All-solid-state secondary battery and method for manufacturing the same

Abstract

To provide an all-solid secondary battery, and a method of manufacturing an all-solid secondary battery.SOLUTION: An all-solid secondary battery includes: a cathode layer including a cathode active material layer; an anode layer; and a solid electrolyte layer including a solid electrolyte, the solid electrolyte layer being disposed between the cathode layer and the anode layer. The anode layer includes an anode current collector, a first anode active material layer which is disposed on the anode current collector and which is in contact with the solid electrolyte layer, and a second anode active material layer disposed between the anode current collector and the first anode active material layer. The first anode active material layer includes a first carbonaceous anode active material, and the second anode active material layer includes a second carbonaceous anode active material. An intensity ratio (I1D / I1G) of an intensity of a D band peak to an intensity of a G band peak in a Raman spectrum of the first carbonaceous anode active material is less than an intensity ratio (I2D / I2G) of an intensity of a D band peak to an intensity of a G band peak of the second carbonaceous anode active material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state secondary battery and a method for manufacturing the same. [Background technology]

[0002] Recently, industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries have been put to practical use not only in the fields of information-related equipment and communication devices, but also in the automotive field. In the automotive field, safety is of particular importance, as this is a matter of life and death.

[0003] Currently available lithium-ion batteries use electrolytes containing flammable organic solvents, which can lead to overheating and fires if a short circuit occurs. In response to this, all-solid-state batteries using solid electrolytes instead of liquid electrolytes have been proposed.

[0004] Since the all-solid-state battery does not use flammable organic solvents, the possibility of fire or explosion can be significantly reduced even if a short circuit occurs, and therefore the all-solid-state battery can be significantly safer than lithium-ion batteries that use electrolytes. Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide an all-solid-state battery that prevents short circuits during charging and discharging and has improved cycle characteristics. [Means for solving the problem]

[0006] According to one embodiment, a positive electrode layer including a positive electrode active material layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer and including a solid electrolyte; 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, the first negative electrode active material layer includes a first carbon-based negative electrode active material, and the second negative electrode active material layer includes a second carbon-based negative electrode active material; The intensity ratio (I) of the D band peak to the G band peak in the Raman spectrum of the first carbon-based negative electrode active material 1 D / I 1 G ) is the intensity ratio (I 2 D / I 2 G ) is provided.

[0007] In another embodiment, providing a solid electrolyte layer; disposing a first negative electrode active material composition on one surface of the solid electrolyte layer; heat-treating the first negative electrode active material composition to form a first negative electrode active material layer; disposing a second negative electrode active material layer on the first negative electrode active material layer; and disposing a positive electrode active material layer on the other surface of the solid electrolyte layer. [Effects of the Invention]

[0008] According to the all-solid-state secondary battery of the present invention, it is possible to provide an all-solid-state secondary battery that is prevented from short-circuiting and has excellent cycle characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an all-solid-state secondary battery according to an illustrative embodiment; [Figure 2] 1 is a cross-sectional view of an all-solid-state secondary battery according to an illustrative embodiment; [Figure 3] 1 is a cross-sectional view of an all-solid-state secondary battery according to an illustrative embodiment; [Figure 4]1 is a cross-sectional view of an all-solid-state secondary battery according to an illustrative embodiment; [Figure 5A] 1 is a scanning electron microscope (SEM) image of the surface of a precursor layer, which is a dried material before being heat-treated at 450° C. in Example 1. [Figure 5B] 1 is an SEM image of the surface of a first negative electrode active material layer obtained after heat treatment at 450° C. in Example 1. [Figure 6A] 1 is a SEM image of a cross section of a solid electrolyte layer / first negative electrode active material layer stack prepared in Example 1. [Figure 6B] 1 is a carbon mapping image of EDX (energy-dispersive X-ray spectroscopy) of a cross section of a solid electrolyte layer / first negative electrode active material layer stack prepared in Example 1. [Figure 7A] 1 is an SEM image of the surface of a first negative electrode active material layer obtained in Example 2. [Figure 7B] 1 is an EDX silver mapping image of the surface of a first negative electrode active material layer prepared in Example 2. [Figure 7C] 1 is an EDX carbon mapping image of the surface of a first negative electrode active material layer prepared in Example 2. [Figure 8A] 1 is a SEM image of a cross section of a solid electrolyte layer / anode layer stack manufactured in Example 2. [Figure 8B] FIG. 8B is a partially enlarged cross-sectional view of the interface region between the solid electrolyte layer and the first negative electrode active material layer in FIG. 8A. [Figure 8C] FIG. 8A is a partially enlarged cross-sectional view of the interface region between the first negative electrode active material layer and the second negative electrode active material layer. [Figure 8D] FIG. 8B is a partially enlarged view of a cross section of an internal region of the second negative electrode active material layer in FIG. 8A. [Figure 8E] FIG. 8A shows an XRD (X-ray diffraction) pattern of the first negative electrode active material layer adjacent to the solid electrolyte layer. [Figure 8F]FIG. 8A shows an XRD pattern of a second negative electrode active material layer adjacent to the first negative electrode active material layer. [Figure 8G] FIG. 8A shows an XRD pattern relating to the region inside the second negative electrode active material layer. [Figure 8H] FIG. 8A is an EDX carbon mapping image of a cross section of the first negative electrode active material layer adjacent to the solid electrolyte layer. [Figure 8I] FIG. 8A is an EDX carbon mapping image of a cross section of a second negative electrode active material layer adjacent to a first negative electrode active material layer. [Figure 8J] FIG. 8A is an EDX carbon mapping image of a cross section of a certain region inside the second negative electrode active material layer. [Figure 9A] FIG. 1 shows a Raman spectrum of the surface of the first negative electrode active material layer obtained after heat treatment at 450°C in Example 1, and a Raman spectrum of the surface of the second negative electrode active material layer (precursor layer of the first negative electrode active material layer) which is a dried product before heat treatment at 450°C. [Figure 9B] FIG. 9B shows the Raman spectrum of the surface of the second negative electrode active material layer (precursor layer) of Example 1, plotting arbitrary units (au) versus Raman shift (cm −1 ). [Figure 9C] FIG. 9C is a plot of arbitrary units (au) versus Raman shift (cm −1 ) showing the Raman spectrum of the surface of the first negative electrode active material layer of Example 1 after heat treatment at 450° C. [Figure 10] 1 is a Nyquist plot showing the impedance measurement results for the all-solid-state secondary batteries produced in Comparative Example 1 and Comparative Example 2. [Figure 11A] 1 shows the charge / discharge profile of the all-solid-state secondary battery produced in Example 1. [Figure 11B] 1 shows a charge / discharge profile of the all-solid-state secondary battery produced in Comparative Example 1. [Figure 11C] 1 shows a charge / discharge profile of an all-solid-state secondary battery produced in Comparative Example 2. [Figure 11D] 1 shows the charge / discharge profile of the all-solid-state secondary battery produced in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] In conventional all-solid-state secondary batteries, because the electrolyte is solid, lithium is locally deposited at the interface between the solid electrolyte layer and the anode layer, and this lithium grows, resulting in penetration of the solid electrolyte layer, which can cause a short circuit in the battery. Furthermore, because the solid electrolyte layer and the anode layer are simply stacked, the effective interface area between the solid electrolyte layer and the anode layer is narrower than the actual contact area. Therefore, the interface resistance at the interface between the solid electrolyte layer and the anode layer increases, which increases the internal resistance of the battery, resulting in a deterioration in the cycle characteristics of the battery.

[0011] One aspect of the present invention is to provide an all-solid-state battery that prevents short circuits during charging and discharging and has improved cycle characteristics.

[0012] The present inventive concept described below can be modified in various ways and can have various embodiments, but specific embodiments are illustrated in the drawings and described in detail. However, it should be understood that these do not limit the present inventive concept to specific embodiments, but include all modifications, equivalents, or alternatives that fall within the technical scope of the present inventive concept.

[0013] The terms used below are merely used to describe specific embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly dictates otherwise. Hereinafter, terms such as "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, ingredient, material, or combination thereof described in the specification, and should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, ingredients, materials, or combinations thereof. The " / " used below can be interpreted as either "and" or "or," depending on the context.

[0014] In the drawings, thicknesses of various layers and regions are exaggerated or reduced for clarity. Similar parts are designated by the same reference numerals throughout the specification. Throughout the specification, when a part, such as a layer, film, region, or plate, is described as being "on" or "above" another part, this refers not only to the part being directly on top of the other part, but also to the part being interposed between them. Throughout the specification, terms such as "first" and "second" may be used to describe various components, but the components are not limited by these terms. These terms are used only to distinguish one component from another. Throughout the specification and drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and redundant description will be omitted.

[0015] Hereinafter, an all-solid-state secondary battery and a method for manufacturing the all-solid-state secondary battery according to an example embodiment will be described in more detail.

[0016] According to an embodiment, there is provided an all-solid-state secondary battery comprising: a cathode layer including a cathode active material layer; an anode layer; and a solid electrolyte layer disposed between the cathode layer and the anode layer and including a solid electrolyte. The anode layer comprises: an anode current collector; a first anode active material layer disposed on the anode current collector and in contact with the solid electrolyte layer; and a second anode active material layer disposed between the anode current collector and the first anode active material layer. The first anode active material layer comprises a first carbon-based anode active material, and the second anode active material layer comprises a second carbon-based anode active material. The first carbon-based anode active material has an intensity ratio (I 1 D / I 1 G ) is the intensity ratio (I 2 D / I 2 G ) is lower than

[0017] The intensity ratio of the D-band peak to the G-band peak in the Raman spectrum of the first carbon-based negative electrode active material (I 1D / I 1 G ) is the intensity ratio (I 2 D / I 2 G ), the number of defects in the first carbon-based negative electrode active material is smaller than the number of defects in the second carbon-based negative electrode active material. Furthermore, defects generated between the first carbon-based negative electrode active material layer containing the first carbon-based negative electrode active material and the solid electrolyte layer can also be reduced. Therefore, localized lithium deposition at the interface between the first carbon-based negative electrode active material layer and the solid electrolyte can be suppressed. Furthermore, when a second negative electrode active material layer is additionally disposed on the first negative electrode active material layer and the second negative electrode active material layer contains a second carbon-based negative electrode active material that contains more defects than the first carbon-based negative electrode active material, these defects act as lithium deposition seeds, facilitating and facilitating uniform lithium deposition within the second negative electrode active material layer. The deposition of a uniform lithium layer between the solid electrolyte layer and the negative electrode current collector enables reversible charge and discharge of the all-solid-state lithium battery, improving cycle characteristics.

[0018] (All-solid-state secondary battery) 1 to 4, the all-solid-state secondary battery 1 includes a positive electrode layer 10 including a positive electrode active material layer 12, a negative electrode layer 20, and a solid electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20 and including a solid electrolyte. The negative electrode layer 20 includes a negative electrode current collector 21, a first negative electrode active material layer 22 disposed on the negative electrode current collector 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 includes a first carbon-based negative electrode active material, and the second negative electrode active material layer 23 includes a second carbon-based negative electrode active material. The intensity ratio (I 1 D / I 1 G ) is the intensity ratio (I 2 D / I 2 G ) is lower than

[0019] (negative electrode layer) 1 to 4, the intensity ratio (I) of the D band peak to the G band peak in the Raman spectrum of the first carbon-based negative electrode active material contained in the first negative electrode active material layer 22 1 D / I 1 G ) is, for example, 0.95 or less, 0.90 or less, 0.85 or less, 0.80 or less, or 0.75 or less. The intensity ratio (I 1 D / I 1 G ) is, for example, 0.1 to 0.95, 0.2 to 0.9, 0.3 to 0.85, 0.4 to 0.80, or 0.5 to 0.75. When the first carbon-based negative electrode active material has an intensity ratio within such a range, defects contained in the first negative electrode active material layer 22 can be reduced, and defects present between the first negative electrode active material layer 22 and the solid electrolyte layer 30 can also be reduced. As a result, the interfacial resistance between the first negative electrode active material layer 22 and the solid electrolyte layer 30 can be reduced, and localized precipitation of lithium can also be suppressed.

[0020] The intensity ratio (I) of the D band peak to the G band peak in the Raman spectrum of the second carbon-based negative electrode active material contained in the second negative electrode active material layer 23 2 D / I 2 G ) is, for example, 1.0 or more, 1.05 or more, or 1.1 or more. The intensity ratio (I 2 D / I 2 G ) is, for example, 1.0 to 10.0, 1.05 to 5.0, or 1.1 to 3.0. When the second carbon-based negative electrode active material has an intensity ratio in such a range, the number of defects in the second negative electrode active material layer 23 may increase. As a result, lithium is easily and uniformly deposited inside and / or on the surface of the second negative electrode active material layer 23.

[0021] The position of the D band peak center in the Raman spectrum of the first carbon-based negative electrode active material contained in the first negative electrode active material layer 22 is, for example, 2.0 cm away from the position of the D band peak center in the Raman spectrum of the second carbon-based negative electrode active material contained in the second negative electrode active material layer 23. -1 Over 2.5cm -1 3.0cm or more -1 or more than 3.5cm -1 The first carbon-based negative electrode active material may have a thickness of, for example, 2.0 cm -1 or 4.0 cm -1 , 3.0cm -1 or 4.0 cm -1 , or 3.5 cm -1 or 4.0 cm -1 The blue shift may occur. The blue shift refers to a shift to a position having a higher energy, i.e., a higher wave number. Since the first carbon-based negative electrode active material has such a D-band peak center position, short circuits in the all-solid-state secondary battery 1 may be suppressed, and the cycle characteristics may be further improved.

[0022] The position of the G band peak center in the Raman spectrum of the first carbon-based negative electrode active material contained in the first negative electrode active material layer 22 is 1.0 cm away from the position of the G band peak center in the Raman spectrum of the second carbon-based negative electrode active material contained in the second negative electrode active material layer 23. -1 Over 1.5cm -1 or more than 2.0cm -1 The first carbon-based negative electrode active material may have a thickness of, for example, 1.0 cm -1 or 3.0 cm -1 , 1.0cm -1 or 2.5 cm -1 , or 2.0 cm -1 or 2.5 cm -1When the first carbon-based negative electrode active material has such a G-band peak center position, short circuiting of the all-solid-state secondary battery 1 can be suppressed and the cycle characteristics can be further improved.

[0023] The D band peak width in the Raman spectrum of the first carbon-based negative electrode active material contained in the first negative electrode active material layer 22 is 80% or less, 75% or less, 70% or less, 65% or less, or even 60% or less of the D band peak width in the Raman spectrum of the second carbon-based negative electrode active material contained in the second negative electrode active material layer 23. The D band peak width in the Raman spectrum of the first carbon-based negative electrode active material is 50% to 80%, 50% to 70%, or 50% to 60% of the D band peak width in the Raman spectrum of the second carbon-based negative electrode active material. When the first carbon-based negative electrode active material has such a D band peak width, short circuits in the all-solid-state secondary battery 1 can be suppressed and the cycle characteristics can be further improved.

[0024] At least one of the first carbon-based negative electrode active material included in the first negative electrode active material layer 22 and the second carbon-based negative electrode active material included in the second negative electrode active material layer 23 may have a particle form. The particle-form first carbon-based negative electrode active material and / or the second carbon-based negative electrode active material may have an average particle size of, for example, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less. The particle-form first carbon-based negative electrode active material and / or the second carbon-based negative electrode active material may have an average particle size of, for example, 10 nm to 4 μm, 10 nm to 3 μm, 10 nm to 2 μm, 10 nm to 1 μm, or 10 nm to 900 nm. The first carbon-based negative electrode active material and / or the second carbon-based negative electrode active material may have an average particle size within such a range, which may facilitate reversible lithium absorption and / or desorption during charging and discharging. The average particle size of the first carbon-based negative electrode active material and / or the second carbon-based negative electrode active material is the median diameter (D50) measured, for example, using a laser particle size analyzer. Alternatively, the average particle size of the first carbon-based negative electrode active material is the arithmetic mean value of particle sizes obtained from a scanning electron microscope image. As used herein, the term "size" of particles refers to the average diameter of particles in the case of spherical particles, or the average length of the major axis in the case of non-spherical particles. The average diameter of particles refers to the median diameter ("D50") of the particles. Furthermore, the median diameter is defined as the particle diameter corresponding to 50% by volume (i.e., volume percent) of the cumulative diameter distribution and refers to the diameter of 50% of the particles in a sample. The median diameter ("D50") of particles can be measured, for example, using a particle size analyzer ("PSA").

[0025] At least one selected from the first carbon-based negative electrode active material contained in the first negative electrode active material layer 22 and the second carbon-based negative electrode active material contained in the second negative electrode active material layer 23 may include, for example, amorphous carbon. Examples of the amorphous carbon include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, carbon nanotubes, and carbon nanofibers. Any material classified as amorphous carbon in the relevant technical field may be used.

[0026] At least one selected from the first negative electrode active material layer 22 and the second negative electrode active material layer 23 may also be made of a carbon-based material. For example, the first negative electrode active material layer 22 may be made of a first carbon-based negative electrode active material, and the second negative electrode active material layer 23 may be made of a second carbon-based negative electrode active material. When the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 are made of a carbon-based material, the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 do not contain a non-carbon-based material such as a metal, a metal oxide, or a ceramic.

[0027] The first negative electrode active material layer 22 may further include a metal negative electrode active material or a quasi-metallic negative electrode active material in addition to the first carbon-based negative electrode active material. The second negative electrode active material layer 23 may further include a metal negative electrode active material or a quasi-metallic negative electrode active material in addition to the second carbon-based negative electrode active material. The metal negative electrode active material or the quasi-metallic negative electrode active material may include, but is not limited to, one or more selected from the group consisting of 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), and zinc (Zn). The metal negative electrode active material or the quasi-metallic negative electrode active material may be any metal negative electrode active material or quasi-metallic negative electrode active material known in the art that forms an alloy or compound with lithium.

[0028] The first negative electrode active material layer 22 may include, for example, the first carbon-based negative electrode active material and one of a metal negative electrode active material and a semi-metal negative electrode active material, or may include a composite of a plurality of different negative electrode active materials. For example, the first negative electrode active material layer 22 may include only amorphous carbon, or may include one or more metals or semi-metals selected from 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), and zinc (Zn). Alternatively, the first negative electrode active material layer 22 may include a composite of amorphous carbon and one or more metal or semi-metal negative electrode active materials selected from the group consisting of 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), and zinc (Zn). The weight ratio of the composite of amorphous carbon and silver, etc., may be, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to these ranges and may be selected depending on the desired characteristics of the all-solid-state secondary battery 1. The first negative electrode active material layer 22 having such a composition further improves the cycle characteristics of the all-solid-state secondary battery 1.

[0029] The second negative electrode active material layer 23 may include, for example, the second carbon-based negative electrode active material and one of a metal negative electrode active material and a metalloid negative electrode active material, or a mixture of a plurality of different negative electrode active materials. For example, the second negative electrode active material layer 23 may include only amorphous carbon, or may include one or more metals or metalloids selected from 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), and zinc (Zn). Alternatively, the second negative electrode active material layer 23 may include a mixture of amorphous carbon and one or more metals or metalloids selected from the group consisting of 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), and zinc (Zn). The weight ratio of the mixture of amorphous carbon and silver, etc., is, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to these ranges and may be selected depending on the desired characteristics of the all-solid-state secondary battery 1. The second negative electrode active material layer 23 having such a composition further improves the cycle characteristics of the all-solid-state secondary battery 1.

[0030] The first negative electrode active material contained in the first negative electrode active material layer 22 includes a composite of first particles made of amorphous carbon and second particles made of a metal or metalloid. The composite is not a simple mixture of the first particles and the second particles, nor a mixture physically bound by a binder, but rather a resultant product obtained by thermochemically reacting the mixture through heat treatment or mechanochemically reacting the mixture through mechanical milling. Examples of metals or metalloids include 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), and zinc (Zn). Alternatively, the metalloid may be a semiconductor. The content of the second particles is 1 to 60 wt %, 8 to 60 wt %, 10 to 50 wt %, 15 to 40 wt %, or 20 to 30 wt %, based on the total weight of the composite. When the second particles have a content in such a range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0031] The negative electrode active material of the second negative electrode active material layer 23 includes a mixture of first particles made of amorphous carbon and second particles made of a metal or metalloid. The mixture may be a simple mixture of the first particles and the second particles, or a mixture physically bound by a binder. The metal or metalloid may include, for example, one or more selected from the group consisting of 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), and zinc (Zn). Alternatively, the metalloid may be a semiconductor. The content of the second particles is 8 to 60 wt %, 10 to 50 wt %, 15 to 40 wt %, or 20 to 30 wt %, based on the total weight of the mixture. When the second particles have a content in such a range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0032] In the all-solid-state secondary battery 1, for example, the content of the metal negative electrode active material or quasi-metal negative electrode active material contained in the second negative electrode active material layer 23 may be different from the content of the metal negative electrode active material or quasi-metal negative electrode active material contained in the first negative electrode active material layer 22. For example, the content of the metal negative electrode active material or quasi-metal negative electrode active material contained in the second negative electrode active material layer 23 may be higher than the content of the metal negative electrode active material or quasi-metal negative electrode active material contained in the first negative electrode active material layer 22. Because the content of the metal negative electrode active material or quasi-metal negative electrode active material contained in the second negative electrode active material layer 23 is higher than the content of the metal negative electrode active material or quasi-metal negative electrode active material contained in the first negative electrode active material layer 22, lithium may be more easily deposited inside and / or on the surface of the second negative electrode active material layer 23. The weight ratio of the metal or quasi-metallic negative electrode active material contained in the second negative electrode active material layer 23 to the metal or quasi-metallic negative electrode active material contained in the first negative electrode active material layer 22 is, for example, 51:49 to 99:1, 55:45 to 95:5, or 60:40 to 90:10.

[0033] The average particle size of the first particles made of amorphous carbon contained in the second negative electrode active material layer 23 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the average particle size of the first particles made of amorphous carbon contained in the first negative electrode active material layer 22. The average particle size of the second particles made of a metal or quasi-metal contained in the second negative electrode active material layer 23 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the average particle size of the first particles made of a metal or quasi-metal contained in the first negative electrode active material layer 22. When the first particles and second particles contained in the second negative electrode active material layer 23 have such a reduced average particle size, the second particles are more uniformly dispersed within the second negative electrode active material layer 23, and lithium is more uniformly deposited within or on the surface of the second negative electrode active material layer 23.

[0034] The first carbon-based negative electrode active material contained in the first negative electrode active material layer 22 can form, for example, a covalent bond and / or an ionic bond with the solid electrolyte contained in the solid electrolyte layer 30. The covalent bond and / or the ionic bond is formed, for example, by thermal bonding generated during a heat treatment process of precursors of the solid electrolyte layer 30 and the first negative electrode active material layer 22. By forming a covalent bond between the first negative electrode active material layer 22 and the solid electrolyte layer 30, for example, the interfacial resistance between the first negative electrode active material layer 22 and the solid electrolyte layer 30 is reduced.

[0035] The first negative electrode active material layer 22 is, for example, an inorganic layer that does not contain an organic material. The first negative electrode active material layer 22 does not contain, for example, an organic binder such as a polymer binder. When the first negative electrode active material layer 22 is an inorganic layer that contains an inorganic carbon-based material and / or a metal-based material, side reactions that occur due to the organic material during charging and discharging are suppressed. The first negative electrode active material layer 22 is, for example, an inorganic carbon layer made of amorphous carbon. The first negative electrode active material layer 22 is, for example, an inorganic carbon-metal composite layer made of amorphous carbon and a metal or semi-metal.

[0036] The first carbon-based negative electrode active material included in the first negative electrode active material layer 22 is, for example, a sintered product of a carbon-based precursor. That is, the first carbon-based negative electrode active material is a resultant product obtained by heat-treating the carbon-based precursor. The carbon-based precursor of the first carbon-based negative electrode active material is, for example, a second carbon-based negative electrode active material. For example, the first carbon-based negative electrode active material is obtained by heat-treating the second carbon-based negative electrode active material included in the second carbon-based negative electrode active material layer 23. The first carbon-based negative electrode active material is, for example, a resultant product of heat-treating the second carbon-based negative electrode active material, i.e., a sintered product. Therefore, the first negative electrode active material layer 22 is sintered with the solid electrolyte layer 30, for example, during the heat treatment process, to form a single body with the solid electrolyte layer 30. During the heat treatment, organic materials such as binders contained in the carbon-based precursor are carbonized or vaporized by pyrolysis or the like and removed, leaving only the carbon-based material and / or metal-based material.

[0037] The thickness of the first negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the positive electrode active material layer 10. The thickness of the first negative electrode active material layer 22 is thinner than the thickness of the positive electrode active material layer 10, thereby improving the energy density of the all-solid-state secondary battery 1. The thickness of the first negative electrode active material layer 22 is, for example, 10 nm to 10 μm, 100 nm to 10 μm, 200 nm to 10 μm, 300 nm to 10 μm, 400 nm to 10 μm, 500 nm to 10 μm, 1 μm to 10 μm, 1 μm to 9 μm, 1 μm to 8 μm, 2 μm to 7 μm, or 3 μm to 7 μm. When the first negative electrode active material layer 22 has a thickness within such a range, short circuits in the all-solid-state secondary battery 1 are suppressed, and the cycle characteristics are improved. If the thickness of the first negative electrode active material layer 22 is excessively thin, it is difficult for it to function as a negative electrode active material layer. If the thickness of the first negative electrode active material layer 22 is excessively thick, the energy density of the all solid state secondary battery 1 decreases, the internal resistance of the all solid state secondary battery 1 due to the first negative electrode active material layer 22 increases, and it is difficult to improve the cycle characteristics of the all solid state secondary battery 1.

[0038] The thickness of the second negative electrode active material layer 23 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the positive electrode active material layer 10. When the thickness of the second negative electrode active material layer 23 is thinner than that of the positive electrode active material layer, the energy density of the all-solid-state secondary battery 1 is improved.

[0039] The thickness of the second negative electrode active material layer 23 is, for example, 1 μm to 50 μm, 5 μm to 45 μm, 10 μm to 40 μm, 15 μm to 35 μm, or 20 μm to 30 μm. When the second negative electrode active material layer 23 has a thickness within such a range, short-circuiting of the all-solid-state secondary battery 1 is suppressed, and the cycle characteristics are improved. If the thickness of the second negative electrode active material layer 23 is excessively thin, lithium dendrites formed between the second negative electrode active material layer 23 and the negative electrode current collector 21 collapse the second negative electrode active material layer 23, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the thickness of the second negative electrode active material layer 23 is excessively thick, the energy density of the all-solid-state secondary battery 1 decreases, and the internal resistance of the all-solid-state secondary battery 1 due to the second negative electrode active material layer 23 increases, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0040] The thickness of the first anode active material layer 22 is thinner than the thickness of the second anode active material layer 23, for example. The thickness of the first anode active material layer 22 is 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the second anode active material layer 23. When the first anode active material layer 22 has a thickness within such a range, short circuits in the all-solid-state secondary battery 1 are suppressed and cycle characteristics are improved. The first anode active material layer 22 can be formed by, for example, spin coating, drop coating, spray coating, spray pyrolysis, solution filtration, or the like, followed by heat treatment, and then disposed on the solid electrolyte layer 30. However, the method is not necessarily limited to such a method, and any wet method known in the art that can form the first anode active material layer 22 is possible. Alternatively, the first negative electrode active material layer 22 may be disposed on the solid electrolyte layer 30 by a vacuum deposition method, a sputtering method, a plating method, or the like. However, the method is not necessarily limited to these methods, and any dry method capable of forming the first negative electrode active material layer 22 in the art is acceptable.

[0041] One or more of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 may further include, for example, a binder.

[0042] The second negative electrode active material layer 23 includes, for example, a binder. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or the like, but is not necessarily limited thereto. Any binder commonly used in the art may be used. The binder may be composed of a single binder or multiple different binders.

[0043] The inclusion of a binder in the second negative electrode active material layer 23 stabilizes the second negative electrode active material layer 23 on the negative electrode current collector 21. Furthermore, cracking of the second negative electrode active material layer 23 is suppressed despite volume changes and / or relative position changes of the second negative electrode active material layer 23 during charge / discharge processes. For example, if 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. The portion of the second negative electrode active material layer 23 that separates from the negative electrode current collector 21 exposes the negative electrode current collector 21 and comes into contact with the solid electrolyte layer 30, increasing the likelihood of a short circuit. The second negative electrode active material layer 23 is prepared, for example, by applying a slurry, in which materials constituting the second negative electrode active material layer 23 are dispersed, onto the negative electrode current collector 21 and drying the slurry. The inclusion of a binder in the second negative electrode active material layer 23 allows the negative electrode active material to be stably dispersed in the slurry. For example, when the slurry is applied onto the negative electrode current collector 21 by screen printing, clogging of the screen (for example, clogging due to aggregates of the negative electrode active material) can be suppressed.

[0044] The negative electrode current collector 21 is made of, for example, a material that does not react with lithium, i.e., does not form any alloy or compound. Materials for the negative electrode current collector 21 include, but are not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material used as an electrode current collector in the art can be used. The negative electrode current collector 21 may be made of one of the aforementioned metals, or an alloy of two or more metals, or a coating material. The negative electrode current collector 21 may be, for example, in the form of a plate or foil.

[0045] The second negative electrode active material layer 23 may further include additives used in the conventional all-solid-state secondary battery 1, such as a filler, a dispersant, an ion conductive agent, and the like.

[0046] In the all-solid-state secondary battery 1, for example, the second anode active material layer 23 contains a second carbon-based anode active material and a metal anode active material or a quasi-metallic anode active material, and the first anode active material layer 22 is made of a carbon-based material. That is, the first anode active material layer 22 does not contain a metal-based material such as a metal anode active material or a quasi-metallic anode active material. When the all-solid-state secondary battery 1 has such a structure, short circuits in the all-solid-state secondary battery 1 can be suppressed and the cycle characteristics can be improved.

[0047] Alternatively, in the all-solid-state secondary battery 1, for example, the second anode active material layer 23 is made of a carbon-based material, and the first anode active material layer 22 includes a first carbon-based anode active material and a metal anode active material or a quasi-metal anode active material. That is, the second anode active material layer 23 does not include a metal-based material such as a metal anode active material or a quasi-metal anode active material. When the all-solid-state secondary battery 1 has such a structure, short circuits in the all-solid-state secondary battery 1 can be suppressed, and the cycle characteristics can be improved.

[0048] Referring to FIG. 2 , the all-solid-state secondary battery 1 further includes, for example, a thin film 24 on the anode current collector 21, the thin film 24 including an element capable of forming an alloy with lithium. The thin film 24 is disposed between the anode current collector 21 and the second anode active material layer 23. The thin film 24 includes, for example, an element capable of forming an alloy with lithium. Examples of elements capable of forming an alloy with lithium include, but are not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, and bismuth. Any element known in the art to be capable of forming an alloy with lithium may be used. The thin film 24 may be composed of one of these metals or an alloy of various metals. By disposing the thin film 24 on the anode current collector 21, for example, the deposition morphology of a third anode active material layer (not shown) deposited between the thin film 24 and the second anode active material layer 23 may be more even, thereby further improving the cycle characteristics of the all-solid-state secondary battery 1.

[0049] The thickness of the thin film 24 is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film 24 is less than 1 nm, the thin film 24 will not easily function. If the thin film 24 is excessively thick, the thin film 24 itself will absorb lithium, reducing the amount of lithium deposited in the negative electrode, lowering the energy density of the all-solid-state battery, and deteriorating the cycle characteristics of the all-solid-state secondary battery 1. The thin film 24 may also be disposed on the negative electrode current collector 21 by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to such methods. Any method known in the art that can form the thin film 24 is possible.

[0050] 3 and 4, the all-solid-state secondary battery 1 further includes a third anode active material layer 25, which is disposed, for example, between the anode current collector 21 and the second anode active material layer 23 or between the first anode active material layer 22 and the second anode active material layer 23 during charging. The third anode active material layer 25 is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, the third anode active material layer 25 functions as a lithium reservoir. Examples of the lithium alloy include, but are not limited to, Li·Al alloy, Li·Sn alloy, Li·In alloy, Li·Ag alloy, Li·Au alloy, Li·Zn alloy, Li·Ge alloy, and Li·Si alloy. Any lithium alloy commonly used in the art can be used. The third anode active material layer 25 may be made of one of these alloys, lithium, or various types of alloys.

[0051] The thickness of the third negative electrode active material layer 25 is not particularly limited, and may be, for example, 1 μm to 1,000 μm, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the third negative electrode active material layer 25 is excessively thin, it is difficult for the third negative electrode active material layer 25 to function as a lithium reservoir. If the thickness of the third negative electrode active material layer 25 is excessively thick, the mass and volume of the all-solid-state secondary battery 1 may increase, which may result in a decrease in cycle characteristics. The third negative electrode active material layer 25 may be, for example, a metal foil having a thickness within this range.

[0052] In the all solid state secondary battery 1, the third negative electrode active material layer 25 is, for example, disposed between the negative electrode current collector 21 and the second negative electrode active material layer 23, or disposed between the first negative electrode active material layer 22 and the second negative electrode active material layer 23, before assembly of the all solid state secondary battery 1. Alternatively, in the all solid state secondary battery 1, the third negative electrode active material layer 25 is, for example, deposited between the negative electrode current collector 21 and the second negative electrode active material layer 23, or deposited between the first negative electrode active material layer 22 and the second negative electrode active material layer 23, by charging after assembly of the all solid state secondary battery 1.

[0053] Before assembling the all-solid-state secondary battery 1, if a third anode active material layer 24 is disposed between the anode current collector 21 and the second anode active material layer 23, or if a third anode active material layer 25 is disposed between the first anode active material layer 22 and the second anode active material layer 23, the third anode active material layer 25 is a metal layer containing lithium and therefore acts as a lithium reservoir. The cycle characteristics of the all-solid-state secondary battery 1 including the third anode active material layer 25 are further improved. For example, before assembling the all-solid-state secondary battery 1, lithium foil is disposed between the anode current collector 21 and the second anode active material layer 23, or lithium foil is disposed between the first anode active material layer 22 and the second anode active material layer 23.

[0054] When the third anode active material layer 25 is disposed by charging after assembling the all solid state secondary battery 1, the energy density of the all solid state secondary battery 1 increases because the third anode active material layer 25 is not included when the all solid state secondary battery 1 is assembled. For example, when charging the all solid state secondary battery 1, charging is performed beyond the charge capacity of the first anode active material layer 22 and / or the second anode active material layer 23. That is, the first anode active material layer 22 and / or the second anode active material layer 23 are overcharged. At the beginning of charging, lithium is absorbed into the first anode active material layer 22 and / or the second anode active material layer 23. That is, the anode active material contained in the first anode active material layer 22 and / or the second anode active material layer 23 forms an alloy or a compound with the lithium ions that have migrated from the positive electrode layer 10. When the first anode active material layer 22 and / or the second anode active material layer 23 are charged beyond their capacity, lithium is deposited on the back surface of the second anode active material layer 23, i.e., between the anode current collector 21 and the second anode active material layer 23, and the deposited lithium forms a metal layer corresponding to the third anode active material layer 25. Alternatively, when the second anode active material layer 23 is charged beyond its capacity, lithium is deposited on the front surface of the second anode active material layer 23, i.e., between the first anode active material layer 22 and the second anode active material layer 23, and the deposited lithium forms a metal layer corresponding to the third anode active material layer 25. The third anode active material layer 25 is a metal layer composed mainly of lithium (i.e., metallic lithium). This result can be achieved, for example, by using a material that forms an alloy or compound with lithium as the anode active material contained in the first anode active material layer 22 and the second anode active material layer 23. During discharge, lithium in the first anode active material layer 22, the second anode active material layer 23, and the third anode active material layer 25, i.e., the metal layers, is ionized and moves toward the positive electrode layer 10. This allows lithium to be used as the anode active material in the all-solid-state secondary battery 1. Furthermore, the first anode active material layer 22 and / or the second anode active material layer 23 coat the third anode active material layer 25, thereby serving as a protective layer for the third anode active material layer 25, i.e., the metal layer, and also serving to suppress the precipitation and growth of lithium dendrites. This therefore suppresses short circuits and capacity reduction in the all-solid-state secondary battery 1, and as a result, improves the cycle characteristics of the all-solid-state secondary battery 1.Furthermore, after assembling the all solid state secondary battery 1, when the third negative electrode active material layer 25 is disposed by charging, the negative electrode current collector 21, the first negative electrode active material layer 22, the second negative electrode active material 23, and the region therebetween are Li-free regions that do not contain lithium (Li), for example, in the initial state or post-discharge state of the all solid state secondary battery 1.

[0055] (Solid electrolyte layer) 1 to 4, the solid electrolyte layer 30 includes a solid electrolyte disposed between the positive electrode layer 10 and the negative electrode layer 20.

[0056] The solid electrolyte is, for example, an oxide-based solid electrolyte. 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2、0≦y<3)、BaTiO3、Pb(Zr,Ti)O3(PZT)、Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≦x<1, O≦y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2、0<y<3)、Li x Al y Ti z (PO4)3(0 <x<2、0<y<1、0<z<3)、Li 1+x+y (Al,Ga) x (Ti,Ge) 2-x Si y P 3-y O 12 (0≦x≦10≦y≦1), Li x La y TiO3(0 <x<2、0<y<3)、Li2O、LiOH、Li2CO3、LiAlO2、Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2、Li3+x La3M2O 12 (M is Te, Nb or Zr, and x is an integer of 1 to 10) The solid electrolyte is produced by a sintering method or the like.

[0057] The oxide-based solid electrolyte is, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M-doped LLZO; M is Ga, W, Nb, Ta, or Al, and x is an integer from 1 to 10, 0≦a<2) is a garnet-type solid electrolyte selected from the group consisting of:

[0058] Alternatively, the solid electrolyte may be, for example, a sulfide-based solid electrolyte, such as LiS-P2S5, LiS-P2S5-LiX (X is a halogen element), LiS-P2S5-Li2O, LiS-P2S5-Li2O-LiI, LiS-SiS2, LiS-SiS2-LiI, LiS-SiS2-LiBr, LiS-SiS2-LiCl, LiS-SiS2-B2S3-LiI, LiS-SiS2-P2S5-LiI, LiS-B2S3, or LiS-P2S5-Z. m S n (m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 7-x PS 6-x Cl x (0≦x≦2), Li 7-x PS 6-x Br x (0≦x≦2) and Li 7-x PS 6-x I x(0≦x≦2) is one or more selected from the group consisting of Li2S and P2S5. The sulfide-based solid electrolyte is prepared by processing starting materials such as Li2S and P2S5 by melt quenching or mechanical milling. After such processing, heat treatment can be performed. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0059] The sulfide-based solid electrolyte may be, for example, the sulfide-based solid electrolyte material described above, containing at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the sulfide-based solid electrolyte may be a material containing Li2S-P2S5. When the sulfide-based solid electrolyte material contains Li2S-P2S5, the molar ratio of Li2S to P2S5 is, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0060] The sulfide-based solid electrolyte may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 1: [Chemical formula 1] Li + 12-n-x A n+ X 2- 6-x Y - x In Chemical Formula 1, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; X is S, Se, or Te; Y is Cl, Br, I, F, CN, OCN, SCN, or N3; and 1≦n≦5, 0≦x≦2.

[0061] The sulfide solid electrolyte is Li 7-x PS 6-x Cl x (0≦x≦2), Li 7-x PS 6-x Br x (0≦x≦2) and Li 7-x PS 6-x I x(0≦x≦2). In particular, the sulfide-based solid electrolyte contained in the solid electrolyte is an argyrodite-type compound containing one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0062] The solid electrolyte layer 30 further includes, for example, a binder. Examples of the binder included in the solid electrolyte layer 30 include, but are not limited to, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. Any binder used in the art may be used. The binder in the solid electrolyte layer 30 may be the same as or different from the binders in the positive electrode active material layer 12 and the negative electrode active material layer 22.

[0063] (positive electrode layer) The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 . The positive electrode current collector 11 is, for example, a plate or foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector 11 is optional.

[0064] The positive electrode active material layer 12 contains, for example, a positive electrode active material. The positive electrode active material is a positive electrode active material capable of reversibly absorbing and releasing lithium ions. Examples of the positive electrode active material include, but are not limited to, 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, and lithium iron phosphate oxide; nickel sulfide; copper sulfide; lithium sulfide; iron oxide; or vanadium oxide. Any positive electrode active material commonly used in the art can be used. The positive electrode active material can be used alone or in a mixture of two or more types.

[0065] The positive electrode active material is, for example, Li a A 1-b B' b D2 (wherein, in the formula, 0.90≦a≦1 and 0≦b≦0.5); Li a E 1-b B' b O 2-c D c (wherein, 0.90≦a≦1, 0≦b≦0.5, and 0≦c≦0.05); LiE 2-b B' b O 4-c D c (wherein 0≦b≦0.5 and 0≦c≦0.05); Li a Ni 1-b-c Co b B' c D α (wherein, 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 (wherein, 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-αF'2 (wherein, in the formula, 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 (wherein, 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 (wherein, 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 (wherein, in the formula, 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 (wherein the formula is 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 GeO2 (wherein the formula is 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 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); Li a CoG b O2 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); Li a MnG b O2 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); Li a Mn2G b O4 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li 3-f J2(PO4)3(0≦f≦2);Li 3-fA compound represented by any one of the chemical formulas Fe2(PO4)3 (0≦f≦2); LiFePO4. In such a compound, A is Ni, Co, Mn, or a combination thereof, B’ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, D is O, F, S, P, or a combination thereof, E is Co, Mn, or a combination thereof, F’ is F, S, P, or a combination thereof, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, Q is Ti, Mo, Mn, or a combination thereof, I’ is Cr, V, Fe, Sc, Y, or a combination thereof, and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound with a coating layer added to the surface of such a compound, and it is also possible to use a mixture of the aforementioned compound and a compound with a coating layer added. The coating layer added to the surface of such a compound contains, for example, a coating element compound such as an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. The compound forming such a coating layer is amorphous or crystalline. The coating elements contained in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating layer forming method is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method is, for example, spray coating, dipping method, etc. Since specific coating methods are well understood by those skilled in the art, detailed descriptions are omitted. For example, such a lithium transition metal oxide having a layered rock salt structure is, 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 zO2 (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 w O2 (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.

[0066] The positive electrode active material includes, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the aforementioned lithium transition metal oxides. The "layered rock salt type structure" is a structure in which oxygen atom layers and metal atom layers are regularly arranged alternately in the <111> direction of a cubic rock salt type structure, so that each atom layer forms a two-dimensional plane. The "cubic rock salt type structure" refers to a sodium chloride type (NaCl type) structure which is a kind of crystal structure. Specifically, it shows a structure in which face-centered cubic lattices (FCC) formed by cations and anions are arranged offset from each other by about 1 / 2 of the ridge of the unit lattice. Such a lithium transition metal oxide having a layered rock salt type structure is, for example, LiNi x Co y Al z O2 (NCA) or LiNi x Co y Mn z O2 (NCM) (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1), which is a ternary lithium transition metal oxide. When the positive electrode active material includes a ternary lithium transition metal oxide having a layered rock salt type structure, the energy density and thermal stability of the all-solid-state secondary battery 1 are further improved.

[0067] The positive electrode active material is also covered by a coating layer as described above. Any coating layer may be used as long as it is known as a coating layer for the positive electrode active material of the all-solid-state secondary battery 1. The coating layer is, for example, Li2O-ZrO2 or the like.

[0068] When the positive electrode active material is, for example, LiNi x Co y Al z O2 (NCA) or LiNi x Co y Mn zAs a ternary lithium transition metal oxide such as O2(NCM) (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1), when nickel (Ni) is included, the capacity density of the all-solid-state secondary battery 1 can be increased, and in the charged state, the metal elution of the positive electrode active material can be reduced. As a result, the cycle characteristics of the all-solid-state secondary battery 1 in the charged state are improved.

[0069] The shape of the positive electrode active material is, for example, a particle shape such as a true spherical shape or an elliptical spherical shape. The particle size of the positive electrode active material is not particularly limited and is within the range applicable to the positive electrode active material of the conventional all-solid-state secondary battery 1. The content of the positive electrode active material in the positive electrode layer 10 is also not particularly limited and is within the range applicable to the positive electrode layer of the conventional all-solid-state secondary battery 1.

[0070] In addition to the aforementioned positive electrode active material, the positive electrode layer 10 can further contain additives such as a conductive agent, a binder, a filler, a dispersant, and an ion conductivity assisting agent. Such a conductive agent is, for example, graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, etc. The binder is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc. As the filler, dispersant, ion conductivity assisting agent, etc. that can be incorporated into the positive electrode layer 10, generally, known materials used for the electrodes of all-solid-state secondary batteries are used.

[0071] The positive electrode layer 10 can further contain a solid electrolyte. The solid electrolyte contained in the positive electrode layer 10 may be similar to or different from the solid electrolyte contained in the solid electrolyte layer 30. For the detailed content of the solid electrolyte, refer to the solid electrolyte layer 30 section.

[0072] The solid electrolyte contained in the positive electrode layer 10 is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte used in the solid electrolyte layer 30 can be used as the sulfide-based solid electrolyte contained in the positive electrode layer 10.

[0073] Alternatively, the positive electrode layer 10 may be impregnated with, for example, a liquid electrolyte. The liquid electrolyte may include a lithium salt and one or more of an ionic liquid and a polymeric ionic liquid. The liquid electrolyte is also nonvolatile. The ionic liquid has a melting point below room temperature and refers to a salt that is in a liquid state at room temperature, or a room-temperature molten salt, composed only of ions. The ionic liquid may include: a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof; and b) BF4 - , PF6 - , AsF 6- , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N -and (CF3SO2)2N. The ionic liquid is, for example, one or more selected from the group consisting of N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide. The polymeric ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , (CF3SO2)2N - , (FSO2)2N - , Cl - , Br - , I - , SO4 - , 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 - and (O(CF3)2C2(CF3)2O)2PO - and one or more anions selected from the group consisting of: The lithium salt may include a repeating unit containing one or more anions selected from the group consisting of: 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 natural numbers), LiCl, LiI, or a mixture thereof. The concentration of the lithium salt contained in the liquid electrolyte is 0.1 M to 5 M. The content of the liquid electrolyte impregnated into the positive electrode layer 10 is 0 to 100 parts by weight, 0 to 50 parts by weight, 0 to 30 parts by weight, 0 to 20 parts by weight, 0 to 10 parts by weight, or 0 to 5 parts by weight, relative to 100 parts by weight of the positive electrode active material layer 12 not including the liquid electrolyte.

[0074] A method for manufacturing an all-solid-state secondary battery 1 according to another embodiment includes the steps of disposing a first anode active material composition on one surface of a solid electrolyte layer 30, heat-treating the first anode active material composition to dispose a first anode active material layer 22, disposing a second anode active material layer 23 on the first anode active material layer 22, and disposing a cathode active material layer 10 on the other surface of the solid electrolyte layer 30. By disposing the first anode active material layer 22 and the second anode active material layer 23 sequentially on the solid electrolyte layer 30, short-circuiting of the all-solid-state secondary battery 1 is suppressed and the cycle characteristics of the all-solid-state secondary battery 1 are improved.

[0075] The all-solid-state secondary battery 1 is manufactured, for example, by manufacturing a solid electrolyte layer 30 in which a first negative electrode active material layer 22 and a second negative electrode active material layer 23 are sequentially stacked, and a positive electrode layer 10, and then stacking such layers.

[0076] (Manufacturing solid electrolyte layer / negative electrode layer stacks) Materials constituting the first anode active material layer 22, such as a first carbon-based anode active material, a metal anode active material, or a semi-metallic anode active material, and a binder, are added to a polar or non-polar solvent to prepare a slurry (i.e., a first anode active material composition). The prepared slurry is applied to the solid electrolyte layer 30 and dried to prepare a first laminate in which the first anode active material composition is disposed on one side of the solid electrolyte layer 30. The laminate is heat-treated to prepare a second laminate in which the first anode active material layer 22, which is a sintered product, is disposed on the solid electrolyte layer 30. The heat treatment temperature is, for example, 300 to 900°C, 350 to 800°C, 400 to 700°C, 400 to 600°C, or 400 to 500°C. If the heat treatment temperature is too low, organic materials such as the binder remain, resulting in insufficient sintering of the solid electrolyte layer 30 and the first anode active material layer 22. If the heat treatment temperature is too high, the first carbon-based negative electrode active material and / or the metal or semi-metallic negative electrode active material may be deteriorated. The heat treatment time may be 0.1 to 20 hours, 0.5 to 15 hours, 1 to 10 hours, 1 to 5 hours, or 1 to 3 hours, but is not necessarily limited to these ranges and may be adjusted depending on the required conditions. The heat treatment atmosphere may be an inert atmosphere. The inert gas may be argon, nitrogen, or the like.

[0077] Next, materials constituting the second negative electrode active material layer 23 on the first negative electrode active material layer 22 of the second laminate, such as a second carbon-based negative electrode active material, a metal negative electrode active material or a semi-metallic negative electrode active material, and a binder, are added to a polar or non-polar solvent to prepare a slurry (i.e., a second negative electrode active material composition). The prepared slurry is applied to the solid electrolyte layer 30 and dried to prepare a third laminate in which the second negative electrode active material layer 23 is disposed on one side of the first negative electrode active material layer 22. The second negative electrode active material composition may have the same composition as the first negative electrode active material composition.

[0078] Next, the negative electrode current collector 21 is placed on the dried second laminate and pressed to prepare a solid electrolyte layer 30 / negative electrode layer 20 laminate. The pressing method may be, for example, a roll press, a flat press, warm isotactic pressing (WIP), or cold isotactic pressing (CIP), but is not limited to these methods. Any pressing method commonly used in the art may be used. The pressure applied during pressing is, for example, 50 MPa to 500 MPa. The pressure application time is, for example, 5 ms to 10 minutes. The pressing may be performed at a temperature of room temperature to 90°C or less, such as 20 to 90°C. Alternatively, the pressing may be performed at a high temperature of 100°C or higher.

[0079] Furthermore, before disposing 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. By washing the surface of the first negative electrode active material layer 22 with an acidic solution, surface impurities can be removed, and the interfacial resistance between the first negative electrode active material layer 22 and the second negative electrode active material layer 23 can be reduced. The acidic solution can be, for example, hydrochloric acid, nitric acid, sulfuric acid, or the like, but is not limited to these. Any acidic solution that can be used to remove surface impurities can be used. The pH of the acidic solution can be, for example, 0.1 to 6, 0.5 to 5, 1 to 4, 1 to 3, or 1 to 2.

[0080] (Production of positive electrode layer) A slurry is produced by adding the cathode active material and binder, which are materials constituting the cathode active material layer 12, to a nonpolar solvent. The produced slurry is applied to a cathode current collector 11 and dried. The resulting laminate is pressed to produce the cathode layer 10. The pressing method is, for example, roll pressing, flat plate pressing, or pressing using hydrostatic pressure, but is not necessarily limited to these methods. Any pressing method used in the relevant technical field is acceptable. The pressing step may be omitted. The cathode layer 10 is produced by compacting a mixture of materials constituting the cathode active material layer 12 into a pellet or stretching (molding) it into a sheet. When the cathode layer 10 is produced by such a method, the cathode current collector 11 can be omitted. Alternatively, the cathode layer can be impregnated with the aforementioned liquid electrolyte.

[0081] (Manufacturing of solid electrolyte layer) The solid electrolyte layer 30 containing an oxide-based solid electrolyte is produced, for example, by heat treating a precursor of an oxide-based solid electrolyte material.

[0082] The oxide-based solid electrolyte can also be prepared by contacting precursors in stoichiometric amounts to form a mixture and then heat-treating the mixture. The contacting may include milling, such as ball milling, or grinding. The stoichiometrically mixed precursor mixture can be subjected to a primary heat treatment in an oxidizing atmosphere to prepare a primary heat-treated product. The primary heat treatment can be performed at a temperature below 1,000°C for 1 to 36 hours. The primary heat-treated product can be ground. The primary heat-treated product can be ground dry or wet. Wet grinding can be performed by mixing the primary heat-treated product with a solvent, such as methanol, and then milling it in a ball mill for 0.5 to 10 hours. Dry grinding can also be performed without a solvent, such as ball milling. The ground primary heat-treated product can have a particle size of 0.1 μm to 10 μm, or 0.1 μm to 5 μm. The crushed product of the primary heat treatment can be dried, mixed with a binder solution and formed into pellets, or simply pressed under a pressure of 1 to 10 tons to form pellets.

[0083] The molded product may be subjected to a secondary heat treatment at a temperature of 1,000°C or less for 1 to 36 hours. A sintered solid electrolyte layer 30 is obtained by the secondary heat treatment. The secondary heat treatment may be performed at, for example, 550 to 1,000°C, 600 to 900°C, or 700 to 850°C. The secondary heat treatment time is 1 to 36 hours. To obtain a sintered product, the secondary heat treatment temperature is higher than the primary heat treatment temperature. For example, the secondary heat treatment temperature may be 10°C or higher, 20°C or higher, 30°C or higher, or 50°C or higher than the primary heat treatment temperature. The molded product may be subjected to a secondary heat treatment in one or more of an oxidizing atmosphere and a reducing atmosphere. The secondary heat treatment may be performed in a) an oxidizing atmosphere, b) a reducing atmosphere, or c) both an oxidizing atmosphere and a reducing atmosphere.

[0084] The solid electrolyte layer 30 containing a sulfide-based solid electrolyte is manufactured using a solid electrolyte formed from, for example, a sulfide-based solid electrolyte material.

[0085] The sulfide-based solid electrolyte is prepared by processing the starting materials using, for example, melt quenching or mechanical milling, but is not limited to these methods. Any method known in the art for producing sulfide-based solid electrolytes is acceptable. For example, when using the melt quenching method, starting materials such as Li2S and P2S5 are mixed in predetermined amounts, pelletized, reacted under vacuum at a predetermined reaction temperature, and then quenched to produce a sulfide-based solid electrolyte material. The reaction temperature for the Li2S and P2S5 mixture is, for example, about 400°C to 1,000°C, or about 800°C to 900°C. The reaction time is, for example, 0.1 to 12 hours, or 1 to 12 hours. The quenching temperature for the reaction mixture is 10°C or below, or 0°C or below, and the quenching rate is 1°C / sec to 10,000°C / sec, 1°C / sec to 1,000°C / sec, or 1°C / sec to 100°C / sec. For example, when using a mechanical milling method, starting materials such as LiS and P2S5 are stirred and reacted using a ball mill or the like to produce a sulfide-based solid electrolyte material. The stirring speed and stirring time in the mechanical milling method are not particularly limited, but the faster the stirring speed, the faster the rate at which the sulfide-based solid electrolyte material is produced, and the longer the stirring time, the higher the conversion rate of the raw materials to the sulfide-based solid electrolyte material. Next, the mixed raw materials obtained by a melt quenching method, mechanical milling method, or the like are heat-treated at a predetermined temperature and then pulverized to produce a particulate solid electrolyte. If the solid electrolyte has glass transition properties, it can be converted from amorphous to crystalline by heat treatment.

[0086] The solid electrolyte obtained in this manner is deposited using a known film formation method, such as aerosol deposition, cold spray, or sputtering, to produce the solid electrolyte layer 30. Alternatively, the solid electrolyte layer 30 can be produced by pressing solid electrolyte particles alone. Alternatively, the solid electrolyte layer 30 can be produced by mixing the solid electrolyte with a solvent and a binder, applying the mixture, drying, and pressing the mixture.

[0087] (Manufacturing of all-solid-state secondary batteries) The positive electrode layer 10 and the negative electrode layer 20 / solid electrolyte layer 30 laminate produced by the above-mentioned method are laminated so that the positive electrode layer 10 and the negative electrode layer 20 sandwich the solid electrolyte layer 30, and then pressurized to produce an all-solid-state secondary battery 1.

[0088] For example, a second stack is prepared by placing an anode layer 20 / solid electrolyte layer 30 stack on the cathode layer 10 so that the cathode layer 10 and the solid electrolyte layer 30 are in contact with each other, and the second stack is then pressed to manufacture an all-solid-state secondary battery 1. The pressing may be performed using, for example, roll pressing, flat plate pressing, or hydrostatic pressure, but is not limited to these methods. Any pressing method commonly used in the art is acceptable. The pressure applied during pressing is, for example, 50 MPa to 750 MPa. The pressure is applied for 5 ms to 5 minutes. The pressing may be performed at a temperature of, for example, room temperature to 90°C or less, such as 20 to 90°C. Alternatively, the pressing may be performed at a high temperature of 100°C or higher. The configuration and fabrication method of the all-solid-state secondary battery 1 described above are merely examples of embodiments, and the components and fabrication procedures may be modified as appropriate. Pressing may be omitted.

[0089] The present invention will be described in more detail with reference to the following examples and comparative examples, but the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention. [Example]

[0090] Example 1: First layer (Ag+CB, 5 μm) / Second layer (Ag+CB, 25 μm), First layer heat treated at 450° C. (Manufacturing of solid electrolyte layer / negative electrode layer laminate) As the negative electrode active material, carbon black (CB) having a primary particle size of about 38 nm and silver (Ag) particles having an average particle diameter of about 100 nm were prepared.

[0091] 3 g of carbon black (CB) and 1 g of silver particles were placed in a container, and 2.692 g of PVA-PAA binder solution (AG binder, manufactured by Sumitomo Seika Chemicals Co., Ltd.) was mixed with 7 g of distilled water and then placed in the container and stirred at 1,000 rpm for 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 stirred at 1,000 rpm for 30 minutes to prepare a second slurry. 20 g of distilled water was added to the second slurry and stirred at 1,000 rpm for 30 minutes to prepare a third slurry.

[0092] The solid electrolyte layer is Li7La3Zr2O with a thickness of 495 μm. 12 (LLZO) pellets were prepared.

[0093] The third slurry was spin-coated onto one side of the LLZO pellet, dried at room temperature for 1 hour, and then vacuum-dried for 12 hours to obtain a laminate of a solid electrolyte layer and a precursor layer. The resulting laminate was heat-treated at 450°C for 2 hours to obtain a first negative electrode active material layer, which was a sintered product of the precursor layer. The surface of the resulting first negative electrode active material layer was washed with a hydrochloric acid solution to remove impurities from the surface of the first negative electrode active material layer. The thickness of the first negative electrode active material layer was approximately 5 μm.

[0094] The third slurry composition prepared above was spin-coated 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 a second negative electrode active material layer. The thickness of the second negative electrode active material layer was approximately 25 μm. The second negative electrode active material layer was prepared using the same composition and method as the precursor layer for the first negative electrode active material layer, except for the heat treatment.

[0095] A negative electrode current collector made of copper (Cu) foil with a thickness of 10 μm was placed on the second negative electrode active material layer, and a pressure of 250 MPa was applied at 25°C by cold isostatic pressing (CIP) to attach the negative electrode current collector, thereby preparing a solid electrolyte layer / negative electrode layer laminate.

[0096] (Positive electrode layer manufacturing) As the positive electrode active material, LiNi 0.8 Co 0.15 Mn 0.05 O2 (NCM) was prepared. Polytetrafluoroethylene (Teflon (registered trademark), manufactured by DuPont) binder was prepared. Carbon nanofiber (CNF) was prepared as a conductive additive. These materials were then mixed in a mass ratio of positive electrode active material:conductive additive:binder = 100:2:1. The mixture was stretched into a sheet to prepare a positive electrode active material sheet. The positive electrode active material sheet was then pressed onto a positive electrode current collector made of 18 μm-thick aluminum foil to prepare a positive electrode layer. The thickness of the positive electrode active material layer of the prepared positive electrode layer was approximately 100 μm.

[0097] The prepared positive electrode active material layer of the positive electrode layer was immersed in an electrolyte solution in which 2.0M of LiFSI was dissolved in N-propyl-N-methyl-pyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI), which is an ionic liquid.

[0098] (Manufacturing of all-solid-state secondary batteries) The positive electrode layer was placed in a SUS cap so that the positive electrode active material layer impregnated with an ionic liquid electrolyte faced upward. A solid electrolyte layer / negative electrode layer laminate, with the negative electrode layer attached, was placed on the positive electrode active material layer so that the solid electrolyte layer was placed on top of the positive electrode active material layer, and the assembly was sealed to produce an all-solid-state secondary battery. The positive electrode layer and the negative electrode layer were insulated by an insulating layer. Portions of the positive electrode current collector and the negative electrode current collector protruded outside the sealed battery and were used as positive electrode layer terminals and negative electrode layer terminals.

[0099] Example 2: First layer (Ag+CB, 5 μm) / Second layer (Ag+CB, 25 μm), First layer heat treated at 600° C. An 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. when manufacturing the first negative electrode active material layer.

[0100] Example 3: First layer (CB, 5 μm) / Second layer (Ag+CB, 25 μm) An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that 4 g of carbon black (CB) was used instead of 3 g of carbon black (CB) and 1 g of silver particles when manufacturing the first negative electrode active material layer.

[0101] Example 4: First layer (CB, 5 μm) / Second layer (CB, 25 μm) An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that 4 g of carbon black (CB) was used instead of 3 g of carbon black (CB) and 1 g of silver particles when manufacturing the first negative electrode active material layer and the second negative electrode active material layer.

[0102] Example 5: First layer (Ag+CB, 5 μm) / Second layer (Ag+CB, 25 μm), First layer heat treated at 300° C. An 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. when manufacturing the first negative electrode active material layer.

[0103] Example 6: First layer (Ag 1g + CB 3g, 5µm) / Second layer (Ag 1.5g + CB 2.5g, 25µm), First layer heat treated at 450°C During the production of the second negative electrode active material layer, the amounts of carbon black (CB) and silver particles in the first slurry changed to 2.5 g of carbon black (CB) and 1.5 g of silver particles, respectively.

[0104] Comparative Example 1: First layer (Ag+CB, 3 μm) alone An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the step of manufacturing the second negative electrode active material layer was omitted, the thickness of the first layer was changed to 3 μm, and a solid electrolyte / negative electrode layer stack including only the first negative electrode active material layer was manufactured.

[0105] Comparative Example 2: Second layer (Ag+CB, 27 μm) alone An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the step of manufacturing the first negative electrode active material layer was omitted, the thickness of the second layer was changed to 27 μm, and a solid electrolyte / negative electrode layer stack including only the second negative electrode active material layer was manufactured.

[0106] Comparative Example 3: First layer (Ag+CB, 5 μm) / Second layer (Ag+CB, 25 μm), heat treatment of the first layer omitted An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that in the step of preparing the first negative electrode active material layer, instead of the additional heat treatment at 450°C, vacuum drying was performed at 150°C for 12 hours, and the heat treatment was omitted.

[0107] Evaluation example 1: Evaluation of surface morphology and composition In Example 1, scanning electron microscope (SEM) images of the surface of the precursor layer, which is a dried product before heat treatment at 450°C, and the surface of the first negative electrode active material layer, which is a sintered product obtained after heat treatment at 450°C, are shown in Figures 5A and 5B, respectively.

[0108] As can be seen from FIGS. 5A and 5B, the average particle size of the carbon black particles contained in the first negative electrode active material layer was larger than the average particle size of the carbon black particles contained in the precursor layer. Although not shown in the drawings, the average particle size of the silver (Ag) particles contained in the first negative electrode active material layer was larger than the average particle size of the silver (Ag) particles contained in the precursor layer.

[0109] The carbon black (CB) contained in the precursor layer had an average particle size of about 38 nm, and the carbon black (CB) contained in the first negative electrode active material layer had an average particle size of about 450 nm.

[0110] The average particle size of the silver (Ag) particles contained in the precursor layer was about 100 nm, and the average particle size of the silver (Ag) particles contained in the first negative electrode active material layer was about 500 nm.

[0111] The average particle sizes of carbon black (CB) and silver (Ag) particles contained in the first negative electrode active material layer were determined by analyzing scanning electron microscope (SEM) images.

[0112] The first negative electrode active material layer was thinned and its density increased because the binder was decomposed and removed by sintering, and the size of the carbon black (CB) particles and silver (Ag) particles increased by sintering.

[0113] FIG. 6A is an SEM image of a cross section of the solid electrolyte layer / first negative electrode active material layer stack prepared in Example 1. FIG.

[0114] As can be seen from FIG. 6A, it was confirmed that the first negative electrode active material layer was disposed on the surface of the solid electrolyte layer.

[0115] FIG. 6B is a carbon mapping image of EDX (energy-dispersive X-ray spectroscopy) of a cross section of the solid electrolyte layer / first negative electrode active material layer stack prepared in Example 1.

[0116] As can be seen from FIG. 6B, it was confirmed that the first negative electrode active material layer disposed on the surface of the solid electrolyte layer contained carbon.

[0117] In Example 2, a scanning electron microscope (SEM) image of the surface of the first negative electrode active material layer, which is a sintered product obtained after heat treatment at 600° C., is shown in FIG. 7A.

[0118] 7B and 7C are EDX silver (Ag) mapping and carbon mapping images of the surface of the first negative electrode active material layer prepared in Example 2.

[0119] As can be seen from FIGS. 7B and 7C, it was confirmed that the first negative electrode active material layer disposed on the surface of the solid electrolyte layer contained silver particles and carbon particles, respectively.

[0120] It was confirmed that impurities such as Li2CO3 were removed through a surface acid treatment of the first negative electrode active material layer present after the 600°C heat treatment, and that carbon was still exposed and present on the surface of the first negative electrode active material layer after the acid treatment.

[0121] FIG. 8A is a scanning electron microscope (SEM) image of a cross section of the solid electrolyte layer / anode layer stack prepared in Example 2.

[0122] FIG. 8B is a partially enlarged cross-sectional view of the interface region between the solid electrolyte layer and the first negative electrode active material layer (heat-treated layer) in FIG. 8A.

[0123] FIG. 8C is a partially enlarged view of a cross section of the interface region between the first negative electrode active material layer (heat-treated layer) and the second negative electrode active material layer (dried layer) in FIG. 8A.

[0124] FIG. 8D is a partially enlarged cross-sectional view of the inner region of the second negative electrode active material layer (dry layer) in FIG. 8A.

[0125] FIG. 8E is an XRD (X-ray diffraction) pattern of the first negative electrode active material layer (heat-treated layer) adjacent to the solid electrolyte layer in FIG. 8A.

[0126] FIG. 8F shows an XRD pattern of the second negative electrode active material layer (dried layer) adjacent to the first negative electrode active material layer (heat-treated layer) in FIG. 8A.

[0127] FIG. 8G is an XRD pattern of the region inside the second negative electrode active material layer (dry layer) in FIG. 8A.

[0128] As can be seen from FIG. 8E, a diffraction pattern due to crystallized carbon was partially observed in the first negative electrode active material layer, but as can be seen from FIGS. 8F and 8G, such a diffraction pattern was not observed in the second negative electrode active material layer.

[0129] Therefore, it was confirmed that the carbon contained in the first negative electrode active material layer had higher crystallinity than the carbon contained in the second negative electrode active material layer, and that the first negative electrode active material layer had a higher density than the second negative electrode active material layer.

[0130] FIG. 8H is an EDX carbon mapping image of a cross section of the first negative electrode active material layer (heat-treated layer) adjacent to the solid electrolyte layer in FIG. 8A.

[0131] FIG. 8I is an EDX carbon mapping image of a cross section of the second negative electrode active material layer (dried layer) adjacent to the first negative electrode active material layer (heat-treated layer) in FIG. 8A.

[0132] FIG. 8J is an EDX carbon mapping image of a cross section of a certain region inside the second negative electrode active material layer (dry layer) in FIG. 8A.

[0133] As can be seen from FIGS. 8H to 8J, it was confirmed that carbon was distributed in both the first negative electrode active material layer and the second negative electrode active material layer.

[0134] Evaluation example 2: Raman spectrum evaluation In Example 1, Raman spectrum images of the surface of the precursor layer (dried before heat treatment at 450°C) and the surface of the first negative electrode active material layer (sintered after heat treatment at 450°C) are shown in FIGS. 9A and 9B, respectively, and the Raman spectrum data are shown in Table 1 below. The precursor layer was prepared using the same slurry and method as the second negative electrode active material layer. Although not shown in the drawings, the Raman spectrum of the second negative electrode active material layer was also identical to that of the precursor layer.

[0135] FIG. 9B is an enlarged view of the superimposed Raman peaks in FIG. 9A, showing the intensity of each Raman peak. In FIGS. 9A and 9B, the D-band peak intensity (I D ) and G-band peak intensity (I G ) is the height to the highest point of the peak at the baseline.

[0136] As can be seen from FIGS. 9A and 9B, 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 ) was 0.74. Therefore, the I between the D band peak and the G band peak of the carbon black (CB) contained in the first negative electrode active material layer 1 D / I 1G 9A and 9B, the intensity ratio 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, was 0.74. 2 D / I 2 G ) was 1.13. Therefore, the difference (I 2 D / I 2 G The carbon black (CB) contained in the second negative electrode active material layer had an increased intensity ratio (I ) of the D band peak to the G band peak in the Raman spectrum compared to the carbon black (CB) contained in the first negative electrode active material layer. D / I G ) was confirmed.

[0137] Therefore, it was confirmed that the carbon black (CB) contained in the first negative electrode active material layer had reduced defects and improved crystallinity compared to the carbon black (CB) contained in the second negative electrode active material layer.

[0138] [Table 1]

[0139] As can be seen from Table 1, the position of the D-band peak center in the Raman spectrum of the first carbon-based negative electrode active material is 3.9 cm apart from the position of the D-band peak center in the Raman spectrum of the second carbon-based negative electrode active material. -1 The position of the G-band peak center in the Raman spectrum of the first carbon-based negative electrode active material was shifted by 2.4 cm compared to the position of the G-band peak center in the Raman spectrum of the second carbon-based negative electrode active material. -1 The width of the D band peak in the Raman spectrum of the first carbon-based negative electrode active material was about 58% of the width of the D band peak in the Raman spectrum of the second carbon-based negative electrode active material.

[0140] Evaluation example 3: Interface resistance evaluation The overall resistance of each of the all-solid-state secondary batteries manufactured in Comparative Example 1 and Comparative Example 2 was measured.

[0141] For the all-solid-state secondary batteries manufactured in Comparative Examples 1 and 2, impedance was measured by the two-probe method using an impedance analyzer (Solartron 1400A / 1455A impedance analyzer). The frequency range was 0.1 Hz to 1 MHz, and the amplitude voltage was 10 mV. Measurements were performed in an air atmosphere at 25°C. A Nyquist plot of the impedance measurement results is shown in FIG. 10.

[0142] As a result of fitting the Nyquist plot of FIG. 10 to an equivalent circuit, the interface resistance of the all-solid-state secondary battery of Comparative Example 1 was found to be approximately 100 Ωcm 2 The interface resistance of the all-solid-state secondary battery of Comparative Example 2 was about 350 Ω cm 2 It was.

[0143] 10, the ohmic resistance of the all solid state secondary battery of Comparative Example 1 was also reduced compared to the all solid state secondary battery of Comparative Example 2.

[0144] Therefore, it was confirmed that the total resistance, which is the sum of the interface resistance and the ohmic resistance, of the all-solid-state secondary battery of Comparative Example 1 was reduced compared to the all-solid-state secondary battery of Comparative Example 2.

[0145] In the all-solid-state secondary battery of Comparative Example 1, such a reduction in overall resistance is believed to be due to the fact that the precursor layer is sintered together with the solid electrolyte layer during the heat treatment process of the precursor layer, forming a covalent bond between the solid electrolyte layer and the first negative electrode active material layer, increasing the active interfacial area and increasing the diffusion rate of lithium ions.

[0146] Evaluation example 4: Charge / discharge test The charge-discharge characteristics of the all-solid-state secondary batteries produced in Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated by the following charge-discharge test. The charge-discharge test was carried out by placing the all-solid-state secondary batteries in a constant temperature bath at 60°C.

[0147] The first cycle was 0.6 mA / cm until the battery voltage reached 4.2 V. 2 The battery was then charged at a constant current of 0.6 mA / cm until the battery voltage reached 2.8 V. 2 Discharge was carried out at a constant current of .

[0148] From the second cycle to the thirteenth cycle, the current was 1.5 mA / cm until the battery voltage reached 4.2 V. 2 The battery was then charged at a constant current of 1.5 mA / cm until the battery voltage reached 2.8 V. 2 Discharge was carried out at a constant current of .

[0149] From the 14th to 18th cycles, the current was 2.0 mA / cm until the battery voltage reached 4.2 V. 2 The battery was then charged at a constant current of 2.0 mA / cm until the battery voltage reached 2.8 V. 2 Discharge was carried out at a constant current of .

[0150] From the 19th to the 23rd cycle, the current was 3.0 mA / cm until the battery voltage reached 4.2 V. 2 The battery was then charged at a constant current of 3.0 mA / cm until the battery voltage reached 2.8 V. 2 Discharge was carried out at a constant current of .

[0151] From the 24th to the 26th cycle, the current was 4.0 mA / cm until the battery voltage reached 4.2 V. 2 The battery was then charged at a constant current of 4.0 mA / cm until the battery voltage reached 2.8 V. 2 Discharge was carried out at a constant current of .

[0152] From the 27th to the 40th cycle, the current was 6.0 mA / cm until the battery voltage reached 4.2 V. 2The battery was then charged at a constant current of 6.0 mA / cm until the battery voltage reached 2.8 V. 2 Discharge was carried out at a constant current of . Some of the charge / discharge results are shown in FIGS. 11A, 11B, 11C, and 11D.

[0153] As can be seen from FIG. 11A, the all-solid-state secondary battery of Example 1 simultaneously includes a first negative electrode active material layer sintered together with a solid electrolyte layer and a second negative electrode active material layer disposed on the first negative electrode active material layer. It was charged and discharged for up to 40 cycles without short circuiting, and achieved a current of 6.0 mA / cm 2 The battery showed stable charge and discharge even at a high current density of 1000 kJ / s. Although not shown in the drawings, it also showed a high charge and discharge efficiency of 98.5% or more at the 40th cycle. The charge and discharge efficiency at the 40th cycle is the percentage of the charge capacity at the 40th cycle related to the charge capacity at the 40th cycle. Therefore, it was confirmed that the all-solid-state secondary battery of Example 1 maintained a stable interface during the charge and discharge process, and induced uniform deposition of lithium.

[0154] As can be seen from FIG. 11B, the all-solid-state secondary battery of Comparative Example 1, which included only the first negative electrode active material layer, experienced a short circuit during charging in the first cycle.

[0155] As can be seen from FIG. 11C, the all-solid-state secondary battery of Comparative Example 2, which included only the second negative electrode active material layer, experienced a short circuit during charging in the first cycle.

[0156] Although not shown in the drawings, the all-solid-state secondary battery of Comparative Example 3, which has a multi-layer structure in which heat treatment is omitted in the first negative electrode active material layer, also experienced a short circuit during charging and discharging.

[0157] Although not shown in the drawings, the all-solid-state secondary batteries of Examples 2, 3, 5 and 6 also exhibited stable charge and discharge.

[0158] As can be seen from FIG. 11D, the all-solid-state secondary battery of Example 4 also exhibited stable charge and discharge. As explained above, the all-solid-state secondary battery according to this embodiment is also applicable to various portable devices, vehicles, and the like.

[0159] Although one illustrative embodiment has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an example. It is obvious that a person skilled in the art to which the present invention pertains can derive various modifications or alterations within the scope of the technical idea described in the claims, and it goes without saying that such modifications or alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0160] 1 All-solid-state secondary battery 10 Positive electrode layer 11 Positive electrode current collector 12 Cathode active material layer 20 negative electrode layer 21 Negative electrode current collector 22 First negative electrode active material layer 23 Second negative electrode active material layer 24 Thin Film 25 Third negative electrode active material layer 30 Solid electrolyte layer

Claims

1. a positive electrode layer including a positive electrode active material layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer and including a solid electrolyte; 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, the first negative electrode active material layer contains a first carbon-based negative electrode active material, and the second negative electrode active material layer contains a second carbon-based negative electrode active material; The intensity ratio (I) of the D band peak to the G band peak in the Raman spectrum of the first carbon-based negative electrode active material １ Ｄ / I １ Ｇ ) is the intensity ratio (I ２ Ｄ / I ２ Ｇ ) is lower than the first carbon-based negative electrode active material has a D-band peak to G-band peak intensity ratio (I 1 D / I 1 G ) of 0.5 to 0.75 in a Raman spectrum; an intensity ratio (I 2 D / I 2 G ) of a D-band peak to a G-band peak in a Raman spectrum of the second carbon-based negative electrode active material is 1.1 or more;

2. The position of the D-band peak center in the Raman spectrum of the first carbon-based negative electrode active material is 2.0 cm apart from the position of the D-band peak center in the Raman spectrum of the second carbon-based negative electrode active material. －１ More blue moving, The position of the G-band peak center in the Raman spectrum of the first carbon-based negative electrode active material is 1.0 cm apart from the position of the G-band peak center in the Raman spectrum of the second carbon-based negative electrode active material. －１ More blue moving, 2. The all-solid-state secondary battery according to claim 1, wherein a width of a D-band peak in a Raman spectrum of the first carbon-based negative electrode active material is 80% or less of a width of a D-band peak in a Raman spectrum of the second carbon-based negative electrode active material.

3. At least one of the first carbon-based negative electrode active material and the second carbon-based negative electrode active material has a particle form; The all-solid-state secondary battery according to claim 1 , wherein at least one of the first carbon-based negative electrode active material and the second carbon-based negative electrode active material has an average particle size of 4 μm or less.

4. The all-solid-state secondary battery according to claim 1 , wherein at least one of the first carbon-based negative electrode active material and the second carbon-based negative electrode active material contains amorphous carbon.

5. The all-solid-state secondary battery according to claim 1 , wherein at least one of the first negative electrode active material layer and the second negative electrode active material layer is made of a carbon-based material.

6. The all-solid-state secondary battery according to claim 1 , wherein at least one of the first negative electrode active material layer and the second negative electrode active material layer further contains a metal negative electrode active material or a quasi-metal negative electrode active material.

7. 7. The all-solid-state secondary battery according to claim 6, wherein the metal negative electrode active material or the quasi-metal negative electrode active material comprises one or more selected from the group consisting of 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), and zinc (Zn).

8. the first negative electrode active material layer includes a composite of first particles made of amorphous carbon and second particles made of a metal or semi-metal; The all-solid-state secondary battery of claim 6 , wherein the content of the second particles is 1 to 60 wt % based on the total weight of the composite.

9. the second negative electrode active material layer includes a mixture of first particles made of amorphous carbon and second particles made of a metal or semi-metal; The all-solid-state secondary battery of claim 6 , wherein the content of the second particles is 1 to 60 wt % based on the total weight of the mixture.

10. the content of the metal negative electrode active material or the quasi-metal negative electrode active material contained in the second negative electrode active material layer is different from the content of the metal negative electrode active material or the quasi-metal negative electrode active material contained in the first negative electrode active material layer; 7. The all-solid-state secondary battery of claim 6, wherein the second negative electrode active material layer contains a higher amount of the metal negative electrode active material or the quasi-metal negative electrode active material than the first negative electrode active material layer.

11. the average particle size of the first particles contained in the second negative electrode active material layer is 50% or less of the average particle size of the first particles contained in the first negative electrode active material layer; 7. The all-solid-state secondary battery according to claim 6, wherein the average particle size of the second particles contained in the second negative electrode active material layer is 50% or less of the average particle size of the second particles contained in the first negative electrode active material layer.

12. The all-solid-state secondary battery according to claim 1 , wherein the first carbon-based negative electrode active material forms at least one of a covalent bond and an ionic bond with the solid electrolyte.

13. The all-solid-state secondary battery according to claim 1 , wherein the first negative electrode active material layer does not contain an organic material.

14. 2. The all-solid-state secondary battery according to claim 1, wherein the first carbon-based negative electrode active material is a sintered product of a carbon-based precursor, and the carbon-based precursor is the second carbon-based negative electrode active material.

15. the thickness of the first negative electrode active material layer is 50% or less of the thickness of the positive electrode active material layer, The all-solid-state secondary battery according to claim 1 , wherein the first negative electrode active material layer has a thickness of 10 nm to 10 μm.

16. the thickness of the second negative electrode active material layer is 50% or less of the thickness of the positive electrode active material layer, The all-solid-state secondary battery according to claim 1 , wherein the second negative electrode active material layer has a thickness of 1 μm to 50 μm.

17. The all-solid-state secondary battery according to claim 1 , wherein the first negative electrode active material layer has a thickness smaller than that of the second negative electrode active material layer.

18. The all-solid-state secondary battery according to claim 1 , wherein at least one of the first negative electrode active material layer and the second negative electrode active material layer further contains a binder.

19. 2. The all-solid-state secondary battery according to claim 1, wherein the second anode active material layer includes a second carbon-based anode active material and a metal anode active material or a quasi-metallic anode active material, and the first anode active material layer is made of a carbon-based material.

20. 2. The all-solid-state secondary battery according to claim 1, wherein the second anode active material layer is made of a carbon-based material, and the first anode active material layer includes a first carbon-based anode active material and a metal anode active material or a quasi-metal anode active material.

21. 2. The all-solid-state secondary battery according to claim 1, further comprising a third anode active material layer disposed in one or more of between the anode current collector and the second anode active material layer and between the first anode active material layer and the second anode active material layer, wherein the third anode active material layer is a metal layer containing lithium or a lithium alloy.

22. 2. The all-solid-state secondary battery according to claim 1, wherein the negative electrode current collector, the first negative electrode active material layer, the second negative electrode active material layer, and a region therebetween are Li-free regions that do not contain lithium (Li) in an initial state or a post-discharge state of the all-solid-state secondary battery.

23. 2. The all-solid-state secondary battery according to claim 1, wherein the solid electrolyte is an oxide-based solid electrolyte or a sulfide-based solid electrolyte.

24. The oxide-based solid electrolyte is Li １＋ｘ＋ｙ Al ｘ Ti ２－ｘ Si ｙ P ３－ｙ O １２ (0 < x < 2, 0 ≤ y < 3), BaTiO ３ , Pb(Zr,Ti)O ３ (PZT), Pb １－ｘ La ｘ Zr １－ｙ Ti ｙ O ３ (PLZT) (0 ≤ x < 1, 0 ≤ y < 1), PB(Mg ３ Nb ２／３ )O ３ - PbTiO ３ (PMN - PT), HfO ２ , SrTiO ３ , SnO ２ , CeO ２ , Na ２ O, MgO, NiO, CaO, BaO, ZnO, ZrO ２ , Y ２ O ３ , Al ２ O ３ , TiO ２ , SiO ２ , Li ３ PO ４ , Li ｘ Ti ｙ (PO ４ ) ３ (0 < x < 2, 0 < y < 3), Li ｘ Al ｙ Ti ｚ (PO ４ ) ３ (0 < x < 2, 0 < y < 1, 0 < z < 3), Li １＋ｘ＋ｙ (Al, Ga) ｘ (Ti, Ge) ２－ｘ Si ｙ P ３－ｙ O １２ (0 ≤ x ≤ 10 ≤ y ≤ 1), Li ｘ La ｙ TiO ３ (0 < x < 2, 0 < y < 3), Li ２ O, LiOH, Li ２ CO ３ , LiAlO ２ , Li ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ -GeO ２ , Li ３＋ｘ La ３ M ２ O １２ (M is Te, Nb, or Zr, and x is an integer of 1 to 10).

25. The oxide-based solid electrolyte is Li ７ La ３ Zr ２ O １２ (LLZO) and Li ３＋ｘ La ３ Zr ２－ａ M ａ O １２ 24. The all-solid-state secondary battery according to claim 23, wherein the garnet-based solid electrolyte is selected from the group consisting of M-doped LLZO; M is Ga, W, Nb, Ta, or Al, and x is an integer from 1 to 10.

26. The sulfide-based solid electrolyte is Li ２ S-P ２ S ５ , Li ２ S-P ２ S ５ -LiX (X is a halogen element), Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ , Li ２ S-SiS ２ - LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ - LiI, Li ２ S-SiS ２ -P ２ S ５ - LiI, Li ２ S-B ２ S ３ , Li ２ S-P ２ S ５ -Z ｍ S ｎ (m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li ２ S-GeS ２ , Li ２ S-SiS ２ -Li ３ P.O. ４ , Li ２ S-SiS ２ -Li ｐ MO ｑ (p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li ７－ｘ P.S. ６－ｘ Cl ｘ (0≦x≦2), Li ７－ｘ P.S. ６－ｘ Br ｘ (0≦x≦2) and Li ７－ｘ P.S. ６－ｘ I ｘ The all-solid-state secondary battery according to claim 23, wherein x is one or more selected from (0≦x≦2).

27. The sulfide-based solid electrolyte is Li ７－ｘ P.S. ６－ｘ Cl ｘ (0≦x≦2), Li ７－ｘ P.S. ６－ｘ Br ｘ (0≦x≦2) and Li ７－ｘ P.S. ６－ｘ I ｘ 24. The all-solid-state secondary battery according to claim 23, wherein the argyrodite-type solid electrolyte contains one or more selected from (0≦x≦2).

28. providing a solid electrolyte layer; disposing a first negative electrode active material composition on one surface of the solid electrolyte layer; heat-treating the first negative electrode active material composition to form a first negative electrode active material layer; disposing a second negative electrode active material layer on the first negative electrode active material layer; and disposing a positive electrode active material layer on the other surface of the solid electrolyte layer, The temperature of the heat treatment is 300°C to 900°C, the first negative electrode active material layer contains a first carbon-based negative electrode active material, and the second negative electrode active material layer contains a second carbon-based negative electrode active material; the intensity ratio (I 1 D / I 1 G ) of a D band peak to a G band peak in a Raman spectrum of the first carbon-based negative electrode active material is lower than the intensity ratio (I 2 D / I 2 G ) of the D band peak to the G band peak in a Raman spectrum of the second carbon-based negative electrode active material.

29. The method for manufacturing an all-solid-state secondary battery according to claim 28, wherein the heat treatment time is 0.1 to 20 hours.

30. Before disposing the second negative electrode active material layer, 30. The method for manufacturing an all-solid-state secondary battery according to claim 28, further comprising washing a surface of the first negative electrode active material layer using an acidic solution.

Images