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

Abstract

To provide an all-solid type secondary battery and a method for manufacturing the same.SOLUTION: An all-solid type secondary battery and a method for manufacturing the same are disclosed. The all-solid type secondary battery comprises: a positive electrode layer including a positive electrode active material layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive and negative electrode layers, and containing 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 metal. A lithium ion reduction potential of the first negative electrode active material layer is higher than a reduction potential of the solid electrolyte. The second negative electrode active material layer contains a second metal. A solid solubility of Li in the second metal is higher than that in the first metal.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 excellent energy density and safety. For example, lithium-ion batteries are being used 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 because life depends on it.

[0003] Currently, commercially available lithium-ion batteries contain flammable organic solvents and use electrolytes, which can overheat and cause fires if a short circuit occurs. To address this issue, all-solid-state batteries using solid electrolytes instead of electrolytes have been proposed.

[0004] By not using flammable organic solvents, all-solid-state batteries can significantly reduce the risk of fire or explosion even if a short circuit occurs, making them significantly safer than lithium-ion batteries that use liquid 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 having a new structure in which short circuits are prevented during charging and discharging and in which cycle characteristics are improved. [Means for solving the problem]

[0006] By way of example, 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 metal, and a lithium ion reduction potential of the first negative electrode active material layer is higher than a reduction potential of the solid electrolyte; The second negative electrode active material layer includes a second metal, and the second metal has a higher solid solubility of lithium in the second metal than the solid solubility of lithium in the first metal.

[0007] From another aspect, providing a solid electrolyte layer; disposing a first negative electrode active material layer including a first metal on one surface of the solid electrolyte layer; disposing a second negative electrode active material layer including a second metal 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 one aspect of the present invention, by employing a negative electrode layer having a multilayer structure, 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 an SEM image of a cross section of an all-solid-state secondary battery produced in Reference Example 1. [Figure 5B] 1 is an SEM image of a cross section of an all-solid-state secondary battery produced in Comparative Reference Example 1. [Figure 6A] 1 is a Nyquist plot showing the impedance measurement results of the all-solid-state secondary battery produced in Reference Example 2. [Figure 6B] 1 is a Nyquist plot showing the impedance measurement results of the all-solid-state secondary battery produced in Comparative Reference Example 2. [Figure 6C] 1 shows a charge / discharge profile of the all-solid-state secondary battery produced in Comparative Reference Example 2. [Figure 7A] 1 shows the charge / discharge profile of the all-solid-state secondary battery produced in Example 1. [Figure 7B] 1 shows a charge / discharge profile of the all-solid-state secondary battery produced in Comparative Example 1. [Figure 7C] 1 shows a charge / discharge profile of an all-solid-state secondary battery produced in Comparative Example 2. [Figure 7D] 10 is a charge / discharge profile of the all-solid-state secondary battery produced in Comparative Example 3. [Figure 7E] 1 shows the charge / discharge profile of the all-solid-state secondary battery produced in Example 3. [Figure 7F] 1 shows the charge / discharge profile of the all-solid-state secondary battery produced in Example 4. [Figure 8A] 1 shows an XRD spectrum of a negative electrode active material powder separated by disassembling the all-solid-state secondary battery produced in Example 1 after completion of charge and discharge. [Figure 8B] 1 shows an XRD spectrum of a negative electrode active material powder separated by disassembling the all-solid-state secondary battery produced in Comparative Example 1 after completion of charging and discharging. 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 and eventually penetrates the solid electrolyte layer, which can cause a battery short circuit. Also, when metal ions contained in the solid electrolyte are reduced at the interface between the solid electrolyte layer and the anode layer, a decomposition reaction of the solid electrolyte progresses, resulting in the generation and growth of conductors in the solid electrolyte layer, which can cause a battery short circuit.

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

[0012] As used herein, "Argyrodite-type" or "Argyrodite structure" refers to a compound having an isostructure with argyrodite, Ag8GeS6.

[0013] In this specification, the term "thin" in thin film refers to a film having a thickness of 1 nm to 100 μm. In this specification, the terms "first metal" and "second metal" include both metals and semi-metals.

[0014] The present inventive concept described below can be modified in various ways and can have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the inventive concept to a specific embodiment, and it should be understood that the inventive concept includes all modifications, equivalents, or alternatives that fall within the technical scope of the inventive concept.

[0015] The terms used below are merely used to describe specific embodiments and are not intended to limit the inventive idea. The singular expressions include the plural expressions unless the context clearly dictates otherwise. It should be understood that the terms "comprise" or "have" below indicate the presence of a feature, number, step, operation, component, part, ingredient, material, or combination thereof described in the specification, but do not preclude the presence or additional possibility 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.

[0016] In the drawings, thicknesses of multiple layers and regions are exaggerated or reduced to clearly illustrate them. Similar parts are designated by the same reference numerals throughout the specification. Throughout the specification, when a layer, film, region, plate, or other part is described as being "on" or "above" another part, this includes not only when it is directly on top of the other part, but also when there is another part interposed therebetween. Throughout the specification, terms such as "first," "second," etc. are used to describe various components, but the components should not be limited by these terms. Terms are used only to distinguish one component from another. In 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.

[0017] Hereinafter, an all-solid-state secondary battery according to an example embodiment and a method for manufacturing the all-solid-state secondary battery will be described in more detail.

[0018] An all-solid-state secondary battery according to an embodiment includes 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, wherein the first negative electrode active material layer includes a first metal and the second negative electrode active material layer includes a second metal.

[0019] An all-solid-state secondary battery according to an embodiment includes: 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 metal, and a lithium ion reduction potential of the first metal is higher than that of the solid electrolyte. The second negative electrode active material layer includes a second metal, and a lithium solid solubility of the second metal is higher than that of the first metal.

[0020] The first metal contained in the first anode active material layer has a higher lithium ion reduction potential during charging than the solid electrolyte, thereby suppressing the reduction decomposition reaction of the solid electrolyte. Furthermore, the second metal contained in the second anode active material layer has a higher solid solubility of lithium in the second metal than the first metal, thereby allowing lithium introduced into the first anode active material layer to be easily dissolved in the second anode active material layer. This suppresses decomposition of the solid electrolyte at the interface between the solid electrolyte layer and the first anode active material layer, while also suppressing localized lithium deposition, allowing for the formation of a lithium deposition layer with a uniform surface. As a result, the stability of the solid electrolyte layer is increased during charge and discharge, enabling reversible deposition and dissolution of the lithium layer, thereby suppressing short-circuiting in the all-solid-state secondary battery and improving cycle performance.

[0021] The "lithium ion reduction potential" of a first metal is the potential at which the first metal reduces lithium ions to form a lithium-first metal alloy, such as a solid solution. In other words, it is the potential that the first metal maintains during charging. The lithium ion reduction potential of indium (In) metal is approximately 0.6 V (vs. Li). The lithium ion reduction potential of magnesium (Mg) metal is approximately 0.02 V (vs. Li). The "lithium ion reduction potential" of the first negative electrode active material layer is the potential at which the first negative electrode active material layer reduces lithium ions to form a lithium-first negative electrode active material alloy, such as a solid solution.

[0022] The "reduction potential of a solid electrolyte" is the potential at which the transition metal contained in the solid electrolyte is reduced, causing the decomposition reaction of the solid electrolyte to proceed. Alternatively, it can be expressed as the reductive decomposition potential of a solid electrolyte or the decomposition potential of a solid electrolyte. For example, the reduction potential of LLZO is approximately 0.05 V (vs. Li).

[0023] "Solid solubility of lithium in the first metal" refers to the maximum amount of lithium that can be dissolved (or solid-dissolved) in the first metal without forming an additional phase. The unit is at%. For example, in a lithium-indium alloy at 25°C, the amount of lithium that can be dissolved by indium is less than 2 at%. If the lithium content increases by more than 2 at%, a separate alloy phase such as LiIn will be formed. For example, in a lithium-silver alloy at 25°C, the amount of lithium that can be dissolved (or solid-dissolved) by silver without forming an additional phase is approximately 45 at%. If the lithium content increases by more than 45 at%, a separate alloy phase such as LiAg will be formed.

[0024] 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 and the negative electrode layer 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, 23a 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 metal, and the second negative electrode active material layer 23, 23a includes a second metal. The first metal has a higher lithium ion reduction potential than the solid electrolyte. The second metal has a higher lithium solid solubility than the first metal.

[0025] (negative electrode layer) 1 , the first negative electrode active material layer 22 includes a first metal, and the difference between the lithium ion reduction potential of the first negative electrode active material layer 22 and the reduction potential of the solid electrolyte is, for example, 0.01 V or more, 0.02 V or more, 0.05 V or more, 0.1 V or more, 0.2 V or more, or 0.3 V or more. For example, the difference between the lithium ion reduction potential of the first negative electrode active material layer 22 and the reduction potential of the solid electrolyte is, for example, 0.01 V to 2.0 V, 0.2 V to 1.5 V, or 0.3 V to 1.0 V. When the difference between the lithium ion reduction potential of the first negative electrode active material layer 22 and the reduction potential of the solid electrolyte is within such a range, the reductive decomposition reaction of the solid electrolyte during charge and discharge is efficiently suppressed.

[0026] The lithium ion reduction potential of the first anode active material layer 22 is, for example, 0.05 V or more, 0.1 V or more, 0.2 V or more, 0.3 V or more, 0.4 V or more, or 0.5 V or more relative to lithium metal. For example, the lithium ion reduction potential of the first metal contained in the first anode active material layer 22 is, for example, 0.05 V to 5 V, 0.1 V to 4.8 V, or 0.5 V to 4.5 V relative to lithium metal. For example, the lithium ion reduction potential of the first metal contained in the first anode active material layer 22 is, for example, 0.05 V to 4 V, 0.05 V to 3.5 V, 0.05 V to 3.0 V, 0.05 V to 2.5 V, 0.05 V to 2 V, 0.05 V to 1.5 V, or 0.05 V to 1.0 V relative to lithium metal. Since the first negative electrode active material layer 22 has such a high lithium ion reduction potential, the decomposition reaction of the solid electrolyte is suppressed.

[0027] The lithium ion reduction potential of the first metal is, for example, 0.05 V or more, 0.1 V or more, 0.2 V or more, 0.3 V or more, 0.4 V or more, or 0.5 V or more relative to lithium metal. For example, the lithium ion reduction potential of the first metal is, for example, 0.05 V to 5 V, 0.1 V to 4.8 V, or 0.5 V to 4.5 V relative to lithium metal. For example, the lithium ion reduction potential of the first metal contained in the first negative electrode active material layer 22 is, for example, 0.05 V to 4 V, 0.05 V to 3.5 V, 0.05 V to 3.0 V, 0.05 V to 2.5 V, 0.05 V to 2 V, 0.05 V to 1.5 V, or 0.05 V to 1.0 V relative to lithium metal. When the first metal has such a high lithium ion reduction potential, the decomposition reaction of the solid electrolyte is suppressed. The reduction potential or reductive decomposition potential of the solid electrolyte included in the solid electrolyte layer 30 is, for example, 0.2 V or less, 0.1 V or less, 0.09 V or less, 0.07 V or less, 0.05 V or less, 0.03 V or less, 0.02 V or less, or 0.01 V or more relative to lithium metal. For example, the reduction potential or reductive decomposition potential of the solid electrolyte is 0.001 V to 0.2 V, 0.005 V to 0.09 V, or 0.005 V to 0.01 V relative to lithium metal. When the solid electrolyte has such a low reduction potential, the solid electrolyte provides a wider electrochemically stable voltage window.

[0028] The lithium ion reduction potential of the first negative electrode active material layer 22 is higher than the lithium ion reduction potential of the second negative electrode active material layer 23. For example, the difference between the lithium ion reduction potential of the first negative electrode active material layer 22 and the lithium ion reduction potential of the second negative electrode active material layer 23 is 0.01 V or more, 0.02 V or more, 0.05 V or more, 0.1 V or more, 0.2 V or more, or 0.3 V or more. For example, the difference between the lithium ion reduction potential of the first negative electrode active material layer 22 and the lithium ion reduction potential of the second negative electrode active material layer 23 is 0.01 V to 4.9 V, 0.2 V to 4.5 V, or 0.3 V to 4.0 V, for example. Because the first anode active material layer 22 has a higher lithium ion reduction potential than the second anode active material layer 23, even when the lithium ion reduction potential of the second anode active material layer 23 is lower than the reduction potential of the solid electrolyte, the reductive decomposition reaction of the solid electrolyte due to the second anode active material layer 23 can be effectively suppressed. In addition, the second metal contained in the second anode active material layer 23 can be easily selected within a range that has a lower lithium ion reduction potential than the first anode active material layer 22 containing the first metal. For example, the lithium ion reduction potential of indium (In), which is the first metal, is about 0.6 V. For example, the lithium ion reduction potential of silver (Ag), which is the second metal, is about 0.2 V.

[0029] Alternatively, the lithium ion reduction potential of the first negative electrode active material layer 22 is lower than the lithium ion reduction potential of the second negative electrode active material layer 23. If the lithium ion reduction potential of the first negative electrode active material layer 22 is higher than the reduction potential of the solid electrolyte, the lithium ion reduction potential of the first negative electrode active material layer 22 is lower than the lithium ion reduction potential of the second negative electrode active material layer 23.

[0030] The lithium ion diffusion coefficient of the first negative electrode active material layer 22 is equal to or greater than the lithium ion diffusion coefficient of the second negative electrode active material layer 23. Because the first negative electrode active material layer 22 has a high lithium diffusion coefficient, lithium introduced into the first negative electrode active material layer 22 quickly moves to the second negative electrode active material layer 23, preventing local lithium deposition within the first negative electrode active material layer 22 or at the interface between the first negative electrode active material layer 22 and the solid electrolyte layer 30. The lithium ion diffusion coefficient of the first negative electrode active material layer 22 is, for example, 1×10 -14 cm 2 / sec or more, 1×10 -13 cm 2 / sec or more, 1×10 -12 cm 2 / sec or more, 1×10 -11 cm 2 / sec or more, 1×10 -10 cm 2 / sec or more, or 5×10 -10 cm 2 / sec or more. The lithium ion diffusion coefficient of the first negative electrode active material layer 22 or the first metal is, for example, 1×10 -16 cm 2 / sec or 1×10 -3 cm 2 / sec, 1×10 -15 cm 2 / sec or 1×10 -4 cm 2 / sec, 1×10 -14 cm 2 / sec or 5×10 -5 cm 2 / sec, 1×10 -13 cm 2 / sec or 5×10 -6 cm 2 / sec, or 1×10 -12 cm 2 / sec or 1×10 -7 cm 2 / sec. The lithium ion diffusion coefficient of the second negative electrode active material layer 23 is, for example, 1×10 -15 cm 2 / sec or more, 1×10 -14 cm 2 / sec or more, 1×10 -13 cm 2 / sec or more, 1×10 -12 cm 2 / sec or more, 1×10 -11 cm 2 / sec or more, or 5×10 -11 cm 2 / sec or more. The lithium ion diffusion coefficient of the second negative electrode active material layer 23 at 25° C. is, for example, 1×10 -16 cm 2 / sec or 1×10 -3 cm 2 / sec, 1×10 -15 cm 2 / sec or 1×10 -3 cm 2 / sec, 1×10 -12 cm 2 / sec or 1×10 -3 cm 2 / sec, or 1×10 -12 cm 2 / sec or x10 -4 cm 2 / sec.

[0031] The difference between the lithium solid solubility of the second metal contained in the second negative electrode active material layer 23 and the lithium solid solubility of the first metal contained in the first negative electrode active material layer 22 is, for example, 10 at% or more, 15 at% or more, 20 at% or more, 25 at% or more, 30 at% or more, 35 at% or more, 40 at% or more, 45 at% or more, or 50 at% or more. The difference between the lithium solid solubility of the second metal and the lithium solid solubility of the first metal is, for example, 10 at% to 60 at%, 20 at% to 55 at%, or 30 at% to 50 at%. When the difference in lithium solid solubility between the second metal and the first metal is within such a range, lithium introduced into the first negative electrode active material layer 22 containing the first metal is easily dissolved in the second metal active material layer containing the second metal. As a result, localized deposition of lithium at the interface between the first negative electrode active material layer 22 and the solid electrolyte layer is suppressed. The lithium solid solubility of the second metal is, for example, 10 at% or more, 15 at% or more, 20 at% or more, 25 at% or more, 30 at% or more, 35 at% or more, or 40 at% or more. The lithium solid solubility of the second metal is, for example, 10 at% to 70 at%, 20 at% to 60 at%, or 40 at% to 60 at%. When the second metal has a lithium solid solubility in the above range, lithium is easily dissolved and easily deposited. The solid solubility of lithium in the first metal is, for example, 40 at% or less, 30 at% or less, 20 at% or less, 10 at% or less, 5 at% or less, 3 at% or less, 20 at% or less, or 1 at% or less. The solid solubility of lithium in the first metal is, for example, 0.1 at% to 30 at%, 0.5 at% to 20 at%, or 0.5 at% to 5 at%.When the first metal has a lithium solid solubility in the above range, local precipitation of lithium is prevented between the first negative electrode active material layer 22 containing the first metal and the solid electrolyte layer.

[0032] The Mohs hardness of the second metal element contained in the second negative electrode active material layer 23 is equal to or higher than the Mohs hardness of the first metal element, and the Mohs hardness of the first metal element contained in the first negative electrode active material layer 22 is equal to or higher than the Mohs hardness of lithium. For example, the Mohs hardness of lithium is 0.6, the Mohs hardness of indium is 1.2, and the Mohs hardness of silver is 2.5. The difference in Mohs hardness between the first metal element and the second metal element is, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 1.0 or more, or 1.1 or more. The difference in Mohs hardness between the first metal element and the second metal element is, for example, 0.1 to 2.0, 0.2 to 1.5, or 0.5 to 1.1. The difference in Mohs hardness between the first metal element and lithium is, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 1.0 or more, or 1.1 or more. The difference in Mohs hardness between the first metal element and lithium is, for example, 0.1 to 2.0, 0.2 to 1.5, or 0.5 to 1.1. For example, the yield strength of the second metal contained in the second negative electrode active material layer 23 is the same as or higher than the yield strength of the first metal, and the yield strength of the first metal contained in the first negative electrode active material layer 22 is the same as or higher than the yield strength of lithium metal. Because the first metal has higher hardness than lithium, lithium can be easily dissolved in the first metal as a solid. Since the second metal has a higher strength than the first metal, when a laminate in which a solid electrolyte layer, a first metal layer, and a second metal layer are sequentially stacked is compressed, the first metal layer adheres more flexibly to the irregular surface of the solid electrolyte layer, thereby more efficiently reducing the interfacial resistance between the solid electrolyte layer 30 and the first anode active material layer 22.

[0033] The first metal contained in the first negative electrode active material layer 22 is, 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), zinc (Zn), gold (Au), platinum (Pt), palladium (Pd), iron (Fe), cobalt (Co), chromium (Cr), cesium (Cs), cerium (Ce), and lanthanum (La). The first metal is, for example, indium (In). When the first negative electrode active material layer 22 contains such a first metal, short-circuiting of the all-solid-state secondary battery is prevented and the cycle characteristics are improved.

[0034] The second metal contained in the second negative electrode active material layer 230 is, for example, one or more selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), aluminum (Al), bismuth (Bi), magnesium (Mg), tin (Sn), and zinc (Zn). When the second negative electrode active material layer 23 contains such a second metal, short-circuiting of the all-solid-state secondary battery is prevented and the cycle characteristics are improved. When the second negative electrode active material layer 23 is disposed between the first negative electrode active material layer 22 and the negative electrode current collector 21, for example, the deposition morphology of the third negative electrode active material layer 24 deposited between the second negative electrode active material layer 23 and the negative electrode current collector 21 is further flattened, further improving the cycle characteristics of the all-solid-state secondary battery 1. The first metal and the second metal are, for example, different from each other.

[0035] According to an embodiment, referring to FIGS. 1 and 2, at least one of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 includes a negative electrode active material in the form of a thin film, for example.

[0036] The first anode active material layer 22 includes an anode active material in the form of, for example, a thin film, and the thin-film anode active material includes a first metal. That is, the first metal may be used in the form of, for example, a thin film. The first anode active material layer 22 is, for example, a metal layer including at least one selected from the first metal, lithium metal, and an alloy of the first metal and lithium. For example, the first anode active material layer 22 is a metal layer formed of a thin film of the first metal, a metal layer including an alloy phase of the first metal and lithium, or a metal layer including the first metal phase, a lithium metal phase, and an alloy phase of the first metal and lithium. The first anode active material layer 22 includes only the first metal when assembled into a battery, but may additionally include lithium metal and an alloy of the first metal and lithium as charging and discharging are performed. The first anode active material layer 22 may, for example, not include a carbon-based material or an organic material. The first negative electrode active material layer 22 may not include a carbon-based material, such as a carbon-based negative electrode active material such as graphite or carbon black, or a carbon-based conductive material such as carbon nanofiber. The first negative electrode active material layer 22 may not include an organic material, such as a binder. The first negative electrode active material layer 22 is a metal layer made of, for example, a metal, a semi-metal, and / or an alloy thereof. By making the first negative electrode active material layer 22 a metal layer, side reactions caused by the carbon-based material and / or the organic material during the charge / discharge process are prevented. In one embodiment, the first negative electrode active material layer 22 is made of, for example, Li a M b (M is the first metal, 0 <a≦5、0<b≦4、a> b) and a Li-rich alloy phase. a M b (M is the first metal, 0 <a≦5、0<b≦4、a> The first negative electrode active material layer 22 does not contain a lithium-rich alloy phase indicated by b). Since the first negative electrode active material layer 22 does not contain a lithium-rich alloy phase, local precipitation of lithium at the interface between the first negative electrode active material layer 22 and the solid electrolyte layer due to the lithium-rich alloy phase can be effectively prevented. The lithium-rich alloy phase is, for example, Li2M, Li3M2, Li4M3, or Li5M4. M is the first metal.

[0037] The second anode active material layer 23 includes an anode active material in the form of, for example, a thin film, and the thin-film anode active material includes a second metal. That is, the second metal may be used in the form of, for example, a thin film. The second anode active material layer 23 may also be a metal layer including at least one selected from the group consisting of the second metal, lithium metal, and an alloy of the second metal and lithium. For example, the second anode active material layer 23 may be a metal layer including a thin film of the second metal, a metal layer including an alloy phase of the second metal and lithium, or a metal layer including a second metal phase, a lithium metal phase, and an alloy phase of the second metal and lithium. The second anode active material layer 23 includes only the second metal when assembled into a battery, but may additionally include lithium metal and an alloy of the second metal and lithium as charging and discharging are performed. The second anode active material layer 23 may, for example, be free of a carbon-based material and an organic material. The second negative electrode active material layer 23 may not contain a carbon-based material, for example, a carbon-based negative electrode active material such as graphite or carbon black, or a carbon-based conductive material such as carbon nanofiber. The second negative electrode active material layer 23 may contain an organic material such as a binder. The second negative electrode active material layer 23 may also be a metal layer made of a metal, a semi-metal, and / or an alloy thereof. By using the second negative electrode active material layer 23 as a metal layer, side reactions due to the carbon-based material and / or the organic material during the charge / discharge process may be prevented.

[0038] The thicknesses of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 are, independently of each other, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the positive electrode active material layer 12. The thicknesses of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 are, independently of each other, for example, 2.5% to 50%, 5% to 40%, or 5% to 20% of the thickness of the positive electrode active material layer 12. When the thickness of the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 is thinner than the positive electrode active material layer 12, the energy density of the all-solid-state secondary battery is improved.

[0039] The first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 containing a thin film negative electrode active material may have a thickness of, for example, 1 nm to 100 μm, 10 nm to 100 μm, 100 nm to 10 μm, 1 μm to 100 μm, 5 μm to 90 μm, 10 μm to 80 μm, 15 μm to 80 μm, 20 μm to 70 μm, 20 μm to 60 μm, 20 μm to 55 μm, or 20 μm to 50 μm. When the first negative electrode active material layer 22 and the second negative electrode active material layer 23 have a thickness within the above range, short circuits in the all-solid-state secondary battery are suppressed, and the cycle characteristics are improved. The first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 are disposed by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but are not necessarily limited to such methods, and any method capable of forming a negative electrode active material layer in the art is possible.

[0040] Furthermore, the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 containing a thin film negative electrode active material may have a thickness of, for example, 1 nm to 500 nm, 10 nm to 500 nm, 10 nm to 400 nm or less, 10 nm to 300 nm, 10 nm to 200 nm, 10 nm to 150 nm, or 10 nm to 100 nm. When the first negative electrode active material layer 22 and the second negative electrode active material layer 23 have a thickness within the above range, short circuits in the all-solid-state secondary battery are suppressed, and the cycle characteristics are improved. If the thickness of the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 is less than 1 nm, they are unlikely to function as negative electrode active material layers. If the thickness of the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 is excessively large, the energy density of the all solid state secondary battery 1 may decrease, and the internal resistance of the all solid state secondary battery 1 due to the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 may increase, thereby deteriorating the cycle characteristics of the all solid state secondary battery 1. The first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 may be disposed by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to such methods, and any method capable of forming a negative electrode active material layer in the art may be used.

[0041] For example, the thickness of the first negative electrode active material layer 22 containing the negative electrode active material in a thin film form is 1 μm to 100 μm, and the thickness of the second negative electrode active material layer 23 containing the negative electrode active material in a thin film form is 1 μm to 100 μm. For example, the thickness of the first negative electrode active material layer 22 containing the negative electrode active material in a thin film form is 1 nm to 500 μm, and the thickness of the second negative electrode active material layer 23 containing the negative electrode active material in a thin film form is 1 nm to 500 nm. For example, the thickness of the first negative electrode active material layer 22 containing the negative electrode active material in a thin film form is 1 μm to 100 μm, and the thickness of the second negative electrode active material layer 23 containing the negative electrode active material in a thin film form is 1 nm to 500 nm. For example, the first negative electrode active material layer 23 containing a negative electrode active material in a thin film form has a thickness of 1 nm to 500 nm, and the second negative electrode active material layer 23 containing a negative electrode active material in a thin film form has a thickness of 1 μm to 100 μm.

[0042] According to another embodiment, referring to FIGS. 1 and 2, at least one of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 includes, for example, a particulate negative electrode active material and a binder.

[0043] The particulate negative electrode active material contained in one or more of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 has 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 particulate negative electrode active material has an average particle size of, for example, 10 nm to 4 μm or less, 10 nm to 3 μm or less, 10 nm to 2 μm or less, 10 nm to 1 μm or less, or 10 nm to 900 nm or less. When the particulate negative electrode active material has an average particle size within the above range, reversible absorbing and / or desorbing of lithium during charging and discharging can be more easily performed. The average particle size of the second negative electrode active material is, for example, a median diameter (D50) measured using a laser particle size distribution analyzer.

[0044] The particulate negative electrode active material contained in the first negative electrode active material layer 22 and the second negative electrode active material layer 23 may include, for example, one or more selected from a carbon-based negative electrode active material and a metal or semi-metallic negative electrode active material. "Semi-metallic" refers to B, Si, Ge, As, Sb, Te, or a combination thereof. The particulate carbon-based negative electrode active material is, in particular, amorphous carbon. Examples of amorphous carbon include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene. Any material classified as amorphous carbon in the art may be used. Amorphous carbon is carbon with no or very low crystallinity and is distinguished from crystalline carbon or graphite-based carbon. The particulate metal or quasi-metallic negative electrode active material contained in the first negative electrode active material layer 22 includes, as the above-mentioned first metal, one or more selected from, for example, indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), zinc (Zn), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), magnesium (Mg), cesium (Cs), cerium (Ce), and lanthanum (La). The particulate metal or quasi-metallic negative electrode active material contained in the second negative electrode active material layer 23 includes, as the second metal, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). For example, nickel (Ni) does not form an alloy with lithium and is therefore not a metal or quasi-metallic negative electrode active material.

[0045] At least one of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 may contain, for example, one type of particulate negative electrode active material or a mixture of multiple different types of particulate negative electrode active materials. For example, the first negative electrode active material layer 22 may contain only first particles made of amorphous carbon, or may contain second particles made of one or more first 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), zinc (Zn), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), magnesium (Mg), cesium (Ce), and lanthanum (La). Alternatively, the first negative electrode active material layer 22 may include a mixture of first particles of amorphous carbon and second particles of one or more first metals 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), zinc (Zn), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), magnesium (Mg), cesium (Ce), and lanthanum (La). The content of the second particles may be 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 within the above range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0046] For example, the second negative electrode active material layer 23 may include only first particles made of amorphous carbon, or may include second particles made of one or more second metals selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the second negative electrode active material layer 23 may include a mixture of first particles made of amorphous carbon and second particles made of one or more second metals selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The content of the second particles may be 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 within the above range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0047] At least one of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 may include, for example, a binder. Examples of binders include, but are not limited to, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. Any binder commonly used in the art may be used. The binder may be a single binder or a plurality of different binders. For example, the first negative electrode active material layer 22 may be stabilized on the solid electrolyte layer 30 by including a binder. Furthermore, cracking of the first negative electrode active material layer 22 may be suppressed despite volume changes and / or relative position changes of the first negative electrode active material layer 22 during charge and discharge. For example, if the first anode active material layer 22 does not contain a binder, the first anode active material layer 22 can be easily separated from the solid electrolyte layer 30. Because lithium ions cannot move in the area where the first anode active material layer 22 separates from the solid electrolyte layer 30, the internal resistance of the all-solid-state secondary battery 1 increases. The first anode active material layer 22 is produced, for example, by applying a slurry containing dispersed materials for the first anode active material layer 22 to the solid electrolyte layer 30 and drying the slurry. By including a binder in the first anode active material layer 22, stable dispersion of the particulate anode active material within the slurry is possible. For example, when the slurry is applied to the solid electrolyte layer 30 by a screen printing method, clogging of the screen (e.g., clogging due to aggregates of the particulate anode active material) can be suppressed. By including a binder in the second anode active material layer 23, for example, the second anode active material layer 23 is stabilized on the first anode active material layer 22 or the anode current collector 21. Furthermore, despite a change in volume and / or relative position of the second negative electrode active material layer 23 during charge / discharge, cracking of the second negative electrode active material layer 23 is suppressed. For example, if the second negative electrode active material layer 23 does not contain a binder, the second negative electrode active material layer 23 may be easily separated from the first negative electrode active material layer 22 and / or the negative electrode current collector 21.Since electrons cannot move in the portion where the second anode active material layer 23 has separated from the anode current collector 21, the internal resistance of the all-solid-state secondary battery 1 increases. The second anode active material layer 23 is produced, for example, by applying a slurry in which materials constituting the second anode active material layer 23 are dispersed onto the first anode active material layer 22 or the anode current collector 21 and drying the slurry. By including a binder in the second anode active material layer 23, it is possible to stably disperse the particulate anode active material in the slurry. For example, when the slurry is applied onto the first anode active material layer 22 or the anode current collector 21 by screen printing, clogging of the screen (for example, clogging by agglomerates of the particulate anode active material) can be suppressed.

[0048] 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 constituting 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 can be made of one of the above-mentioned metals, or an alloy or coating material of two or more metals. The negative electrode current collector 21 can be, for example, in the form of a plate or foil.

[0049] One or more of the first negative electrode active material layer 22 and the second negative electrode active material layer 23 may further contain additives used in conventional all-solid-state secondary batteries 1, such as a filler, a dispersant, an ion conductive agent, etc.

[0050] The thickness of the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 containing the particulate negative electrode active material is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 containing the particulate negative electrode active material is, for example, 2.5% to 50%, 5% to 40%, or 5% to 20% of the thickness of the positive electrode active material layer 12. When the thickness of the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 is thinner than the thickness of the positive electrode active material layer 12, the energy density of the all-solid-state secondary battery 1 is improved.

[0051] The thickness of the first anode active material layer 22 and / or the second anode active material layer 23 containing the particulate anode active material is, for example, 1 μm to 20 μm, 2 μm to 10 μm, or 3 μm to 7 μm. When the first anode active material layer 22 and / or the second anode active material layer 23 containing the particulate anode active material has a thickness within the above range, short-circuiting of the all-solid-state secondary battery is suppressed and the cycle characteristics are improved. If the thickness of the first anode active material layer 22 and / or the second anode active material layer 23 containing the particulate anode active material is excessively increased, 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 first anode active material layer 22 and / or the second anode active material layer 23 increases, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0052] For example, the thickness of the first anode active material layer 22 containing the particulate anode active material is 1 μm to 20 μm, and the thickness of the second anode active material layer 23 containing the particulate anode active material is 1 μm to 20 μm, 2 μm to 15 μm, or 5 μm to 10 μm. For example, the thickness of the first anode active material layer 22 containing the thin film anode active material is 1 μm to 100 μm, and the thickness of the second anode active material layer 23 containing the particulate anode active material is 1 μm to 20 μm, 2 μm to 15 μm, or 5 μm to 10 μm. For example, the thickness of the first anode active material layer 22 containing the thin film anode active material is 1 nm to 500 nm, and the thickness of the second anode active material layer 23 containing the particulate anode active material is 1 μm to 20 μm. For example, the thickness of the first negative electrode active material layer 22 containing the particulate negative electrode active material is 1 μm to 20 μm, and the thickness of the second negative electrode active material layer 23 containing the thin film negative electrode active material is 1 μm to 100 μm. For example, the thickness of the first negative electrode active material layer 22 containing the particulate negative electrode active material is 1 μm to 20 μm, and the thickness of the second negative electrode active material layer 23 containing the thin film negative electrode active material is 1 nm to 500 nm.

[0053] 3 and 4, the all-solid-state secondary battery 1 further includes a third anode active material layer 24, which is disposed, for example, between the anode current collector 21 and the second anode active material layer 23, between the first anode active material layer 22 and the second anode active material layer 23, or between the solid electrolyte layer 30 and the first anode active material layer 22 during charging. The third anode active material layer 24 is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the third anode active material layer 24 is a metal layer containing lithium, it functions as a lithium reservoir, for example. Examples of lithium alloys include, but are not limited to, Li-Al alloys, Li-Sn alloys, Li-In alloys, Li-Ag alloys, Li-Au alloys, Li-Zn alloys, Li-Ge alloys, and Li-Si alloys, and any alloy commonly used as a lithium alloy in the art may be used. The third negative electrode active material layer 24 may be made of one of the above alloys, lithium, or a combination of alloys.

[0054] The thickness of the third negative electrode active material layer 24 is not particularly limited, and may be, for example, 1 μm to 1000 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 23 is excessively thin, it is difficult for the third negative electrode active material layer 24 to perform its role as a lithium reservoir. If the thickness of the third negative electrode active material layer 24 is excessively thick, the mass and volume of the all-solid-state secondary battery 1 increase, which may actually degrade the cycle characteristics. The third negative electrode active material layer 24 may be, for example, a metal foil having a thickness within the above range.

[0055] In the all solid state secondary battery 1, the third negative electrode active material layer 24 is, for example, disposed between the negative electrode current collector 21 and the second negative electrode active material layer 23 before assembly of the all solid state secondary battery 1, or disposed between the first negative electrode active material layer 22 and the second negative electrode active material layer 23. On the other hand, in the all solid state secondary battery 1, the third negative electrode active material layer 24 is, for example, deposited between the negative electrode current collector 21 and the second negative electrode active material layer 23 by charging after assembly of the all solid state secondary battery 1, or deposited between the first negative electrode active material layer 22 and the second negative electrode active material layer 23.

[0056] When the third anode active material layer 24 is disposed between the anode current collector 21 and the second anode active material layer 23, or when the third anode active material layer 24 is disposed between the first anode active material layer 22 and the second anode active material layer 23, before assembling the all-solid-state secondary battery 1, the third anode active material layer 24 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 24 are further improved. For example, before assembling the all-solid-state secondary battery 1, a lithium foil is disposed between the anode current collector 21 and the second anode active material layer 23, or a lithium foil is disposed between the first anode active material layer 22 and the second anode active material layer 23.

[0057] When the third anode active material layer 24 is disposed by charging after the all solid state secondary battery 1 is assembled, the energy density of the all solid state secondary battery 1 increases because the third anode active material layer 24 is not included when the all solid state secondary battery 1 is assembled. For example, when the all solid state secondary battery 1 is charged, it is charged beyond the charge capacity of the first anode active material layer 22 and the second anode active material layer 23. That is, the first anode active material layer 22 and 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 the second anode active material layer 23. That is, the anode active materials contained in the first anode active material layer 22 and the second anode active material layer 23 form 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 the second anode active material layer 23 are charged beyond their capacities, 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 24. On the other hand, when the first anode active material layer 22 and the second anode active material layer 23 are charged beyond their capacities, 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 24. The third anode active material layer 24 is a metal layer mainly composed of lithium (i.e., metallic lithium). As a result, for example, the anode active materials contained in the first anode active material layer 22 and the second anode active material layer 23 are obtained by being composed of a material that forms an alloy or compound with lithium. During discharge, lithium in the first negative electrode active material layer 22, the second negative electrode active material layer 23, and the third negative electrode active material layer 24, i.e., the metal layers, is ionized and moves toward the positive electrode layer 10. Therefore, lithium can be used as the negative electrode active material in the all-solid-state secondary battery 1. Furthermore, the first negative electrode active material layer 22 and / or the second negative electrode active material layer 23 coat the third negative electrode active material layer 24, thereby serving as a protective layer for the third negative electrode active material layer 24, i.e., the metal layer, and also serving to suppress the precipitation and growth of lithium dendrites. Therefore, short circuits and capacity reduction of the all-solid-state secondary battery 1 are suppressed, and as a result, the cycle characteristics of the all-solid-state secondary battery 1 are improved.

[0058] The thickness of the first negative electrode active material layer 22 is, for example, 5% to 150%, 10% to 120%, 20% to 100%, 30% to 80%, or 33% to 66% of the thickness of the third negative electrode active material layer 24 in a charged state. If the thickness of the first negative electrode active material layer 22 is excessively thin, it is difficult for the first negative electrode active material layer 22 to function as the first negative electrode active material layer 22. 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 may decrease.

[0059] Furthermore, when the third negative electrode active material layer 24 is disposed by charging after the all solid state secondary battery 1 is assembled, 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, for example, Li-free regions that do not contain lithium (Li) in the initial state or post-discharge state of the all solid state secondary battery.

[0060] According to an embodiment, an all-solid-state secondary battery includes: a cathode layer including a cathode active material; 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 includes: an anode current collector; a first anode active material layer in contact with the solid electrolyte layer; a second anode active material layer disposed between the anode current collector and the first anode active material layer; and a third anode active material layer disposed between the solid electrolyte and the anode current collector. The third anode active material layer includes lithium or a lithium alloy. The first anode active material layer includes a first metal, and a lithium ion reduction potential of the first anode active material layer is higher than that of the solid electrolyte. The second anode active material layer includes a second metal, and the second metal has a higher solid solubility of lithium in the second metal than that of the first metal. The third anode active material layer is a plated layer. For example, the third negative electrode active material layer may be composed of lithium. The third negative electrode active material layer may be disposed, for example, between the negative electrode current collector and the second negative electrode active material layer, between the first negative electrode active material layer and the second negative electrode active material layer, and between the solid electrolyte and the first negative electrode active material layer. A deposition layer may be disposed between the negative electrode current collector and the solid electrolyte layer upon charging of the all-solid-state battery.

[0061] protected electrode The protective anode includes a current collector; a first layer; a second layer disposed between the current collector and the first layer; and a solid electrolyte, wherein the first layer includes a first metal, and the lithium ion reduction potential of the first layer is higher than the reduction potential of the solid electrolyte, and the second layer includes a second metal, and the solid solubility of lithium in the second metal is higher than the solid solubility of lithium in the first metal.

[0062] The first layer corresponds to the first negative electrode active material layer, and the second layer corresponds to the second negative electrode active material layer, each of which is as described above. In one aspect, a lithium-protected negative electrode is electrochemically provided, for example, by charging.

[0063] (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.

[0064] 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≦1 0≦y≦1),Li x La y TiO3(0 <x<2,0<y<3),Li2O,LiOH,Li2CO3,LiAlO2,Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2,Li 3+x La3M2O 12 (M=Te, Nb, or Zr, x is an integer between 1 and 10). The solid electrolyte is produced by a sintering method or the like. For example, an oxide-based solid electrolyte is Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 The garnet-type solid electrolyte is selected from the group consisting of M-doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer of 1 to 10, and 0≦a<2.

[0065] Alternatively, the solid electrolyte may be, for example, a sulfide-based solid electrolyte, such as Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, or Li2S-P2S5-Z m S n ,m,n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q ,p,q are positive numbers, M is one of P, Si, Ge, B, Al, GaIn, Li 7-x PS 6-x Cl x,0≦x≦2,Li 7-x PS 6-x Br x ,0≦x≦2, and Li 7-x PS 6-x I x , 0≦x≦2. The sulfide-based solid electrolyte is prepared by processing starting materials such as Li2S and P2S5 by a melt quenching method or a mechanical milling method. After the above-described processing, a heat treatment may be performed. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0066] Furthermore, the sulfide-based solid electrolyte may contain, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements of the sulfide-based solid electrolyte material described above. For example, the sulfide-based solid electrolyte may also be a material containing Li2S-P2S5. When a sulfide-based solid electrolyte material containing Li2S-P2S5 is used, the molar ratio of Li2S to P2S5 is, for example, in the range of about Li2S:P2S5=50:50 to 90:10.

[0067] The sulfide-based solid electrolyte is also a compound having an argyrodite crystal structure. Compounds having an argyrodite-type crystal structure include, for example, 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.

[0068] 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 of the solid electrolyte layer 30 may be the same as or different from the binders of the positive electrode active material layer 12 and the negative electrode active material layer 22.

[0069] (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.

[0070] The positive electrode layer 12 contains, for example, a positive electrode active material. The positive electrode active material is a positive electrode active material that reversibly absorbs and desorbs 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 aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate; nickel sulfide, copper sulfide, lithium sulfide, iron oxide, and vanadium oxide. Any positive electrode active material commonly used in the art can be used. The positive electrode active material may be used alone or in combination.

[0071] Lithium transition metal oxides include, for example, Li a A 1-b B b D2 (wherein 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-α F2 (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 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 F2 (wherein, 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 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1); Li a Ni b Co c Mn d GeO2 (wherein 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1); Li a NiG b O2 (wherein 0.90≦a≦1, 0.001≦b≦0.1); Li a CoG b O2 (wherein 0.90≦a≦1, 0.001≦b≦0.1); Li a MnG b O2 (wherein 0.90≦a≦1, 0.001≦b≦0.1); Li a Mn2Gb O4 (wherein 0.90≦a≦1, 0.001≦b≦0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Fe2(PO4)3 (0≦f≦2); LiFePO4. In these compounds, 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. Compounds with a coating layer added to the surface of these compounds can also be used, or mixtures of the above compounds with a coating layer added can also be used. The coating layer added to the surface of these compounds can include, for example, a coating element compound such as an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of the coating element. The compound forming such a coating layer can be amorphous or crystalline. The coating element contained in the coating layer can be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating layer formation method can be selected within a range that does not adversely affect the physical properties of the positive electrode active material. Examples of the coating method include spray coating and dipping. Specific coating methods are readily understood by those skilled in the art, so detailed description will be omitted.

[0072] 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 above-described lithium transition metal oxides. The "layered rock salt type structure" is, for example, a structure in which oxygen atom layers and metal atom layers are regularly arranged in the <111> direction of a cubic rock salt type structure, whereby each atom layer forms a two-dimensional plane. The "cubic rock salt type structure" indicates a sodium chloride type (NaCl type) structure which is a kind of crystal structure. Specifically, it indicates a structure in which face-centered cubic lattices (fcc) formed by cations and anions are displaced from each other by about 1 / 2 of the ridge of a 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) (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1) or LiNi x Co y Mn z O2 (NCM) (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1) and other ternary lithium transition metal oxides. 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.

[0073] The positive electrode active material is also covered by a coating layer as described above. Any coating layer can be used as long as it is known as a coating layer for the positive electrode active material of an all-solid-state secondary battery. The coating layer is, for example, Li2O-ZrO2 or the like.

[0074] When the positive electrode active material contains nickel (Ni) in a ternary lithium transition metal oxide such as NCA or NCM, for example, it is possible to increase the capacity density of the all-solid-state secondary battery 1 and reduce the metal elution of the positive electrode active material in the charged state. As a result, the cycle characteristics of the all-solid-state secondary battery 1 in the charged state are improved.

[0075] The shape of the positive electrode active material is, for example, spherical, oval, or other granular shape. The particle size of the positive electrode active material is not particularly limited, and is within the range applicable to positive electrode active materials in conventional all-solid-state secondary batteries. 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 positive electrode layers in conventional all-solid-state secondary batteries.

[0076] In addition to the above-described positive electrode active material, the positive electrode layer 10 may further contain additives such as a conductive agent, a binder, a filler, a dispersant, and an ion-conducting aid. Examples of such conductive agents include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and metal powder. Examples of binders include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. Known materials commonly used in electrodes for solid-state secondary batteries can be used as coating agents, dispersants, and ion-conducting aids that can be incorporated into the positive electrode layer 10.

[0077] The positive electrode layer 10 may further include a solid electrolyte. The solid electrolyte included in the positive electrode layer 10 may be similar to or different from the solid electrolyte included in the solid electrolyte layer 30. For details about the solid electrolyte, please refer to the solid electrolyte layer 30 section.

[0078] The solid electrolyte included in the positive electrode layer 10 is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be the same as that used in the solid electrolyte layer.

[0079] Alternatively, the positive electrode layer 10 may be impregnated with, for example, a liquid electrolyte. The liquid electrolyte may include one or more of a lithium salt, an ionic liquid, and a polymeric ionic liquid. The liquid electrolyte is also non-volatile. An ionic liquid refers to a salt or a room-temperature molten salt that has a melting point below room temperature and is in a liquid state at room temperature and is composed only of ions. The ionic liquid is a liquid electrolyte that contains A) one or more cations selected from ammonium, pyrrolidium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and BF4 - ,PF6 - ,AsF6 - ,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-propylpyrrolidium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidium 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, pyrrolidium, 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 - ,(O(CF3)2C2(CF3)2O)2PO - The lithium salt may include repeating units 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 in 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 containing the liquid electrolyte.

[0080] A method for manufacturing an all-solid-state secondary battery according to another embodiment includes the steps of providing a solid electrolyte layer 30, disposing a first anode active material layer 22 containing a first metal on one surface of the solid electrolyte layer 30, disposing a second anode active material layer 23 containing a second metal on the first anode active material layer 22, and disposing a cathode active material layer 12 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 circuits in the all-solid-state secondary battery 1 are suppressed and the cycle characteristics of the all-solid-state secondary battery 1 are improved. The all-solid-state secondary battery 1 is manufactured by, for example, first manufacturing the solid electrolyte layer 30 and the cathode layer 10, each of which includes the first anode active material layer 22 and the second anode active material layer 23 stacked sequentially, and then stacking these layers.

[0081] In one embodiment, a method for manufacturing an all-solid-state secondary battery includes: providing a solid electrolyte layer; disposing a first anode active material layer including a first metal on one surface of the solid electrolyte layer; disposing a second anode active material layer including a second metal on the first anode active material layer; disposing a cathode active material layer on the other surface of the solid electrolyte layer; and depositing a third anode active material layer by charging in one or more of between the solid electrolyte layer and the first anode active material layer, between the first anode active material layer and the second anode active material layer, and on one surface of the second anode active material layer that is not in contact with the first anode active material layer.

[0082] (Manufacturing solid electrolyte layer / negative electrode layer stacks) The first negative electrode active material layer can be prepared by coating one surface of the solid electrolyte layer with a first metal by sputtering, vacuum deposition, plating, or other methods. The first negative electrode active material layer can be prepared by placing a foil of the first metal on one surface of the solid electrolyte layer and applying pressure. The pressing method can be, for example, roll pressing, flat pressing, warm isotactic pressing (WIP), or cold isotactic pressing (CIP). However, the method is not limited to these methods and any pressing method commonly used in the art can be used. The pressure applied during pressing is, for example, 50 MPa to 500 MPa. The time for applying pressure is 5 ms to 10 min. Pressing can be performed at a temperature of, for example, room temperature to 90°C or less, such as 20 to 90°C. Alternatively, pressing can be performed at a high temperature of 100°C or higher. The second negative electrode active material layer may be manufactured in the same manner as the first negative electrode active material layer, except that a second metal is used. A negative electrode current collector is placed on the second negative electrode active material layer, and pressure is applied to manufacture a solid electrolyte layer 30 / negative electrode layer 20 laminate. Pressurization may be performed by, for example, roll pressing or flat pressing, but is not limited to these methods and any method commonly used in the art may be used. The pressure applied during pressurization is, for example, 50 MPa to 500 MPa. The time for applying pressure is 5 ms to 10 min. Pressurization may be performed at a temperature of room temperature to 90°C or lower, such as 20 to 90°C. Alternatively, pressurization may be performed at a high temperature of 100°C or higher.

[0083] The second negative electrode active material layer 23 may also be produced using a second negative electrode active material slurry. For example, a slurry is prepared by adding materials constituting the second negative electrode active material layer 23, such as second metal particles and a binder, to a polar or non-polar solvent. The prepared slurry is applied to the first negative electrode active material layer 22 of the prepared first stack of the solid electrolyte layer 30 / first negative electrode active material layer 22, and dried to prepare a second stack. Next, the negative electrode current collector 21 is placed on the dried second stack, and pressure is applied in the manner described above to prepare a stack of the solid electrolyte layer 30 / negative electrode layer 20.

[0084] (Production of positive electrode layer) A positive electrode active material, a binder, and other materials constituting the positive electrode active material layer 12 are added to a non-polar solvent to prepare a slurry. The prepared slurry is applied to a positive electrode current collector 11 and dried. The resulting laminate is pressed to prepare the positive electrode layer 10. The pressing method may be, for example, a roll press, a flat press, or a hydrostatic press. However, the pressing method is not limited to these methods and any pressing method commonly used in the art may be used. The pressing step may be omitted. The positive electrode layer 10 is prepared by compacting a mixture of materials constituting the positive electrode active material layer 12 into a pellet shape or by rolling (molding) it into a sheet shape. When preparing the positive electrode layer 10 using such a method, the positive electrode current collector 11 may be omitted. Alternatively, the positive electrode layer may be used by impregnating it with an electrolyte solution.

[0085] (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.

[0086] An oxide-based solid electrolyte is 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 pulverization. The stoichiometrically mixed precursor mixture may be subjected to a first heat treatment in an oxidizing atmosphere to prepare a first heat-treated product. The first heat treatment is performed at a temperature of less than 1000°C for 1 to 36 hours. The first heat-treated product is then pulverized. The first heat-treated product may be pulverized by either a dry or wet method. Wet pulverization may be performed by mixing the first heat-treated product with a solvent, such as methanol, and then milling it in a ball mill for 0.5 to 10 hours. Dry pulverization may be performed by milling it in a ball mill without a solvent. The pulverized first heat-treated product may have a particle size of 0.1 μm to 10 μm, or 0.1 μm to 5 μm. The pulverized first heat-treated product may be dried. The crushed primary heat treatment result is mixed with a binder solution and formed into pellets, or simply pressed under a pressure of 1 to 10 tons to form pellets.

[0087] The molded product may be subjected to a secondary heat treatment at a temperature of less than 1000°C for 1 to 36 hours. A sintered product, the solid electrolyte layer 30, is obtained by the secondary heat treatment. The secondary heat treatment is performed, for example, at a temperature of 550 to 1000°C. The primary 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 higher than the primary heat treatment temperature by 10°C or more, 20°C or more, 30°C or more, or 50°C or more. The molded product may be subjected to the 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.

[0088] 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.

[0089] Sulfide-based solid electrolytes are prepared by, for example, melt quenching or mechanical milling, but are not limited to these methods. Any method commonly used 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, formed into pellets, reacted at a predetermined reaction temperature under vacuum, 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 1000°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, or 1°C / sec to 1000°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 for the mechanical milling method are not particularly limited; however, a faster stirring speed increases the rate at which the sulfide-based solid electrolyte material is produced, and a longer stirring time increases the conversion rate of the raw materials to the sulfide-based solid electrolyte material. The mixed raw materials obtained by a melt quenching method, mechanical milling method, or the like are then heat-treated at a predetermined temperature and pulverized to produce a granular solid electrolyte. If the solid electrolyte has glass transition properties, it can be converted from amorphous to crystalline by heat treatment.

[0090] The solid electrolyte obtained in this manner is deposited by a known film formation method, such as aerosol deposition, cold spray, or sputtering, to produce the solid electrolyte layer 30. In another embodiment, the solid electrolyte layer 30 may be produced by pressing solid electrolyte particles alone. In yet another embodiment, the solid electrolyte layer 30 may be produced by mixing the solid electrolyte, a solvent, and a binder, applying the mixture, drying, and pressing.

[0091] (Manufacturing of all-solid-state secondary batteries) The positive electrode layer 10 and the negative electrode layer 20 / solid electrolyte layer 30 laminate prepared by the above-described method are laminated such that the positive electrode layer 10 and the negative electrode layer 20 are sandwiched between the solid electrolyte layer 30, and then pressurized to prepare an all-solid-state secondary battery 1.

[0092] For example, a second stack is prepared by placing a stack of the anode layer 20 / solid electrolyte layer 30 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 produce an all-solid-state secondary battery 10. Pressurization may be performed using, for example, a roll press, a flat press, or hydrostatic pressure, but is not limited to these methods and any method commonly used in the art can be used. The pressure applied during pressurization is, for example, 50 MPa to 750 MPa, 100 MPa to 600 MPa, or 200 MPa to 500 MPa. The time for applying pressure is 5 ms to 5 min, or 30 seconds to 2 minutes. Pressurization is performed, for example, at a temperature between room temperature and 90°C or lower, or at a temperature between 20 and 90°C. Alternatively, pressurization 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 an example of an embodiment, and the components and fabrication procedures can be appropriately changed. Pressurization may be omitted.

[0093] The present invention will be explained 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.

[0094] Reference example 1: Li-In alloy / LLZO / Li asymmetric half cell LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12An LLZO pellet was prepared. A 50 μm thick indium (In) foil and a 20 μm thick lithium (Li) foil were sequentially placed on one side of the LLZO pellet, and an indium-lithium alloy precursor layer was deposited by cold isotactic pressing (CIP) at 25°C and applying 250 MPa. The LLZO pellet with the alloy precursor layer was heat-treated at 150°C for 5 hours to fabricate a first electrode consisting of an indium-lithium alloy layer containing an In phase and a LiIn alloy phase.

[0095] A 20 μm thick lithium foil was placed on the opposite side of the LLZO pellet, and a lithium layer, which served as the second electrode, was attached by applying 250 MPa at 25°C using cold isotactic pressing (CIP) to fabricate an asymmetric cell with a first electrode / solid electrolyte / second electrode structure.

[0096] Cu foil current collectors were placed on the first electrode and the second electrode, respectively, and the asymmetric cell was sealed. Parts of the first electrode current collector and the second electrode current collector were protruded outside the sealed asymmetric cell and used as the first electrode terminal and the second electrode terminal.

[0097] Comparison reference example 1: Li-Mg alloy / LLZO / Li asymmetric half cell LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12 A 500 μm thick magnesium-lithium alloy (Li 75 wt% - Mg 25 wt%) foil was placed on one side of the LLZO pellet, and a magnesium-lithium alloy electrode was attached by cold isotactic pressing (CIP) at 25°C under a pressure of 250 MPa.

[0098] A 20 μm thick lithium foil was placed on the opposite side of the LLZO pellet, and a lithium layer, which served as the second electrode, was attached by applying 250 MPa at 25°C using cold isotactic pressing (CIP) to fabricate an asymmetric cell with a first electrode / solid electrolyte / second electrode structure.

[0099] Cu foil current collectors were placed on the first electrode and the second electrode, respectively, and the asymmetric cell was sealed. Parts of the first electrode current collector and the second electrode current collector were protruded outside the sealed asymmetric cell and used as the first electrode terminal and the second electrode terminal.

[0100] Reference example 2: Li-In alloy / LLZO / NCM full cell (Manufacturing of solid electrolyte layer / negative electrode layer laminate) LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12 An LLZO pellet was prepared. A 50 μm thick indium (In) foil and a 20 μm thick lithium (Li) foil were sequentially placed on one side of the LLZO pellet, and an indium-lithium alloy precursor layer was deposited by cold isotactic pressing (CIP) at 25°C and applying 250 MPa. The LLZO pellet with the alloy precursor layer was heat-treated at 150°C for 5 hours to prepare a negative electrode consisting of an indium-lithium alloy layer containing an In phase and a LiIn alloy phase.

[0101] A 10 μm-thick anode current collector made of a SUS304 thin film was placed on the indium-lithium alloy layer anode, and the anode current collector was attached by applying 250 MPa at 25°C using cold isotactic pressing (CIP), to prepare a solid electrolyte layer / anode layer laminate.

[0102] (Positive electrode layer manufacturing) LiNi as the positive electrode active material 0.8 Co 0.15 Mn 0.05O2 (NCM) was prepared. Polytetrafluoroethylene (Teflon (registered trademark) binder manufactured by DuPont) was prepared as a binder. Carbon nanofibers (CNF) were 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. This positive electrode active material sheet was then pressure-bonded to a positive electrode current collector made of 18 μm thick aluminum foil to prepare a positive electrode layer.

[0103] The positive electrode active material layer thus prepared was immersed in an electrolyte solution in which 2.0M of LiFSI was dissolved in Pyr13FSI (N-propyl-N-methyl-pyrrolidinium bis(fluorosulfonyl)imide), an ionic liquid.

[0104] (Manufacturing of all-solid-state secondary batteries) The positive electrode layer was placed inside the SUS cap with the positive electrode active material layer impregnated with an ionic liquid electrolyte facing upward. The solid electrolyte layer / negative electrode layer stack was placed so that the solid electrolyte layer was placed on top of the positive electrode active material layer, and the resulting assembly was sealed to produce an all-solid-state secondary battery.

[0105] The positive electrode layer and the negative electrode layer were insulated by an insulator. Parts of the positive electrode current collector and the negative electrode current collector were protruded outside the sealed battery and used as positive electrode layer terminals and negative electrode layer terminals.

[0106] Comparative Example 2: Li-Mg alloy / LLZO / NCM full cell (Manufacturing of solid electrolyte layer / negative electrode layer laminate) LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12A 500 μm thick magnesium-lithium alloy (Li 75 wt% - Mg 25 wt%) foil was placed on one side of the LLZO pellet, and a 10 μm thick copper thin film negative electrode current collector was placed on the magnesium-lithium alloy layer negative electrode. A pressure of 250 MPa was applied at 25°C by cold isotactic pressing (CIP) to attach the negative electrode current collector, preparing a solid electrolyte layer / negative electrode layer laminate.

[0107] (Manufacturing of positive electrode layers and all-solid-state secondary batteries) A positive electrode layer and an all-solid-state secondary battery were manufactured in the same manner as in Reference Example 2, except that the solid electrolyte layer / negative electrode layer stack prepared above was used.

[0108] Example 1: First layer (In, 50 μm) / second layer (Ag, 100 nm) multilayer structure (Manufacturing of solid electrolyte layer / negative electrode layer laminate) LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12 A LLZO pellet was prepared. A 50 μm-thick indium (In) foil was placed on one side of the LLZO pellet, and a first negative electrode active material layer, an indium metal layer, was deposited by cold isostatic pressing (CIP) at 25°C under a pressure of 250 MPa. A 100 nm-thick silver (Ag) layer, which served as a second negative electrode active material layer, was coated on the indium metal layer by sputtering. A 10 μm-thick copper (Cu) foil negative electrode current collector was placed on the silver (Ag) layer, and a negative electrode current collector was attached by cold isostatic pressing (CIP) at 25°C under a pressure of 250 MPa, preparing a solid electrolyte layer / negative electrode layer stack.

[0109] (Positive electrode layer manufacturing) LiNi as the positive electrode active material 0.8 Co 0.15 Mn 0.05O2 (NCM) was prepared. Polytetrafluoroethylene (Teflon (registered trademark) binder manufactured by DuPont) was prepared as a binder. Carbon nanofibers (CNF) were 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. This positive electrode active material sheet was then pressure-bonded to a positive electrode current collector made of 18 μm thick aluminum foil to prepare a positive electrode layer.

[0110] The positive electrode active material layer thus prepared was immersed in an electrolyte solution in which 2.0M of LiFSI was dissolved in Pyr13FSI (N-propyl-N-methyl-pyrrolidinium bis(fluorosulfonyl)imide), an ionic liquid.

[0111] (Manufacturing of all-solid-state secondary batteries) The positive electrode layer was placed inside the SUS cap so that the positive electrode active material layer impregnated with the ionic liquid electrolyte faced upward. The solid electrolyte layer / negative electrode layer laminate, in which the negative electrode layer was attached, was placed so that the solid electrolyte layer was placed on 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 insulator. Parts of the positive electrode current collector and the negative electrode current collector were protruded outside the sealed battery and used as positive electrode layer terminals and negative electrode layer terminals.

[0112] Comparative Example 1: First layer (In, 50 μm) single layer structure An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the step of coating a 100 nm thick silver (Ag) metal layer as the second negative electrode active material layer was omitted, and only a 50 μm thick indium (In) metal layer as the first negative electrode active material layer was coated.

[0113] Comparative Example 2: Second layer (Ag, 100 nm) single layer structure An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the step of coating a 50 μm thick indium (In) metal layer as the first negative electrode active material layer was omitted, and only a 100 nm thick silver (Ag) layer as the second negative electrode active material layer was coated on one side of the LLZO pellet.

[0114] Comparative example 3: 1st layer (Ag, 100nm) / 2nd layer (In, 50μm) multilayer structure LLZO(Li 6.5 La3Zr 1.5 Ta 0.5 O 12 An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that a 100 nm thick silver (Ag) metal layer was first coated on one side of the pellet as a first negative electrode active material layer, and then a 50 μm thick indium (In) metal layer was coated on the other side as a second negative electrode active material layer to form a solid electrolyte / silver layer / indium layer structure.

[0115] Example 2: First layer (In, 50 μm) / Second layer (Ag+FB, 5 μm) (Manufacturing of solid electrolyte layer / negative electrode layer laminate) LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12 A 50 μm thick indium (In) foil was placed on one side of the LLZO pellet, and a pressure of 250 MPa was applied at 25°C by cold isotactic pressing (CIP) to deposit an indium metal layer, which was the first negative electrode active material layer.

[0116] Furnace black (FB) with a primary particle size of approximately 30 nm and silver (Ag) particles with an average particle size of approximately 60 nm were prepared as the second negative electrode active material. 3 g of furnace black (FB) and 1 g of silver particles were placed in a container, and 4 g of NMP solution containing 5 wt% PVDF binder (Kureha #9300) was added to prepare a mixed solution. Next, NMP was gradually added to the mixed solution while stirring the mixed solution to prepare a slurry. The prepared slurry was applied to the indium metal layer using a blade coater, dried in air at 80°C for 20 minutes, and then vacuum-dried at 100°C for 12 hours to prepare a second negative electrode active material layer 23. The thickness of the second negative electrode active material layer was approximately 5 μm.

[0117] A negative electrode current collector made of a 10 μm-thick SUS304 thin film was placed on the second negative electrode active material layer, and the negative electrode current collector was attached by applying 250 MPa at 25°C using cold isotactic pressing (CIP), thereby preparing a solid electrolyte layer / negative electrode layer laminate.

[0118] (Positive electrode layer manufacturing) LiNi as the positive electrode active material 0.8 Co 0.15 Mn 0.05 O2 (NCM) was prepared. Polytetrafluoroethylene (Teflon (registered trademark) binder manufactured by DuPont) was prepared as a binder. Carbon nanofibers (CNF) were 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 pressure-bonded to a positive electrode current collector made of 18 μm thick aluminum foil to prepare a positive electrode layer.

[0119] The positive electrode active material layer thus prepared was immersed in an electrolyte solution in which 2.0M of LiFSI was dissolved in Pyr13FSI (N-propyl-N-methyl-pyrrolidinium bis(fluorosulfonyl)imide), an ionic liquid.

[0120] (Manufacturing of all-solid-state secondary batteries) The positive electrode layer was placed inside the SUS cap so that the positive electrode active material layer, which was impregnated with an ionic liquid electrolyte, faced upward. The solid electrolyte layer / negative electrode layer laminate, in which the negative electrode layer was attached, was placed 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 negative electrode layer were insulated with an insulator. Portions of the positive electrode current collector and negative electrode current collector protruded outside the sealed battery to serve as the positive electrode layer terminal and negative electrode layer terminal.

[0121] Example 3: First layer (LiIn, 40 μm) / second layer (Au, 100 nm) multilayer structure An all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that a 40 μm-thick lithium-indium alloy (LiIn) foil was used as the first negative electrode active material layer instead of a 50 μm-thick indium (In) foil, and a 100 nm-thick gold (Au) metal layer was coated as the second negative electrode active material layer instead of a 100 nm-thick silver (Ag) metal layer. Example 4: First layer (LiIn, 40 μm) / second layer (Ag, 20 nm) multilayer structure An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that a 40 μm-thick lithium-indium alloy (LiIn) foil was used as the first negative electrode active material layer instead of a 50 μm-thick indium (In) foil, and a 20 nm-thick silver (Ag) metal layer was used as the second negative electrode active material layer instead of a 100 nm-thick silver (Ag) metal layer.

[0122] Evaluation example 1: Interface stability evaluation 0.2 mA / cm at 60°C for the asymmetric cells prepared in Reference Example 1 and Comparative Example 1 2 The first electrode (negative electrode) was charged at a current of 0.05V for 2 hours. The asymmetric cell of Reference Example 1 stably maintained a voltage of 0.2 V or higher during charging.

[0123] On the other hand, the asymmetric cell of Comparative Reference Example 1 had an initial charging potential of 0.005 V, and a short circuit occurred 40 minutes after the start of charging, making further charging impossible.

[0124] After the charging was completed, the cross sections of the asymmetric cells of Reference Example 1 and Comparative Reference Example 1 were measured with a scanning electron microscope to observe the interface between the solid electrolyte and the first electrode (negative electrode).

[0125] As shown in FIG. 5A, the interface between the first electrode (negative electrode) and the solid electrolyte in Reference Example 1 remained stable without any decomposition reaction of the solid electrolyte.

[0126] The first electrode, which is an indium-lithium alloy contained in the asymmetric cell of Reference Example 1, exhibited a voltage drop of about 0.2 V (vs. Li / Li) during charging. + ) or higher (a potential higher than the reduction potential of LLZO, i.e., approximately 0.05 V (vs. Li), which is the potential at which the reductive decomposition reaction of the solid electrolyte begins), thereby suppressing decomposition of the solid electrolyte.

[0127] On the other hand, as shown in FIG. 5B, it was confirmed that a shaded area was generated at the interface between the first electrode (negative electrode) and the solid electrolyte in Comparative Reference Example 1 due to the decomposition reaction of the solid electrolyte.

[0128] The first electrode, which is a magnesium-lithium alloy contained in the asymmetric cell of Reference Example 1, exhibited a voltage drop of about 0.02 V (vs. Li / Li) during charging. + ) (a potential lower than the reduction potential of LLZO, i.e., approximately 0.05 V (vs. Li), which is the potential at which the reductive decomposition reaction of the solid electrolyte begins), thus promoting the decomposition of the solid electrolyte.

[0129] Evaluation example 2: Interface resistance evaluation The full cells produced in Reference Example 2 and Comparative Reference Example 2 were measured for their initial interface resistance and after 100 hours had elapsed.

[0130] The impedance of the pellets was measured by the two-probe method using an impedance analyzer (Solartron 1400A / 1455A impedance analyzer) for the full cells produced in Reference Example 2 and Comparative Reference Example 2. The frequency range was 0.1 Hz to 1 MHz, and the amplitude voltage was 10 mV.

[0131] The measurements were taken in an air atmosphere at 25° C. Nyquist plots of the impedance measurement results are shown in FIGS. 6A and 6B. As shown in FIG. 6A, the full cell of Reference Example 2 showed no change in the resistance of the solid electrolyte even after 100 hours had passed.

[0132] On the other hand, as shown in FIG. 6B, in the full cell of Comparative Reference Example 2, the resistance of the solid electrolyte was 13 Ωcm after 100 hours. 2 ~33Ωcm 2 increased by more than 100%.

[0133] Therefore, in the full cell of Comparative Reference Example 2, by using a negative electrode having a lithium ion reduction potential lower than the reduction potential of the solid electrolyte, the solid electrolyte undergoes a reduction and decomposition reaction, increasing the resistance.

[0134] In the full cell of Reference Example 2, it was confirmed that there was no change in resistance because the solid electrolyte was stable by using a negative electrode having a lithium ion reduction potential higher than the reduction potential of the solid electrolyte.

[0135] Evaluation example 3: Charge / discharge test (I) The charge-discharge characteristics of the all-solid-state secondary batteries prepared in Reference Example 2 and Comparative Reference Example 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.

[0136] 0.3mA / cm until the battery voltage reaches 4.2V in the first cycle 2 The battery was charged at a constant current of 0.3mA / cm until the battery voltage reached 2.8V. 2 The charge and discharge conditions were set so that the battery was discharged at a constant current of 1000 kJ / s.

[0137] However, as shown in FIG. 6C, a short circuit occurred during the charging process in the first cycle. Therefore, in the full cell of Comparative Reference Example 2, it was confirmed that the use of a negative electrode having a lithium ion reduction potential lower than the reduction potential of the solid electrolyte caused the solid electrolyte to undergo a reductive decomposition reaction, and as a result, stable operation of the battery was not possible.

[0138] Although not shown in the drawings, the all-solid-state secondary battery manufactured in Reference Example 2 was charged and discharged under the same charge and discharge conditions as Comparative Reference Example 2 (i.e., 0.3 mA / cm 2 conditions) and charge / discharge current of 0.5mA / cm 2 , and 1.0 mA / cm 2 Under the changed conditions, charging and discharging were performed without short circuit.

[0139] Therefore, in the full cell of Reference Example 2, it was confirmed that by employing a negative electrode having a lithium ion reduction potential higher than the reduction potential of the solid electrolyte, the reductive decomposition reaction of the solid electrolyte is suppressed, and as a result, stable operation of the battery is possible.

[0140] Evaluation Example 4: Charge / Discharge Test (II) The charge-discharge characteristics of the all-solid-state secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 3 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 thermostatic chamber at 60°C.

[0141] The first cycle was 0.3 mA / cm until the battery voltage reached 3.6 V or 4.2 V. 2 The battery was then charged at a constant current of 0.3 mA / cm until the battery voltage reached 2.2 V. 2 Discharge was carried out at a constant current of .

[0142] The second cycle was 0.5 mA / cm until the battery voltage reached 3.6 V or 4.2 V. 2 The battery was then charged at a constant current of 0.5 mA / cm until the battery voltage reached 2.2 V. 2 Discharge was carried out at a constant current of .

[0143] The third cycle was 0.7 mA / cm until the battery voltage reached 3.6 V or 4.2 V. 2The battery was then charged at a constant current of 0.7 mA / cm until the battery voltage reached 2.2 V. 2 Discharge was carried out at a constant current of .

[0144] The fourth cycle was 1.0 mA / cm until the battery voltage reached 3.6 V or 4.2 V. 2 The battery was then charged at a constant current of 1.0 mA / cm until the battery voltage reached 2.2 V. 2 Discharge was carried out at a constant current of .

[0145] Some of the charge / discharge results are shown in Figures 7A, 7B, and 7C. 7A, the all-solid-state secondary battery of Example 1 had a first anode active material layer in contact with the solid electrolyte layer and having a lithium ion reduction potential higher than the reduction decomposition potential of the solid electrolyte, and sequentially included a second anode active material layer having a higher lithium solid solubility than the first anode active material layer, thereby exhibiting stable charge and discharge without capacity degradation over the entire constant current range, i.e., excellent high-rate characteristics.

[0146] That is, it was determined that this is because the first anode active material layer suppresses the decomposition reaction of the solid electrolyte while maintaining a stable interface, and the first anode active material layer has a low lithium solid solubility and a high lithium diffusion coefficient, which allows lithium introduced into the first anode active material layer to quickly diffuse to the interface between the first anode active material layer and the second anode active material layer, thereby suppressing a local increase in lithium concentration at the interface between the solid electrolyte and the first anode active material layer, and the lithium diffused to the interface between the first anode active material layer and the second anode active material layer is easily dissolved in the second anode active material layer, which has high solid solubility, thereby inducing lithium to be precipitated between the second anode active material layer and the anode current collector.

[0147] 8A, after completing the fourth charge-discharge cycle of the all-solid-state secondary battery of Example 1, the battery was disassembled and the negative electrode surface was analyzed by XRD. As a result, it was confirmed that the first negative electrode active material layer contained a LiIn phase. That is, it was confirmed that the excess lithium was dissolved in the silver (Ag) layer, which is the second negative electrode active material layer with high lithium solid solubility.

[0148] 7B, the all-solid-state secondary battery of Comparative Example 1 has only the first anode active material layer (In layer), which suppresses the decomposition reaction of the solid electrolyte and prevents short circuits. However, because the all-solid-state secondary battery of Comparative Example 1 does not have the first anode active material layer (Ag layer), the lithium introduced into the first anode active material layer cannot further diffuse, resulting in non-uniform deposition of lithium within the first anode active material layer and isolation of lithium within the first anode active material layer, resulting in a rapid decrease in high-rate discharge capacity.

[0149] As shown in FIG. 8B, after completing the fourth charge / discharge cycle of the all-solid-state secondary battery of Comparative Example 1, the battery was disassembled and the negative electrode surface was analyzed by XRD. As a result, it was confirmed that the first negative electrode active material layer contained a LiIn phase.

[0150] After completing the second cycle charge of the all solid state secondary battery of Comparative Example 1, the composition of the first negative electrode active material layer was analyzed and found to be Li 27 at % and In 73 at %.

[0151] As shown in FIG. 7C, the all-solid-state secondary battery of Comparative Example 2, which had only the second negative electrode active material layer (Ag layer), was normally charged and discharged in the first cycle, but a short circuit occurred in the second cycle.

[0152] After the first cycle charging of the all solid state secondary battery of Comparative Example 2 was completed, the composition of the second negative electrode active material layer was analyzed and found to be Li 99 at % and Ag 1 at %.

[0153] As shown in FIG. 7D, in the all-solid-state secondary battery of Comparative Example 3 in which Ag was used for the first negative electrode active material layer and In was used for the second negative electrode active material layer, a silver (Ag) layer with a higher lithium solid solubility was used for the first negative electrode active material layer. As a result, lithium was not deposited in the second negative electrode active material layer (In layer) but was deposited at the interface between the solid electrolyte and the negative electrode, resulting in a short circuit during the third cycle.

[0154] Although not shown in the drawings, the all-solid-state secondary battery of Example 2 also exhibited stable charge-discharge characteristics. As shown in FIG. 7E, the all-solid-state secondary battery of Example 3 also exhibited stable charge-discharge characteristics. As shown in FIG. 7F, the all-solid-state secondary battery of Example 4 also exhibited stable charge-discharge characteristics. As described above, the all-solid-state secondary battery according to this embodiment can be applied to various portable devices, cars, and the like.

[0155] Although an exemplary embodiment has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an embodiment. 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 concept set forth 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]

[0156] 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, 23a Second negative electrode active material layer 24 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 metal, and a lithium ion reduction potential of the first negative electrode active material layer is higher than a reduction potential of the solid electrolyte; the second negative electrode active material layer contains a second metal, and the second negative electrode active material layer has a higher lithium solid solubility than the first negative electrode active material layer.

2. 2. The all-solid-state secondary battery according to claim 1, wherein the first negative electrode active material layer has a lithium ion reduction potential of 0.05 V to 2.5 V (vs. Li).

3. the lithium ion diffusion coefficient of the first negative electrode active material layer is equal to or greater than the lithium ion diffusion coefficient of the second negative electrode active material layer at 25°C; The lithium ion diffusion coefficient in the first negative electrode active material layer is 1×10 at 25° C. －１６ cm ２ / sec to 1 x 10 －３ cm ２ The all-solid-state secondary battery according to claim 1 or 2, wherein the charge-discharge time is 1 / sec.

4. 4. The all-solid-state secondary battery according to claim 1, wherein a difference between the lithium solid solubility of the second metal and the lithium solid solubility of the first metal is 10 at% or more.

5. The Mohs hardness of the second metal is equal to or higher than the Mohs hardness of the first metal; The all-solid-state secondary battery according to claim 1 , wherein the Mohs hardness of the first metal is equal to or higher than the Mohs hardness of lithium.

6. 6. The all-solid-state secondary battery according to claim 1, wherein the first metal includes one or more selected from indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), zinc (Zn), gold (Au), platinum (Pt), palladium (Pd), iron (Fe), cobalt (Co), chromium (Cr), cesium (Cs), cerium (Ce), and lanthanum (La).

7. 7. The all-solid-state secondary battery according to claim 1, wherein the second metal includes one or more selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), aluminum (Al), bismuth (Bi), magnesium (Mg), tin (Sn), and zinc (Zn).

8. 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 contains a film-like negative electrode active material.

9. the first negative electrode active material layer includes at least one selected from the first metal, lithium metal, and an alloy of the first metal and lithium; The all-solid-state secondary battery according to claim 8 , wherein the second negative electrode active material layer contains at least one selected from the second metal, lithium metal, and an alloy of the second metal and lithium.

10. a thickness of at least one of the first negative electrode active material layer and the second negative electrode active material layer is 50% or less of a thickness of the positive electrode active material layer; 10. 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 has a thickness of 10 nm to 100 μm.

11. The all-solid-state secondary battery according to claim 10, wherein at least one of the first negative electrode active material layer and the second negative electrode active material layer has a thickness of 10 nm to 500 nm.

12. 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 contains a plurality of particulate negative electrode active materials and a binder.

13. The all-solid-state secondary battery according to claim 12 , wherein the average particle size of the plurality of particles is 4 μm or less.

14. the particulate negative electrode active material comprises at least one selected from amorphous carbon, metal, and semi-metal; The all-solid-state secondary battery according to claim 12 or 13, wherein the first metal and the second metal each independently comprise a metal or a semi-metal.

15. the particulate negative electrode active material comprises a mixture of first particles made of amorphous carbon and second particles made of a metal, a semi-metal, or a combination thereof; The all-solid-state secondary battery of claim 14 , wherein the content of the second particles is 8 to 60 wt % based on the total weight of the mixture.

16. 16. The all-solid-state secondary battery according to claim 12, wherein at least one of the first negative electrode active material layer and the second negative electrode active material layer has a thickness of 1 μm to 20 μm.

17. a third negative electrode active material layer disposed between the negative electrode current collector and the second negative electrode active material layer, between the first negative electrode active material layer and the second negative electrode active material layer, and between the solid electrolyte and the first negative electrode active material layer; The all-solid-state secondary battery according to claim 1 , wherein the third negative electrode active material layer contains lithium or a lithium alloy.

18. 18. The all-solid-state secondary battery according to claim 17, wherein the first negative electrode active material layer thickness is 5% to 150% of the third negative electrode active material layer thickness in a charged state, and the first negative electrode active material layer thickness and the third negative electrode active material layer thickness are determined in a charged state.

19. 19. 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.

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

21. The oxide 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 ≤ 1 0 ≤ 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 = Te, Nb, or Zr, x is an integer of 1 to 10).

22. The oxide 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 (M-doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer of 1 to 10).

23. where the sulfide solid electrolyte is Li ２ S - P ２ S ５ , Li ２ S - P ２ S ５ - LiX, where 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 , where 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 PO ４ , Li ２ S - SiS ２ - Li ｐ MO ｑ , where p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, In, Li ７－ｘ PS ６－ｘ Cl ｘ , where 0 ≤ x ≤ 2, Li ７－ｘ PS ６－ｘ Br ｘ , where 0 ≤ x ≤ 2, and Li ７－ｘ P.S. ６－ｘ I ｘ , 0≦x≦2. The all-solid-state secondary battery according to claim 20 .

24. The sulfide solid electrolyte includes an argyrodite-type solid electrolyte, and the argyrodite-type solid electrolyte contains 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 , 0≦x≦2. The all-solid-state secondary battery according to claim 20 .

25. a positive electrode layer including a positive electrode active material; 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; a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer; and a third negative electrode active material layer disposed between the solid electrolyte and the negative electrode current collector, the third negative electrode active material layer containing lithium or a lithium alloy, the first negative electrode active material layer contains a first metal, and a lithium ion reduction potential of the first negative electrode active material layer is higher than a reduction potential of the solid electrolyte; the second negative electrode active material layer contains a second metal, and the second negative electrode active material layer has a higher lithium solid solubility than the first negative electrode active material layer; The all-solid-state secondary battery, wherein the third negative electrode active material layer is a precipitated layer.

26. 26. The all-solid-state secondary battery according to claim 25, wherein the third negative electrode active material layer is made of lithium.

27. 27. The all-solid-state secondary battery according to claim 25 or 26, wherein the third negative electrode active material layer is disposed in one or more of between the negative electrode current collector and the second negative electrode active material layer, between the first negative electrode active material layer and the second negative electrode active material layer, and between the solid electrolyte and the first negative electrode active material layer.

28. providing a solid electrolyte layer; disposing a first negative electrode active material layer including a first metal on one surface of the solid electrolyte layer; disposing a second negative electrode active material layer including a second metal 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 first negative electrode active material layer contains a first metal, and a lithium ion reduction potential of the first negative electrode active material layer is higher than a reduction potential of the solid electrolyte; the second negative electrode active material layer contains a second metal, and a lithium solid solubility of the second negative electrode active material layer is higher than a lithium solid solubility of the first negative electrode active material layer.

29. providing a solid electrolyte layer; disposing a first negative electrode active material layer including a first metal on one surface of the solid electrolyte layer; disposing a second negative electrode active material layer including a second metal on the first negative electrode active material layer; disposing a positive electrode active material layer on the other surface of the solid electrolyte layer; depositing a third negative electrode active material layer by charging on at least one of a portion between the solid electrolyte layer and the first negative electrode active material layer, a portion between the first negative electrode active material layer and the second negative electrode active material layer, and a portion on a surface of the second negative electrode active material layer that is not in contact with the first negative electrode active material layer; the first negative electrode active material layer contains a first metal, and a lithium ion reduction potential of the first negative electrode active material layer is higher than a reduction potential of the solid electrolyte; the second negative electrode active material layer contains a second metal, and a lithium solid solubility of the second negative electrode active material layer is higher than a lithium solid solubility of the first negative electrode active material layer.

30. A current collector; The first layer, a second layer disposed between the current collector and the first layer; a solid electrolyte; the first layer contains a first metal, and a lithium ion reduction potential of the first layer is higher than a reduction potential of the solid electrolyte; The second layer comprises a second metal, and the second layer has a higher lithium solid solubility than the first layer.

31. 31. The protected anode of claim 30, wherein the second layer further comprises lithium.

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