All-solid-state secondary battery and method for manufacturing all-solid-state secondary battery

Abstract

The present invention relates to an all-solid secondary battery and a method of manufacturing an all-solid secondary battery. The all-solid secondary battery includes: a positive electrode layer including a positive electrode active material layer; a negative electrode layer; and a solid electrolyte layer including a solid electrolyte, wherein the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer, wherein the negative electrode layer includes a negative electrode current collector, a first negative electrode active material layer in contact with the solid electrolyte layer, and a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer, wherein the first negative electrode active material layer includes a first carbonaceous negative electrode active material, the second negative electrode active material layer includes a second carbonaceous negative electrode active material, and a first intensity ratio of an intensity of a D band peak to an intensity of a G band peak in a Raman spectrum of the first carbonaceous negative electrode active material is smaller than a second intensity ratio of an intensity of a D band peak to an intensity of a G band peak in a Raman spectrum of the second carbonaceous negative electrode active material.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefits, and all benefits arising therefrom, to Korean Patent Application No. 10-2020-0019988 filed on February 18, 2020 and Korean Patent Application No. 10-2021-0011513 filed on January 27, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to all-solid-state secondary batteries and methods for manufacturing them. Background Technology

[0004] Batteries with high energy density and high safety have been actively developed to meet industrial demands. For example, lithium-ion batteries are commercially available in the automotive sector, as well as in information and communication equipment. In the automotive sector, the safety of lithium-ion batteries is particularly important.

[0005] Commercial lithium-ion batteries include liquid electrolytes that contain flammable organic solvents, posing a risk of overheating and fire in the event of a short circuit. Therefore, there is a need for all-solid-state batteries that incorporate solid electrolytes instead of liquid electrolytes. Summary of the Invention

[0006] Provided an all-solid-state secondary battery that prevents short circuits during charging and discharging and has improved cycle characteristics, and a method for manufacturing the same.

[0007] Other aspects will be set forth in part in the following description, and in part will become apparent from the description, or may be learned through practice of the aspects presented in this disclosure.

[0008] According to one aspect, all-solid-state secondary batteries include:

[0009] The positive electrode layer includes the positive electrode active material layer;

[0010] Negative electrode layer; and

[0011] A solid electrolyte layer comprising a solid electrolyte, wherein the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer.

[0012] The negative electrode layer includes

[0013] Negative electrode current collector,

[0014] The first negative electrode active material layer in contact with the solid electrolyte layer, and

[0015] A second negative electrode active material layer is disposed between the negative electrode current collector and the first negative electrode active material layer.

[0016] The first negative electrode active material layer includes a first carbonaceous negative electrode active material, and the second negative electrode active material layer includes a second carbonaceous negative electrode active material.

[0017] The intensity ratio of the D band peak to the G band peak in the Raman spectrum of the first carbonaceous anode active material is less than the intensity ratio of the D band peak to the G band peak in the Raman spectrum of the second carbonaceous anode active material.

[0018] According to another method, a method for manufacturing an all-solid-state secondary battery includes:

[0019] Provide a solid electrolyte layer;

[0020] A first negative electrode active material composition is disposed on the first surface of the solid electrolyte layer;

[0021] The first negative electrode active material composition is heat-treated to form a first negative electrode active material layer;

[0022] A second negative electrode active material layer is disposed on the surface of the first negative electrode active material layer; and

[0023] A positive electrode active material layer is disposed on the second surface of the solid electrolyte layer. Attached Figure Description

[0024] The above and other aspects, features and advantages of this disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 A cross-sectional view of an all-solid-state secondary battery based on one aspect;

[0026] Figure 2 A cross-sectional view of an all-solid-state secondary battery based on an example.

[0027] Figure 3 A cross-sectional view of an all-solid-state secondary battery based on an example.

[0028] Figure 4 A cross-sectional view of an all-solid-state secondary battery based on an example.

[0029] Figure 5A The image shows a scanning electron microscope (SEM) image of the surface of the precursor layer as described in Example 1, which is a product formed after spin coating and drying and before heat treatment at 450°C.

[0030] Figure 5BThe image shows a SEM image of the surface of the first negative electrode active material layer after heat treatment at 450°C as described in Example 1.

[0031] Figure 6A This is a SEM image of the cross-section of the solid electrolyte layer / first negative electrode active material layer laminate prepared in Example 1;

[0032] Figure 6B Energy dispersive X-ray spectroscopy (EDX) carbon surface scan image of the cross-section of the solid electrolyte layer / first negative electrode active material layer laminate prepared in Example 1;

[0033] Figure 7A This is a SEM image of the surface of the first negative electrode active material layer prepared in Example 2;

[0034] Figure 7B This is an EDX silver (Ag) surface scan image of the surface of the first negative electrode active material layer prepared in Example 2;

[0035] Figure 7C This is an EDX carbon surface scan image of the surface of the first negative electrode active material layer prepared in Example 2;

[0036] Figure 8A This is a SEM image of the cross-section of the solid electrolyte layer / negative electrode layer laminate prepared in Example 2;

[0037] Figure 8B for Figure 8A A magnified view of the interface region (A) between the solid electrolyte layer and the first negative electrode active material layer;

[0038] Figure 8C for Figure 8A A magnified view of the interface region (B) between the first negative electrode active material layer and the second negative electrode active material layer.

[0039] Figure 8D for Figure 8A A magnified view of a portion of the internal region (C) of the second negative electrode active material layer;

[0040] Figure 8E for Figure 8A X-ray diffraction (XRD) pattern of the first negative electrode active material layer (heat-treated layer) adjacent to the solid electrolyte layer;

[0041] Figure 8F for Figure 8A XRD pattern of the second negative electrode active material layer adjacent to the first negative electrode active material layer;

[0042] Figure 8G for Figure 8AXRD pattern of the internal region of the second negative electrode active material layer;

[0043] Figure 8H for Figure 8A EDX carbon surface scan image of the cross-section of the first negative electrode active material layer adjacent to the solid electrolyte layer;

[0044] Figure 8I for Figure 8A EDX carbon surface scan image of the cross-section of the second negative electrode active material layer adjacent to the first negative electrode active material layer;

[0045] Figure 8J for Figure 8A EDX carbon surface scan image of a cross-section of a certain region (a specific area) in the second negative electrode active material layer;

[0046] Figure 9A For arbitrary units (au), the Raman displacement (per centimeter, cm) is expressed as... -1 The figure shows the Raman spectra of the surface of the precursor layer (i.e., the second negative electrode active material layer) of Example 1 and the surface of the first negative electrode active material layer of Example 1. The precursor layer is a spin-coated and dried product before heat treatment at 450°C, and the first negative electrode active material layer is a sintered product obtained by heat treatment at 450°C.

[0047] Figure 9B For arbitrary units (au) of Raman displacement (cm) -1 The figure shows the Raman spectrum of the surface of the second active material layer (precursor layer) of Example 1;

[0048] Figure 9C For arbitrary units (au), the Raman displacement (cm) -1 The figure shows the Raman spectrum of the surface of the first negative electrode active material layer of Example 1 after heat treatment at 450°C.

[0049] Figure 10 Impedance -Z (ohms square centimeters, Ω·cm) 2 ) for impedance Z' (Ω·cm 2 The graph shows the Nyquist plot, which displays the impedance measurements of the all-solid-state secondary cells fabricated in Comparative Examples 1 and 2.

[0050] Figure 11A Electrode potential (volts, relative to lithium, V, relative to Li / Li) + ) for capacity (milliampere-hours per square centimeter, mAh / cm²) 2 The graph shows the charge-discharge curves of the all-solid-state secondary battery manufactured in Example 1;

[0051] Figure 11B Electrode potential (V, relative to Li / Li) + ) for capacity (mAh / cm 2 The figure shows the charge-discharge curves of the all-solid-state secondary battery manufactured in Comparative Example 1;

[0052] Figure 11C Electrode potential (V, relative to Li / Li) + ) for capacity (mAh / cm 2 The graph shows the charge-discharge curves of the all-solid-state secondary battery fabricated in Comparative Example 2; and

[0053] Figure 11D Electrode potential (V, relative to Li / Li) + ) for capacity (mAh / cm 2 The graph shows the charge-discharge curve of the all-solid-state secondary battery manufactured in Example 4. Detailed Implementation

[0054] The aspects will now be described in detail, examples of which are illustrated in the accompanying drawings, wherein the same reference numerals always refer to the same elements. In this respect, the aspects may take different forms and should not be construed as limited to the description set forth herein. Therefore, the aspects are described below only by reference to the accompanying drawings to illustrate the aspects.

[0055] It will be understood that when an element is referred to as being "on" another element, it may be directly on said other element, or there may be intermediate elements in between. Conversely, when an element is referred to as being "directly on" another element, there are no intermediate elements.

[0056] 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 of" modify the entire list of elements when appearing before or after the list of elements, but do not modify any individual elements of the list.

[0057] The terminology used herein is for descriptive purposes only and is not intended to be limiting. As used herein, “a,” “the,” and “at least one” do not indicate a limitation of quantity and are intended to cover both the singular and plural unless the context clearly indicates otherwise. For example, “(a) element” has the same meaning as “at least one element” unless the context clearly indicates otherwise. As used herein, the term “and / or” includes any and all combinations of one or more of the associated enumerated items. It will be further understood that the terms “comprising” or “including,” when used in this specification, indicate the presence of the stated features, regions, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more additional features, regions, integrals, steps, operations, elements, components, and / or collections thereof.

[0058] Furthermore, relative terms such as “lower” or “bottom” and “upper” or “top” may be used herein to describe the relationship between one element and another element as shown in the figures. It will be understood that, in addition to the orientations shown in the figures, relative terms are also intended to include different orientations of the device. For example, if the device in one of the figures is flipped, an element described as being on the “lower” side of another element will be oriented on the “upper” side of said other element. Thus, depending on the specific orientation of the figure, the exemplary term “lower” can include both “lower” and “upper” orientations. Similarly, if the device in one of the figures is flipped, an element described as being “below” or “under” other elements will be oriented “above” said other elements. Thus, the exemplary terms “below” or “under” can include both “above” and “below” orientations.

[0059] As used herein, “about” or “approximately” includes the stated value and means within an acceptable range of deviations from the specific value, as determined by a person skilled in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., limitations of the measurement system). For example, “about” may mean within one or more standard deviations relative to the stated value, or within ±30%, 20%, 10%, or 5%.

[0060] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their context in the relevant field and in this disclosure, and will not be interpreted in an idealized or overly formal sense unless clearly defined herein.

[0061] All-solid-state batteries do not contain flammable organic solvents, and therefore have a reduced risk of fire or explosion even in the event of a short circuit. Therefore, all-solid-state batteries offer improved safety compared to lithium-ion batteries that use liquid electrolytes.

[0062] In all-solid-state secondary batteries including a solid electrolyte, lithium is locally deposited at the interface between the solid electrolyte layer and the negative electrode layer. This deposited lithium can grow and eventually penetrate the solid electrolyte layer, causing a short circuit in the battery. While not wanting to be bound by theory, it is understood that when the solid electrolyte layer and the negative electrode layer are simply stacked, the effective interface area between them is smaller than the actual contact area. Therefore, the interface resistance at the interface between the solid electrolyte layer and the negative electrode layer can increase, leading to an increase in the battery's internal resistance and consequently deteriorating its cycle characteristics.

[0063] In one aspect, an all-solid-state battery is provided, wherein short circuits are prevented during charging and discharging, and the cycle characteristics of the battery are improved.

[0064] The following sections will describe examples of all-solid-state secondary batteries and methods for manufacturing them in more detail.

[0065] As used in this article, the term "metal" refers to metallic elements selected from groups 1-16 of the periodic table, including the lanthanides and actinides.

[0066] "Metalloids" refers to B, Si, Ge, As, Sb, Te, or combinations thereof.

[0067] As used in this article, “sulfur-silver germanite,” “sulfur-silver germanite structure,” or “sulfur-silver germanite-type structure” means that the compound has a crystal structure isomorphous to sulfur-silver germanite Ag8GeS6.

[0068] Garnet or "garnet-type" compounds are compounds with the same or similar crystal structures (e.g., isomorphic) as compounds having the formula X3Y2(SiO4)3, where X is a divalent cation such as Ca. 2+ Mg 2+ Fe 2+ Mn 2+ , or combinations thereof, where Y is a trivalent cation such as Al 3+ Fe 3+ Cr 3+ , or a combination thereof.

[0069] According to one aspect, an all-solid-state secondary battery may include: a positive electrode layer comprising a positive electrode active material layer; a negative electrode layer; and a solid electrolyte layer comprising a solid electrolyte, wherein the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer, wherein the negative electrode layer includes a negative electrode current collector, a first negative electrode active material layer disposed on the negative electrode current collector and in contact with the solid electrolyte layer, and a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer. The first negative electrode active material layer comprises a first carbonaceous negative electrode active material, the second negative electrode active material layer comprises a second carbonaceous negative electrode active material, and a first intensity ratio (I0) of the intensity of the D band peak to the intensity of the G band peak in the Raman spectrum of the first carbonaceous negative electrode active material is defined as follows: 1 D / I 1 G The intensity ratio (I) of the D band peak intensity to the G band peak intensity of the second carbonaceous anode active material is less than that of the second carbonaceous anode active material. 2 D / I 2 G ).

[0070] Although I don't want to be bound by theory, I understand that when the intensity ratio (I0.1) of the D band peak to the G band peak in the Raman spectrum of the first carbonaceous anode active material is... 1 D / I 1 G The intensity ratio (I) of the D band peak intensity to the G band peak intensity of the second carbonaceous anode active material is less than that of the second carbonaceous anode active material. 2 D / I 2 G When the first carbonaceous negative electrode active material has a lower defect content than the second carbonaceous negative electrode active material, the defect content can be reduced. Furthermore, defects generated between the solid electrolyte layer and the first negative electrode active material layer comprising the first carbonaceous negative electrode active material can be reduced. Therefore, localized lithium deposition at the interface between the solid electrolyte and the first negative electrode active material layer can be suppressed. Additionally, since the second negative electrode active material layer is disposed on the first negative electrode active material layer, and the second negative electrode active material layer contains more defects than the first carbonaceous negative electrode active material, it is understood that these defects can act as seeds for lithium deposition, thereby promoting lithium deposition on the second negative electrode active material layer, and the lithium deposition (i.e., the formation of a lithium layer) on the second negative electrode active material layer can be more uniform. Due to the deposition of a uniform lithium layer between the solid electrolyte layer and the negative electrode current collector, the all-solid-state secondary battery can be reversibly charged and discharged and has improved cycle characteristics.

[0071] All-solid-state secondary battery

[0072] refer to Figures 1 to 4 According to the present invention, the all-solid-state secondary battery 1 may include: a positive electrode layer 10 comprising a positive electrode active material layer 12 and a positive electrode current collector 11; a negative electrode layer 20; and a solid electrolyte layer 30 comprising a solid electrolyte disposed between the positive electrode layer 10 and the negative electrode layer 20. The negative electrode layer 20 may include: a negative electrode current collector 21; a first negative electrode active material layer 22 disposed on the negative electrode current collector 21 and in contact with the solid electrolyte layer 30; and a second negative electrode active material layer 23 disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The first negative electrode active material layer 22 may include a first carbonaceous negative electrode active material, and the second negative electrode active material layer 23 may include a second carbonaceous negative electrode active material. The intensity ratio (Ig) of the D-band peak to the G-band peak in the Raman spectrum of the first carbonaceous negative electrode active material is defined as follows: 1 D / I 1 G The intensity ratio (I) of the D band peak to the G band peak in the Raman spectrum of the second carbonaceous anode active material can be less than that of the second intensity ratio (I). 2 D / I 2 G ).

[0073] negative electrode layer

[0074] refer to Figures 1 to 4 The first intensity ratio (I0.1) of the D-band peak intensity to the G-band peak intensity in the Raman spectrum of the first carbonaceous anode active material included in the first anode active material layer 22. 1 D / I 1 G The strength ratio (I) can be, for example, about 0.95 or less, about 0.9 or less, about 0.85 or less, about 0.8 or less, or about 0.75 or less. 1 D / I 1 G The strength can be, for example, about 0.1 to about 0.95, about 0.2 to about 0.9, about 0.3 to about 0.85, about 0.4 to about 0.80, or about 0.5 to about 0.75. Because the first carbonaceous anode active material has an strength ratio within these ranges, defects in the first anode active material layer can be reduced, and defects between the first anode active material layer and the solid electrolyte layer can also be reduced. As a result, the interfacial resistance between the first anode active material layer and the solid electrolyte layer can be reduced, and localized lithium deposition can be suppressed.

[0075] The intensity ratio (I2) of the D band peak to the G band peak in the Raman spectrum of the second carbonaceous negative electrode active material included in the second negative electrode active material layer 23. 2 D / I 2 G The intensity ratio (I0) can be, for example, about 1.0 or greater, about 1.05 or greater, or about 1.1 or greater. The second intensity ratio (I0) of the intensity of the D band peak to the intensity of the G band peak in the Raman spectrum of the second carbonaceous negative electrode active material included in the second negative electrode active material layer 23 is also mentioned. 2 D / I 2 G The strength can be, for example, about 1.0 to about 10, about 1.05 to about 5, or about 1.1 to about 3. Because the second carbonaceous anode active material has an strength ratio within these ranges, defects in the second anode active material layer can increase. As a result, lithium can be easily and uniformly deposited within and / or on the surface of the second anode active material layer.

[0076] The position of the center of the D-band peak in the Raman spectrum of the first carbonaceous negative electrode active material included in the first negative electrode active material layer 22 may differ from the position of the center of the D-band peak in the Raman spectrum of the second carbonaceous negative electrode active material included in the second negative electrode active material layer 23 by, for example, approximately 2 cm. -1 Or larger, approximately 2.5cm -1 Or larger, about 3cm -1 Or larger, or about 3.5cm -1 Or a larger blue shift. For example, the first carbonaceous anode active material can exhibit a blue shift of approximately 2 cm. -1 Approximately 4cm -1 or about 3cm -1 Approximately 4cm -1 or about 3.5cm -1 Approximately 4cm -1 The blue shift. A blue shift refers to a shift to a position with higher energy, i.e., a higher wavenumber. In embodiments where the first carbonaceous anode active material has such a D-band peak center position, short circuits in the all-solid-state secondary battery can be suppressed, and its cycle characteristics can be further improved.

[0077] The position of the center of the G-band peak in the Raman spectrum of the first carbonaceous negative electrode active material included in the first negative electrode active material layer 22 is approximately 1 cm relative to the position of the center of the G-band peak in the Raman spectrum of the second carbonaceous negative electrode active material included in the second negative electrode active material layer 23. -1 Or larger, approximately 1.5cm -1 Or larger, or about 2cm -1Or a greater blue shift. For example, the first carbonaceous anode active material can exhibit a blue shift of approximately 1 cm. -1 Approximately 3cm -1 or about 1cm -1 To approximately 2.5cm -1 or about 2cm -1 To approximately 2.5cm -1 The blue shift. In embodiments where the first carbonaceous anode active material has such a G-band center position, short circuits in the all-solid-state secondary battery can be suppressed, and its cycle characteristics can be further improved.

[0078] The width of the D-band peak of the first carbonaceous anode active material included in the first anode active material layer 22, for example, the half-width (FWHM), can be about 80% or less, about 75% or less, about 70% or less, about 65% or less, or about 60% or less of the width of the D-band peak of the second carbonaceous anode active material included in the second anode active material layer 23. For example, the width of the D-band peak of the first carbonaceous anode active material can be about 50% to about 80%, or about 50% to about 70%, or about 50% to about 60% of the width of the D-band peak of the second carbonaceous anode active material. While not wishing to be bound by theory, it is understood that when the first carbonaceous anode active material has such a D-band peak width, short circuits in the all-solid-state secondary battery can be suppressed, and its cycle characteristics can be further improved.

[0079] At least one of the first or second carbonaceous anode active material may be in particulate form, for example. The particles of the first and / or second carbonaceous anode active materials may have an average particle diameter of, for example, about 4 micrometers (μm) or less, about 3 μm or less, about 2 μm or less, about 1 μm or less, or about 900 nanometers (nm) or less. The particles of the first and / or second carbonaceous anode active materials may have an average particle diameter of, for example, about 10 nm to 4 μm, about 10 nm to 3 μm, about 10 nm to 2 μm, about 10 nm to 1 μm, or about 10 nm to 900 nm. Because the first and / or second carbonaceous anode active materials have average particle diameters within these ranges, reversible absorption and / or desorption of lithium during charging and discharging can be further promoted. In another aspect, the average particle diameter of the first carbonaceous anode active material and / or the second carbonaceous anode active material may be the arithmetic mean of particle sizes obtained from scanning electron microscopy (SEM) images. As used herein, the term "particle size" refers to the average diameter of the particles in the case of spherical particles or the average length of the major axis in the case of non-spherical particles. The average particle diameter refers to the median diameter of the particles ("D50"), defined as the particle diameter corresponding to 50% (i.e., volume percentage) of the cumulative diameter distribution and 50% of the particle diameter in the sample. The median diameter of the particles ("D50") can be measured using a particle size analyzer ("PSA").

[0080] At least one of the first carbonaceous negative electrode active material included in the first negative electrode active material layer 22 or the second carbonaceous negative electrode active material included in the second negative electrode active material layer 23 may include, for example, amorphous carbon. The amorphous carbon may be at least one of the following: carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, carbon nanotubes, or carbon nanofibers. However, the aspect is not limited to this. Any suitable amorphous carbon may be used.

[0081] At least one of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 may be composed of a carbonaceous material. For example, the first negative electrode active material layer 22 may be composed of the first carbonaceous negative electrode active material, and / or the second negative electrode active material layer 23 may be composed of the second carbonaceous negative electrode active material. When the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 are composed of carbonaceous materials, the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 do not include non-carbonaceous materials such as metals, metal oxides, or ceramics.

[0082] In addition to the first carbonaceous anode active material, the first anode active material layer 22 may further include a metallic or quasi-metallic anode active material. In addition to the second carbonaceous anode active material, the second anode active material layer 23 may further include a metallic or quasi-metallic anode active material. The metallic or quasi-metallic anode active material may include at least one of the following: indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), or zinc (Zn). However, the embodiments are not limited thereto. Any suitable metallic or quasi-metallic anode active material that forms an alloy or compound with lithium can be used.

[0083] The first negative electrode active material layer 22 may include, for example, a single negative electrode active material, and therefore the first negative electrode active material layer 22 may include, for example, the first carbonaceous negative electrode active material or a metallic or quasi-metallic negative electrode active material. Alternatively, the first negative electrode active material layer 22 may include a composite of a variety of different negative electrode active materials. For example, the first negative electrode active material layer 22 may include amorphous carbon alone or in combination with at least one of the following metallic or quasi-metallic materials: indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), or zinc (Zn). In another aspect, the first negative electrode active material layer 22 may comprise a composite of amorphous carbon and at least one of the following metallic or quasi-metallic negative electrode active materials: indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), or zinc (Zn). The weight ratio between the amorphous carbon and the metallic or quasi-metallic material in the composite may be, for example, about 10:1 to 1:2, about 5:1 to 1:1, or about 4:1 to 2:1. For example, the metallic material in the composite may be silver. However, the aspect is not limited to these ranges, and the weight ratio may be selected according to the desired characteristics of the all-solid-state secondary battery 1. Since the first negative electrode active material layer 22 has a composition within these ratios, the cycle characteristics of the all-solid-state secondary battery 1 can be further improved.

[0084] The second negative electrode active material layer 23 may include, for example, a single negative electrode active material from the second carbonaceous active material, or may be a composite of multiple different negative electrode active materials. For example, the second negative electrode active material layer 23 may include amorphous carbon alone or in combination with at least one of the following metals or metalloids: indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), or zinc (Zn). In another aspect, the second negative electrode active material layer 23 may comprise a mixture of amorphous carbon and at least one of the following metals or metalloids: indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), or zinc (Zn). The weight ratio of amorphous carbon to silver, etc., in the mixture may be, for example, about 10:1 to 1:2, about 5:1 to 1:1, or about 4:1 to 2:1. However, the aspect is not limited to this. The weight ratio may be selected according to the desired characteristics of the all-solid-state secondary battery 1. Since the second negative electrode active material layer 23 has such a composition, the all-solid-state secondary battery 1 may have further improved characteristics.

[0085] The first negative electrode active material included in the first negative electrode active material layer 22 may include, for example, a composite of first particles and second particles. The first particles may be composed of amorphous carbon and the second particles may be composed of metal or quasi-metal. As used herein, "composite" refers to a material formed by combining two or more materials with different physical and / or chemical properties, wherein the composite has properties different from those of the individual materials constituting the composite, and wherein in the completed structure of the composite, the particles of the individual materials are at least microscopically separated and distinguishable from each other. The composite may be a product obtained by a thermochemical reaction via heat treatment of the mixture or by a mechanochemical reaction via mechanical milling of the mixture. The composite may be distinct from a mixture of the first and second particles or a mixture of the first and second particles bonded together by a binder. The metal or metalloid in the composite may include at least one of the following: indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), or zinc (Zn). In one aspect, the metalloid is a semiconductor. The amount of the second particle may be from about 1 wt% to about 60 wt%, from about 8 wt% to about 60 wt%, from about 10 wt% to about 50 wt%, from about 15 wt% to about 40 wt%, or from about 20 wt% to about 30 wt%, relative to the total weight of the composite. Because the amount of the second particle is within these ranges, the all-solid-state secondary battery 1 may have, for example, further improved cycle characteristics.

[0086] The negative electrode active material included in the second negative electrode active material layer 23 may include, for example, a mixture of first particles and second particles. The first particles may be composed of amorphous carbon and the second particles may be composed of a metal or metalloid. The mixture may be a product formed by mixing the first particles and the second particles, or by physically bonding the first particles and the second particles together with a binder. The metal or metalloid may include at least one of the following: indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), or zinc (Zn). In one aspect, the metalloid is a semiconductor. The amount of the second particles may be from about 8 wt% to about 60 wt%, from about 10 wt% to about 50 wt%, from about 15 wt% to about 40 wt%, or from about 20 wt% to about 30 wt%, relative to the total weight of the mixture. Since the amount of the second particle is within these ranges, for example, the all-solid-state secondary battery 1 can have further improved cycle characteristics.

[0087] In the all-solid-state secondary battery 1, for example, the amount of the metallic or quasi-metallic anode active material included in the second anode active material layer 23 and the amount of the metallic or quasi-metallic anode active material included in the first anode active material layer 22 may differ from each other. For example, the amount of the metallic or quasi-metallic anode active material included in the second anode active material layer 23 may be greater than the amount of the metallic or quasi-metallic anode active material included in the first anode active material layer 22. Because the amount of the metallic or quasi-metallic anode active material included in the second anode active material layer 23 is greater than the amount of the metallic or quasi-metallic anode active material included in the first anode active material layer 22, lithium can be deposited more easily in and / or on the surface of the second anode active material layer 23. The weight ratio of the amount of the metallic or quasi-metallic anode active material included in the second anode active material layer 23 to the amount of the metallic or quasi-metallic anode active material included in the first anode active material layer 22 can be, for example, about 51:49 to about 99:1, about 55:45 to about 95:5, or about 60:40 to about 90:10.

[0088] The average particle diameter of the first particles composed of amorphous carbon in the second negative electrode active material layer 23 may be smaller than the average particle diameter of the first particles composed of amorphous carbon in the first negative electrode active material layer 22. The average particle diameter of the first particles composed of amorphous carbon in the second negative electrode active material layer 23 may be, for example, about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less of the average particle diameter of the first particles composed of amorphous carbon in the first negative electrode active material layer 22.

[0089] The average particle diameter of the second particles composed of metal or quasi-metal in the second negative electrode active material layer 23 may be smaller than the average particle diameter of the second particles composed of metal or quasi-metal in the first negative electrode active material layer 22. The average particle diameter of the second particles composed of metal or quasi-metal in the second negative electrode active material layer 23 may be, for example, about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less of the average particle diameter of the second particles composed of metal or quasi-metal in the first negative electrode active material layer 22. Because the first and second particles in the second negative electrode active material layer 23 have a reduced particle diameter relative to those in the first negative electrode active material layer 22, the second particles (e.g., metal or quasi-metal particles) can be more uniformly dispersed in the second negative electrode active material layer 23, and therefore lithium can be more uniformly deposited inside or on the surface of the second negative electrode active material layer 23.

[0090] The first carbonaceous negative electrode active material included in the first negative electrode active material layer can form at least one of, for example, covalent bonds or ionic bonds with the solid electrolyte included in the solid electrolyte layer 30. The first carbonaceous negative electrode active material included in the first negative electrode active material layer can therefore be bonded to the solid electrolyte layer via at least one of covalent or ionic bonds. For example, the formation of covalent and / or ionic bonds can occur during the heat treatment of the precursors of the solid electrolyte layer 30 and the first negative electrode active material layer 22. Because the first negative electrode active material layer 22 forms covalent and / or ionic bonds with the solid electrolyte layer 30, the interfacial resistance between the first negative electrode active material layer 22 and the solid electrolyte layer 30 can be reduced, for example.

[0091] The first negative electrode active material layer 22 may be an inorganic layer, for example, excluding organic materials or organic compounds. As used herein, "organic compound" or "organic material" refers to a compound in which one or more carbon atoms are covalently bonded to hydrogen atoms, and optionally other elements. Organic compounds or organic materials do not include carbonaceous materials disclosed herein. For example, the first negative electrode active material layer 22 does not include organic binders such as polymer binders. In other words, the first negative electrode active material layer 22 may be an inorganic layer composed of inorganic materials. Because the first negative electrode active material layer 22 is an inorganic layer comprising inorganic carbonaceous materials and / or metal or quasi-metallic materials, side reactions during charging and discharging processes can be suppressed, for example. For example, the first negative electrode active material layer 22 may be an inorganic carbon layer composed of amorphous carbon. For example, the first negative electrode active material layer 22 may be an inorganic carbon-metal or quasi-metallic composite layer composed of amorphous carbon and metal or quasi-metal.

[0092] The first carbonaceous negative electrode active material included in the first negative electrode active material layer 22 may be, for example, a sintered product of a carbonaceous precursor. That is, the first carbonaceous negative electrode active material may be a product obtained by heat treatment of a carbonaceous precursor. The carbonaceous precursor of the first carbonaceous negative electrode active material may be, for example, a second carbonaceous negative electrode active material. For example, the first carbonaceous negative electrode active material may be obtained by heat treatment of the second carbonaceous negative electrode active material included in the second carbonaceous negative electrode active material layer 23. The first carbonaceous negative electrode active material may be, for example, a heat-treated product of the second carbonaceous negative electrode active material, i.e., a sintered product. Therefore, for example, the first negative electrode active material layer 22 may be sintered together with the solid electrolyte layer 23 during the heat treatment process to form an integral part of the solid electrolyte layer 30. Furthermore, during the heat treatment process, any organic materials, such as binders, included in the carbonaceous precursor may be removed by carbonization or gasification during the thermal decomposition process, and thus only the carbonaceous material and / or metallic material remains.

[0093] The thickness of the first negative electrode active material layer 22 may be about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less of the total thickness of the positive electrode active material layer 12. For example, the thickness of the first negative electrode active material layer 22 may be about 1% to about 50%, or about 1% to about 40%, or about 1% to about 30% of the total thickness of the positive electrode active material layer 12. Since the thickness of the first negative electrode active material layer 22 is reduced relative to the thickness of the positive electrode active material layer, the all-solid-state secondary battery may have improved energy density. The thickness of the first negative electrode active material layer 22 can be, for example, about 10 nm to about 10 μm, about 100 nm to about 10 μm, about 200 nm to about 10 μm, about 300 nm to about 10 μm, about 400 nm to about 10 μm, about 500 nm to about 10 μm, about 1 μm to about 10 μm, about 1 μm to about 9 μm, about 1 μm to about 8 μm, about 2 μm to about 7 μm, or about 3 μm to about 7 μm. When the first negative electrode active material layer 22 has a thickness within these ranges, short circuits in the all-solid-state secondary battery can be suppressed, and cycle characteristics can be improved. When the thickness of the first negative electrode active material layer 22 is too small, the first negative electrode active material layer 22 may not be able to effectively function as a negative electrode active material layer. When the thickness of the first negative electrode active material layer 22 is too large, the all-solid-state secondary battery 1 may have a reduced energy density and increased internal resistance due to the first negative electrode active material layer 22, and therefore the all-solid-state secondary battery 1 may have difficulty having improved cycle characteristics.

[0094] The thickness of the second negative electrode active material layer 23 may be, for example, about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less of the total thickness of the positive electrode active material layer. For example, the thickness of the second negative electrode active material layer 23 may be about 1% to about 50%, or about 1% to about 40%, or about 1% to about 30% of the total thickness of the positive electrode active material layer 12. Because the thickness of the second negative electrode active material layer 23 is less than the thickness of the positive electrode active material layer, the all-solid-state secondary battery may have improved energy density.

[0095] The thickness of the second negative electrode active material layer 23 can be, for example, about 1 μm to about 50 μm, about 5 μm to about 45 μm, about 10 μm to about 40 μm, about 15 μm to about 35 μm, or about 20 μm to about 30 μm. When the second negative electrode active material layer 23 has a thickness within these ranges, short circuits in the all-solid-state secondary battery can be suppressed, and cycle characteristics can be improved. When the thickness of the second negative electrode active material layer 23 is too small, lithium dendrites formed between the second negative electrode active material layer 23 and the negative electrode current collector 21 can cause the second negative electrode active material layer 23 to collapse, and therefore the all-solid-state secondary battery 1 may have difficulty having improved cycle characteristics. When the thickness of the second negative electrode active material layer 23 is excessively increased, the all-solid-state secondary battery 1 may have a reduced energy density and increased internal resistance due to the second negative electrode active material layer 23, and therefore the all-solid-state secondary battery 1 may have difficulty having improved cycle characteristics.

[0096] For example, the thickness of the first negative electrode active material layer 22 may be less than the thickness of the second negative electrode active material layer 23. The thickness of the first negative electrode active material layer 22 may be about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less of the thickness of the second negative electrode active material layer 23. For example, the thickness of the first negative electrode active material layer 22 may be about 5% to about 50%, or about 10% to about 40%, or about 20% to about 30% of the thickness of the second negative electrode active material layer 23. When the first negative electrode active material layer 22 has a thickness within these ranges, short circuits in the all-solid-state secondary battery can be suppressed, and cycle characteristics can be improved.

[0097] For example, a first negative electrode active material layer 22 can be formed on the solid electrolyte layer 30 using film-forming methods such as spin coating, drop coating, spray coating, pyrolysis, or solution filtration, followed by heat treatment. However, the aspect is not limited to this. Any wet method suitable for forming the first negative electrode active material layer 22 can be used. In another aspect, the first negative electrode active material layer 22 can be formed on the solid electrolyte layer 30 using vacuum deposition, sputtering, or plating. However, the aspect is not limited to these methods. Any dry method suitable for forming the first negative electrode active material layer 22 can be used.

[0098] At least one of the first negative electrode active material layer 22 or the second negative electrode active material layer 23 may further include, for example, an adhesive.

[0099] For example, the second negative electrode active material layer 23 may include an adhesive. The adhesive may be at least one of the following: styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, or polymethyl methacrylate. However, the aspect is not limited thereto. Any suitable adhesive may be used. The adhesive may be a single adhesive or may include a variety of different adhesives.

[0100] When the second negative electrode active material layer 23 includes a binder, the second negative electrode active material layer 23 can be stabilized on the negative electrode current collector 21. Furthermore, despite volume changes and / or relative positional changes in the second negative electrode active material layer 23 during charging and discharging processes, breakage of the second negative electrode active material layer 23 can be suppressed. For example, when the second negative electrode active material layer 23 does not include a binder, the second negative electrode active material layer 23 can be easily separated from the negative electrode current collector 21. If a portion of the second negative electrode active material layer 23 separates from the negative electrode current collector 21, the negative electrode current collector 21 can be exposed and come into contact with the solid electrolyte layer 30, and therefore a short circuit is more likely to occur. For example, the second negative electrode active material layer 23 can be formed by coating a slurry onto the negative electrode current collector 21 and drying it. The slurry may include components for forming the second negative electrode active material layer 23. If a binder is included in the second negative electrode active material layer 23, the negative electrode active material can be stably dispersed in the slurry. For example, when the paste is coated onto the negative electrode current collector 21 using screen printing, screen clogging (e.g., clogging by aggregates of the negative electrode active material) can be suppressed.

[0101] For example, the negative electrode current collector 21 may be composed of a material that does not react with lithium to form an alloy or compound. The material of the negative electrode current collector 21 may be at least one of the following metals: copper (Cu), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), or nickel (Ni). However, the aspect is not limited to this. Any material suitable as a negative electrode current collector may be used. The negative electrode current collector 21 may comprise one of the metals listed above or may be an alloy or compound of two or more of the metals listed above. The negative electrode current collector 21 may be in the form of, for example, a plate or foil.

[0102] The second negative electrode active material layer 23 of the all-solid-state secondary battery 1 may further include additives, such as at least one of fillers, dispersants, or ion conductors.

[0103] In the all-solid-state secondary battery 1, for example, the second negative electrode active material layer 23 may include a second carbonaceous negative electrode active material and a metallic or quasi-metallic negative electrode active material, and the first negative electrode active material layer 22 may be composed of a first carbonaceous negative electrode active material. That is, the first negative electrode active material layer 22 does not include metallic materials, and in particular, does not include metallic or quasi-metallic negative electrode active materials. Because the all-solid-state secondary battery 1 has this structure, short circuits in the all-solid-state secondary battery 1 can be suppressed, and cycle characteristics can be improved.

[0104] In another aspect, in the all-solid-state secondary battery 1, the second negative electrode active material layer 23 may be composed of a second carbonaceous negative electrode active material, and the first negative electrode active material layer 22 may include a first carbonaceous negative electrode active material and a metallic or quasi-metallic negative electrode active material. That is, the second negative electrode active material layer 23 does not include metallic materials, and in particular, does not include metallic or quasi-metallic active materials. Because the all-solid-state secondary battery 1 has this structure, short circuits in the all-solid-state secondary battery 1 can be suppressed, and cycle characteristics can be improved.

[0105] refer to Figure 2 For example, the all-solid-state secondary battery 1 may further include a thin film 24 on the negative electrode current collector 21, the thin film 24 comprising an element capable of alloying with lithium. The thin film 24 may be disposed between the negative electrode current collector 21 and the second negative electrode active material layer 23. For example, the thin film 24 may comprise an element capable of alloying with lithium. The element (metal) capable of alloying with lithium may be at least one of the following: gold, silver, zinc, tin, indium, silicon, aluminum, or bismuth. However, the aspect is not limited to this, and any element capable of alloying with lithium may be used. The thin film 24 may be composed of one of these metals or an alloy of two or more different metals. Since the thin film 24 is disposed on the negative electrode current collector 21, for example, a third negative electrode active material layer (not shown) deposited between the thin film 24 and the second negative electrode active material layer 23 may have a flatter form, and the all-solid-state secondary battery 1 may have further improved cycle characteristics.

[0106] The thin film 24 may have a thickness of, for example, 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. When the thickness of the thin film 24 is less than 1 nm, the thin film 24 may be difficult to function properly. When the thickness of the thin film 24 is too large, the thin film 24 itself may absorb lithium, thereby reducing the amount of lithium deposited on the negative electrode and the all-solid-state secondary battery may have a lower energy density and therefore deteriorated cycle characteristics. The thin film 24 may be disposed on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, or coating. However, the method is not limited to these methods. Any suitable method may be used to form the thin film 24.

[0107] refer to Figure 3 and 4According to one aspect, the all-solid-state secondary battery 1 can further be configured between the negative electrode current collector 21 and the second negative electrode active material layer 23. Figure 4 Or between the first negative electrode active material layer 22 and the second negative electrode active material layer 23 ( Figure 3 The battery includes a third negative electrode active material layer 25. The third negative electrode active material layer 25 can be deposited during charging of the all-solid-state secondary battery 1. The third negative electrode active material layer 25 can be a metal layer comprising lithium or a lithium alloy. Therefore, the third negative electrode active material layer 25, as a metal layer comprising lithium or a lithium alloy, can be used as a lithium reservoir. The lithium alloy can be at least one of, for example: Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, or Li-Si alloy. However, the aspect is not limited to these alloys, and any lithium alloy suitable for all-solid-state secondary batteries can be used. The third negative electrode active material layer 25 can be composed of lithium, a single lithium alloy, or a combination of multiple alloys.

[0108] The thickness of the third negative electrode active material layer 25 is not particularly limited, and can be, for example, about 1 μm to about 1000 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. When the thickness of the third negative electrode active material layer 23 is too thin, the third negative electrode active material layer 25 may not be usable as a lithium reservoir. When the thickness of the third negative electrode active material layer 25 is too thick, the all-solid-state secondary battery 1 may increase in mass and volume, and the cycle characteristics may deteriorate. The third negative electrode active material layer 25 may be, for example, a metal foil having a thickness within the above range.

[0109] For example, the third negative electrode active material layer 25 of the all-solid-state secondary battery 1 may be disposed between the negative electrode current collector 21 and the second negative electrode active material layer 23, or between the first negative electrode active material layer 22 and the second negative electrode active material layer 23, during the assembly of the all-solid-state secondary battery 1. Alternatively, the third negative electrode active material layer 25 of the all-solid-state secondary battery 1 may be deposited after assembly and during charging of the all-solid-state secondary battery 1, and may be disposed between the negative electrode current collector 21 and the second negative electrode active material layer 23, or between the first negative electrode active material layer 22 and the second negative electrode active material layer 23.

[0110] In cases where the third negative electrode active material layer 25 is disposed between the negative electrode current collector 21 and the second negative electrode active material layer 23, or between the first negative electrode active material layer 22 and the second negative electrode active material layer 23, during the assembly of the all-solid-state secondary battery 1, the third negative electrode active material layer 25 (which is a metal layer including lithium) can serve as a lithium reservoir. The all-solid-state secondary battery 1 including the third negative electrode active material layer 25 can have further improved cycle characteristics. For example, during the assembly of the all-solid-state secondary battery 1, a lithium foil serving as the third negative electrode active material layer 25 can be disposed between the negative electrode current collector 21 and the second negative electrode active material layer 23, or between the first negative electrode active material layer 22 and the second negative electrode active material layer 23.

[0111] In cases where the third negative electrode active material layer 25 is provided after assembly and during charging of the all-solid-state secondary battery 1, the all-solid-state secondary battery 1 can have increased energy density because the third negative electrode active material layer 25 is not present at the time of assembly. For example, the all-solid-state secondary battery 1 can be charged to exceed the charging capacity of at least one of the first negative electrode active material layer 22 or the second negative electrode active material layer 23. That is, the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 can be overcharged. During the initial charging phase, lithium can be absorbed into at least one of the first negative electrode active material layer 22 or the second negative electrode active material layer 23. That is, when lithium ions move from the positive electrode layer 10 during charging of the all-solid-state secondary battery, the negative electrode active material in at least one of the first negative electrode active material layer 22 or the second negative electrode active material layer 23 can form an alloy or compound with the lithium ions. When the all-solid-state secondary battery 1 is overcharged, i.e., charged beyond the capacity of the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23, lithium may, for example, be deposited on the rear surface of the second negative electrode active material layer 23, i.e., between the negative electrode current collector 21 and the second negative electrode active material layer 23, thereby forming a metal layer corresponding to the third negative electrode active material layer 25. Alternatively, when the all-solid-state secondary battery 1 is charged beyond the capacity of the second negative electrode active material layer 23, lithium may, for example, be deposited on the front surface of the second negative electrode active material layer 23, i.e., between the first negative electrode active material layer 22 and the second negative electrode active material layer 23, thereby forming a metal layer corresponding to the third negative electrode active material layer 25.

[0112] The third negative electrode active material layer 25 may be a metal layer including lithium (i.e., metallic lithium) as a main component. This may be attributed to, for example, the fact that the negative electrode active materials in the first negative electrode active material layer 22 and the second negative electrode active material layer 23 include materials capable of forming an alloy or a compound with lithium. During discharge, lithium in at least one of the first negative electrode active material layer 22, the second negative electrode active material layer 23, or the third negative electrode active material layer 25 (i.e., the lithium metal layer) may be ionized and then move toward the positive electrode layer 10. Therefore, the all-solid-state secondary battery 1 may use lithium as the negative electrode active material. Since at least one of the first negative electrode active material layer 22 or the second negative electrode active material layer 23 covers the third negative electrode active material layer 25, at least one of the first negative electrode active material layer 22 or the second negative electrode active material layer 23 can be used as a protective layer for the third negative electrode active material layer 25, i.e., the metal layer, and at the same time suppress the precipitation and growth of lithium dendrites. Therefore, short circuits and reduction of capacity of the all-solid-state secondary battery 1 can be suppressed, and the cycle characteristics of the all-solid-state secondary battery 1 can be improved. In the case where the third negative electrode active material layer 25 is provided by charging the all-solid-state secondary battery 1 after assembly, the negative electrode current collector 21, the first negative electrode active material layer 22, the second negative electrode active material layer 23, and the region therebetween may be, for example, a Li-free region that does not include lithium (Li) in the initial state or the discharged state of the all-solid-state secondary battery.

[0113] (Solid electrolyte layer)<B

[0114] Reference Figures 1 to 4 , the solid electrolyte layer 30 between the positive electrode layer 10 and the negative electrode layer 20 may contain a solid electrolyte.

[0115] The solid electrolyte may be, for example, a solid electrolyte containing an oxide. The solid electrolyte containing an oxide may be at least one of the following: Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (where 0 < x < 2 and 0 ≤ y < 3), BaTiO3, Pb(Zr a Ti 1-a )O3 (where 0 ≤ a ≤ 1) (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (where 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 (where 0 < x < 2 and 0 < y < 3), Li x Al y Ti z (PO4)3 (where 0 < x < 2, 0 < y < 1, and 0 < z < 3), Li 1+x+y (Al a Ga 1-a ) x (Ti b Ge 1-b ) 2-x Si y P 3-y O 12 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ a ≤ 1, and 0 ≤ b ≤ 1), Li x La y TiO3 (where 0 < x < 2 and 0 < y < 3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2, and Li 3+x La3M2O 12 (where M is Te, Nb, or Zr, and x is 1 ≤ x ≤ 10). The solid electrolyte can be prepared, for example, by sintering.

[0116] The solid electrolyte containing oxides can be, for example, at least one of the following garnet - type solid electrolytes: Li7La3Zr2O 12 (LLZO) or Li 3+x La3Zr 2-a M a O 12 (M - doped LLZO, where M is Ga, W, Nb, Ta, or Al, 1 ≤ x ≤ 10, and 0 ≤ a < 2).

[0117] In another aspect, the solid electrolyte may be, for example, a solid electrolyte containing a sulfide. The solid electrolyte containing a sulfide may be at least one of the following: Li₂S-P₂S₅, Li₂S-P₂S₅-LiX (where X is a halogen), Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, Li₂S-P₂S₅-Z m S n (where m and n are each independently positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (where p and q are each independently positive, and M is selected from P, Si, Ge, B, Al, Ga, and In), Li 7-x PS 6-x Cl x (where 0≤x≤2), Li 7-x PS 6-x Br x (where 0≤x≤2), or Li 7-x PS 6-x I x (Where 0 ≤ x ≤ 2). The sulfide-containing solid electrolyte can be prepared using at least one precursor material such as Li₂S or P₂S₅, by quenching or mechanically grinding the precursor material melt. Further heat treatment may be performed after these processes. The sulfide-containing solid electrolyte can be amorphous, crystalline, or a mixture thereof.

[0118] Furthermore, the sulfide-containing solid electrolyte can be, for example, any of the above-listed solid electrolyte materials containing sulfides and including at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the sulfide-containing solid electrolyte can be a material comprising Li₂S-P₂S₅. When using a sulfide-containing solid electrolyte comprising Li₂S-P₂S₅, the mixing molar ratio of Li₂S to P₂S₅ (Li₂S:P₂S₅) can be, for example, in the range of about 50:50 to about 90:10, or about 60:40 to about 90:10, or about 70:30 to about 80:20.

[0119] The solid electrolyte containing sulfides may include, for example, a sulfosilgermanium ore type solid electrolyte represented by Formula 1.

[0120] Formula 1

[0121] Li + 12-n-x A n+ X 2- 6-x Y - x

[0122] In Equation 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; 1≤n≤5; and 0≤x≤2.

[0123] The sulfide-containing solid electrolyte may be a compound having a sulforaphite-germanium-type crystal structure. The compound having a sulforaphite-germanium-type crystal structure may include at least one of the following: Li 7-x PS 6-x Cl x (where 0≤x≤2), Li 7-x PS 6-x Br x (where 0≤x≤2), or Li 7-x PS 6-x I x (where 0 ≤ x ≤ 2). In particular, the sulfide-containing solid electrolyte may be a sulfide-germanium ore type compound including at least one of the following: Li6PS5Cl, Li6PS5Br, or Li6PS5I.

[0124] For example, the solid electrolyte layer 30 may further include a binder. The binder in the solid electrolyte layer 30 may be at least one of the following: styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or polyethylene. However, the aspect is not limited to this. Any suitable binder may be used. The binder of the solid electrolyte layer 30 may be the same as or different from the binder of the positive electrode active material layer 12 and the second negative electrode active material layer 23.

[0125] Positive electrode layer

[0126] The positive electrode layer 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12.

[0127] The positive current collector 11 may be a plate or foil comprising at least one of the following: indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof. The positive current collector 11 may be omitted.

[0128] The positive electrode active material layer 12 may include, for example, a positive electrode active material.

[0129] The positive electrode active material is capable of lithium-ion intercalation and deintercalation. The positive electrode active material may be at least one of the following: lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide, or lithium iron phosphate; nickel sulfide; copper sulfide; lithium sulfide; iron oxide; or vanadium oxide. However, the aspect is not limited to these. Any suitable positive electrode active material can be used. These positive electrode active materials can be used alone or in combination of at least two positive electrode active materials.

[0130] The positive electrode active material may be, for example, a compound represented by the following formula: Li a A 1-b B' b D2 (where 0.90≤a≤1 and 0≤b≤0.5); Li a E 1-b B' b O 2-c D c (where 0.90≤a≤1, 0≤b≤0.5, and 0≤c≤0.05); LiE 2-b B' b O 4- c D c (where 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2); Li a Ni 1-b-c Co b B' c O 2-α F' α (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); Li a Ni 1-b-c Co 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 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, and 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (where 0.90 ≤ a ≤ 1, and 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (where 0.90 ≤ a ≤ 1, and 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (where 0.90≤a≤1 and 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3 (where 0≤f≤2); Li (3-f)Fe2(PO4)3 (where 0≤f≤2); and LiFePO4. In the above formula, A can be nickel (Ni), cobalt (Co), manganese (Mn), or a combination thereof; B' can be aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), iron (Fe), magnesium (Mg), strontium (Sr), vanadium (V), rare earth elements, or a combination thereof; D can be oxygen (O), fluorine (F), sulfur (S), phosphorus (P), or a combination thereof; E can be cobalt (Co), manganese (Mn), or a combination thereof; F' can be fluorine (F), sulfur (S), phosphorus (P), or a combination thereof. G can be aluminum (Al), chromium (Cr), manganese (Mn), iron (Fe), magnesium (Mg), lanthanum (La), cerium (Ce), strontium (Sr), vanadium (V), or a combination thereof; Q can be titanium (Ti), molybdenum (Mo), manganese (Mn), or a combination thereof; I' can be chromium (Cr), vanadium (V), iron (Fe), scandium (Sc), yttrium (Y), or a combination thereof; and J can be vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), or a combination thereof.

[0131] The positive electrode active material may further include a surface coating layer (hereinafter also referred to as "coating layer"). Alternatively, a mixture of compounds without a coating layer and compounds with a coating layer may be used, the compounds being selected from the compounds listed above. In one aspect, the coating layer on the surface of such a compound may include a coating element compound selected from at least one of the following: oxides, hydroxides, hydroxyoxides, oxycarbonates, or hydroxycarbonates of the coating element. In one aspect, the compound used for the coating layer may be amorphous or crystalline. In one aspect, the coating element used for the coating layer may be at least one of the following: magnesium (Mg), aluminum (Al), cobalt (Co), potassium (K), sodium (Na), calcium (Ca), silicon (Si), titanium (Ti), vanadium (V), tin (Sn), germanium (Ge), gallium (Ga), boron (B), arsenic (As), or zirconium (Zr). In one aspect, the coating layer may be formed using any method that does not adversely affect the physical properties of the positive electrode active material. For example, the coating layer may be formed using a spraying method, an impregnation method, etc. The coating methods mentioned above are understood by those skilled in the art, and therefore their detailed description will be omitted.

[0132] The positive electrode active material may include, for example, a lithium transition metal oxide having a layered rock salt structure among the lithium transition metal oxides listed above. The term "layered rock salt structure" as used herein refers to a structure in which oxygen atom layers and metal atom layers are alternately and regularly arranged in the (111) crystal direction, and each atom layer forms a two-dimensional (2D) plane. The "cubic rock salt structure" refers to the crystal structure of sodium chloride (NaCl), and in particular, a structure in which a face-centered cubic (fcc) lattice formed by corresponding cations and anions is arranged in such a way that the ridges of the unit lattice (unit cell) are offset by 1 / 2. The lithium transition metal oxide having such a layered rock salt structure may be, for example, a ternary lithium transition metal oxide such as LiNi x Co y Al z O2 (NCA) or LiNi x Co y Mn z O2 (NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1). When the positive electrode active material includes such a ternary lithium transition metal oxide having a layered rock salt structure, the all-solid-state secondary battery 1 may have further improved energy density and thermal stability. For example, the lithium transition metal oxide having such a layered rock salt structure may be, for example, LiNi x Co y Mn z O2 (0.6 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1), LiNi x Co y Al z O2 (0.6 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1), LiNi x Co y Al v Mn w O2 (0.6 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < v ≤ 0.2, 0 < w ≤ 0.2, and x + y + v + w = 1), LiNi x Co y Mn z O2 (0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1), LiNi x Co y Al z O2 (0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1), LiNi x Co y Al v Mn wO2 (0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < v ≤ 0.2, 0 < w ≤ 0.2, and x + y + v + w = 1), LiNi x Co y Mn z O2 (0.85 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2 and x + y + z = 1), LiNi x Co y Al z O2 (0.85 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1), LiNi x Co y Al v Mn w O2 (0.85 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < v ≤ 0.2, 0 < w ≤ 0.2, and x + y + v + w = 1), etc.

[0133] The positive electrode active material may include the coating layer as described above. The coating layer may be any suitable coating layer for the positive electrode active material of a all-solid-state secondary battery. The coating layer may include, for example, Li2O-ZrO2.

[0134] When the positive electrode active material includes, for example, a ternary lithium transition metal oxide containing Ni such as NCA or NCM, the all-solid-state secondary battery 1 may have an increased capacity density, and elution of metal ions from the positive electrode active material in a charged state may be reduced. As a result, the all-solid-state secondary battery 1 may have improved cycle characteristics.

[0135] The positive electrode active material may be in the form of particles having, for example, a true spherical shape or an ellipsoidal shape. The particle diameter of the positive electrode active material is not particularly limited and may be within the range applicable to the positive electrode active material of a commercially available lithium secondary battery. The amount of the positive electrode active material in the positive electrode layer 10 is not particularly limited and may be within the range applicable to the positive electrode active material of a commercially available lithium secondary battery.

[0136] In addition to the positive electrode active material described above, the positive electrode layer 10 may further include at least one additive such as a conductive agent, a binder, a filler, a dispersant, an auxiliary ion conductor, or a coating agent. The conductive agent may be, for example, at least one of the following: graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or metal powder. The binder may be, for example, at least one of the following: styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. The filler, dispersant, auxiliary ion conductor, and coating agent that can be added to the positive electrode layer 10 may be any materials suitable for the positive electrode of a all-solid-state secondary battery.

[0137] The positive electrode layer 10 may further include a solid electrolyte. The solid electrolyte included in the positive electrode layer 10 may be the same as (similar to) or different from the solid electrolyte included in the solid electrolyte layer 30. For a detailed description of the solid electrolyte of the positive electrode layer 10, please refer to the above detailed description of the solid electrolyte layer 30.

[0138] The solid electrolyte included in the positive electrode layer 10 may be, for example, a solid electrolyte containing sulfides. This solid electrolyte containing sulfides may also be used in the solid electrolyte layer 30.

[0139] In another aspect, the positive electrode layer 10 may include, for example, a liquid electrolyte. For example, the positive electrode layer may be immersed in the liquid electrolyte. The liquid electrolyte may include a lithium salt and at least one of an ionic liquid or a polymeric ionic liquid. The liquid electrolyte may be non-volatile. The ionic liquid may refer to a salt that is liquid at room temperature or a molten salt at room temperature, each having a melting point equal to or below room temperature and composed of ions. The ionic liquid may include at least one cation and at least one anion. The cation may be at least one of the following: ammonium cation, pyrrolidine... Cations, Pyridine Cations, pyrimidines Cationic, imidazole Cations, piperidine cationic, pyrazole cation, azole cationic, pyridazine cation, Cation, sulfonium cation, or triazole The cation, and the anion may be at least one of the following: BF4 - PF6 - AsF6 - SbF6 - AlCl4 - HSO4 - ClO4 - CH3SO3 - CF3CO2 - Cl - ,Br - I - SO4 2- CF3SO3 - (FSO2)2N - (C2F5SO2)2N - (C2F5SO2)(CF3SO2)N - or (CF3SO2)2N -The ionic liquid may be at least one of the following, for example: bis(trifluoromethanesulfonyl)imide N-methyl-N-propylpyrrolidine. Bis(trifluoromethanesulfonyl)imide N-butyl-N-methylpyrrolidine Or bis(trifluoromethanesulfonyl)imide 1-butyl-3-methylimidazolium

[0140] The polymeric ionic liquid (PIL) may include repeating units comprising at least one cation and at least one anion. The cation may be at least one of the following: ammonium cation, pyrrolidine... Cations, Pyridine Cations, pyrimidines Cationic, imidazole Cations, piperidine cationic, pyrazole cation, azole cationic, pyridazine cation, Cation, sulfonium cation, or triazole The cation, and the anion may be at least one of the following: BF4 - PF6 - AsF6 - SbF6 - AlCl4 - HSO4 - ClO4 - CH3SO3 - CF3CO2 - (CF3SO2)2N - (FSO2)2N - Cl - ,Br - I - SO4 2- CF3SO3 - (C2F5SO2)2N - (C2F5SO2)(CF3SO2)N - NO3 - Al2Cl7 - (CF3SO2)3C - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - SF5CF2SO3 - SF5CHFCF2SO3- CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - , or (O(CF3)2C2(CF3)2O)2PO - .

[0141] The lithium salt can be any lithium salt used in the art. For example, the lithium salt can be at least one of the following: 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 independent natural numbers), LiCl, or LiI. The concentration of the lithium salt in the liquid electrolyte can be from about 0.1 molar concentration (M) to about 5M. The amount of the liquid electrolyte immersed in the positive electrode layer 10 can be from 0 to about 100 parts by weight, from 0 to about 50 parts by weight, from 0 to about 30 parts by weight, from 0 to about 20 parts by weight, from 0 to about 10 parts by weight, or from 0 to about 5 parts by weight, relative to 100 parts by weight of the positive electrode active material layer 12 excluding the liquid electrolyte.

[0142] According to another aspect, a method for manufacturing an all-solid-state secondary battery includes: providing a solid electrolyte layer; depositing a first negative electrode active material composition on a first surface of the solid electrolyte layer 30; heat-treating the first negative electrode active material composition to deposit a first negative electrode active material layer 22; depositing a second negative electrode active material layer on the surface of the first negative electrode active material layer; and depositing a positive electrode active material layer 12 on a second surface of the solid electrolyte layer 30. Due to the sequential arrangement of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 on the solid electrolyte layer 30, short circuits in the all-solid-state secondary battery 1 can be suppressed, and the cycle characteristics of the all-solid-state secondary battery 1 can be improved.

[0143] For example, according to one aspect, the all-solid-state secondary battery 1 can be manufactured by separately manufacturing the positive electrode layer and the first negative electrode active material layer 22 and the second negative electrode active material layer 23, sequentially disposing of a solid electrolyte layer 30 thereon, and then stacking these layers on top of each other.

[0144] (Preparation of a laminate of solid electrolyte layer / negative electrode layer)

[0145] At least one of the following materials constituting the first negative electrode active material layer 22, such as a first carbonaceous negative electrode active material, optionally a metallic or quasi-metallic negative electrode active material, and optionally a binder or additive, can be added to a polar or non-polar solvent to prepare a slurry (the first negative electrode active material composition). The prepared slurry can be coated onto the surface of the solid electrolyte layer 30 and dried to prepare a first laminate in which the first negative electrode active material composition is disposed on a first surface of the solid electrolyte layer 30. The first laminate can be heat-treated to prepare a second laminate in which the first negative electrode active material layer 22 (which is a sintered product) is disposed on the solid electrolyte layer 30. The heat treatment temperature can be, for example, about 300°C to about 900°C, about 350°C to about 800°C, about 400°C to about 700°C, about 400°C to about 600°C, or about 400°C to about 500°C. When the heat treatment temperature is too low, organic materials such as binders may be retained, and the sintering of the solid electrolyte layer 30 and the first negative electrode active material layer 22 may be insufficient. When the heat treatment temperature is too high, the first carbonaceous anode active material and / or metallic or quasi-metallic anode active material may deteriorate. The heat treatment time can be from about 0.1 hours to about 20 hours, from about 0.5 hours to about 15 hours, from about 1 hour to about 10 hours, from about 1 hour to about 5 hours, or from about 1 hour to about 3 hours. However, the heat treatment temperature and time are not limited to these ranges and can be adjusted as needed. The heat treatment atmosphere can be an inert gas atmosphere. The inert gas can be, for example, argon or nitrogen.

[0146] Subsequently, at least one of the following materials constituting the second negative electrode active material layer 23, such as a second carbonaceous negative electrode active material, optionally a metallic or quasi-metallic negative electrode active material, and optionally a binder or additive, can be added to a polar or non-polar solvent to prepare a slurry (second negative electrode active material composition). The prepared slurry can be coated on the surface of the first negative electrode active material layer 22 and dried to prepare a third laminate in which the second negative electrode active material layer 23 is disposed on the surface of the first negative electrode active material layer 22, and the first negative electrode active material layer 22 is between the solid electrolyte layer 30 and the second negative electrode active material layer 23. The second negative electrode active material composition may be the same as or different from the first negative electrode active material composition.

[0147] Subsequently, the negative electrode current collector 21 can be placed on the surface of the dried third laminate, and then pressed to form a laminate of a solid electrolyte layer 30 and a negative electrode layer 20. The pressing can be performed, for example, by rolling or flat pressing. However, the aspect is not limited to these methods, and any pressing method used in the art can be used. The pressure applied during pressing can be, for example, from about 50 MPa to about 500 MPa, or from about 100 MPa to about 450 MPa, or from about 100 MPa to about 350 MPa. The pressing time for applying pressure can be from about 5 milliseconds (ms) to about 10 minutes (min). The pressing can be performed, for example, at a temperature from room temperature to (20°C) to about 90°C, or at a temperature from about 25°C to about 90°C. In another aspect, the pressing can be performed at a temperature of about 100°C or higher, for example, from about 100°C to about 300°C, or from about 100°C to about 250°C.

[0148] Before depositing the second negative electrode active material layer 23 on the first negative electrode active material layer 22, the surface of the first negative electrode active material layer 22 can be washed with an acidic solution. Washing the surface of the first negative electrode active material layer 22 with the acidic solution removes impurities from the surface of the first negative electrode active material layer 22, thereby reducing the interfacial resistance between the first negative electrode active material layer 22 and the second negative electrode active material layer 23. The acidic solution may include an acid, such as at least one of hydrochloric acid, nitric acid, or sulfuric acid, but the acid and acidic solution are not limited to these, and any acid / acidic solution used to remove surface impurities can be used. The acidic solution may have a pH of, for example, 0.1 to 6, 0.5 to 5, 1 to 4, 1 to 3, or 1 to 2.

[0149] (Preparation of the positive electrode layer)

[0150] Materials for the positive electrode active material layer 12 (e.g., positive electrode active material, binder) can be added to a nonpolar solvent to prepare a slurry (positive electrode active material layer composition). The prepared slurry can be coated onto the positive electrode current collector 11 and then dried to form a laminate. The resulting laminate can be pressed to form the positive electrode layer 10. The pressing can be performed using any suitable pressing method and is not limited to a particular method. For example, the pressing can include rolling, flat pressing, or isostatic pressing. The pressing can be omitted. In another aspect, the positive electrode layer 10 can be formed by compressing the positive electrode active material layer composition into a sheet (disc) or by stretching the mixture into a sheet form. When the positive electrode layer 10 is formed using these methods, the positive electrode current collector 11 can be omitted. In another aspect, the positive electrode layer 10 can be impregnated with a liquid electrolyte before use.

[0151] (Preparation of solid electrolyte layer)

[0152] For example, a solid electrolyte layer 30 comprising a solid electrolyte containing oxides can be prepared by heat-treating a precursor of a solid electrolyte material containing oxides.

[0153] The oxide-containing solid electrolyte can be prepared by contacting precursors in stoichiometric amounts to form a mixture, and then heat-treating the mixture. For example, the contact may include grinding, such as ball milling, or milling. The mixture of precursors combined in stoichiometric amounts can be subjected to a first heat treatment under an oxidizing atmosphere to prepare a first heat-treated product. The first heat treatment can be carried out at a temperature less than 1,000°C for about 1 hour to about 36 hours. For example, the first heat treatment can be carried out at a temperature of about 100°C to about 900°C, or about 200°C to about 750°C. The first heat-treated product can then be milled. The first heat-treated product can be milled by wet milling or dry milling. For example, wet milling can be carried out by mixing the first heat-treated product with a solvent such as methanol, and then milling the mixture using, for example, a ball mill for about 0.5 hours to about 10 hours. Dry milling can be carried out using, for example, a ball mill in the absence of a solvent. The milled first heat-treated product can have a particle diameter of about 0.1 μm to about 10 μm, or about 0.1 μm to about 5 μm. The milled first heat-treated product can be dried. The milled first heat-treated product can be formed into a sheet (disc) after being mixed with a binder solution, or it can be formed into a sheet (disc) by simply pressing it under a pressure of about 0.09 to about 1 MPa, or about 0.1 MPa to about 1 MPa.

[0154] The formed product in sheet form can be subjected to a second heat treatment at a temperature of less than or equal to about 1,000°C for about 1 hour to about 36 hours. Through the second heat treatment, a solid electrolyte layer 30 as a sintered product can be obtained. The second heat treatment can be performed, for example, at a temperature of about 550 to 1,000°C, or about 600°C to about 900°C, or about 700°C to about 850°C. For example, the second heat treatment time can be about 1 to about 36 hours. The second heat treatment temperature for obtaining the sintered product can be greater than the first heat treatment temperature. For example, the second heat treatment temperature can be about 10°C or more, about 20°C or more, about 30°C or more, or about 50°C or more higher than the first heat treatment temperature. The second heat treatment of the formed product can be performed under at least one of an oxidizing atmosphere or a reducing atmosphere. The second heat treatment can be performed under a) an oxidizing atmosphere, b) a reducing atmosphere, or c) a combination of oxidizing and reducing atmospheres.

[0155] For example, the solid electrolyte layer 30, which includes a solid electrolyte containing sulfides, can be prepared using a solid electrolyte material containing sulfides.

[0156] The sulfide-containing solid electrolyte can be prepared by treating the precursor (source) material, for example, by melt quenching or mechanical grinding. However, the method is not limited to this. Any suitable method for preparing a sulfide-containing solid electrolyte can be used. For example, in the case of melt quenching, a predetermined amount of source material, such as Li2S and P2S5, is mixed together, formed into a sheet (disc), reacted under vacuum at a predetermined reaction temperature, and then quenched to thereby prepare a sulfide-containing solid electrolyte. The reaction temperature of the Li2S and P2S5 mixture can be, for example, from about 400°C to about 1000°C, or from about 800°C to about 900°C. The reaction time can be, for example, from about 0.1 hours to about 12 hours, or from about 1 hour to about 12 hours. The quenching temperature of the reaction product can be from about 10°C or lower, or from about 0°C or lower, and the quenching rate can be from about 1°C / sec to about 10,000°C / sec, or from about 1°C / sec to about 1,000°C / sec. For example, in the case of mechanical grinding, the source materials, such as Li₂S and P₂S₅, can be reacted while being stirred using, for example, a ball mill to prepare a sulfide-containing solid electrolyte. There are no particular limitations on the stirring rate and time in the mechanical grinding. A higher stirring rate results in a greater production rate of the sulfide-containing solid electrolyte. A longer stirring time results in a greater conversion rate of the source materials to the sulfide-containing solid electrolyte. The mixture of source materials obtained by melt quenching or mechanical grinding can then be heat-treated at a predetermined temperature and then milled to prepare a granular solid electrolyte. When the solid electrolyte exhibits glass transition properties, it can be transformed from an amorphous form to a crystalline form through heat treatment.

[0157] The solid electrolyte obtained by the method described above can be deposited using film-forming methods such as aerosol deposition, cold spraying, or sputtering to prepare the solid electrolyte layer 30. In one or more aspects, the solid electrolyte layer 30 can be prepared by pressing solid electrolyte particles. In another aspect, the solid electrolyte layer 30 can be formed by mixing a solid electrolyte, a solvent, and a binder together to obtain a mixture, coating the mixture on a surface, drying, and then pressing the mixture.

[0158] (Manufacturing of all-solid-state secondary batteries)

[0159] The positive electrode layer 10, the negative electrode layer 20, and the solid electrolyte layer 30 formed according to the above method can be stacked, such that the solid electrolyte layer 30 is located between the positive electrode layer 10 and the negative electrode layer 20. The stacked layers are then pressed to manufacture an all-solid-state secondary battery 1.

[0160] For example, a first stack of a negative electrode layer 20 and a solid electrolyte layer 30 can be disposed on a positive electrode layer 10, such that the solid electrolyte layer 30 contacts the positive electrode layer 10, thereby preparing a second stack. The second stack can then be pressed to thereby manufacture an all-solid-state secondary battery 1. For example, the pressing can be performed using, for example, rolling, flat pressing, or isostatic pressing. However, the aspect is not limited to this, and any suitable pressing method can be used. The pressure applied during pressing can be from about 50 MPa to about 750 MPa, or from about 100 MPa to about 700 MPa, or from about 100 MPa to about 500 MPa. The pressing time for applying pressure can be from about 5 ms to about 5 minutes. The pressing can be performed, for example, at a temperature from room temperature (20°C) to about 90°C, or at a temperature from 25°C to about 90°C. In another aspect, the pressing can be performed at a temperature of 100°C or higher, for example, from about 100°C to about 900°C, or from about 100°C to about 500°C. Although the structure of the all-solid-state secondary battery 1 and the method of manufacturing the all-solid-state secondary battery 1 have been described above as aspects, this disclosure is not limited thereto, and the constituent components and manufacturing process of the all-solid-state secondary battery may be appropriately modified. The pressing may be omitted.

[0161] One or more aspects of this disclosure will now be described in detail with reference to the following embodiments. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of one or more aspects of this disclosure.

[0162] Example

[0163] Example 1: First layer (Ag+CB, 5μm) / Second layer (Ag+CB, 25μm), and heat treatment of the first layer at 450℃.

[0164] (Preparation of a laminate of solid electrolyte layer / negative electrode layer)

[0165] Carbon black (CB) particles with a primary particle diameter of approximately 38 nm and silver (Ag) particles with an average particle diameter of approximately 100 nm were prepared as negative electrode active materials.

[0166] 3 grams (g) of the carbon black (CB) and 1 g of the silver particles were placed in a container. 2.692 g of polyvinyl alcohol-polyacrylic acid (PVA-PAA) binder solution (SUMITOMO SEIKACHEMICALS CO., LTD; AG binder) was mixed with 7 g of distilled water and added to the container. The contents were stirred at approximately 1,000 rpm for approximately 30 minutes to prepare a first slurry. 4 g of zirconia balls and 20 g of distilled water were added to the first slurry, and the mixture was stirred at approximately 1,000 rpm for approximately 30 minutes (second stirring) to prepare a second slurry. 20 g of distilled water was added to the second slurry, and the mixture was stirred at 1,000 rpm for 30 minutes to prepare a third slurry.

[0167] Prepare Li7La3Zr2O with a thickness of approximately 495 μm. 12 (LLZO) sheets (circular sheets) are used as the solid electrolyte layer.

[0168] The third slurry was spin-coated onto the surface of the LLZO sheet, dried at room temperature for 1 hour, and then vacuum-dried for 12 hours to obtain a laminate of the solid electrolyte layer and the precursor layer. The obtained laminate was heat-treated at 450°C for 2 hours to obtain a first negative electrode active material layer as a sintering product. The surface of the first negative electrode active material layer was washed with hydrochloric acid solution to remove impurities. The first negative electrode active material layer has a thickness of approximately 5 μm.

[0169] The previously prepared third slurry was spin-coated again onto the first negative electrode active material layer, dried at room temperature for 1 hour, and then vacuum-dried at 150°C for 12 hours to obtain the second negative electrode active material layer. The second negative electrode active material layer has a thickness of approximately 25 μm. The second negative electrode active material layer was prepared using the same composition and the same method as those used for the precursor layer applied to the first negative electrode active material layer, except for heat treatment.

[0170] A negative electrode current collector consisting of copper (Cu) foil with a thickness of 10 μm is disposed on the second negative electrode active material layer, and then the negative electrode current collector is attached by cold isostatic pressing (CIP) at a pressure of 250 MPa and a temperature of about 25 °C, thereby preparing a laminate of solid electrolyte layer / negative electrode layer.

[0171] (Preparation of the positive electrode layer)

[0172] Preparing LiNi 0.8 Co 0.15 Mn 0.05 O2 (NCM) is used as the positive electrode active material. Additionally, a polytetrafluoroethylene (PTFE) binder (Teflon) is prepared. TMA binder (available from DuPont) is used. Carbon nanofibers (CNFs) are prepared as a conductive agent. The positive electrode active material, conductive agent, and binder are then mixed at a mass ratio of 100:2:1. The mixture is stretched into a sheet to prepare a positive electrode active material sheet. This positive electrode active material sheet is pressed onto a positive electrode current collector formed of aluminum foil with a thickness of 18 μm to form a positive electrode layer. The thickness of the positive electrode active material layer in the positive electrode layer is approximately 100 μm.

[0173] The positive and negative electrode active material layers of the formed positive electrode layer are immersed in a liquid electrolyte, wherein the liquid electrolyte comprises Pyr13FSI (bis(fluorosulfonyl)imide N-propyl-N-methyl-pyrrolidine) dissolved in the ionic liquid. 2.0M lithium bis(fluorosulfonyl)imide (LiFSI) in ).

[0174] (Manufacturing of all-solid-state secondary batteries)

[0175] The positive electrode layer is configured such that the positive electrode active material layer, immersed in an ionic liquid electrolyte solution, faces the upper end of the SUS cap. A solid electrolyte / negative electrode layer stack is configured such that the solid electrolyte layer is placed on the surface of the positive electrode active material layer, and then sealed to manufacture an all-solid-state secondary battery. An insulator is used to insulate the positive and negative electrode layers. A portion of each of the positive and negative current collectors protrudes outside the sealed battery and serves as the positive and negative terminals, respectively.

[0176] Example 2: First layer (Ag+CB, 5μm) / Second layer (Ag+CB, 25μm), first layer heat-treated at 600℃

[0177] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the heat treatment temperature was changed to 600°C in the preparation of the first negative electrode active material layer.

[0178] Example 3: First layer (CB, 5μm) / Second layer (Ag+CB, 25μm)

[0179] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the first negative electrode active material layer, 4g of carbon black was used instead of 3g of carbon black (CB) and 1g of silver particles.

[0180] Example 4: First layer (CB, 5μm) / Second layer (CB, 25μm)

[0181] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the first negative electrode active material layer and the second negative electrode active material layer, 4g of carbon black was used instead of 3g of carbon black (CB) and 1g of silver particles.

[0182] Example 5: First layer (Ag+CB, 5μm) / Second layer (Ag+CB, 25μm), and heat treatment of the first layer at 300℃.

[0183] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the heat treatment temperature was changed to 300°C in the preparation of the first negative electrode active material layer.

[0184] Example 6: First layer (Ag 1g + CB 3g, 5μm) / Second layer (Ag 1.5g + CB 2.5g, 25μm), and heat treatment of the first layer at 450℃.

[0185] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the second negative electrode active material layer, the amounts of carbon black (CB) and Ag particles in the first slurry were changed to 2.5 g of carbon black (CB) and 1.5 g of silver particles, respectively.

[0186] Comparative Example 1: First layer alone (Ag+CB, 3μm)

[0187] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the step of forming the second negative electrode active material layer was omitted, the thickness of the first layer was changed to 3 μm, and a solid electrolyte / a laminate comprising a negative electrode layer consisting of only the first negative electrode active material layer was prepared.

[0188] Comparative Example 2: A separate second layer (Ag+CB, 27μm)

[0189] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the step of forming the first negative electrode active material layer was omitted, the thickness of the second layer was changed to 27 μm, and a solid electrolyte / laminate comprising only the second negative electrode active material layer was prepared.

[0190] Comparative Example 3: First layer (Ag+CB, 5μm) / Second layer (Ag+CB, 25μm) / Heat treatment without first layer

[0191] The all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that: in the preparation of the first negative electrode active material layer, vacuum drying was performed only at 150°C for 12 hours, without any additional heat treatment at 450°C.

[0192] Evaluation Example 1: Surface Morphology and Composition Evaluation

[0193] Scanning electron microscope (SEM) images of the surface of the precursor layer in Example 1 and the surface of the first negative electrode active material layer in Example 1 are shown in the figures below. Figure 5Aand 5B In this process, the precursor layer is a product dried prior to heat treatment at 450°C, and the first negative electrode active material layer is a product sintered by heat treatment at 450°C.

[0194] like Figure 5A and 5B As shown, the carbon black particles in the first negative electrode active material layer have a larger average particle diameter than the carbon black particles included in the precursor layer.

[0195] Although not shown, the silver (Ag) particles included in the first negative electrode active material layer have a larger average particle diameter than the average particle diameter of the silver (Ag) particles included in the precursor layer.

[0196] The carbon black (CB) included in the precursor layer has an average particle diameter of about 38 nm, and the carbon black (CB) included in the first negative electrode active material layer has an average particle diameter of about 450 nm.

[0197] The silver (Ag) particles included in the precursor layer have an average particle diameter of about 100 nm, and the silver (Ag) particles included in the first negative electrode active material layer have an average particle diameter of about 500 nm.

[0198] The average particle diameter of the carbon black (CB) and silver (Ag) particles included in the first negative electrode active material layer was determined by analyzing its SEM images.

[0199] Since the binder is decomposed and removed through sintering, the first negative electrode active material layer has a reduced thickness and an increased density, and the carbon black (CB) particles and silver (Ag) particles have an increased particle size due to sintering.

[0200] Figure 6A This is a SEM image of the cross-section of the solid electrolyte layer / first negative electrode active material layer laminate prepared in Example 1.

[0201] like Figure 6A As shown, the first negative electrode active material layer is found to be disposed on the surface of the solid electrolyte layer.

[0202] Figure 6B Energy dispersive X-ray spectroscopy (EDX) carbon elemental surface scan image of the cross-section of the solid electrolyte layer / first negative electrode active material layer laminate prepared in Example 1.

[0203] like Figure 6B As shown, the first negative electrode active material layer disposed on the surface of the solid electrolyte layer is found to include carbon.

[0204] SEM images of the surface of the first negative electrode active material layer obtained in Example 2, which is a sintered product obtained by heat treatment at 600°C, are shown below. Figure 7A middle.

[0205] Figure 7B and 7C The images are EDX silver (Ag) and carbon element surface scan images of the surface of the first negative electrode active material layer prepared in Example 2, respectively.

[0206] like Figure 7B and 7C As shown, the first negative electrode active material layer disposed on the surface of the solid electrolyte layer comprises silver particles and carbon particles.

[0207] It was also found that, since impurities such as Li2CO3 remaining after the heat treatment at 600°C were removed by treating the surface of the first negative electrode active material layer with acid, carbon was still exposed and present on the surface of the first negative electrode active material layer after the acid treatment.

[0208] Figure 8A This is a SEM image of the cross-section of the solid electrolyte / negative electrode layer laminate prepared in Example 2.

[0209] Figure 8B for Figure 8A A partial enlarged view of the interface region (A) between the solid electrolyte layer and the first negative electrode active material layer.

[0210] Figure 8C This is a magnified view of the interface region (B) between the first negative electrode active material layer (the heat-treated layer) and the second negative electrode active material layer (the dried layer or the layer prepared by CIP).

[0211] Figure 8D for Figure 8A A partial enlarged view of the internal region (C) of the second negative electrode active material layer (a dried layer or a layer prepared by CIP).

[0212] Figure 8E for Figure 8A The X-ray diffraction (XRD) pattern of the first negative electrode active material layer (the heat-treated layer) adjacent to the solid electrolyte layer.

[0213] Figure 8F for Figure 8A The XRD pattern of the second negative electrode active material layer (dried layer or layer prepared by CIP) adjacent to the first negative electrode active material layer (heat-treated layer).

[0214] Figure 8G for Figure 8A XRD pattern of the internal region of the second negative electrode active material layer (dried layer or layer prepared by CIP).

[0215] refer to Figure 8E It was found that the diffraction pattern of crystalline carbon appeared locally in the first negative electrode active material layer, while such a diffraction pattern did not appear in the second negative electrode active material layer. Figure 8F and 8G As shown in the image.

[0216] Therefore, the carbon included in the first negative electrode active material layer has a higher degree of crystallinity than the carbon included in the second negative electrode active material layer. It was also found that the first negative electrode active material layer has a higher density than the second negative electrode active material layer.

[0217] Figure 8H for Figure 8A An EDX carbon elemental surface scan image of the cross-section of the first negative electrode active material layer (the heat-treated layer) adjacent to the solid electrolyte layer.

[0218] Figure 8I for Figure 8A An EDX carbon elemental surface scan image of the cross-section of the second negative electrode active material layer (dried layer or layer prepared by CIP) adjacent to the first negative electrode active material layer (heat-treated layer).

[0219] Figure 8J for Figure 8A An EDX carbon elemental surface scan image of a cross-section of a region in the second negative electrode active material layer (a dried layer or a layer prepared by CIP).

[0220] like Figures 8H to 8J As shown, carbon was found to be distributed in both the first negative electrode active material layer and the second negative electrode active material layer.

[0221] Evaluation Example 2: Raman Spectroscopy Evaluation

[0222] Raman spectra of the surfaces of the precursor layer and the first negative electrode active material layer in Example 1 are shown below. Figure 9A and 9B In this diagram, the precursor layer is a dried product prior to heat treatment at 450°C, and the first negative electrode active material layer is a sintered product obtained by heat treatment at 450°C. Raman spectral data are shown in Table 1. The precursor layer was prepared using the same method and with the same slurry as that used for the second negative electrode active material layer. Although not shown in the figures, the Raman spectrum of the second negative electrode active material layer is the same as that of the precursor layer.

[0223] Analysis Figure 9A The overlapping Raman peaks in the image, and the magnified diagram of the intensity of each Raman peak. Figure 9B and 9C In. Figure 9A , 9B In 9C, the intensity of the D band peak (I) D ) and the intensity of the G-band peak (I G () represents the height of each peak from the baseline to the highest peak.

[0224] like Figure 9A , 9B As shown in Figure 9C, in the Raman spectrum of the first negative electrode active material layer, the intensity ratio of the D band peak to the G band peak (I 1 D / I 1 G The intensity ratio (I) of the D band peak to the G band peak of the carbon black (CB) included in the first negative electrode active material layer is 0.74. 1 D / I 1 G The value is 0.74. For example... Figure 9A , 9B As shown in Figure 9C, the intensity ratio (ID to GB) of the D-band peak to the G-band peak in the Raman spectrum of the precursor layer (i.e., the second negative electrode active material layer) 2 D / I 2 G The intensity ratio (I) of the D band peak to the G band peak of the carbon black (CB) included in the second negative electrode active material layer is 1.13. 2 D / I 2 G The value is 1.13. It is confirmed that, compared to the carbon black (CB) included in the first negative electrode active material layer, the carbon black (CB) included in the second negative electrode active material layer has an increased intensity ratio (Ig) of the D band peak to the G band peak in its Raman spectrum. D / I G ).

[0225] Therefore, it has been confirmed that the carbon black (CB) included in the first negative electrode active material layer has reduced defects and improved crystallinity compared to the carbon black (CB) included in the second negative electrode active material layer.

[0226] Table 1

[0227]

[0228] As shown in Table 1, the position of the center of the D band peak in the Raman spectrum of the first carbonaceous anode active material differs from the position of the center of the D band peak in the Raman spectrum of the second carbonaceous anode active material by 3.9 units per centimeter (cm). -1 The blue shift of the first carbonaceous anode active material is observed. Furthermore, the position of the G-band peak in the Raman spectrum of the first carbonaceous anode active material differs from the position of the center of the G-band peak in the Raman spectrum of the second carbonaceous anode active material by 2.4 cm⁻¹. -1 The blue shift is observed. Furthermore, the D-band peak width in the Raman spectrum of the first carbonaceous anode active material is approximately 58% of the D-band peak width in the Raman spectrum of the second carbonaceous anode active material.

[0229] Evaluation Example 3: Interface Resistance Evaluation

[0230] The total resistance of each all-solid-state secondary cell manufactured in Comparative Examples 1 and 2 was measured.

[0231] The impedances of the all-solid-state secondary cells fabricated in Comparative Examples 1 and 2 were measured using an impedance analyzer (Solartron 1400A / 1455A impedance analyzer) according to the two-probe method. The frequency range was 0.1 Hz to 1 MHz, and the amplitude voltage was 10 mV. The impedance measurements were performed in ambient air at 25°C. The Nyquist plot showing the results of the impedance measurements is shown in [image missing]. Figure 10 middle.

[0232] As a general Figure 10 The Nyquist plot fitting results for the equivalent circuit show that the all-solid-state secondary cell in Comparative Example 1 has approximately 100 Ωcm. 2 The interface resistance, and the all-solid secondary cell of Comparative Example 2 has approximately 350 Ωcm. 2 Interface resistance.

[0233] In addition, such as Figure 10 As described above, compared with the all-solid-state secondary battery of Comparative Example 2, the all-solid-state secondary battery of Comparative Example 1 has a reduced ohmic resistance.

[0234] Therefore, it is confirmed that, compared with the all-solid-state secondary battery of Comparative Example 2, the total resistance of the all-solid-state secondary battery of Comparative Example 1 is reduced in terms of interface resistance and ohmic resistance.

[0235] Without being bound by theory, it is understood that the reduction in the total resistance of the all-solid-state secondary battery in Comparative Example 1 is attributed to the sintering of the precursor layer together with the solid electrolyte layer during the heat treatment of the precursor layer, and the formation of covalent bonds between the solid electrolyte layer and the first negative electrode active material layer to thereby increase the active interface area, resulting in an increased lithium ion diffusion rate.

[0236] Evaluation Example 4: Charge-Discharge Test

[0237] The charge and discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1 and 2 were evaluated according to the following charge-discharge tests. The charge-discharge tests of the all-solid-state secondary batteries were conducted in a 60°C thermostat.

[0238] In the first cycle, use 0.6 mA / cm 2 A constant current is applied to charge the battery until a voltage of 4.2V is reached, and then charged at 0.6mA / cm². 2 Discharge is carried out with a constant current until the battery voltage reaches 2.8V.

[0239] In cycles 2 through 13, 1.5 mA / cm was used. 2 A constant current is applied to charge the battery until a voltage of 4.2V is reached, and then 1.5mA / cm is applied. 2 Discharge is carried out with a constant current until the battery voltage reaches 2.8V.

[0240] In cycles 14 through 18, 2.0 mA / cm was used. 2 A constant current is applied to charge the battery until a voltage of 4.2V is reached, and then charged at 2.0mA / cm². 2 Discharge is carried out with a constant current until the battery voltage reaches 2.8V.

[0241] In cycles 19 through 23, 3.0 mA / cm was used. 2 A constant current is applied to charge the battery until a voltage of 4.2V is reached, and then charged at 3.0mA / cm². 2 Discharge is carried out with a constant current until the battery voltage reaches 2.8V.

[0242] In cycles 24 through 26, 4.0 mA / cm was used. 2 A constant current is applied to charge the battery until a voltage of 4.2V is reached, and then charged at 4.0mA / cm². 2 Discharge is carried out with a constant current until the battery voltage reaches 2.8V.

[0243] In cycles 27 through 40, 6.0 mA / cm was used. 2 A constant current is applied to charge the battery until a voltage of 4.2V is reached, and then charged at 6.0mA / cm². 2 Discharge is carried out with a constant current until the battery voltage reaches 2.8V.

[0244] Some of the charge-discharge test results are shown in Figure 11A , 11B In 11C and 11D.

[0245] like Figure 11A As shown, since the all-solid-state secondary battery of Example 1 includes a first negative electrode active material layer sintered together with the solid electrolyte layer and a second negative electrode active material layer disposed on the first negative electrode active material layer, the all-solid-state secondary battery of Example 1 can undergo up to 40 charge and discharge cycles and even at 6.0 mA / cm 2 Even at high current densities, it exhibits stable charge and discharge performance. Although not shown in the figure, the all-solid-state secondary battery of Example 1 exhibits a charge and discharge efficiency of 98.5% or higher even at the 40th cycle. The charge and discharge efficiency at the 40th cycle is the percentage of the discharge capacity at the 40th cycle relative to the charge capacity at the 40th cycle. Therefore, it is confirmed that the all-solid-state secondary battery of Example 1 maintains a stable interface during the charge and discharge process and induces uniform lithium deposition.

[0246] like Figure 11B As shown, in the all-solid-state secondary battery of Comparative Example 1, which includes a separate first negative electrode active material layer, a short circuit occurs during charging during the first cycle.

[0247] like Figure 11C As shown, in the all-solid-state secondary battery of Comparative Example 2, which includes a separate second negative electrode active material layer, a short circuit occurs during charging during the first cycle.

[0248] Although not shown, in the all-solid-state secondary battery of Comparative Example 3, in which a multilayer structure is formed and the first negative electrode active material layer is not heat-treated, a short circuit occurs during charging and discharging.

[0249] Although not shown, the all-solid-state secondary batteries of Examples 2, 3, 5 and 6 also exhibited stable charging and discharging characteristics.

[0250] like Figure 11D As shown, the all-solid-state secondary battery of Example 4 exhibits stable charging and discharging performance.

[0251] As described above, all-solid-state secondary batteries according to any of the aspects described above can be applied to a variety of portable devices or automobiles.

[0252] According to the present invention, the all-solid-state secondary battery can prevent short circuits and has excellent cycle characteristics.

[0253] It should be understood that the aspects described herein should be considered only in a descriptive sense and not for limiting purposes. Descriptions of features or aspects in one aspect should be interpreted as applicable to other similar features or aspects in other aspects. Although one or more aspects have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope defined by the appended claims.

Claims

1. All-solid-state secondary batteries, including: The positive electrode layer includes the positive electrode active material layer; Negative electrode layer; and A solid electrolyte layer comprising a solid electrolyte, wherein the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer. The negative electrode layer includes Negative electrode current collector, The first negative electrode active material layer in contact with the solid electrolyte layer, and A second negative electrode active material layer is disposed between the negative electrode current collector and the first negative electrode active material layer. The first negative electrode active material layer includes a first carbonaceous negative electrode active material, and the second negative electrode active material layer includes a second carbonaceous negative electrode active material. The first intensity ratio of the D band peak to the G band peak in the Raman spectrum of the first carbonaceous anode active material is less than the second intensity ratio of the D band peak to the G band peak in the Raman spectrum of the second carbonaceous anode active material. The first strength ratio is 0.95 or less, and the second strength ratio is 1.0 or greater.

2. The all-solid-state secondary battery of claim 1, wherein the first strength ratio is 0.1 to 0.95, and The second strength ratio is 1.0 to 10.

3. The all-solid-state secondary battery as described in claim 1, wherein the position of the center of the D-band peak in the Raman spectrum of the first carbonaceous anode active material is 2 cm relative to the position of the center of the D-band peak in the Raman spectrum of the second carbonaceous anode active material. -1 Up to 4 cm -1 Blue shift, The position of the center of the G-band peak in the Raman spectrum of the first carbon-based anode active material differs from the position of the center of the G-band peak in the Raman spectrum of the second carbon-based anode active material by 1 cm. -1 Up to 3 cm -1 Blueshift, and The half-width of the D band peak of the first carbonaceous anode active material is 50% to 80% of the half-width of the D band peak of the second carbonaceous anode active material.

4. The all-solid-state secondary battery as claimed in claim 1, wherein at least one of the first carbonaceous negative electrode active material or the second carbonaceous negative electrode active material is in particulate form, and The particles have an average particle diameter of 10 nm to 4 micrometers.

5. The all-solid-state secondary battery as claimed in claim 1, wherein at least one of the first carbonaceous negative electrode active material or the second carbonaceous negative electrode active material comprises amorphous carbon.

6. The all-solid-state secondary battery as claimed in claim 1, wherein at least one of the first negative electrode active material layer or the second negative electrode active material layer is respectively composed of the first carbonaceous negative electrode active material or the second carbonaceous negative electrode active material.

7. The all-solid-state secondary battery of claim 1, wherein at least one of the first negative electrode active material layer or the second negative electrode active material layer further comprises a metal or quasi-metal negative electrode active material including a metal, a quasi-metal, or a combination thereof.

8. The all-solid-state secondary battery of claim 7, wherein the metal or quasi-metallic anode active material comprises at least one of the following: indium, silicon, gallium, tin, aluminum, titanium, zirconium, niobium, germanium, antimony, bismuth, gold, platinum, palladium, magnesium, silver, or zinc.

9. The all-solid-state secondary battery of claim 7, wherein the first negative electrode active material layer and the second negative electrode active material layer each further comprise the metal or quasi-metal negative electrode active material, and The amount of the metallic or quasi-metallic anode active material in the second anode active material layer is greater than the amount of the metallic or quasi-metallic anode active material in the first anode active material layer.

10. The all-solid-state secondary battery of claim 7, wherein the first negative electrode active material layer comprises a composite of first particles and second particles. The first particle is composed of the first carbonaceous anode active material, and the second particle is composed of the metal or quasi-metal anode active material. The first carbonaceous negative electrode active material is amorphous carbon, and The amount of the second particle is from 1% to 60% by weight, based on the total weight of the complex.

11. The all-solid-state secondary battery of claim 10, wherein the second negative electrode active material layer comprises a mixture of first particles and second particles. The first particle is composed of the second carbonaceous anode active material, and the second particle is composed of the metal or quasi-metal anode active material. The second carbonaceous negative electrode active material is amorphous carbon, and The amount of the second particle is from 1% to 60% by weight, based on the total weight of the mixture.

12. The all-solid-state secondary battery of claim 11, wherein the average particle diameter of the first particles in the second negative electrode active material layer is 50% or less of the average particle diameter of the first particles in the first negative electrode active material layer, and The average particle diameter of the second particles included in the second negative electrode active material layer is 50% or less of the average particle diameter of the second particles included in the first negative electrode active material layer.

13. The all-solid-state secondary battery of claim 1, wherein the first carbonaceous negative electrode active material is bonded to the solid electrolyte layer by at least one covalent bond or ionic bond.

14. The all-solid-state secondary battery of claim 1, wherein the first negative electrode active material layer does not include organic materials.

15. The all-solid-state secondary battery as claimed in claim 1, wherein the first carbonaceous negative electrode active material is a sintered product of a carbonaceous precursor, and the carbonaceous precursor is the second carbonaceous negative electrode active material.

16. The all-solid-state secondary battery of claim 1, wherein the thickness of the first negative electrode active material layer is 5% to 50% of the total thickness of the positive electrode active material layer, and The first negative electrode active material layer has a thickness of 10 nanometers to 10 micrometers.

17. The all-solid-state secondary battery of claim 1, wherein the thickness of the second negative electrode active material layer is 5% to 50% of the total thickness of the positive electrode active material layer, and The second negative electrode active material layer has a thickness of 1 micrometer to 50 micrometers.

18. The all-solid-state secondary battery of claim 1, wherein the thickness of the first negative electrode active material layer is less than the thickness of the second negative electrode active material layer.

19. The all-solid-state secondary battery of claim 1, wherein at least one of the first negative electrode active material layer or the second negative electrode active material layer further comprises a binder.

20. The all-solid-state secondary battery of claim 1, wherein the second negative electrode active material layer comprises the second carbonaceous negative electrode active material and a metallic or quasi-metallic negative electrode active material, and the first negative electrode active material layer is composed of the first carbonaceous negative electrode active material; or The second negative electrode active material layer is composed of the second carbonaceous negative electrode active material, and the first negative electrode active material layer includes the first carbonaceous negative electrode active material and a metal or quasi-metal negative electrode active material.

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

22. The all-solid-state secondary battery of claim 21, wherein the negative electrode current collector, the first negative electrode active material layer, the second negative electrode active material layer, and the region therebetween are Li-free regions that do not include lithium in the initial state or the post-discharge state of the all-solid-state secondary battery.

23. The all-solid-state secondary battery of claim 1, wherein the solid electrolyte is a solid electrolyte containing oxides or a solid electrolyte containing sulfides.

24. The all-solid-state secondary battery according to claim 23, wherein the solid electrolyte containing an oxide comprises at least one of the following: Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 , where 0 < x < 2 and 0 ≤ y < 3; BaTiO3; Pb(Zr a Ti 1-a )O3, where 0 ≤ a ≤ 1; Pb 1-x La x Zr 1-y Ti y O3, where 0 ≤ x < 1 and 0 ≤ y < 1; Pb(Mg 1 / 3 Nb 2 / 3 )O3 - PbTiO3; HfO2; SrTiO3; SnO2; CeO2; Na2O; MgO; NiO; CaO; BaO; ZnO; ZrO2; Y2O3; Al2O3; TiO2; SiO2; Li3PO4; Li x Ti y (PO4)3, where 0 < x < 2 and 0 < y < 3; Li x Al y Ti z (PO4)3, where 0 < x < 2, 0 < y < 1, and 0 < z < 3; Li 1+x+y (Al a Ga 1-a ) x (Ti b Ge 1-b ) 2-x Si y P 3-y O 12 , where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ a ≤ 1, and 0 ≤ b ≤ 1; Li x La y TiO3, where 0 < x < 2 and 0 < y < 3; Li2O; LiOH; Li2CO3; LiAlO2; Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2; or Li 3+x La3M2O 12 , where M is Te, Nb, or Zr, and 0 ≤ x ≤ 10.

25. The all-solid-state secondary battery of claim 23, wherein the oxide-containing solid electrolyte comprises a garnet-type solid electrolyte, and the garnet-type solid electrolyte comprises at least one of the following: Li7La3Zr2O 12 and Li 3+ x La3Zr 2-a M a O 12 , where M is at least one of Ga, W, Nb, Ta, or Al, 1≤x≤10, and 0≤a<2.

26. The all-solid-state secondary battery of claim 23, wherein the sulfide-containing solid electrolyte comprises at least one of the following: Li₂S-P₂S₅; Li₂S-P₂S₅-LiX, wherein X is a halogen; Li₂S-P₂S₅-Li₂O; Li₂S-P₂S₅-Li₂O-LiI; Li₂S-SiS₂; Li₂S-SiS₂-LiI; Li₂S-SiS₂-LiBr; Li₂S-SiS₂-LiCl; Li₂S-SiS₂-B₂S₃-LiI; Li₂S-SiS₂-P₂S₅-LiI; Li₂S-B₂S₃; Li₂S-P₂S₅-Z m S n Where m and n are each independently positive numbers, and Z is Ge, Zn, or Ga; Li2S-GeS2; Li2S-SiS2-Li3PO4; Li2S-SiS2-Li p MO q Where p and q are each independently positive, and M is P, Si, Ge, B, Al, Ga, or In; Li 7-x PS 6-x Cl x , where 0≤x≤2; Li 7-x PS 6-x Br x Where 0≤x≤2; or Li 7- x PS 6-x I x , where 0≤x≤2.

27. The all-solid-state secondary battery of claim 23, wherein the sulfide-containing solid electrolyte comprises a sulforaphane-germanium ore type solid electrolyte, and the sulforaphane-germanium ore type solid electrolyte comprises at least one of the following: Li 7-x PS 6-x Cl x , where 0≤x≤2; Li 7-x PS 6-x Br x Where 0≤x≤2; or Li 7-x PS 6-x I x , where 0≤x≤2.

28. A method for manufacturing an all-solid-state secondary battery as described in any one of claims 1-27, the method comprising: Provide a solid electrolyte layer; A first negative electrode active material composition is disposed on the first surface of the solid electrolyte layer; The first negative electrode active material composition is heat-treated to form a first negative electrode active material layer; A second negative electrode active material layer is disposed on the surface of the first negative electrode active material layer; and A positive electrode active material layer is disposed on the second surface of the solid electrolyte layer.

29. The method of claim 28, wherein the heat treatment is performed at a temperature of 300°C to 900°C for 0.1 hours to 20 hours.

30. The method of claim 28, further comprising washing the surface of the first negative electrode active material layer with an acidic solution before applying the second negative electrode active material.

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