F, S, Cl, Br, or a combination thereof.

[0154] Formula 3

[0155] LiNi x Co y Mn z O2

[0156] Formula 4

[0157] LiNi x Co y Al z O2

[0158] In Formulas 3 and 4, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1,

[0159] Formula 5

[0160] LiNi x Co y Mn z Al w O2

[0161] In Formula 5, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, 0 < w ≤ 0.2, and x + y + z + w = 1,

[0162] Formula 6

[0163] Li a Co x M y O 2-b A b

[0164] In Formula 6, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.9 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, and x + y = 1, M can be manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and A can be F, S, Cl, Br, or a combination thereof.

[0165] Formula 7

[0166] Li a Ni x Mn y M' z O 2-b A b

[0167] In Formula 7, 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' can be 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 can be F, S, Cl, Br, or a combination thereof.

[0168] Formula 8

[0169] Li a M1 x M2 y PO 4-b X b

[0170] In Formula 8, 0.90 ≤ a ≤ 1.1, 0 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.5, 0.9 < x + y < 1.1, and 0 ≤ b ≤ 2, M1 can be chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof, M2 can be magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y), or a combination thereof, and X can be O, F, S, P, or a combination thereof.

[0171] Formula 9

[0172] Li a M3 z PO4

[0173] In Formula 9, 0.90 ≤ a ≤ 1.1 and 0.9 ≤ z ≤ 1.1, and M3 can be chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0174] The oxide-based positive electrode active material can be covered with a coating layer. The coating layer can be any material known in the art as a coating layer for positive electrode active materials in all-solid-state secondary batteries. The coating layer can be, for example, Li2O-ZrO2 (LZO), etc.

[0175] The size of the oxide-based positive electrode active material may be, for example, from about 0.1 µm to about 30 µm, from about 0.5 µm to about 20 µm, or from about 1 µm to about 15 µm. The oxide-based positive electrode active material may be, for example, single crystal particles or polycrystalline particles.

[0176] The sulfide-based positive electrode active material may include, for example, a complex containing Li2S. The complex containing Li2S may include, for example, a complex of Li2S and carbon, a complex of Li2S, carbon, and a solid electrolyte, a complex of Li2S and a solid electrolyte, a complex of Li2S and a lithium salt, a complex of Li2S, a lithium salt, and carbon, a complex of Li2S and a metal carbide, a complex of Li2S, carbon, and a metal carbide, a complex of Li2S and a metal nitride, a complex of Li2S, carbon, and a metal nitride, or a combination thereof.

[0177] The complex of Li2S and carbon may include carbon. The carbon may be, for example, any carbon-containing material available in the art that can be used as a conductive material. The carbon may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon may be, for example, a sintered product of a carbon precursor. The carbon may be, for example, a carbon nanostructure. Examples of the carbon nanostructure may include one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, or a combination thereof. The carbon nanostructure may include, for example, carbon nanotubes, carbon nanofibers, carbon nanobelts, carbon nanorods, graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene balls (GB), or a combination thereof. The carbon may be, for example, porous carbon or non-porous carbon. The porous carbon may contain, for example, periodic and regular two-dimensional or three-dimensional pores. Examples of the porous carbon may include carbon blacks such as Ketjen black, acetylene black, super conducting acetylene black (Denka black), pyrolytic carbon black, and channel black; and graphite, activated carbon, or a combination thereof. The form of the carbon may be in particle form, sheet form, fiber form, etc., but is not limited thereto, and any material available in the art that can be used as carbon may be used. The complex of Li2S and carbon may be prepared by a method including, but not limited to, a dry method, a wet method, or a combination thereof. In addition, methods available in the art for preparing the complex of Li2S and carbon include grinding, heat treatment, deposition, etc., but are not limited to the foregoing methods, and any method available in the art may be used.

[0178] The composite of Li2S, carbon, and solid electrolyte may include carbon and solid electrolyte. For details of the carbon, refer to the composite of Li2S and carbon described above. The solid electrolyte may be, for example, an amorphous solid electrolyte and may be any material that can be used as an ion-conducting material in the art. The solid electrolyte may be, for example, an inorganic solid electrolyte. The solid electrolyte may be, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte may be, for example, a sulfide solid electrolyte, an oxide solid electrolyte, or a combination thereof. The sulfide solid electrolyte may contain, for example, Li, S, and P and may optionally further contain a halogen element. The sulfide solid electrolyte is selected from sulfide solid electrolytes used in the solid electrolyte layer. For details of the sulfide solid electrolyte and the oxide solid electrolyte, refer to the aforementioned sulfide solid electrolyte and oxide solid electrolyte of the solid electrolyte layer.

[0179] The composite of Li2S and solid electrolyte may include solid electrolyte. For details of the solid electrolyte, refer to the composite of Li2S, carbon, and solid electrolyte above.

[0180] The composite of Li2S and a lithium salt may include a lithium salt compound. The lithium salt compound does not contain, for example, a sulfur (S) sulfur atom. For example, the lithium salt compound may be a binary compound composed of lithium and one element selected from Groups 13 to 17 of the periodic table and hydrogen (H). The binary compound may include, for example, one or more selected from the following: LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and Li3B. For example, the lithium salt compound may be a ternary compound composed of lithium and two elements selected from Groups 13 to 17 of the periodic table and hydrogen (H). The ternary compound may include, for example, one or more selected from the following: Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. In some embodiments, the lithium salt compound may be at least one lithium halide compound selected from LiF, LiCl, LiBr, and LiI. The composite of Li2S and a solid electrolyte may include a solid electrolyte. For details of the solid electrolyte, refer to the solid electrolyte used in the composite of Li2S, carbon, and a solid electrolyte described above. The composite of Li2S and a lithium salt may include, for example, a composite of Li2S and one or more lithium salts selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and Li3B.

[0181] The composite of Li2S, a lithium salt, and carbon may include a lithium salt compound and carbon. For details of the carbon, refer to the composite of Li2S and carbon described above. For details of the lithium salt, refer to the composite of Li2S and a lithium salt described above.

[0182] The composite of Li2S and a metal carbide may include a metal carbide. The metal carbide may be, for example, a two-dimensional metal carbide. The two-dimensional metal carbide may be, for example, MXene. The two-dimensional metal carbide may be represented by, for example, M n+1 C n T x (where M is a transition metal, T is a terminal group, T is O, OH, and / or F, n = 1, 2, or 3, and x is the number of terminal groups). The two-dimensional metal carbide may be, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CTx , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5 )3C2T x , Ti3C2T x , Ta4C3T x , Nb4C3T x , or a combination thereof. The surface of the two-dimensional metal carbide may be terminated with O, OH, and / or F.

[0183] The Li2S, carbon, and metal carbide composite may include carbon and metal carbide. For details of the carbon, refer to the composite of Li2S and carbon described above. For details of the metal carbide, refer to the composite of Li2S and metal carbide described above.

[0184] The composite of Li2S and metal nitride may include metal nitride. The metal nitride may be, for example, a two-dimensional metal nitride. The two-dimensional metal nitride may be represented by, for example, M n+1 N n T x (where M is a transition metal, T is a terminal group, T is O, OH, and / or F, n = 1, 2, or 3, and x is the number of terminal groups). The surface of the two-dimensional metal nitride may be terminated with O, OH, and / or F.

[0185] The Li2S, carbon, and metal nitride composite may include carbon and metal nitride. For details of the carbon, refer to the composite of Li2S and carbon described above. For details of the metal carbide, refer to the composite of Li2S and metal nitride described above.

[0186] The composite containing Li2S may further include, for example, a sulfide solid electrolyte.

[0187] The size of the sulfide-based positive electrode active material may be, for example, about 0.1 µm to about 50 µm, about 0.5 µm to about 30 µm, about 0.5 µm to about 20 µm, or about 1 µm to about 10 µm. The size of Li2S may be, for example, about 1 nm to about 10 µm, about 10 nm to about 5 µm, about 10 nm to about 3 µm, or about 10 nm to about 1 µm. The size of the composite containing Li2S may be, for example, about 0.1 µm to about 50 µm, about 0.5 µm to about 30 µm, about 0.5 µm to about 20 µm, or about 1 µm to about 10 µm.

[0188] The form of the positive electrode active material may be in the form of particles, such as a perfect spherical shape, an ellipsoidal shape, etc. The particle diameter of the positive electrode active material is not limited and may be within the range applicable to positive electrode active materials of conventional all-solid-state secondary batteries.

[0189] The positive electrode active material may be covered with a coating layer. The coating layer may be any material known in the art as a coating layer for positive electrode active materials in all-solid-state secondary batteries. The coating layer may be, for example, Li2O-ZrO2, etc.

[0190] If the positive electrode active material contains nickel (Ni) as a ternary lithium transition metal oxide such as NCA and NCM, for example, the capacity density of the all-solid-state secondary battery 1 increases, which enables a reduction in the elution of metal from the positive electrode active material when in a charged state. As a result, the cycle performance of the all-solid-state secondary battery can be improved.

[0191] The form of the positive electrode active material may be in the form of particles, such as a perfect spherical shape, an ellipsoidal shape, etc. The particle diameter of the positive electrode active material is not limited and may be within the range applicable to positive electrode active materials of conventional all-solid-state secondary batteries. The content of the positive electrode active material in the positive electrode 10 is not limited and may be within the range applicable to positive electrodes of conventional all-solid-state secondary batteries.

[0192] In addition to the aforementioned positive electrode active material and solid electrolyte, the positive electrode 10 may further include, for example, additives such as a conductive material, a binder, a filler, a dispersant, and an ion conduction aid. Examples of the conductive material may include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc. Fillers, dispersants, ion conduction aids, etc. that can be combined with the positive electrode 10 may be any known materials in the art for use in electrodes of solid secondary batteries.

[0193] An all-solid-state secondary battery can be prepared by the following process: wherein a solid electrolyte layer 30 is laminated on the positive electrode 10, and a negative electrode 20 is laminated on the solid electrolyte layer 30.

[0194] According to another embodiment, the solid electrolyte layer 30 can be prepared by: coating and drying a composition forming a solid electrolyte on a separate carrier, and separating the solid electrolyte film from the carrier; or it can be prepared in the form of a sheet including a carrier. Non-limiting examples of the carrier may include polyethylene terephthalate film, polyethylene non-woven fabric, etc.

[0195] According to another embodiment, the solid electrolyte layer 30 can be formed by coating and drying the composition for forming the solid electrolyte on top of the positive electrode 10, or transferring it on top of the positive electrode 10. The solid electrolyte layer 30 can be in the form of a sheet.

[0196] Subsequently, the positive electrode, the solid electrolyte layer, and the negative electrode can be packaged with a packaging material and then pressed to manufacture a all-solid battery. The pressing can be carried out by a roll press, a hot press, an isostatic press, etc. In particular, isostatic pressing can be carried out at a temperature of about 85°C and a pressure of about 490 MPa for about 30 minutes.

[0197] Using a roll press or a hot press for the pressing can enable mass production and allow for the formation of a tight interface during the compression process of the electrode layer and the solid electrolyte layer.

[0198] Preparation of the negative electrode

[0199] The components constituting the negative electrode active material layer 22 (including the negative electrode active material, the conductive material, the binder, the solid electrolyte, etc.) can be added to a polar solvent or a non-polar solvent to prepare a slurry. The prepared slurry can be applied and dried on the negative electrode current collector 21 to prepare a first laminate. Then, the dried first laminate can be pressed to prepare the negative electrode 20. The pressing can be carried out by a roll press, a flat press, etc. However, it is not limited to the foregoing examples, and any pressing available in the art can be used. The pressing process can be omitted.

[0200] Preparation of the positive electrode

[0201] The components constituting the positive electrode active material layer 12 (including the bimodal positive electrode active material, the conductive material, the binder, the solid electrolyte, etc.) can be added to a non-polar solvent to prepare a slurry. The prepared slurry can be applied and dried on the positive electrode current collector 11. The obtained laminate can be pressed to prepare the positive electrode 10. The pressing can be carried out by a roll press, a flat press, a press using isostatic pressing, etc. However, it is not limited to the foregoing examples, and any press available in the art can be used. The pressing process can be omitted. Alternatively, the positive electrode 10 can be prepared by consolidating the mixture of the materials constituting the positive electrode active material layer 12 in the form of a wafer, or stretching (forming) it into the form of a sheet. If the positive electrode 10 is prepared by this method, the positive electrode current collector 11 can be omitted.

[0202] The positive electrode current collector can be made of, for example, a plate, foil, etc. formed of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector can be omitted. The positive electrode current collector can have a thickness of, for example, about 1 μm to about 100 μm, about 1 μm to about 50 μm, about 5 μm to about 25 μm, or about 10 μm to about 20 μm.

[0203] The positive electrode current collector can include, for example, a base film and a metal layer provided on one or both sides of the base film. For example, the base film can include a polymer. For example, the polymer can include polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. For example, the metal layer can include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. By using a positive electrode current collector having the foregoing structure, the weight of the electrode can be reduced, and as a result, the energy density of the lithium battery can be improved.

[0204] Preparation of Solid Electrolyte

[0205] The solid electrolyte layer 30 can be prepared, for example, by using a solid electrolyte made of a sulfide solid electrolyte material. The solid electrolyte layer 30 can be prepared, for example, by the following process: in this process, a sulfide solid electrolyte, a solvent, and a binder are mixed, and the mixture is applied, dried, and then pressed to prepare the solid electrolyte layer 30. Alternatively, the solid electrolyte layer 30 can be prepared by depositing a sulfide solid electrolyte obtained by the foregoing sulfide solid electrolyte preparation method by a known film-forming method such as aerosol deposition, cold spraying, sputtering, etc. Alternatively, the solid electrolyte layer 30 can be prepared by pressing a substance of pure solid electrolyte particles (elemental solid electrolyte particles).

[0206] Preparation of All-Solid-State Secondary Battery

[0207] A method for preparing an all-solid-state secondary battery according to an embodiment can include: providing a negative electrode; preparing a solid electrolyte layer; manufacturing a negative electrode-solid electrolyte subassembly by laminating the solid electrolyte layer on the negative electrode; and disposing a positive electrode on the solid electrolyte of the negative electrode-solid electrolyte subassembly, wherein the step of providing the negative electrode can include disposing a second negative electrode active material layer on the negative electrode current collector; and disposing a first negative electrode active material layer on the second negative electrode active material layer.

[0208] The first negative electrode active material layer may include a first negative electrode active material, and the first negative electrode active material contains: i) a first carbon negative electrode active material and ii) a mixture of one or more first elements selected from metals and metalloids; i) a composite of a first carbon negative electrode active material and ii) one or more first elements selected from metals and metalloids; or a combination thereof. The second negative electrode active material layer may include a second negative electrode active material, and the second negative electrode active material contains: i) a second carbon negative electrode active material and ii) a mixture of one or more second elements selected from metals and metalloids; i) a composite of a second carbon negative electrode active material and ii) one or more second elements selected from metals and metalloids; or a combination thereof.

[0209] The amount of the first element in the first negative electrode active material layer may be greater than the amount of the second element in the second negative electrode active material layer, and the amount of the first element may be about 25% by weight to about 80% by weight relative to the total weight of the first negative electrode active material included in the negative electrode active material layer.

[0210] When manufacturing an all-solid-state secondary battery, the foregoing positive electrode, solid electrolyte, and negative electrode may be arranged and subjected to pressing.

[0211] The pressing may be carried out at a temperature ranging from room temperature to 90 °C or lower, for example, in the range of about 20 °C to about 90 °C. Alternatively, the pressing may be carried out at a temperature of up to 100 °C or higher. The duration of the pressing may be, for example, 30 minutes or less, 20 minutes or less, 15 minutes or less, or 10 minutes or less. The duration of the pressing may be, for example, about 1 ms to about 30 minutes, about 1 ms to about 20 minutes, about 1 ms to about 15 minutes, or about 1 ms to about 10 minutes. Pressing methods may use, for example, an isostatic press, a roll press, a flat press, etc.; however, it is not limited thereto, and any press available in the art may be used. The pressure applied during pressing may be, for example, 500 MPa or less, 450 MPa or less, 350 MPa or less, 300 MPa or less, 200 MPa or less, 150 MPa or less, or 100 MPa or less. The pressure applied during pressing may be, for example, about 50 MPa to about 500 MPa, about 50 MPa to about 300 MPa, about 50 MPa to about 150 MPa, or about 50 MPa to about 100 MPa. Through this pressing process, the solid electrolyte powder, for example, can be sintered to form a single solid electrolyte layer.

[0212] The foregoing composition and manufacturing method of the all-solid-state secondary battery are an example of an embodiment, and thus, components and manufacturing steps, etc. may be appropriately modified.

[0213] Hereinafter, the present disclosure will be described in more detail in conjunction with examples and comparative examples, but it is not limited to the examples disclosed below.

[0214] Preparation of Cathode Active Material

[0215] Preparation Example 1: LiNi with a Li2O-ZrO2 Coating Layer 0.8 Co 0.15 Al 0.05 O2 (NCA) (D50 = 14 µm)

[0216] The cathode active material with a Li2O-ZrO2 coating layer prepared by the following method is used.

[0217] Lithium methoxide, zirconium propoxide, ethanol, and ethyl acetoacetate are mixed to prepare a mixed solution, and the mixed solution is stirred and mixed for 30 minutes to prepare an alcohol solution of a Li2O-ZrO2 (a = 1) (coating solution for the Li2O-ZrO2 coating layer). Here, the respective amounts of lithium methoxide and zirconium propoxide are adjusted such that the amount of a Li2O-ZrO2 (a = 1) coated on the surface of the cathode active material is 0.25 mol% relative to 100 mol% of the cathode active material.

[0218] Then, the coating solution for the Li2O-ZrO2 coating layer is mixed with the cathode active material LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA) (D50 = 14 µm) powder, and the mixed solution is heated to about 40°C with stirring, thereby evaporating and drying the solvent such as alcohol. Here, the mixed solution is agitated with ultrasonic waves.

[0219] Carrying out this process allows the precursor of a Li2O-ZrO2 to be loaded on the particle surface of the cathode active material powder.

[0220] In addition, the precursor of a Li2O-ZrO2 (a = 1) loaded on the particle surface of the cathode active material is heat-treated in an oxygen atmosphere at about 350°C for 1 hour. During this heat treatment process, the precursor of a Li2O-ZrO2 (a = 1) present on the surface of the cathode active material becomes a Li2O-ZrO2 (a = 1). The amount of a Li2O-ZrO2 (LZO) is about 0.4 parts by weight relative to 100 parts by weight of NCA.

[0221] Through the preparation process described above, LiNi with a Li2O-ZrO2 coating film is obtained 0.8 Co 0.15 Al 0.05O2(NCA) (D50 = 14 µm). In aLi2O-ZrO2, a is 1.

[0222] Production Example 2: LiNi with an aLi2O-ZrO2 coating 0.8 Co 0.15 Al 0.05 O2 (NCA) (D50 = 5 µm)

[0223] Prepare LiNi with an aLi2O-ZrO2 coating according to the same process as in Production Example 1 0.8 Co 0.15 Al 0.05 O2(NCA) (D50 = 5 µm), except as follows: Use the cathode active material LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA) (D50 = 5µm) instead of LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA) (D50 = 14 µm).

[0224] Preparation of CB Supporting Ag Particles

[0225] Production Example 3: Preparation of Carbon Black Supporting Ag Particles (Ag 40 wt%)

[0226] Disperse CB in 1.0 M sulfuric acid solution and stir for 2 hours, then filter and dry to prepare acid-treated CB.

[0227] 80 g of the acid-treated CB was introduced into a mixed solvent containing 1,500 g of distilled water, 1,500 g of ethanol, and 30 g of glycerol and stirred, and then AgNO3 was introduced thereto and stirred to prepare a mixed solution. The amount of AgNO3 was adjusted such that the amount of Ag in the carbon black supporting silver particles was 40 wt%. The respective amounts of the acid-treated CB and AgNO3 were adjusted such that the amount of silver-containing particles included in the composite negative electrode active material (carbon black supporting Ag particles) became 40 wt%. By introducing a reducing agent into the mixed solution, silver ions were reduced and supported on the CB. Sodium borohydride (NaBH4) was used as the reducing agent. The CB supporting silver-containing particles was filtered, washed, and dried to prepare a composite negative electrode active material. It was confirmed by scanning electron microscopy and XPS that a plurality of silver-containing particles were supported on the CB particles. The silver-containing particles were Ag particles, silver oxide (Ag2O) particles, and composite particles of Ag and Ag2O. The amount of silver-containing particles included in the composite negative electrode active material was 40 wt%. The average particle diameter of the Ag particles was 40 nm, and the average particle diameter of the carbon black was 550 nm.

[0228] Preparation Example 4: Preparation of Carbon Black Supporting Ag Particles (Ag 15 wt%)

[0229] The CB supporting silver particles was prepared according to the same procedure as in Preparation Example 3, except that: the respective amounts of the acid-treated CB and AgNO3 were adjusted such that the amount of silver-containing particles included in the composite negative electrode active material (carbon black supporting Ag particles) became 15 wt%.

[0230] Preparation of Negative Electrode-Solid Electrolyte Subassembly and All-Solid-State Secondary Battery Including the Same

[0231] Example 1: Positive Electrode / Solid Electrolyte (SE) / First AA (Ag 40 wt%-C) / Second AA (Ag 15 wt%-C) / Negative Electrode Current Collector (Ag 15 wt% (bottom) / C / / Ag 40 wt% (top) / C)

[0232] The large-diameter positive electrode active material NCA (first positive electrode active material) (D50 = 14 µm) obtained from Preparation Example 1, the small-diameter positive electrode active material NCA (second positive electrode active material) (D50 = 5 µm) obtained from Preparation Example 2, and the solid electrolyte Li 5.75 PS 4.75 Cl 1.25(D50 = 3 µm) were mixed in a mixer to prepare a mixture. The total weight of the large-diameter cathode active material NCA (the first cathode active material) and the small-diameter cathode active material NCA (the second cathode active material) was 6 g, and the amount of the solid electrolyte was 1.12 g. The mixing weight ratio of the large-diameter cathode active material NCA (D50 = 14 µm) obtained from Preparation Example 1 and the small-diameter cathode active material NCA (D50 = 5 µm) obtained from Preparation Example 2 was 4:1.

[0233] The mixture was stirred, and the conductive material carbon nanotubes (CNT), the binder polytetrafluoroethylene (PTFE), and the solid electrolyte Li 5.75 PS 4.75 Cl 1.25 were added to the mixture and stirred. The solvent xylene was added to the mixed particles, thereby producing a dough-like cathode composition, and the cathode composition was stretched to a thickness of about 150 µm by a dry kneading method to thereby prepare a cathode sheet. Subsequently, the cathode sheet was dried under vacuum at 45°C for 2 hours.

[0234] The mixing weight ratio of the cathode active material, the conductive material, the binder, and the solid electrolyte was 85:0.4:0.6:14. A compressed cathode was prepared as follows: A warm isostatic pressing process was carried out, in which the cathode sheet was compressed onto an 18-µm-thick aluminum foil of the cathode current collector and placed in an intermittent oil chamber, and then it was subjected to the application of a pressure of 490 MPa.

[0235] A SUS foil (thickness: 10 µm) was prepared as the anode current collector. Silver particles (average particle diameter: 60 nm) as the anode active material and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 15:85 to prepare a mixture of carbon black and silver. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with a polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming a second anode active material layer. The amount of the polyvinylidene fluoride binder was 7% by weight based on the total weight of the composition for forming the second anode active material layer. The composition for forming the second anode active material layer was coated on the SUS foil by a doctor blade coater, and dried in air at 80°C for 20 minutes, and then dried under vacuum at 100°C for 12 hours to thereby form a second anode active material layer (second AA).

[0236] In addition, silver particles of the negative electrode active material (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 40:60 to prepare a mixture of carbon black and silver particles. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with a polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming a first negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7% by weight based on the total weight of the composition for forming the first negative electrode active material layer. The composition for forming the first negative electrode active material layer was coated on a second negative electrode active material layer previously formed on a SUS foil by a doctor blade coater, and dried in air at 80°C for 20 minutes, and then vacuum dried at 100°C for 12 hours to thereby form a first negative electrode active material layer (First AA) and prepare a negative electrode.

[0237] The thickness of the first negative electrode active material layer was about 5 µm, and the thickness of the second negative electrode active material layer was 5 µm. The total thickness of the negative electrode active material layer containing the first negative electrode active material layer and the second negative electrode active material layer was about 10 µm.

[0238] The solid electrolyte Li 5.75 PS 4.75 Cl 1.25 (D50 = 3 µm) was mixed with a binder acrylic resin (A334 manufactured by Xeon) at a weight ratio of 98.5:1.5 to prepare a mixture. Then, the mixture was combined with a solvent isobutyl isobutyrate (IBIB) and stirred to prepare a composition for forming a solid electrolyte.

[0239] The composition for forming the solid electrolyte layer was coated on a polyethylene terephthalate (PET) film as a release film, and the resulting product was dried in air at 25°C for 12 hours in a drying chamber, and then vacuum dried at 70°C for 2 hours to form a sheet-shaped solid electrolyte on the PET film. Then, the PET film was separated and removed to prepare a solid electrolyte.

[0240] The positive electrode, solid electrolyte, and negative electrode obtained through the above process were sequentially stacked, and the resulting stack was subjected to warm isostatic pressing at 85°C under a pressure of 500 MPa for about 30 minutes to prepare a all-solid-state secondary battery. In the all-solid-state battery, the thickness of the solid electrolyte after pressing was 45 µm.

[0241] Example 2: Cathode / Solid Electrolyte (SE) / First AA (Ag 40 wt%-C) / Second AA (Ag 25 wt%-C) / Anode Current Collector (Ag 25 wt% (bottom) / C / / Ag 40 wt% (top) / C)

[0242] A all-solid-state secondary battery was prepared according to the same process as in Example 1, except that: the mixing weight ratio of silver to carbon black powder in the composition forming the second anode active material layer was changed from 15:85 to 25:75.

[0243] Example 3: Ag 25 wt% (bottom) / C / / Zn 40 wt% (top) / C

[0244] A all-solid-state secondary battery was prepared according to the same process as in Example 2, except that: when preparing the composition forming the first anode active material layer, zinc was used instead of silver, and the average particle diameter of the zinc particles was about 100 nm.

[0245] Example 4

[0246] A all-solid-state secondary battery was prepared according to the same process as in Example 1, except that: when forming the first anode active material layer, carbon black loaded with silver particles prepared according to Preparation Example 3 was used instead of the mixture of silver and carbon black.

[0247] Example 5

[0248] A all-solid-state secondary battery was prepared according to the same process as in Example 1, except that: when forming the second anode active material layer, carbon black loaded with silver particles prepared according to Preparation Example 4 was used instead of the mixture of silver and carbon black.

[0249] Example 6: Ag 10 wt% (bottom) / C / / Ag 25 wt% (top) / C

[0250] A all-solid-state secondary battery was prepared according to the same process as in Example 1, except that: the silver content of each of the first anode active material layer and the second anode active material layer was modified as shown in Table 1.

[0251] Example 7: Ag 10 wt% (bottom) / C / / Ag 40 wt% (top) / C

[0252] A all-solid-state secondary battery was prepared according to the same process as in Example 1, except that: the silver content of each of the first anode active material layer and the second anode active material layer was modified as shown in Table 1.

[0253] Table 1

[0254]

[0255] *Silver content difference = (the difference between the silver content in the first negative electrode active material layer and the silver content in the second negative electrode active material layer)

[0256] Example 8

[0257] A all-solid-state secondary battery was prepared according to the same process as in Example 1, except as follows: the thickness of the first negative electrode active material layer was about 3.5 µm, and the thickness of the second negative electrode active material layer was changed to 6.5 µm. The total thickness of the negative electrode active material layer containing the first negative electrode active material layer and the second negative electrode active material layer was about 10 µm.

[0258] Comparative Example 1: Ag 15 wt% / C

[0259] A all-solid-state secondary battery was prepared according to the same process as in Example 1, except that the negative electrode was formed by the following process.

[0260] Prepare SUS foil (thickness: 10 µm) as the negative electrode current collector. Silver particles (average particle diameter: 60 nm) as the negative electrode active material and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 15:85 to prepare a mixture of carbon black and silver. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming the negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7 wt% based on the total weight of the composition for forming the negative electrode active material layer. The composition for forming the negative electrode active material layer was coated on the SUS foil by a doctor blade coater and dried in air at 80°C for 20 minutes, and then vacuum dried at 100°C for 12 hours to thereby form the negative electrode active material layer and prepare a negative electrode including the negative electrode active material layer.

[0261] The thickness of the negative electrode active material layer was about 10 µm.

[0262] Comparative Example 2: Ag 25 wt% / C

[0263] A all-solid-state secondary battery was prepared according to the same process as in Comparative Example 1, except as follows: when preparing the mixture of carbon black and silver, silver particles (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 25:75 as the negative electrode active material to prepare the negative electrode.

[0264] Comparative Example 3: Ag 25 wt% (bottom) / C / / Ag 15 wt% (top) / C

[0265] A all-solid secondary battery was prepared in the same process as in Example 1, except that the negative electrode was prepared by the following process.

[0266] Prepare a SUS foil (thickness: 10 µm) as the negative electrode current collector. Silver particles (average particle diameter: 60 nm) as the negative electrode active material and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 25:75 to prepare a mixture of carbon black and silver. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with a polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming a second negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7% by weight based on the total weight of the composition for forming the second negative electrode active material layer. The composition for forming the second negative electrode active material layer was coated on the SUS foil by a doctor blade coater, dried in air at 80°C for 20 minutes, and then vacuum dried at 100°C for 12 hours to thereby form a second negative electrode active material layer (Second AA).

[0267] In addition, silver particles (average particle diameter: 60 nm) as the negative electrode active material and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 15:85 to prepare a mixture of carbon black and silver particles. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with a polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming a first negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7% by weight based on the total weight of the composition for forming the first negative electrode active material layer. The composition for forming the first negative electrode active material layer was coated on the second negative electrode active material layer previously formed on the SUS foil by a doctor blade coater, dried in air at 80°C for 20 minutes, and then vacuum dried at 100°C for 12 hours to thereby form a first negative electrode active material layer (First AA) and prepare the negative electrode.

[0268] The thickness of the first negative electrode active material layer was about 5 µm, and the thickness of the second negative electrode active material layer was 5 µm. The total thickness of the negative electrode active material layer containing the first negative electrode active material layer and the second negative electrode active material layer was about 10 µm.

[0269] Comparative Example 4: Ag 40 wt% / C

[0270] A all-solid-state secondary battery was prepared according to the same process as Comparative Example 1, except as follows: When preparing the mixture of carbon black and silver, silver particles (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 40:60 as the negative electrode active material to prepare the negative electrode.

[0271] Comparative Example 5: Ag 40 wt% (bottom) / C / / Ag 15 wt% (top) / C

[0272] A all-solid-state secondary battery was prepared according to the same process as Example 1, except that the negative electrode was prepared by the following process.

[0273] Prepare a SUS foil (thickness: 10 µm) as the negative electrode current collector. Silver particles (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) as the negative electrode active material were mixed at a weight ratio of 40:60 to prepare a mixture of carbon black and silver. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with the polyvinylidene fluoride binder (#9300, Kureha) for the negative electrode and stirred to prepare a composition for forming a second negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7 wt% based on the total weight of the composition for forming the second negative electrode active material layer. The composition for forming the second negative electrode active material layer was coated on the SUS foil by a doctor blade coater and dried in air at 80 °C for 20 minutes, and then vacuum dried at 100 °C for 12 hours to form a second negative electrode active material layer (second AA).

[0274] In addition, silver particles (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) as the negative electrode active material were mixed at a weight ratio of 15:85 to prepare a mixture of carbon black and silver particles. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with the polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming a first negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7 wt% of the composition based on the total weight of the composition for forming the first negative electrode active material layer. The composition for forming the first negative electrode active material layer was coated on the second negative electrode active material layer previously formed on the SUS foil by a doctor blade coater and dried in air at 80 °C for 20 minutes, and then vacuum dried at 100 °C for 12 hours to form a first negative electrode active material layer (first AA) and prepare the negative electrode.

[0275] The thickness of the first negative electrode active material layer is about 5 µm, and the thickness of the second negative electrode active material layer is 5 µm. The total thickness of the negative electrode active material layer containing the first negative electrode active material layer and the second negative electrode active material layer is about 10 µm.

[0276] Comparative Example 6: Ag 40 wt% (bottom) / C / / Ag 25 wt% (top) / C

[0277] A all-solid secondary battery was prepared according to the same process as in Example 1, except that the negative electrode was prepared by the following process.

[0278] Prepare SUS foil (thickness: 10 µm) as the negative electrode current collector. Silver particles (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) as the negative electrode active material were mixed at a weight ratio of 40:60 to prepare a mixture of carbon black and silver. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming the second negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7 wt% based on the total weight of the composition for forming the second negative electrode active material layer. The composition for forming the second negative electrode active material layer was coated on the SUS foil by a doctor blade coater, and dried in air at 80°C for 20 minutes, and then vacuum dried at 100°C for 12 hours to form the second negative electrode active material layer (Second AA).

[0279] Furthermore, silver particles (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) as the negative electrode active material were mixed at a weight ratio of 25:75 to prepare a mixture of carbon black and silver particles. In a container, silver (average particle diameter: 60 nm) and carbon black powder (average particle diameter: 35 nm) were added to N-methylpyrrolidone (NMP) together with polyvinylidene fluoride binder (#9300, Kureha) and stirred to prepare a composition for forming the first negative electrode active material layer. The amount of the polyvinylidene fluoride binder was 7 wt% based on the total weight of the composition for forming the first negative electrode active material layer. The composition for forming the first negative electrode active material layer was coated on the second negative electrode active material layer previously formed on the SUS foil by a doctor blade coater, and dried in air at 80°C for 20 minutes, and then vacuum dried at 100°C for 12 hours to thereby form the first negative electrode active material layer (First AA) and prepare the negative electrode.

[0280] The thickness of the first negative electrode active material layer is about 5 µm, and the thickness of the second negative electrode active material layer is 5 µm. The total thickness of the negative electrode active material layer containing the first negative electrode active material layer and the second negative electrode active material layer is about 10 µm.

[0281] Comparative Example 7: Zn 40 wt% / C

[0282] A all-solid-state secondary battery was prepared according to the same process as in Comparative Example 1, except that: when preparing the mixture of carbon black and silver, zinc was used instead of silver, and zinc particles (average particle diameter: 100 nm) and carbon black powder (average particle diameter: 35 nm) were mixed at a weight ratio of 40:60 as the negative electrode active material to prepare the negative electrode.

[0283] Evaluation Example 1: SEM-EDX analysis

[0284] The all-solid-state secondary batteries prepared according to Example 1 and Comparative Examples 3 and 5 were each charged at a constant current of 0.1 C until the battery voltage reached 4.2 V. Subsequently, each battery was discharged at a constant current of 0.1 C until the battery voltage reached 2.5 V. After formation, the batteries were disassembled and subjected to cross-sectional SEM-EDX analysis to characterize the distribution of silver.

[0285] The all-solid-state secondary battery of Example 1 was subjected to EDX surface scanning to characterize the silver content. As a result, it was found that the silver content in the second region in the discharged state was higher than that in the first region. Here, the first region refers to the region from the contact point between the negative electrode active material layer and the solid electrolyte up to 50% of the thickness, and the second region refers to the remaining region of the negative electrode active material layer excluding the first region, that is, the region from the contact point between the negative electrode active material layer and the negative electrode current collector up to 50% of the thickness. As used herein, the thickness % is relative to the total thickness of the negative electrode active material layer.

[0286] After discharge, the silver concentration in the first region (top) at the interface of the solid electrolyte layer can be maintained at an appropriate concentration, while the lithium diffusion and deposition resistance are reduced. After discharge, the silver content in the second region (bottom) is 32 wt%, and the silver content in the first region (top) is 23 wt%, and thus, the difference in silver content between the first region and the second region is 9 wt%. Here, the difference in silver content was evaluated as follows: reconstructing the Ag point region based on the EDX image and comparing the difference in the number of silver particles.

[0287] Meanwhile, it was found that after discharging, the all-solid secondary battery prepared according to Comparative Example 3 showed that silver was more locally concentrated in the negative electrode active material layer adjacent to the current collector. In this case, after discharging, the silver content in the second region (bottom) was 28 wt%, and the silver content in the first region (top) was 12 wt%, and thus the difference in silver content between the first region and the second region was 16 wt%. Therefore, compared with Example 1, for Comparative Example 3, the difference in silver content between the first region and the second region in the negative electrode active material layer after discharging increased significantly.

[0288] In addition, it was found that in the all-solid secondary battery of Comparative Example 5 having a silver composition distribution opposite to that of the negative electrode active material layer of Example 1, silver predominantly (the vast majority) existed in the interfacial region of the negative electrode active material layer adjacent to the current collector.

[0289] In addition, the all-solid secondary batteries prepared according to Examples 4 and 5 after discharging were subjected to EDX surface scanning to characterize the silver content.

[0290] As a result, it was found that in the all-solid secondary batteries of Examples 4 and 5, silver was relatively more uniformly present in the negative electrode active material layer compared with the all-solid secondary batteries of Examples 1 to 3.

[0291] Evaluation Example 2: High-rate discharge capacity and average discharge voltage

[0292] The all-solid batteries prepared according to Examples 1 and 2 and Comparative Examples 1 to 6 were each evaluated by a charge-discharge process at 45 °C under 2.5 V - 4.25 V, 0.1 C cut-off CCCV (constant current constant voltage).

[0293] The charge-discharge characteristics of the all-solid secondary battery were evaluated by the following charge-discharge test. The all-solid secondary battery placed in a thermostatic bath at 45 °C was subjected to a charge-discharge test.

[0294] In the first cycle, the battery was charged at a constant current of 0.1 C until the battery voltage reached 4.2 V. Subsequently, the battery was discharged at a constant current of 0.1 C until the battery voltage reached 2.5 V. In the second cycle, the battery was charged at a constant current of 0.33 C until the battery voltage reached 4.25 V. Subsequently, the battery was discharged at a constant current of 0.33 C until the battery voltage reached 2.5 V.

[0295] In the third cycle, the battery was charged at a constant current of 1.0 C until the battery voltage reached 4.2 V. Subsequently, the battery was discharged at a constant current of 1.0 C until the battery voltage reached 2.5 V.

[0296] In each cycle, a 10-minute rest period is provided after charging and discharging.

[0297] Alternatively, in the 3rd cycle, charging and discharging are performed as follows: charging and discharging at a constant current of 2.0 C instead of charging and discharging at a constant current of 1.0 C.

[0298] The discharge capacities at 1.0 C and 2.0 C are studied and are respectively shown in Figure 3A and 3B respectively. In addition, the average voltages at 1.0 C and 2.0 C are studied and are respectively shown in Figure 3C and 3D respectively.

[0299] Refer to Figure 3A and 3B . Compared with the 1C discharge capacity and 2C discharge capacity of the all-solid secondary batteries of Comparative Examples 1 to 6, the all-solid secondary batteries of Examples 1 and 2 show improved 1C discharge capacity and 2C discharge capacity.

[0300] In addition, refer to Figure 3C and 3D . The all-solid secondary batteries of Examples 1 and 2 show an average discharge voltage higher than that of the all-solid secondary batteries of Comparative Examples 1 to 6, and thus can show a high energy density at high rates. In addition, it is found that when discharging at 2 C (a rate faster than 1C discharge), the all-solid secondary batteries of Examples 1 and 2 maintain excellent discharge capacity and a very high average discharge voltage.

[0301] In addition, it is found that compared with Examples 1 and 2, the all-solid secondary batteries of Examples 4 and 5 show improved discharge capacity and average discharge voltage. In addition, it is found that the all-solid secondary batteries of Examples 3, 6 and 7 show discharge capacity and average discharge voltage comparable to those of Example 1.

[0302] Meanwhile, it can be confirmed that a lithium metal layer is formed between the negative electrode current collector and the second negative electrode active material layer after charging in the all-solid secondary batteries of Examples 1 and 2.

[0303] Evaluation Example 3: Low-temperature charge-discharge characteristics

[0304] The all-solid batteries prepared according to Examples 1 and 2 and Comparative Examples 1 to 6 are each evaluated through a charge-discharge process at 0 °C under 2.5 V - 4.25 V, 0.1 C cut-off CCCV (constant current constant voltage).

[0305] The charge-discharge characteristics of the all-solid-state secondary battery were evaluated through the following charge-discharge tests. The charge-discharge tests were performed on the all-solid-state secondary battery placed in a thermostatic bath at 0°C.

[0306] In the first cycle, the battery was charged at a constant current of 0.1 C until the battery voltage reached 4.2 V. Subsequently, the battery was discharged at a constant current of 0.1 C until the battery voltage reached 2.5 V. In the second cycle, the battery was charged at a constant current of 0.33 C until the battery voltage reached 4.25 V. Subsequently, the battery was discharged at a constant current of 0.33 C until the battery voltage reached 2.5 V.

[0307] In the third cycle, the battery was charged at a constant current of 0.5 C until the battery voltage reached 4.2 V. Subsequently, the battery was discharged at a constant current of 0.5 C until the battery voltage reached 2.5 V.

[0308] In each cycle, a 10-minute rest period was provided after charging and discharging.

[0309] The discharge capacity at 0.5 C was studied and shown in Figure 4B .

[0310] Refer to Figure 4A , when the low-temperature evaluation was carried out at 0°C, the all-solid-state secondary battery of Example 2 showed the highest discharge capacity. This result confirmed that the resistance generated during the lithium diffusion and creep process at the solid electrolyte membrane interface could be reduced, and the high silver concentration in the first negative electrode active material layer effectively played a role.

[0311] In addition, as a result of measuring the low-temperature charge / discharge characteristics of the all-solid-state secondary batteries of Examples 1 and 2, compared with Comparative Examples 1 to 6, they showed improved discharge capacity characteristics.

[0312] Moreover, the all-solid-state secondary batteries of Examples 1, 2 and Comparative Example 2 were each evaluated through the charge-discharge process at 2.5 V - 4.25 V, 0.1 C cut-off CCCV (constant current constant voltage) at 0°C.

[0313] In the all-solid-state secondary batteries of Example 2 and Comparative Example 2, when the discharge rate was fixed at 0.1 C and the charge rate was increased to 0.1 C, 0.2 C and 0.33 C, the results of evaluating the voltage characteristics were shown in Figure 4B and in the all-solid-state secondary batteries of Example 3 and Comparative Example 2, when the discharge rate was fixed at 0.1 C and the charge rate was increased to 0.1 C and 0.2 C, the results of studying the change of voltage characteristics were shown in Figure 4C .

[0314] As Figure 4B shown in the figure, compared with the all-solid secondary battery of Comparative Example 2, when the discharge rate is fixed at 0.1 C and the charge rate is increased to 0.1 C, 0.2 C, or 0.33 C, the all-solid secondary battery of Example 2 shows improved low-temperature charge / discharge characteristics because the overvoltage decreases as the charge rate increases.

[0315] In addition, as Figure 4C shown in the figure, compared with the all-solid secondary battery of Comparative Example 2, the all-solid secondary battery of Example 3 shows a decreasing overvoltage as the charge rate increases.

[0316] Furthermore, it was found that compared with Examples 1 and 2, the all-solid secondary batteries of Examples 4 and 5 showed improved low-temperature charge-discharge characteristics. Additionally, it was found that the all-solid secondary batteries of Examples 3, 6, and 7 showed comparable low-temperature charge-discharge characteristics to Example 1.

[0317] Through the above description, one or more embodiments have been described; however, the present disclosure is not limited to the embodiments described herein and can be modified and varied within the scope of the claims, detailed description, and drawings of the present disclosure, and it will be understood that such modifications and variations are also within the scope of the present disclosure.

[0318] According to one aspect of the present disclosure, there is provided a negative electrode-solid electrolyte subassembly for an all-solid secondary battery and an all-solid secondary battery, the negative electrode-solid electrolyte subassembly for an all-solid secondary battery having an increased charge-discharge rate by having a reduced lithium diffusion overpotential due to an increased metal concentration at the interface between the solid electrolyte and the negative electrode active material layer, and the all-solid secondary battery being capable of improving high-rate and low-temperature operating performance by including the negative electrode-solid electrolyte subassembly.

[0319] It should be understood that the embodiments described herein should be considered only in a descriptive sense and not for the purpose of limitation. The description of the features or aspects in each embodiment should typically be considered applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the drawings, those of ordinary skill in the art will understand that various changes in form and detail can be made therein without departing from the spirit and scope as defined by the appended claims.

Claims

1. A negative electrode - solid electrolyte sub - assembly for an all - solid secondary battery, the negative electrode - solid electrolyte sub - assembly comprising: A negative electrode current collector; A negative electrode active material layer provided on the negative electrode current collector; And a solid electrolyte provided on the negative electrode active material layer and opposite to the negative electrode current collector, Wherein the negative electrode active material layer includes a first negative electrode active material layer in contact with the solid electrolyte and a second negative electrode active material layer in contact with the negative electrode current collector, Wherein the first negative electrode active material layer includes a first negative electrode active material, and the first negative electrode active material contains: i) a first carbon negative electrode active material and ii) a mixture of one or more first elements selected from metals and metalloids; i) a composite of a first carbon negative electrode active material and ii) one or more first elements selected from metals and metalloids; or a combination thereof, Wherein the second negative electrode active material layer includes a second negative electrode active material, and the second negative electrode active material contains: i) a second carbon negative electrode active material and ii) a mixture of one or more second elements selected from metals and metalloids; i) a composite of a second carbon negative electrode active material and ii) one or more second elements selected from metals and metalloids; or a combination thereof, and Wherein the amount of the first element in the first negative electrode active material layer is greater than the amount of the second element in the second negative electrode active material layer, and the amount of the first element is 25 wt% to 80 wt% relative to the total weight of the first negative electrode active material.

2. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the amount of the first element in the first negative electrode active material layer is 25 wt% to 40 wt% relative to the total weight of the first negative electrode active material.

3. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the amount of the second element in the second negative electrode active material layer is 10 wt% to 25 wt% relative to the total weight of the second negative electrode active material.

4. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the total amount of the first element and the second element in the negative electrode active material layer is 1 wt% to 65 wt% relative to the total weight of the first and second negative electrode active materials in the negative electrode active material layer.

5. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein each of the first negative electrode active material layer and the second negative electrode active material layer has a thickness of 1 µm to 10 µm.

6. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the first negative electrode active material layer includes a material having the first element supported on the first carbon negative electrode active material, and the second negative electrode active material layer includes a material having the second element supported on the second carbon negative electrode active material.

7. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the thickness of the second negative electrode active material layer is equal to the thickness of the first negative electrode active material layer, or wherein the thickness of the second negative electrode active material layer is greater than the thickness of the first negative electrode active material layer.

8. The negative electrode - solid electrolyte sub - assembly according to claim 1, wherein the ratio of the thickness of the second negative electrode active material layer to the thickness of the first negative electrode active material layer is from 1:0.25 to 1:

1.

9. The negative electrode - solid electrolyte sub - assembly according to claim 1, wherein the difference between the amount of the first element in the first negative electrode active material layer and the amount of the second element in the second negative electrode active material layer is from 10 wt% to 50 wt%.

10. The negative electrode - solid electrolyte sub - assembly according to claim 1, wherein in the all - solid - state secondary battery in a discharged state after formation, the difference between the amount of one or more selected from metals and metalloids in a first region of the negative electrode active material layer and the amount of one or more selected from metals and metalloids in a second region of the negative electrode active material layer is 25 wt% or less, wherein the negative electrode active material layer has a first surface adjacent to the solid electrolyte layer and an opposite second surface adjacent to the negative electrode current collector, the first region has a thickness of 50% to 80% of the total thickness of the negative electrode active material layer extending from the first surface of the negative electrode active material layer towards the second surface of the negative electrode active material layer, and the second region has a thickness of 20% to 50% of the total thickness of the negative electrode active material layer extending from the second surface of the negative electrode active material layer towards the first surface of the negative electrode active material layer.

11. The negative electrode - solid electrolyte sub - assembly according to claim 10, wherein the amount of one or more selected from metals and metalloids in the second region is greater than the amount of one or more selected from metals and metalloids in the first region, and the difference therebetween is from 1 wt% to 25 wt%.

12. The negative electrode - solid electrolyte sub - assembly according to claim 1, wherein the first and second carbon negative electrode active materials independently comprise amorphous carbon, and the one or more first elements and the one or more second elements independently comprise silver, indium, silicon, gallium, tin, aluminum, titanium, zirconium, niobium, germanium, antimony, gold, platinum, palladium, magnesium, zinc, nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

13. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the first negative electrode active material layer includes: a first element selected from silicon, aluminum, tin, zinc, nickel, and silver; and the first carbon negative electrode active material, wherein the amount of the first element relative to the total weight of the first negative electrode active material layer is from 25 wt% to 40 wt%.

14. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the second negative electrode active material layer comprises: a second element selected from silicon, aluminum, tin, zinc, nickel, and silver; and the second carbon negative electrode active material, wherein the amount of the second element relative to the total weight of the second negative electrode active material layer is from 10 wt% to 25 wt%.

15. The negative electrode - solid electrolyte sub - assembly according to claim 1, Wherein the first and second negative electrode active materials each independently include a mixture of first particles and second particles, the first particles are composed of amorphous carbon and the second particles are composed of metals and metalloids.

16. A all-solid-state secondary battery, comprising: a positive electrode; and a negative electrode-solid electrolyte subassembly as claimed in any one of claims 1-15 disposed on the positive electrode, wherein the solid electrolyte of the negative electrode-solid electrolyte subassembly is disposed between the positive electrode and the negative electrode active material layer.

17. The all-solid-state secondary battery as claimed in claim 16, further comprising a third negative electrode active material layer disposed at least between the negative electrode current collector and the negative electrode active material layer, or between the negative electrode current collector and the solid electrolyte, wherein the third negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

18. The all-solid-state secondary battery as claimed in claim 16, wherein the solid electrolyte of the negative electrode-solid electrolyte subassembly includes a solid electrolyte, or a combination of a solid electrolyte and a gel electrolyte, wherein the solid electrolyte includes a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a combination thereof, and the gel electrolyte includes a polymer gel electrolyte.

19. The all-solid-state secondary battery as claimed in claim 16, wherein the positive electrode includes a positive electrode current collector, wherein at least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, wherein the base film includes a polymer, the polymer includes polyethylene terephthalate, polyethylene, polypropylene, polybutylene terephthalate, polyimide, or a combination thereof, and wherein the metal layer includes indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, lithium, or an alloy thereof.

20. The all-solid-state secondary battery as claimed in claim 16, wherein the solid electrolyte of the negative electrode-solid electrolyte subassembly includes a sulfide solid electrolyte, Wherein the sulfide solid electrolyte is one or more selected from the following: Li2S-P2S5 and 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 where m and n are each positive numbers and Z is Ge, Zn or Ga m S n ; Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li p MO q ; where 0 ≤ x ≤ 2 of Li 7-x PS 6-x Cl x ; where 0 ≤ x ≤ 2 of Li 7-x PS 6-x Br x ; and where 0 ≤ x ≤ 2 of Li 7-x PS 6-x I x .

Images