All-solid secondary battery

Abstract

To provide an all-solid secondary battery.SOLUTION: An all-solid secondary battery includes a cathode layer, an anode layer, and a solid electrolyte layer between the cathode layer and the anode layer. The cathode layer includes a cathode current collector and a cathode active material layer on one surface of the cathode current collector. The anode layer includes an anode current collector and a first anode active material layer on one surface of the anode current collector. The first anode active material layer includes a first anode active material that can form an alloy or a compound with lithium, a second anode active material, and a fibrous carbon material. A ratio (B / A) of the initial charging capacity (B) of the first anode active material layer to the initial charging capacity (A) of the cathode active material layer is 0.01 to 0.75.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an all-solid-state secondary battery.

Background Art

[0002] In recent years, with the rapid spread of electronic devices that use batteries, such as mobile phones, notebook computers, and electric vehicles, the demand for secondary batteries with high energy density and high capacity has increased rapidly. For this reason, research and development for improving the performance of lithium secondary batteries have been actively promoted. A lithium secondary battery is a battery including a positive electrode containing an active material capable of intercalating and deintercalating lithium ions and a negative electrode, and an electrolyte. A lithium secondary battery produces electrical energy by oxidation and reduction reactions when lithium ions are intercalated into and deintercalated from the positive electrode and the negative electrode.

[0003] Recently, the development of batteries with high energy density and high safety has been actively carried out according to industrial requirements. For example, lithium batteries are used in various applications such as information devices, communication devices, and automobiles. Automobiles are related to life, and safety is also important.

[0004] A lithium battery that employs a liquid electrolyte may have an increased possibility of catching fire and / or exploding during a short circuit. Instead of a liquid electrolyte, an all-solid-state secondary battery that employs a solid electrolyte has been proposed. A solid electrolyte has a lower possibility of ignition than a liquid electrolyte.

[0005] An all-solid-state secondary battery can reduce the possibility of fire and explosion by employing a solid electrolyte instead of a liquid electrolyte. An all-solid-state battery can provide improved safety.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem to be solved by the present invention is to provide an all-solid-state secondary battery having improved cycle characteristics in which a negative electrode active material layer having an initial charge capacity smaller than that of the positive electrode active material layer includes a fibrous carbon-based material and a binder, thereby suppressing volume change during charge and discharge.

Means for Solving the Problem

[0007] According to one embodiment, including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on one surface of the positive electrode current collector, the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector, the first negative electrode active material layer includes a first negative electrode active material capable of forming an alloy or a compound with lithium, a second negative electrode active material, and a fibrous carbon-based material, the ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer is 0.01 to 0.75, the initial charge capacity of the positive electrode active material layer is determined by charging from the first open circuit voltage (1 st open circuit voltage) to the maximum charging voltage with respect to Li / Li + as a reference, and the initial charge capacity of the first negative electrode active material layer is determined by charging from the second open circuit voltage (2 nd open circuit voltage) to 0.01 V with respect to Li / Li + as a reference, and an all-solid-state secondary battery is provided.

[0008] According to one embodiment, including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on one surface of the positive electrode current collector, the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector, Provided is an all-solid-state secondary battery including a first negative electrode active material capable of forming an alloy or a compound with lithium, a second negative electrode active material, and a fibrous carbon-based material in a first negative electrode active material layer.

[0009] According to another embodiment, including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector, the positive electrode active material layer includes a lithium-containing sulfide-based positive electrode active material, and the lithium-containing sulfide-based positive electrode active material includes a Li2S-containing composite, Provided is an all-solid-state secondary battery in which the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

Advantages of the Invention

[0010] According to an embodiment of the present invention, in a negative electrode active material layer having an initial charge capacity smaller than that of the positive electrode active material layer, by including a fibrous carbon-based material and a binder, it is possible to provide an all-solid-state secondary battery having a reduced volume change during charge and discharge and improved cycle characteristics.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0012] Unless otherwise defined, all terms (including technical and scientific terms) used in this disclosure have the meanings as commonly understood by those of ordinary skill in the technical field to which this disclosure belongs. Also, terms defined as in a commonly used dictionary should be interpreted to have a meaning that conforms to the meaning in the context of the related art and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0013] The present disclosure is described based on cross-sectional views which are schematic views of exemplary embodiments. Thus, for example, deformations from the illustrated shapes must be expected as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described in this disclosure should not be construed as being limited to the specific shapes of the regions illustrated in this disclosure, and should include, for example, shape deviations that can be considered from manufacturing. For example, regions illustrated or described as flat may typically be rough and / or have non-linear features. Further, sharp corners illustrated may be rounded. Thus, the regions illustrated in the drawings are essentially schematic, and their shapes are not for showing the exact shape of the regions and are not intended to limit the scope of the claims.

[0014] This creative idea is embodied in various different forms and should not be construed as being limited to the embodiments described in this disclosure. The examples are provided so that this disclosure will be thorough and complete and will fully teach the scope of this creative idea to those of ordinary skill in the art. Like reference numerals refer to like elements.

[0015] When an element is referred to as being “on” another element, it will be understood that it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements therebetween.

[0016] Terms such as “first,” “second,” and “third” may be used herein to describe various elements, components, regions, layers, and / or sections, but these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another. Thus, a first element, component, region, layer, or section described below could be termed a second element, component, region, layer, or section without departing from the teachings of this disclosure.

[0017] The terms used in this disclosure are for the purpose of describing particular embodiments only and are not intended to be limiting of this creative idea. The singular forms used in this application include the plural forms as well, unless the content clearly dictates otherwise. “At least one” should not be construed as being limited to the singular. As used in this disclosure, the term “and / or” includes any and all combinations of one or more of the listed items. The terms “comprising” and / or “comprises” used in the detailed description specify the presence of the stated features, regions, integers, steps, operations, elements, and / or components, and do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0018] Spatially relative terms such as "lower", "lower side", "lower part", "upper", "upper side", "upper part" may be used herein to facilitate the description of the relationship of one component or feature to another component or feature. Spatially relative terms are to be understood as being intended to include different orientations of the device in addition to the orientation shown in the drawings when used or operating in additional directions. For example, if the device in the drawings is inverted, a component described as "lower" or "beneath" another component or feature will be oriented "above" the other component or feature. Accordingly, the exemplary term "beneath" can include both above and beneath. The device may be otherwise oriented (rotated 90 degrees or rotated in other directions), and the spatially relative terms used in this disclosure may be interpreted accordingly.

[0019] "Group" means a group of the periodic table according to the group classification system of the International Union of Pure and Applied Chemistry ("IUPAC") groups 1-18.

[0020] Unless otherwise defined herein, the particle size refers to the average particle size. Also, the particle size means the average particle size (D50), which is the diameter of the particle at a cumulative volume of 50% in the particle size distribution. The measurement of the average particle size (D50) is carried out by methods widely known to those skilled in the art. For example, it can be measured with a particle size analyzer, or measured from a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. As another method, it can be measured using a measuring device that uses the dynamic light-scattering method, perform data analysis, and calculate the result of counting the number of particles for each particle size range to obtain the average particle size (D50) value. Or it can be measured using the laser diffraction method. When measuring by the laser diffraction method, more specifically, after dispersing the particles to be measured in a dispersion medium, introduce them into a commercially available laser diffraction particle size measuring device (for example, Microtrac MT3000), irradiate with ultrasonic waves of about 28 kHz at an output of 60 W, and then calculate the average particle size (D50) based on the 50% standard of the particle size distribution in the measuring device.

[0021] In the present disclosure, "particle size" indicates the average diameter when the particle is spherical, and the average major axis length when the particle is non-spherical. "Average particle size" is, for example, D50 which is the median particle size.

[0022] D50 is the particle size corresponding to the 50% cumulative volume calculated from the side of the particles having a small particle size in the particle size distribution measured by the laser diffraction method.

[0023] D90 is the particle size corresponding to the 90% cumulative volume calculated from the side of the particles having a small particle size in the particle size distribution measured by the laser diffraction method.

[0024] D10 is the particle size corresponding to the 10% cumulative volume calculated from the side of the particles having a small particle size in the particle size distribution measured by the laser diffraction method.

[0025] In the present disclosure, "metal" includes both metals and metalloids such as silicon and germanium in elemental or ionic states.

[0026] In the present disclosure, "alloy" means a mixture of two or more metals.

[0027] In the present disclosure, "positive electrode active material" means an electrode material capable of lithiation and delithiation.

[0028] In the present disclosure, "positive electrode active material" means a positive electrode material capable of lithiation and delithiation.

[0029] In the present disclosure, "negative electrode active material" means a negative electrode material capable of lithiation and delithiation.

[0030] In the present disclosure, "lithiation" and "lithiate" mean the process of adding lithium to the positive electrode active material.

[0031] In the present disclosure, "delithiation" and "delithiate" mean the process of removing lithium from the positive electrode active material.

[0032] In the present disclosure, "charging" and "charge" mean the process of supplying electrochemical energy to the battery.

[0033] In the present disclosure, "discharging" and "discharge" mean the process of removing electrochemical energy from the battery.

[0034] In the present disclosure, "positive electrode" and "cathode" mean the electrode where electrochemical reduction and lithiation occur during the discharging process.

[0035] In the present disclosure, "negative electrode" and "anode" mean the electrode where electrochemical oxidation and delithiation occur during the discharging process.

[0036] Although specific embodiments have been described, at present, alternatives, modifications, variations, improvements, and substantial equivalents that are unforeseen or cannot be foreseen may be provided by the applicant or a person skilled in the art. Accordingly, the claims filed and amended are intended to include all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0037] Hereinafter, the all-solid-state secondary battery according to an exemplary embodiment will be described in more detail.

[0038] [All-solid-state secondary battery] An all-solid-state secondary battery according to an embodiment includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on one or both surfaces of the positive electrode current collector. The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector. The first negative electrode active material layer includes a first negative electrode active material, a second negative electrode active material, and a fibrous carbon-based material that can form an alloy or a compound with lithium. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer is 0.01 to 0.75. The initial charge capacity of the positive electrode active material layer is determined by charging from the first open circuit voltage (1 st open circuit voltage) to the maximum charging voltage with respect to Li / Li + . The initial charge capacity of the first negative electrode active material layer is determined by charging from the second open circuit voltage (2 nd open circuit voltage) to 0.01 V with respect to Li / Li + .

[0039] By providing a conductive path between the plurality of negative electrode active materials, the increase in the internal resistance of the first negative electrode active material layer can be more easily suppressed. The increase in the internal resistance of the all-solid-state secondary battery can be suppressed.

[0040] When the fibrous carbon-based material acts as a support / buffer among a plurality of negative electrode active materials, during charge and discharge, the volume change of the first negative electrode active material layer due to the precipitation and / or dissolution of lithium can be further easily alleviated. Therefore, during charge and discharge of the all-solid-state secondary battery, the volume change can be reduced.

[0041] By the binder binding the negative electrode active material and the fibrous carbon-based material, during the precipitation and / or dissolution process of lithium during charge and discharge, the disconnection of the conductive path between the negative electrode active material and the fibrous carbon-based material due to the volume change of the negative electrode active material can be more effectively suppressed. The non-uniformity of the electrode reaction of the all-solid-state secondary battery can be suppressed.

[0042] The binder can improve the binding force between the first negative electrode active material layer and the solid electrolyte layer, or between the first negative electrode active material layer and the current collector. For example, the binder can improve the wettability between the first negative electrode active material layer and the solid electrolyte layer, or between the first negative electrode active material layer and the current collector. Therefore, the increase in interface resistance due to void formation and the like between the first negative electrode active material layer and the solid electrolyte layer, or between the first negative electrode active material layer and the current collector, can be more effectively reduced. The cycle characteristics of the all-solid-state secondary battery can be improved.

[0043] When the binder is not included in the first negative electrode active material layer, the first negative electrode active material layer may be detached from the solid electrolyte layer and / or the negative electrode current collector, and thus the surface of the solid electrolyte layer and / or the negative electrode current collector may be exposed. For example, the exposed negative electrode current collector may cause a short circuit. The cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0044] Referring to FIGS. 1 to 12, the all-solid-state secondary battery 1 includes a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 between the positive electrode layer 10 and the negative electrode layer 20. The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 on one surface of the positive electrode current collector 11. The negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material layer 22 on one surface of the negative electrode current collector 21. The first negative electrode active material layer 22 includes a first negative electrode active material capable of forming an alloy or a compound with lithium, a second negative electrode active material, and a fibrous carbon-based material. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer is 0.01 to 0.75. The initial charge capacity of the positive electrode active material layer is determined by charging from the first open circuit voltage (1 st open circuit voltage) to the maximum charging voltage with respect to Li / Li + . The initial charge capacity of the first negative electrode active material layer is determined by charging from the second open circuit voltage (2 nd open circuit voltage) to 0.01 V with respect to Li / Li + .

[0045] [Negative electrode layer] [Negative electrode layer: First negative electrode active material] Referring to FIGS. 1 to 12, the negative electrode layer 20 includes a first negative electrode active material layer 22. The first negative electrode active material layer 22 includes a first negative electrode active material capable of forming an alloy or a compound with lithium.

[0046] The first negative electrode active material is, for example, a negative electrode material that forms an alloy with lithium or a negative electrode material that forms a compound with lithium.

[0047] The first negative electrode active material layer 22 contains a first negative electrode active material, and the first negative electrode active material is, for example, particulate. The size of the particulate first negative electrode active material is, for example, 2 μm or less, 1 μm or less, 500 nm or less, 300 nm or less, or 200 nm or less. The size of the particulate negative electrode active material is, for example, 100 nm to 2 μm, 100 nm to 2 μm, 200 nm to 2 μm, 500 nm to 2 μm, or 500 nm to 1.5 μm. On the other hand, the size of the particulate first negative electrode active material is, for example, 10 nm to 2 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having such a size range, the first negative electrode active material can more easily perform reversible absorption (absorbing) and / or desorption (desorbing) of lithium during charge and discharge. The size of the first negative electrode active material is, for example, the average particle diameter of the first negative electrode active material. The average particle diameter of the first negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer.

[0048] The aspect ratio of the first negative electrode active material is, for example, 5 or less, 4 or less, 3 or less, or 2 or less. The aspect ratio of the first negative electrode active material is, for example, 1 to 5, 1 to 4, 1 to 3, or 1 to 2. By having such an aspect ratio range, the first negative electrode active material can be more uniformly distributed within the first negative electrode active material layer 22. As a result, the non-uniformity of the volume change of the first negative electrode active material during charge and discharge can be suppressed. The aspect ratio of the first negative electrode active material can be measured, for example, with a scanning electron microscope.

[0049] The first negative electrode active material contained in the first negative electrode active material layer 22 includes, for example, a first metal-based negative electrode active material.

[0050] The first metal-based negative electrode active material includes, for example, silicon (Si), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof, but is not necessarily limited thereto. Any material can be used as long as it is a metal-based negative electrode active material that forms an alloy or compound with lithium in the relevant technical field. For example, nickel (Ni) does not form an alloy with lithium, so nickel (Ni) is not a metal-based negative electrode active material.

[0051] [Negative electrode layer: fibrous carbon-based material] The first negative electrode active material layer 22 contains a fibrous carbon-based material in addition to the first negative electrode active material.

[0052] The first negative electrode active material layer 22 contains a mixture of a first negative electrode active material that forms an alloy or compound with lithium and a fibrous carbon-based material. For example, the first negative electrode active material layer 22 contains a fibrous carbon-based material and a mixture of one or more first negative electrode active materials selected from the group consisting of silicon (Si), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the fibrous carbon-based material and the mixture such as silicon can be, for example, 99:1 to 1:99, 10:1 to 1:10, 1:1 to 1:9, 1:1 to 1:8, 1:1 to 1:7, 1:1 to 1:6, 1:1 to 1:5, 1:1 to 1:4, or 1:1 to 1:3 by weight, but is not necessarily limited to such a range and is selected according to the required characteristics of the all-solid-state secondary battery 1. When the fibrous carbon-based material and the negative electrode active material have such a composition, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0053] The first negative electrode active material layer 22 contains a mixture of first particles made of a metal and second particles made of a fibrous carbon-based material. The metal includes, for example, silicon (Si), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof. The content of the second particles is 1 to 99% by weight, 1 to 70% by weight, more than 10% to 70% by weight, 11 to 60% by weight, or 12 to 50% by weight based on the total weight of the mixture. When the fibrous carbon-based material has such a content range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0054] The size of the first negative electrode active material capable of forming an alloy or a compound with lithium is, for example, even smaller than the length of the fibrous carbon-based material. When the length of the fibrous carbon-based material is even larger than the size of the first negative electrode active material, the fibrous carbon-based material can act as a support and / or a buffer between a plurality of the first negative electrode active materials. By arranging the fibrous carbon-based material between a plurality of the first negative electrode active materials, the stress caused by the volume change of the first negative electrode active material due to the precipitation and / or dissolution of lithium during charge and discharge can be effectively alleviated. As a result, the volume change of the first negative electrode active material layer 22 during charge and discharge can be further effectively suppressed. The ratio of the size of the first negative electrode active material to the length of the fibrous carbon-based material may be, for example, 1:10 to 1:2000, 1:10 to 1:1000, 1:10 to 1:500, 1:10 to 1:200, 1:10 to 1:100, 1:10 to 1:50, or 1:10 to 1:20. When the ratio of the size of the first negative electrode active material to the length of the fibrous carbon-based material has such a range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0055] The fibrous carbon-based material may be, for example, a conductive carbon-based material. Since the fibrous carbon-based material has conductivity, a conductive path can be provided inside the first negative electrode active material layer 22. The fibrous carbon-based material can more effectively reduce the internal resistance of the first negative electrode active material layer 22. As a result, the cycle characteristics of the all-solid-state secondary battery 1 are improved. The first negative electrode active material layer 22 does not additionally contain other carbon-based conductive materials in addition to the fibrous carbon-based material. Since the first negative electrode active material layer 22 does not contain other carbon-based conductive materials in addition to the fibrous carbon-based material, the energy density of the first negative electrode active material layer 22 can be further improved.

[0056] The aspect ratio of the fibrous carbon-based material may be, for example, 10 or more, 20 or more, 30 or more, or 50 or more. The aspect ratio of the fibrous carbon-based material may be, for example, 2000 or less, 1000 or less, 500 or less, 200 or less, or 100 or less. The aspect ratio of the fibrous carbon-based material may be, for example, 10 to 2000, 20 to 2000, 30 to 2000, or 50 to 2000. The aspect ratio of the fibrous carbon-based material may be, for example, 10 to 2000, 10 to 1000, 10 to 500, 10 to 200, 10 to 100, 10 to 50, or 10 to 20. The aspect ratio of the fibrous carbon-based material is, for example, the ratio of the major axis length of the fibrous carbon-based material, that is, the minor axis length perpendicular to the major axis with respect to the length of the fibrous carbon-based material, that is, the diameter of the second carbon-based material. Since the fibrous carbon-based material has an aspect ratio within such a range, the conductive path inside the first negative electrode active material layer 22 can be made longer. By the fibrous carbon-based material forming a three-dimensional conductive network in the first negative electrode active material layer 22, the internal resistance of the first negative electrode active material layer 22 can be more effectively reduced. As a result, the internal resistance of the all-solid-state secondary battery 1 is reduced. For example, the high-rate characteristics of the all-solid-state secondary battery 1 may be improved.

[0057] The fibrous carbon-based material can include, for example, an amorphous fibrous carbon-based material, a crystalline fibrous carbon-based material, or a combination thereof. By including an amorphous fibrous carbon-based material in the fibrous carbon-based material, the side reaction between lithium and the fibrous carbon-based material can be more effectively suppressed. During charge and discharge of the all-solid-state secondary battery 1, the reversibility of the electrode reaction is improved, thereby improving the cycle characteristics of the all-solid-state secondary battery 1.

[0058] The diameter of the fibrous carbon-based material may be, for example, 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. The diameter of the fibrous carbon-based material may be, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. By having a diameter within such a range, the internal resistance of the first negative electrode active material layer 22 can be effectively reduced, and furthermore, it can be easily dispersed in the solvent and / or slurry during the production of the first negative electrode active material layer 22.

[0059] The length of the fibrous carbon-based material may be, for example, 1000 μm or less, 100 μm or less, 50 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, or 300 nm or less. The length of the fibrous carbon-based material may be, for example, 100 nm to 1000 μm, 100 nm to 500 μm, 100 nm to 100 μm, 100 nm to 50 μm, 100 nm to 10 μm, 100 nm to 5 μm, 100 nm to 2 μm, 100 nm to 1 μm, 100 nm to 500 nm, or 100 nm to 300 nm. The length of the fibrous carbon-based material may be, for example, 500 nm to 1000 μm, 500 nm to 500 μm, 500 nm to 100 μm, 500 nm to 50 μm, 500 nm to 10 μm, 1 μm to 10 μm, or 2 μm to 8 μm. The greater the length of the fibrous carbon-based material, the more the internal resistance of the electrode can be reduced.

[0060] The fibrous carbon-based material can include, for example, a fibrous carbon nanostructure. The fibrous carbon nanostructure can include, for example, carbon nanofibers, carbon nanotubes, carbon nanobelts, or a combination thereof.

[0061] The carbon nanotube can include, for example, a carbon nanotube primary structure, a carbon nanotube secondary structure formed by aggregation of a plurality of carbon nanotube primary particles, or a combination thereof.

[0062] The carbon nanotube primary structure is a single carbon nanotube unit. The carbon nanotube unit has a graphite sheet in a cylindrical form with a nanosize diameter and has an sp2 bonding structure. Depending on the curvature angle and structure of the graphite sheet, it can exhibit conductor characteristics or semiconductor characteristics. The carbon nanotube unit can be classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT) according to the number of walls forming the wall. That is, carbon nanotubes can be categorized into three main types or categories: single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT). The smaller the wall thickness of the carbon nanotube unit, the lower the resistance.

[0063] The primary carbon nanotube structure can include, for example, single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), multi-walled carbon nanotubes (MWCNTs), or combinations thereof. The diameter of the primary carbon nanotube structure can be, for example, 1 nm or more, or 2 nm or more. The diameter of the primary carbon nanotube structure can be, for example, 20 nm or less, or 10 nm or less. The diameter of the primary carbon nanotube structure can be, for example, 1 nm to 20 nm, 1 nm to 15 nm, or 1 nm to 10 nm. The length of the primary carbon nanotube structure can be, for example, 100 nm or more, or 200 nm or more. The length of the primary carbon nanotube structure can be, for example, 2 μm or less, 1 μm or less, 500 nm or less, or 300 nm or less. The length of the primary carbon nanotube structure can be, for example, 100 nm to 2 μm, 100 nm to 1 μm, 100 nm to 500 nm, 100 nm to 400 nm, 100 nm to 300 nm, or 200 nm to 300 nm. The diameter and length of the primary carbon nanotube structure can be measured from a scanning electron microscope (SEM) image or a transmission electron microscope (TEM) image. On the other hand, the diameter and / or length of the primary carbon nanotube structure can be measured by a laser diffraction method.

[0064] The carbon nanotube secondary structure is a structure formed by aggregating carbon nanotube primary structures so that they form a bundle type or rope type as a whole or in part. The carbon nanotube secondary structure can include, for example, bundle-type carbon nanotubes, rope-type carbon nanotubes, or combinations thereof. The diameter of the carbon nanotube secondary structure may be, for example, 2 nm or more, or 3 nm or more. The diameter of the carbon nanotube secondary structure may be, for example, 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. The diameter of the carbon nanotube secondary structure may be, for example, 2 nm to 50 nm, 2 nm to 30 nm, or 2 nm to 20 nm. The length of the carbon nanotube secondary structure may be, for example, 500 nm or more, 700 nm or more, 1 μm or more, or 10 μm or more. The length of the carbon nanotube secondary structure may be, for example, 1000 μm or less, 500 μm or less, or 100 μm or less. The length of the carbon nanotube secondary structure may be, for example, 500 nm to 1000 μm, 500 nm to 500 μm, 500 nm to 200 μm, 500 nm to 100 μm, 500 nm to 50 μm, 500 nm to 10 μm, 1 μm to 10 μm, or 2 μm to 8 μm. The diameter and length of the carbon nanotube secondary structure can be measured from a scanning electron microscope (SEM) image or an optical microscope. On the other hand, the diameter and / or length of the carbon nanotube secondary structure can be measured by a laser diffraction method.

[0065] The carbon nanotube secondary structure can be used, for example, in the production of the first negative electrode active material layer 22 after being dispersed in a solvent or the like and converted into a carbon nanotube primary structure.

[0066] [Negative electrode layer: Second negative electrode active material] Referring to FIGS. 1 to 12, the negative electrode layer 20 includes a first negative electrode active material layer 22. The first negative electrode active material layer 22 contains a second negative electrode active material.

[0067] The second negative electrode active material is, for example, a negative electrode material that forms an alloy with lithium or a negative electrode material that forms a compound with lithium. The second negative electrode active material is clearly distinguishable from the first negative electrode active material. The size of the second negative electrode active material is, for example, smaller than that of the first negative electrode active material. The size of the second negative electrode active material is, for example, 80% or less, 60% or less, 40% or less, 20% or less, or 10% or less of the size of the first negative electrode active material.

[0068] The first negative electrode active material layer 22 contains the second negative electrode active material, and the second negative electrode active material is, for example, in the form of particles. The size of the particulate second negative electrode active material is, for example, less than 1 μm, 500 nm or less, 300 nm or less, or 100 nm or less. The size of the particulate second negative electrode active material is, for example, from 10 nm to less than 1 μm, from 10 nm to 900 nm, from 10 to 700 nm, from 10 nm to 500 nm, from 10 nm to 300 nm, from 10 nm to 200 nm, or from 10 nm to 100 nm. By having such a size range for the second negative electrode active material, the second negative electrode active material can more easily perform reversible absorption (absorbing) and / or desorption (desorbing) of lithium during charge and discharge. The size of the second negative electrode active material is, for example, the average particle size of the second negative electrode active material. The average particle size of the second negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer.

[0069] The aspect ratio of the second negative electrode active material is, for example, 5 or less, 4 or less, 3 or less, or 2 or less. The aspect ratio of the second negative electrode active material is, for example, from 1 to 5, from 1 to 4, from 1 to 3, or from 1 to 2. By having such an aspect ratio range for the second negative electrode active material, it can be more uniformly distributed within the first negative electrode active material layer 22. As a result, the non-uniformity of the volume change during charge and discharge of the second negative electrode active material can be suppressed. The aspect ratio of the second negative electrode active material can be measured, for example, with a scanning electron microscope.

[0070] The second negative electrode active material contained in the first negative electrode active material layer 22 includes, for example, a carbon-based negative electrode active material, a second metal-based negative electrode active material distinguishable from the first negative electrode active material, or a combination thereof.

[0071] The carbon-based negative electrode active material includes, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0072] The carbon-based negative electrode active material is particularly amorphous carbon. Amorphous carbon includes, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., but is not necessarily limited thereto. In the technical field, any material classified as amorphous carbon can be used. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0073] The carbon-based negative electrode active material may be, for example, porous carbon. The pore volume of the porous carbon is, for example, 0.1 cc / g to 10.0 cc / g, 0.5 cc / g to 5 cc / g, or 0.1 cc / g to 1 cc / g. The average pore diameter of the porous carbon is, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The BET specific surface area of the porous carbon is, for example, 100 m 2 / g to 3000 m 2 / g.

[0074] The second metal-based negative electrode active material includes one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited thereto. In the technical field, any metal negative electrode active material or semi-metal negative electrode active material that forms an alloy or compound with lithium can be used. For example, nickel (Ni) does not form an alloy with lithium, so it is not a metal negative electrode active material.

[0075] The first negative electrode active material layer 22 contains one type of the second negative electrode active material among such second negative electrode active materials, or contains a mixture of a plurality of different second negative electrode active materials. For example, the first negative electrode active material layer 22 contains only amorphous carbon, or contains one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). On the other hand, the first negative electrode active material layer 22 contains a mixture of amorphous carbon and 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). The mixing ratio of the mixture of amorphous carbon and gold, etc. is by weight ratio, for example, 99:1 to 1:99, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to such a range and is selected according to the required characteristics of the all-solid-state secondary battery 1. When the second negative electrode active material has such a composition, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0076] The second negative electrode active material contained in the first negative electrode active material layer 22 contains, for example, a mixture of first particles made of amorphous carbon and second particles made of a second metal-based negative electrode active material. The second metal-based negative electrode active material contains, for example, gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), etc. The content of the second particles is 1 to 99% by weight, 1 to 60% by weight, 8 to 60% by weight, 10 to 50% by weight, 15 to 40% by weight, or 20 to 30% by weight based on the total weight of the mixture. When the second particles have a content within such a range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0077] On one hand, the first negative electrode active material layer 22 contains a second negative electrode active material, and the second negative electrode active material can include, for example, a composite negative electrode active material. The composite negative electrode active material can include, for example, a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support. By having such a structure for the composite negative electrode active material, the uneven distribution of the metal-based negative electrode active material is prevented within the first negative electrode active material layer 22, and a uniform distribution is obtained. As a result, the cycle characteristics of the all-solid-state secondary battery 1 including the first negative electrode active material layer 22 are further improved.

[0078] The metal-based negative electrode active material supported on the carbon-based support includes, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn), etc. The metal oxide includes, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, tellurium (Te) oxide, and zinc (Zn) oxide, etc. The metal oxide is, for example, Au x O y (0 < x ≤ 2, 0 < y ≤ 3), Pt x O y (0 < x ≤ 1, 0 < y ≤ 2), Pd x O y (0 < x ≤ 1, 0 < y ≤ 1), Ag x O y (0 < x ≤ 2, 0 < y ≤ 1), Al x O y (0 < x ≤ 2, 0 < y ≤ 3), Bi x O y (0 < x ≤ 2, 0 < y ≤ 3), Sn x O y (0 < x ≤ 1, 0 < y ≤ 2), Te x O y (0 < x ≤ 1, 0 < y ≤ 3), Zn x O y (0 < x ≤ 1, 0 < y ≤ 1), or can include a combination thereof. The composite of a metal and a metal oxide is, for example, Au and Au x O yComposite of (0 < x ≤ 2, 0 < y ≤ 3), Pt and Pt x O y Composite of (0 < x ≤ 1, 0 < y ≤ 2), Pd and Pd x O y Composite of (0 < x ≤ 1, 0 < y ≤ 1), Ag and Ag x O y Composite of (0 < x ≤ 2, 0 < y ≤ 1), Al and Al x O y Composite of (0 < x ≤ 2, 0 < y ≤ 3), Bi and Bi x O y Composite of (0 < x ≤ 2, 0 < y ≤ 3), Sn and Sn x O y Composite of (0 < x ≤ 1, 0 < y ≤ 2), Te and Te x O y (0 < x ≤ 1, 0 < y ≤ 3), Zn and Zn x O y It can include a composite of (0 < x ≤ 1, 0 < y ≤ 1), or a combination thereof.

[0079] The carbon-based support is, for example, amorphous carbon. Amorphous carbon is, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, etc., but is not necessarily limited thereto. In the technical field, any material classified as amorphous carbon can be used. Amorphous carbon is distinguished from crystalline carbon or graphite-based carbon as carbon that has no crystallinity or very low crystallinity.

[0080] The composite negative electrode active material is, for example, particulate. The particle size of the particulate composite negative electrode active material is, for example, 10 nm to 2 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having a particle size in such a range, the reversible absorption (absorbing) and / or desorption (desorbing) of lithium during charge and discharge becomes easier. The metal-based negative electrode active material supported on the support is, for example, particulate. The particle size of the metal-based negative electrode active material may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 5 nm to 100 nm, or 10 nm to 50 nm. The carbon-based support is, for example, particulate. The particle size of the carbon-based support may be, for example, 10 nm to 2 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having a particle size in such a range, the carbon-based support can be arranged more uniformly within the first negative electrode active material layer. The carbon-based support may be, for example, nanoparticles having a particle size of 500 nm or less. The particle size of the composite negative electrode active material, the particle size of the metal-based negative electrode active material, and the particle size of the carbon-based support are, for example, average particle sizes. The average particle size is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer. On the other hand, the average particle size can be automatically determined using software from an electron microscope image or manually determined manually, for example.

[0081] [Negative electrode layer: Binder] The first negative electrode active material layer 22 contains a binder. The binder is, for example, a polymer binder. The binder contained in the first negative electrode active material layer 22 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder that can be used in the relevant technical field can be used. The binder can be composed of a single binder or a plurality of different binders. The binder can include, for example, a fluorine-based binder.

[0082] By including a binder in the first negative electrode active material layer 22, the first negative electrode active material layer 22 is stabilized on the negative electrode current collector 21. Also, during the charge and discharge process, even if a volume change and / or relative position change of the first negative electrode active material layer 22 occurs, cracks in the first negative electrode active material layer 22 are suppressed. For example, if the first negative electrode active material layer 22 does not contain a binder, the first negative electrode active material layer 22 may easily detach from the negative electrode current collector 21. When the first negative electrode active material layer 22 detaches from the negative electrode current collector 21, in the portion where the negative electrode current collector 21 is exposed, the negative electrode current collector 21 comes into contact with the solid electrolyte layer 30, and as a result, the possibility of short circuit increases. The first negative electrode active material layer 22 is produced, for example, by applying a slurry in which the materials constituting the first negative electrode active material layer 22 are dispersed onto the negative electrode current collector 21 and drying it. By including a binder in the first negative electrode active material layer 22, stable dispersion of the negative electrode active material and the fibrous carbon-based material in the slurry is possible. For example, when applying the slurry onto the negative electrode current collector 21 by the screen printing method, it is possible to suppress clogging of the screen (for example, clogging due to aggregates of the negative electrode active material).

[0083] The binder content may be 0.1 to 20 parts by weight, 0.1 to 15 parts by weight, 1 to 10 parts by weight, or 5 to 10 parts by weight with respect to 100 parts by weight of the mixture of the first negative electrode active material and the second negative electrode active material. By having a binder content within such a range, the cycle characteristics of the all-solid-state secondary battery 1 can be further improved.

[0084] [Negative electrode layer: Other additives] The first negative electrode active material layer 22 may further contain additives used in conventional all-solid-state secondary batteries 1, such as fillers, coating agents, dispersants, ion conductivity assisting agents, and the like.

[0085] [Negative electrode layer: First negative electrode active material layer] The initial charge capacity (B) of the first negative electrode active material layer 22 is, for example, 75% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the initial charge capacity (A) of the positive electrode active material layer 12.

[0086] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer 22 to the initial charge capacity (A) of the positive electrode active material layer 12 is, for example, 0.01 to 0.75, 0.01 to 0.7, 0.01 to 0.6, 0.01 to 0.5, 0.01 to 0.6, 0.01 to 0.5, 0.01 to 0.4, 0.01 to 0.3, 0.01 to 0.2, or 0.01 to 0.1. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer 22 to the initial charge capacity (A) of the positive electrode active material layer 12 is, for example, 0.05 to 0.75, 0.1 to 0.7, 0.1 to 0.6, 0.2 to 0.6, 0.2 to 0.5, or 0.2 to 0.45. The initial charge capacity of the positive electrode active material layer 12 is determined by charging from the first open circuit voltage (1 st open circuit voltage) to the maximum charging voltage with respect to Li / Li + as a reference. The initial charge capacity of the first negative electrode active material layer 22 is from the second open circuit voltage (2 nd open circuit voltage) to Li / Li +It is determined by charging up to 0.01 V with reference to [reference]. The maximum charging voltage is determined by the type of the positive electrode active material. The maximum charging voltage may be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charging voltage of Li2S or a Li2S composite can be determined between 2.5 and 3.0 V with reference to Li / Li + with reference to [reference]. For example, the maximum charging voltage of a lithium transition metal oxide can be determined between 3.0 and 4.5 V with reference to Li / Li + with reference to [reference].

[0087] The initial charge capacity (mAh) of the positive electrode active material layer 12 is obtained by multiplying the charge specific capacity (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer 12. When a plurality of types of positive electrode active materials are used, the product of the charge capacity density and the mass value is calculated for each positive electrode active material, and the sum of these values is the initial charge capacity of the positive electrode active material layer 12. The initial charge capacity of the first negative electrode active material layer 22 is also calculated in the same manner. The initial charge capacity of the first negative electrode active material layer 22 is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer 22. When a plurality of types of negative electrode active materials are used, the product of the charge capacity density and the mass value is calculated for each negative electrode active material, and the sum of these values is the initial charge capacity of the first negative electrode active material layer 22. The charge capacity density of each of the positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell with lithium metal as a counter electrode. The current density at which the initial charge capacity of each of the positive electrode active material layer 12 and the first negative electrode active material layer 22 is determined, for example, 0.1 mA / cm 2 can be directly measured using an all-solid-state half-cell. For the positive electrode, the measurement is from the first open circuit voltage (OCV) to the maximum charging voltage, for example, 3.0 V (vs. Li / Li +) can be performed with respect to the operating voltage up to. With respect to the negative electrode, the measurement can be performed with respect to the operating voltage from the second open circuit voltage (OCV) to the negative electrode, for example, up to 0.01 V with respect to lithium metal. For example, an all-solid-state half-cell having a positive electrode active material layer can be charged at a constant current of 0.1 mA / cm² from the first open circuit voltage up to 3.0 V. 2 An all-solid-state half-cell having a first negative electrode active material layer can be charged at a constant current of 0.1 mA / cm² from the second open circuit voltage up to 0.01 V. 2 The current density during constant current charging can be, for example, 0.2 mA / cm² 2 or 0.5 mA / cm² 2 may also be used. An all-solid-state half-cell having a positive electrode active material layer can be charged, for example, from the first open circuit voltage up to 2.5 V, 2.0 V, 3.5 V, 4.0 V, or 4.5 V. The maximum charging voltage of the positive electrode active material layer may be determined by the maximum voltage of the battery that satisfies the safety conditions according to JIS C 8712:2015 of the Japanese Standards Association.

[0088] If the initial charging capacity of the first negative electrode active material layer 22 is excessively small, the thickness of the first negative electrode active material layer 22 becomes very small, so that lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 in the repeated charge and discharge process collapse the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the charging capacity of the first negative electrode active material layer 22 increases excessively, the energy density of the all-solid-state secondary battery 1 decreases, the internal resistance of the all-solid-state secondary battery 1 increases due to the first negative electrode active material layer 22, and it becomes difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0089] The thickness of the first negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, 1 to 50%, 1 to 40%, 1 to 30%, 1 to 20%, or 1 to 10% of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, 1 to 50 μm, 2 to 40 μm, 3 to 30 μm, 4 to 20 μm, or 5 μm to 20 μm. The thickness of the first negative electrode active material layer 22 is, for example, 5 to 50 μm, 10 to 50 μm, 15 to 50 μm, 20 to 50 μm, or 25 μm to 50 μm. If the thickness of the first negative electrode active material layer 22 is excessively thin, the lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 will collapse the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the thickness of the first negative electrode active material layer 22 increases excessively, the energy density of the all-solid-state secondary battery 1 will decrease, the internal resistance of the all-solid-state secondary battery 1 will increase due to the first negative electrode active material layer 22, and it will be difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the thickness of the first negative electrode active material layer 22 decreases, for example, the initial charge capacity of the first negative electrode active material layer 22 also decreases.

[0090] [Negative electrode: Second negative electrode active material layer] Referring to FIG. 3, after charging, the all-solid-state secondary battery 1 can further include a second negative electrode active material layer 24 disposed, for example, between the negative electrode current collector 21 and the first negative electrode active material layer 22. The second negative electrode active material layer 24 is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer 24 is a metal layer containing lithium, it acts, for example, as a lithium reservoir. The lithium alloy is, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., but is not limited thereto, and any alloy that can be used as a lithium alloy in the relevant technical field can be used. The second negative electrode active material layer 24 consists of one of such alloys or lithium, or consists of various alloys. The second negative electrode active material layer 24 is, for example, a plated layer. The second negative electrode active material layer 24 is deposited, for example, between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charging process of the all-solid-state secondary battery 1.

[0091] The thickness of the second negative electrode active material layer 24 is not particularly limited, but is, for example, 1 to 200 μm, 1 to 150 μm, 1 to 100 μm, 1 to 50 μm, 1 to 30 μm, 1 to 22 μm, or 1 μm to 10 μm. If the thickness of the second negative electrode active material layer 24 is excessively small, it becomes difficult for the second negative electrode active material layer 24 to serve as a lithium reservoir. If the thickness of the second negative electrode active material layer 24 is excessively large, the mass and volume of the all-solid-state secondary battery 1 increase, and the cycle characteristics of the all-solid-state secondary battery 1 may rather deteriorate.

[0092] The thickness of the second negative electrode active material layer 24 may be, for example, even smaller than the thickness of the first negative electrode active material layer 22. The thickness of the second negative electrode active material layer 24 may be, for example, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less of the thickness of the first negative electrode active material layer 22. The thickness of the second negative electrode active material layer 24 is, for example, 1 to 70%, 1 to 60%, 1 to 50%, 1 to 40%, or 1 to 30% of the thickness of the first negative electrode active material layer 22. When the thickness of the second negative electrode active material layer 24 is smaller than the thickness of the first negative electrode active material layer 22, volume change can be suppressed during charge and discharge of the all-solid-state secondary battery. As a result, deterioration due to volume change of the all-solid-state secondary battery can be suppressed.

[0093] On the other hand, in the all-solid-state secondary battery 1, the second negative electrode active material layer 24 may be disposed, for example, between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembly of the all-solid-state secondary battery 1. When the second negative electrode active material layer 24 is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembly of the all-solid-state secondary battery 1, since the second negative electrode active material layer 24 is a metal layer containing lithium, it acts as a lithium reservoir. For example, a lithium foil may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembly of the all-solid-state secondary battery 1.

[0094] After the assembly of the all-solid-state secondary battery 1, when the second negative electrode active material layer 24 is deposited by charging, since the second negative electrode active material layer 24 is not included at the time of assembling the all-solid-state secondary battery 1, the energy density of the all-solid-state secondary battery 1 increases. When the all-solid-state secondary battery 1 is charged, charging is performed in excess of the charge capacity of the first negative electrode active material layer 22. That is, the first negative electrode active material layer 22 is overcharged. At the initial stage of charging, lithium is occluded in the first negative electrode active material layer 22. The negative electrode active material included in the first negative electrode active material layer 22 forms an alloy or a compound with lithium ions that have migrated from the positive electrode 10. If charging is performed in excess of the capacity of the first negative electrode active material layer 22, for example, lithium is deposited on the back surface of the first negative electrode active material layer 22, that is, between the negative electrode current collector 21 and the first negative electrode active material layer 22, and a metal layer corresponding to the second negative electrode active material layer 24 is formed by the deposited lithium. The second negative electrode active material layer 24 is a metal layer mainly composed of lithium (that is, metallic lithium). Such a phenomenon can be realized, for example, by the negative electrode active material included in the first negative electrode active material layer 22 containing a substance that forms an alloy or a compound with lithium. During discharging, the lithium in the first negative electrode active material layer 22 and the second negative electrode active material layer 24, that is, the metal layer, is ionized and moves in the direction of the positive electrode 10. Therefore, in the all-solid-state secondary battery 1, lithium can be used as the negative electrode active material. Further, since the first negative electrode active material layer 22 covers the second negative electrode active material layer 24, it serves as a protective layer for the second negative electrode active material layer 24, that is, the metal layer, and also serves to suppress the precipitation and growth of lithium dendrites. Therefore, short circuit 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. Further, when the second negative electrode active material layer 24 is disposed by charging after the assembly of the all-solid-state secondary battery 1, the negative electrode 20, that is, the negative electrode current collector 21, the first negative electrode active material layer 22, and the region therebetween are in the initial state of the all-solid-state secondary battery 1 or the state after complete discharge, and are Li-free regions that do not contain lithium (Li).

[0095] [Negative electrode: Negative electrode current collector] The negative electrode current collector 21 is made of a material that does not react with lithium, that is, does not form any alloys or compounds. The material constituting the negative electrode current collector 21 is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), etc., but is not necessarily limited to these, and any material that can be used as an electrode current collector in the relevant technical field can be used. The negative electrode current collector 21 may be composed of one of the above-mentioned metals, or an alloy or coating material of two or more metals. The negative electrode current collector 21 is, for example, in the form of a plate or a foil.

[0096] Referring to FIG. 2, the all-solid-state secondary battery 1 can further include a thin film 23 containing an element capable of forming an alloy with lithium on one surface of the negative electrode current collector 21. The thin film 23 is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The thin film 23 contains, for example, an element that forms an alloy with lithium. The elements that form an alloy with lithium are, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but are not necessarily limited to these, and any element that can form an alloy with lithium in the relevant technical field can be used. The thin film 23 is composed of one of these metals or an alloy of various metals. By disposing the thin film 23 on one surface of the negative electrode current collector 21, for example, the deposition form of the second negative electrode active material layer 24 deposited between the thin film 23 and the first negative electrode active material layer 22 is further flattened, and the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0097] The thickness of the thin film 23 is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. When the thickness of the thin film 23 is less than 1 nm, it is difficult to exhibit the function by the thin film 23. When the thickness of the thin film 23 is excessively large, the thin film 23 itself occludes lithium, the amount of lithium deposition at the negative electrode decreases, the energy density of the all-solid-state battery decreases, and the cycle characteristics of the all-solid-state secondary battery 1 may deteriorate. The thin film 23 can be disposed on the negative electrode current collector 21 by, for example, a vacuum evaporation method, a sputtering method, a plating method, etc., but is not necessarily limited to such a method, and any method that can form the thin film 23 in the technical field can be used.

[0098] Although not shown, the negative electrode current collector 21 can include, for example, a base film and a metal layer disposed on one or both surfaces of the base film. The base film can include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer can include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. When the base film includes an insulating thermoplastic polymer, at the time of short circuit occurrence, the base film can be softened or liquefied to interrupt the battery operation and suppress a sudden increase in current. The metal layer can include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative electrode current collector 21 may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode current collector 21, refer to the positive electrode current collector 11 described above. By having such a structure for the negative electrode current collector 21, the weight of the negative electrode can be reduced, and as a result, the energy density of the negative electrode and the lithium battery can be improved.

[0099] [Negative electrode layer: First inert member] Referring to FIGS. 4, 5, 8 to 12, the all-solid-state secondary battery 1 can further include first inert members 40, 40a, 40b disposed on at least one of the other surfaces of the negative electrode current collector 21 and the other surface of the positive electrode current collector 11.

[0100] The first inert members 40, 40a, 40b do not contain a positive electrode active material. The first inert members 40, 40a, 40b may be, for example, insulating members.

[0101] The first inert members 40, 40a, 40b can have conductivity by additionally containing a conductive material. The first inert members 40, 40a, 40b can also function as flame-retardant inert members, for example, by additionally containing a flame-retardant material.

[0102] The first inert members 40, 40a, 40b may be, for example, elastic members. The first inert members 40, 40a, 40b may be, for example, porous elastic members. The first inert members 40, 40a, 40b may be, for example, elastic members having one or more of porosity, conductivity, and flame retardancy.

[0103] The first inert members 40, 40a, 40b impart a buffering function to the all-solid-state secondary battery 1. The first inert members 40, 40a, 40b can achieve, for example, stress relaxation and provide a restoring force. The first inert members 40, 40a, 40b can effectively accommodate the volume change of the all-solid-state secondary battery 1 and apply a certain pressure to the all-solid-state secondary battery 1.

[0104] The first inert members 40, 40a, 40b have, for example, a lower elastic modulus than the negative electrode current collector 21. By having a lower elastic modulus than the negative electrode current collector 21, the first inert members 40, 40a, 40b can more effectively accommodate the volume change of the negative electrode layer 20 during charge and discharge of the all-solid-state secondary battery 1. The first inert member 50 can effectively relieve the internal stress due to the volume change of the all-solid-state secondary battery 1 during charge and discharge of the all-solid-state secondary battery 1 and improve the cycle characteristics of the all-solid-state secondary battery 1.

[0105] The first inactive members 40, 40a, and 40b can be disposed, for example, on the negative electrode layer 20 of the all-solid-state secondary battery 1. When the volume change of the negative electrode layer 20 during charge and discharge of the all-solid-state secondary battery 1 is relatively large compared to the positive electrode layer 10 and the solid electrolyte layer 30, by disposing the first inactive members 40, 40a, and 40b adjacent to the negative electrode layer 20, the volume change of the negative electrode layer 20 can be more effectively accommodated. Further, by applying a certain pressure to the negative electrode layer 20 by the first inactive members 40, 40a, and 40b, for example, uniform deposition of lithium metal can be induced in the negative electrode layer 20. Therefore, generation of defects in the all-solid-state secondary battery 1 due to non-uniform deposition of lithium metal can be more effectively prevented.

[0106] On the other hand, the first inactive members 40, 40a, and 40b can be disposed, for example, on the positive electrode layer 10 of the all-solid-state secondary battery 1. By disposing the first inactive members 40, 40a, and 40b adjacent to the positive electrode layer 10, the volume change of the all-solid-state secondary battery 1 can be more effectively accommodated. Further, by applying a certain pressure to the all-solid-state secondary battery 1 by the first inactive members 40, 40a, and 40b, for example, uniform deposition of lithium metal can be induced in the negative electrode layer 20. Therefore, generation of defects in the all-solid-state secondary battery 1 due to non-uniform deposition of lithium metal can be more effectively prevented.

[0107] The first inert members 40, 40a, and 40b can include a polymer material, a rubber material, or a combination thereof. By including a polymer material, a rubber material, or a combination thereof, the first inert members 40, 40a, and 40b can have a function of relaxing stress and a restoring force. The polymer material can include, for example, a polyurethane-based polymer, a polyacrylic-based polymer, a polystyrene-based polymer, a polyester-based polymer, a polyamide-based polymer, a polyolefin-based polymer, or a combination thereof. The polymer material may be, for example, a polymer resin. The polymer material may be, for example, an adhesive resin. The rubber material can include, for example, natural rubber (NR), butadiene rubber (BR), nitrile rubber, silicone rubber, isoprene rubber (IR), styrene-butadiene rubber (SBR), isoprene-butadiene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber, halogenated butyl rubber, chloroprene (CR), halogenated isoprene rubber, halogenated isobutylene copolymer, chloroprene rubber, butyl rubber (IIR), halogenated isobutylene-p-methylstyrene rubber, or a combination thereof. The polyurethane-based polymer can include, for example, a polyester-based polyurethane, a polyether-based polyurethane, or a combination thereof. The polyacrylic-based polymer can include, for example, polyacrylate, methyl polyacrylate, polymethacrylate, polymethyl methacrylate, or a combination thereof.Polystyrene-based polymers can include, for example, styrene-ethylene-butylene copolymer (SEB), styrene-butadiene-styrene copolymer (SBS), hydrogenated SBS (styrene-ethylene-butylene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), hydrogenated SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), styrene-isobutylene-styrene copolymer (SIBS), styrene-butadiene-styrene-butadiene (SBSB), styrene-butadiene-styrene-butadiene-styrene (SBSBS), polystyrene (PS), acrylonitrile-styrene copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS), or combinations thereof. Polyester-based polymers can include, for example, polyethylene terephthalate, polybutylene terephthalate, or combinations thereof. Polyamide-based polymers can include, for example, polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, or combinations thereof. Polyolefin-based polymers can include, for example, polyethylene, polypropylene, ethylene-propylene copolymer, propylene-1-hexene copolymer, propylene-4-methyl-1-pentene copolymer, propylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-4-methyl-pentene copolymer, ethylene-1-butene copolymer, 1-butene-1-hexene copolymer, 1-butene-4-methyl-pentene, ethylene-methacrylic acid copolymer, ethylene-ethyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, propylene-methacrylic acid copolymer, propylene-methyl methacrylate copolymer, propylene-ethyl methacrylate copolymer, propylene-butyl methacrylate copolymer, propylene-methyl acrylate copolymer, propylene-ethyl acrylate copolymer, propylene-butyl acrylate copolymer, ethylene-vinyl acetate copolymer (EVA), polyolefin of propylene-vinyl acetate copolymer, or combinations thereof.

[0108] The first inert members 40, 40a, 40b can include, for example, a porous foam, a porous sponge, or a combination thereof. The first inert members 40, 40a, 40b can include, for example, a porous foam sheet, a porous sponge sheet, or a combination thereof. By having such a form, the first inert members 40, 40a, 40b can provide both porosity and a buffering function at the same time. The porous foam can include, for example, a closed cell, an open cell, or a combination thereof. The porous sponge can include, for example, a closed cell, an open cell, or a combination thereof. A closed cell means, for example, a closed pore, a cell or pore that does not reach the surrounding atmosphere. An open cell means, for example, an open pore, a cell or pore that reaches the surrounding atmosphere. The first inert members 40, 40a, 40b can include, for example, a closed cell porous foam, an open cell porous foam, a closed cell porous sponge, an open cell porous sponge, or a combination thereof. The porous foam can include, for example, both a closed cell and an open cell at the same time. The porous sponge can include, for example, both a closed cell and an open cell at the same time.

[0109] The first inactive members 40, 40a, and 40b can contain, for example, a conductive material. The conductive material is, for example, graphite, carbon black, acetylene black, Ketjen black, Denka black, carbon fiber, carbon nanotube (CNT), graphene, metal fiber, metal powder, etc. The content of the conductive material contained in the first inactive members 40, 40a, and 40b is, for example, 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 15 parts by weight, 1 to 10 parts by weight, 5 to 40 parts by weight, 5 to 30 parts by weight, or 5 to 35 parts by weight with respect to 100 parts by weight of the first inactive members 40, 40a, and 40b. Since the first inactive member 50 has conductivity, it can serve as the negative electrode current collector 50.

[0110] The first inactive members 40, 40a, and 40b contain, for example, a matrix and a filler. The matrix contains, for example, a base material and a reinforcing material. The matrix contains, for example, a fibrous base material and a fibrous reinforcing material. By the matrix containing the fibrous base material, the matrix can have elasticity. The fibrous base material contains, for example, one or more selected from pulp fiber, insulating polymer fiber, and ion-conductive polymer fiber. By the matrix containing the reinforcing material, the strength of the matrix is improved. The fibrous reinforcing material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc. The fibrous reinforcing material is, for example, a flame-retardant material. The filler is, for example, a moisture getter and / or a flame retardant. The filler is, for example, a metal hydroxide having moisture adsorption properties. The metal hydroxide contained in the filler is, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, TI(OH)3, Zr(OH) 4、 Al(OH)3, or a combination thereof.

[0111] The thicknesses of the first inactive members 40, 40a, and 40b are, for example, even greater than the thickness of the first negative electrode active material layer 22. By having the first inactive members 40, 40a, and 40b have a greater thickness compared to the first negative electrode active material layer 22, the volume change of the negative electrode layer 20 during charge and discharge can be more effectively accommodated. The thickness of the first negative electrode active material layer 22 is 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thicknesses of the first inactive members 40, 40a, and 40b. The thickness of the first negative electrode active material layer 22 is, for example, 1% to 50%, 1% to 40%, 1% to 30%, 1% to 20%, or 1% to 10% of the thicknesses of the first inactive members 40, 40a, and 40b. The thicknesses of the first inactive members 40, 40a, and 40b are, for example, 10 μm to 300 μm, 20 μm to 300 μm, 50 μm to 300 μm, or 100 μm to 200 μm. If the thicknesses of the first inactive members 40, 40a, and 40b are excessively small, it is difficult to achieve the intended effect, and if the thicknesses of the first inactive members 40, 40a, and 40b are excessively large, the energy density of the all-solid-state secondary battery 1 may decrease. The form of the first inactive members 40, 40a, and 40b is not particularly limited and may be selected according to the form of the all-solid-state secondary battery 1. The first inactive members 40, 40a, and 40b may be, for example, sheet-like, rod-like, or gasket-like. The first inactive members 40, 40a, and 40b may be omitted.

[0112] [Positive electrode layer] [Positive electrode layer: Positive electrode active material]

[0113] Referring to FIGS. 1 to 12, the positive electrode active material layer 12 includes, for example, a positive electrode active material.

[0114] The positive electrode active material included in the positive electrode active material layer 12 is a positive electrode active material that can reversibly absorb and desorb lithium ions. The positive electrode active material can include, for example, an oxide-based positive electrode active material, a sulfide-based positive electrode active material, or a combination thereof.

[0115] The oxide-based positive electrode active material includes, for example, lithium transition metal oxides, metal oxides, or combinations thereof. The lithium transition metal oxides include, for example, Lithium cobalt oxide, Lithium nickel oxide, Lithium nickel cobalt oxide, Lithium nickel cobalt aluminium oxide, Lithium nickel cobalt mangense oxide, Lithium Manganate, Lithium iron phosphate, or combinations thereof. The lithium oxides include, for example, iron oxide, vanadium oxide, or combinations thereof.

[0116] The sulfide-based positive electrode active material includes, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing composites, or combinations thereof.

[0117] As the oxide-based positive electrode active material, for example, one or more of composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof and lithium can be used. The lithium-containing oxide-based positive electrode active material is, for example, Li a A 1-b B’ b D2 (in the above formula, 0.90 ≦ a ≦ 1 and 0 ≦ b ≦ 0.5); Li a E 1-b B’ b O 2-c D c (in the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); LiE 2-b B’ b O 4-c D c (in the above formula, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Lia Ni 1-b-c Co b B’ c D α (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B’ c O 2-α F’ α (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B’ c D α (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B’ c O 2-α F’ α (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (In the above formula, 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 G e O2 (In the above formula, 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 (In the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (In the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (In the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G bO4 (in the above formula, 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1); LiV2O5; LiI’O2; LiNiVO4; Li (3-f) J2(PO4)3 (0 ≦ f ≦ 2); Li (3-f) It can contain a compound represented by any one of the chemical formulas of Fe2(PO4)3 (0 ≦ f ≦ 2); LiFePO4.

[0118] In the chemical formula representing the above-mentioned compound, A is Ni, Co, Mn, or a combination thereof, B’ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, D is O, F, S, P, or a combination thereof, E is Co, Mn, or a combination thereof, F’ is F, S, P, or a combination thereof, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, Q is Ti, Mo, Mn, or a combination thereof, I’ is Cr, V, Fe, Sc, Y, or a combination thereof, and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound with a coating layer added to the surface of the above-mentioned compound, and it is also possible to use a mixture of the above-mentioned compound and a compound with a coating layer added. The coating layer added to the surface of the above-mentioned compound includes, for example, a coating element compound such as an oxide of the coating element, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. The compound with such a coating layer is amorphous or crystalline. The coating element contained in the coating layer is Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating layer formation method is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method is, for example, spray coating, dipping method, etc. Since the specific coating method is well understood by those skilled in the art, detailed description is omitted.

[0119] The oxide-based positive electrode active material contains, for example, a lithium transition metal oxide represented by the following Chemical Formulas 1 to 8.

[0120] <Chemical Formula 1> Li a Ni x Co y M z O 2-b A b

[0121] In Chemical Formula 1, 1.0 ≦ a ≦ 1.2, 0 ≦ b ≦ 0.2, 0.8 ≦ x < 1, 0 ≦ y ≦ 0.3, 0 < z ≦ 0.3, and x + y + z = 1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, A is F, S, Cl, Br, or a combination thereof.

[0122] <Chemical Formula 2> LiNi x Co y Mn z O2 <Chemical Formula 3> LiNi x Co y Al z O2

[0123] In Chemical Formulas 2 and 3, 0.8 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.2, 0 < z ≦ 0.2 and x + y + z = 1.

[0124] <Chemical Formula 4> LiNi x Co y Mn z Al w O2

[0125] In Chemical Formula 4, 0.8 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.2, 0 < z ≦ 0.2, 0 < w ≦ 0.2, and x + y + z + w = 1.

[0126] <Chemical Formula 5> Li a Co x M y O 2-b A b

[0127] In Chemical Formula 5, 1.0 ≦ a ≦ 1.2, 0 ≦ b ≦ 0.2, 0.9 ≦ x ≦ 1, 0 ≦ y ≦ 0.1, and x + y = 1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, A is F, S, Cl, Br, or a combination thereof.

[0128] <Chemical Formula 6> Li a Ni x Mn y M’ z O 2-b A b

[0129] In Chemical Formula 6, 1.0 ≦ a ≦ 1.2, 0 ≦ b ≦ 0.2, 0 < x ≦ 0.3, 0.5 ≦ y < 1, 0 < z ≦ 0.3, and x + y + z = 1, M’ is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, A is F, S, Cl, Br, or a combination thereof.

[0130] <Chemical formula 7> Li a M1 x M2 y PO 4-b X b

[0131] In Chemical formula 7, 0.90 ≤ a ≤ 1.1, 0 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.5, 0.9 < x + y < 1.1, 0 ≤ b ≤ 2, M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof, M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y), or a combination thereof, and X is O, F, S, P, or a combination thereof.

[0132] <Chemical formula 8> Li a M3 z PO4

[0133] In Chemical formula 8, 0.90 ≤ a ≤ 1.1, 0.9 ≤ z ≤ 1.1, M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0134] The oxide-based positive electrode active material is covered by a coating layer. Any coating layer known as a coating layer for the positive electrode active material of an all-solid-state secondary battery can be used. The coating layer is, for example, Li2O-ZrO2 (LZO), etc.

[0135] The size of the oxide-based positive electrode active material may be, for example, 0.1 to 30 μm, 0.5 to 20 μm, or 1 to 15 μm. The oxide-based positive electrode active material may be, for example, single crystal particles or polycrystalline particles.

[0136] The sulfide-based positive electrode active material can include, for example, a Li2S-containing composite. The Li2S-containing composite includes, for example, a composite of Li2S and a conductive material, a composite of Li2S, a solid electrolyte, and a conductive material, a composite of Li2S and a solid electrolyte, a composite of Li2S and a lithium salt, a composite of Li2S, a lithium salt, and a conductive material, a composite of Li2S and a metal carbide, a composite of Li2S, a metal carbide, and a conductive material, a composite of Li2S and a metal nitride, a composite of Li2S, a metal nitride, and a conductive material, or a combination thereof. The Li2S-containing composite is distinguished from a simple mixture of Li2S and a conductive material, a solid electrolyte, a lithium salt, a metal carbide, a metal nitride, etc. A simple mixture of Li2S and a conductive material, a solid electrolyte, a lithium salt, a metal carbide, a metal nitride, etc. cannot maintain a dense interface between Li2S and other components, exhibits a high interfacial resistance, and as a result, may deteriorate the life characteristics of the all-solid-state secondary battery.

[0137] The Li2S-containing composite contains Li2S. Since Li2S has a high theoretical capacity, a secondary battery having a high energy density can be provided. However, since Li2S has low ionic conductivity and / or electronic conductivity, in order to eliminate such disadvantages, a composite is formed with a lithium salt, a metal halide, a conductive material, etc. In the Li2S-containing composite, the content of Li2S may be, for example, 10 to 80 wt%, 20 to 80 wt%, 30 to 80 wt%, or 40 to 80 wt% of the total weight of the Li2S-containing composite. When the content of Li2S in the Li2S-containing composite increases excessively, it is not easy to improve the ionic conductivity and / or electronic conductivity of the Li2S-containing composite. When the content of Li2S in the Li2S-containing composite is excessively low, the energy density of the all-solid-state secondary battery may decrease.

[0138] The composite of Li2S and the conductive material contains the conductive material. The conductive material includes, for example, carbon-based materials. The carbon-based material is a material containing carbon atoms, and any material can be used as long as it is used as a conductive material in the relevant technical field. The carbon-based material may be, for example, a crystalline carbon-based material, an amorphous carbon-based material, or a combination thereof. The carbon-based material may be, for example, a fired product of a carbon precursor. The carbon-based material may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene ball (GB), or a combination thereof. The carbon-based material may be, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material can contain, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon-based material may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black, graphite, activated carbon, or a combination thereof. The form of the carbon-based material is, for example, particulate, sheet-like, fibrous form, etc., but is not limited thereto, and any material can be used as long as it is used as a carbon-based material in the relevant technical field. The manufacturing method of the composite of Li2S and the carbon-based material may be a dry method, a wet method, or a combination thereof, but is not limited thereto. The manufacturing method of the composite of Li2S and the carbon-based material in the relevant technical field is, for example, milling, heat treatment, vapor deposition, etc., but is not necessarily limited thereto, and any method can be used as long as it is a method used in the relevant technical field.

[0139] The composite of Li2S, a solid electrolyte, and a conductive material contains a conductive material and a solid electrolyte. The conductive material includes, for example, a carbon-based material. Regarding the carbon-based material, refer to the carbon-based material used in the aforementioned composite of Li2S and the conductive material. Any solid electrolyte can be used as long as it is an ion-conductive material used in the art as an amorphous solid electrolyte, for example. The solid electrolyte is, for example, an inorganic solid electrolyte. The solid electrolyte is, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte is, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte contains, for example, Li, S, and P, and may further selectively contain a halogen element. The sulfide-based solid electrolyte can be selected from the sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte can have, for example, an ionic conductivity of 1×10 -5 S / cm or more at room temperature. The sulfide-based solid electrolyte is, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX (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, 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 xOne or more selected from among (0 ≦ x ≦ 2) can be included. The oxide-based solid electrolyte contains, for example, Li, O, and a transition metal element, and may further selectively contain other elements. The oxide-based solid electrolyte may be, for example, a solid electrolyte having an ionic conductivity of 1×10 -5 S / cm or more at room temperature. The oxide-based solid electrolyte can be selected from among the oxide-based solid electrolytes used for the solid electrolyte layer. The solid electrolyte may be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, a mixture of Li3PO4-Li2SO4 and a two-component lithium salt or a mixture of Li3PO4-Li2SO4 and a three-component lithium salt may be used.

[0140] The composite of Li2S and the solid electrolyte contains the solid electrolyte. Regarding the solid electrolyte, refer to the solid electrolyte used for the composite of Li2S, the conductive material, and the solid electrolyte described above.

[0141] The composite of Li2S, a lithium salt, and a conductive material contains Li2S, a lithium salt, and a conductive material. The conductive material includes, for example, a carbon-based material. Regarding the carbon-based material, refer to the aforementioned composite of Li2S and the conductive material. The lithium salt includes, for example, a lithium salt compound. The lithium salt compound does not contain, for example, sulfur (S) atoms. The lithium salt compound may be, for example, a binary compound or a ternary compound. The lithium salt compound is, for example, a binary compound composed of lithium and one element selected from Group 13 to Group 17 of the periodic table. The binary compound can include, for example, one or more selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3. The lithium salt compound may be, for example, a ternary compound composed of lithium and two elements selected from Group 13 to Group 17 of the periodic table. The ternary compound includes, for example, one or more selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. The lithium salt compound is particularly one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. The composite of Li2S, a lithium salt, and a conductive material may be, for example, a composite of Li2S, a lithium halide, and a carbon-based material. By the composite of Li2S, a lithium salt, and a carbon-based material containing a lithium halide compound, further improved ionic conductivity can be provided. The composite of Li2S, a lithium salt, and a carbon-based material is distinguished from a simple mixture of Li2S, a lithium salt, and a carbon-based material. A simple mixture of Li2S, a lithium salt, and a carbon-based material cannot form a dense interface between Li2S, a lithium salt, and a carbon-based material, generates a high interfacial resistance, and as a result, may reduce the life characteristics of all-solid-state secondary batteries.

[0142] The composite of Li2S and a lithium salt contains Li2S and a lithium salt. For the lithium salt, refer to the lithium salt used in the composite of Li2S, a lithium salt, and a conductive material described above.

[0143] The composite of Li2S and a metal carbide contains a metal carbide. The metal carbide is, for example, a two-dimensional metal carbide. The two-dimensional metal carbide is, for example, a MAX phase (MXene). The two-dimensional metal carbide is, for example, M n+1 C n T x (where M is a transition metal, T is a terminal group, T is O, OH, and / or F, n = 1, 2, or 3, and x is the number of terminal groups). The two-dimensional metal carbide is, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5 )3C2T x , Ti3CNT x , Ta4C3T x , Nb4C3T x , or a combination thereof. The surface of the two-dimensional metal carbide is terminated by O, OH, and / or F.

[0144] The composite of Li2S, a metal carbide, and a conductive material contains Li2S, a metal carbide, and a conductive material. The conductive material includes, for example, a carbon-based material. For the carbon-based material, refer to the carbon-based material used in the composite of Li2S and a conductive material described above. For the metal carbide, refer to the metal carbide used in the composite of Li2S and a metal carbide described above.

[0145] The composite of Li2S and a metal nitride contains Li2S and a metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x(M is a transition metal, T is a terminal group, T is O, OH and / or F, n = 1, 2, or 3, and x is the number of terminal groups). The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0146] The composite of Li2S, metal nitride and conductive material contains Li2S, metal nitride and conductive material. The conductive material includes, for example, carbon-based materials. For carbon-based materials, refer to the carbon-based materials used in the above-mentioned composite of Li2S and conductive material. For metal nitrides, refer to the metal nitrides used in the above-mentioned composite of Li2S and metal nitride.

[0147] The Li2S-containing composite is, for example, a composite of Li2S and lithium salt (Li a X1 b , where X1 is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof, 1 ≤ a ≤ 5, 1 ≤ b ≤ 5), a composite of Li2S and lithium salt (Li a X1 b ) and conductive material (C), a composite of Li2S and metal halide (M c X2 d , where M is one or more metals selected from Groups 2 to 15 of the Periodic Table of the Elements, X2 is I, Br, Cl, F, or a combination thereof, 1 ≤ c ≤ 5, 1 ≤ d ≤ 5), a composite of Li2S and metal halide (M c X2 d ) and conductive material (C), a composite of Li2S and lithium salt (Li a X1 b ) and metal halide (M c X2 d ), a composite of Li2S and lithium salt (Li a X1 b ) and metal halide (M c X2 d) and a composite of the conductive material (C), or a combination thereof can be included. The Li2S-containing composite is distinguished from a simple mixture of Li2S and a lithium salt, a metal halide, a conductive material, etc. A simple mixture of Li2S and a metal halide, a lithium salt, a conductive material, etc. cannot form a dense interface between Li2S and these other components, generates a high interfacial resistance, and as a result, may deteriorate the life characteristics of the all-solid-state secondary battery.

[0148] The composite of Li2S and a lithium salt (Li a X1 b ) is represented by, for example, Li2S-Li a X1 b (1 ≤ a ≤ 5, 1 ≤ b ≤ 5), where X1 is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof.

[0149] The composite of Li2S and a lithium salt (Li a X1 b ) and the conductive material (C) is represented by, for example, Li2S-Li a X1 b -C(1 ≤ a ≤ 5, 1 ≤ b ≤ 5), where X1 is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof. The conductive material is, for example, a carbon-based material.

[0150] The composite of Li2S and a metal halide (M c X2 d ) is represented by, for example, Li2S-M c X2 d C(1 ≤ c ≤ 5, 1 ≤ d ≤ 5), where M is one or more metals selected from Groups 2 to 15 of the periodic table of elements, and X2 is I, Br, Cl, F, or a combination thereof. The conductive material is, for example, a carbon-based material.

[0151] Li2S and metal halide (M c X2 d ) and the composite of the conductive material (C) is, for example, Li2S-M c X2 d C (1 ≤ c ≤ 5, 1 ≤ d ≤ 5), where M is one or more metals selected from Group 2 to Group 15 of the periodic table of elements, and X2 is I, Br, Cl, F, or a combination thereof. The conductive material is, for example, a carbon-based material.

[0152] Li2S and lithium salt (Li a X1 b ) and metal halide (M a X2 b ) composite may be represented by Li2S-Li a X1 b -M c X2 d (1 ≤ a ≤ 5, 1 ≤ b ≤ 5, 1 ≤ c ≤ 5, 1 ≤ d ≤ 5), where X1 is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof, M is one or more metals selected from Group 2 to Group 15 of the periodic table of elements, and X2 is I, Br, Cl, F, or a combination thereof. The conductive material is, for example, a carbon-based material.

[0153] Li2S and lithium salt (Li a X1 b ) and metal halide (M a X2 b ) and the composite of the conductive material (C) is Li2S-Li a X1 b -M c X2 d-C (where 1 ≦ a ≦ 5, 1 ≦ b ≦ 5, 1 ≦ c ≦ 5, 1 ≦ d ≦ 5) may be represented, X1 is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof, M is one or more metals selected from Groups 2 to 15 of the Periodic Table of the Elements, and X2 is I, Br, Cl, F, or a combination thereof. The conductive material is, for example, a carbon-based material.

[0154] In the Li2S-containing composite, for example, 1 ≦ a ≦ 4, 1 ≦ b ≦ 4, 1 ≦ c ≦ 4, 1 ≦ d ≦ 4, 1 ≦ a ≦ 3, 1 ≦ b ≦ 3, 1 ≦ c ≦ 3, 1 ≦ d ≦ 3, 1 ≦ a ≦ 2, 1 ≦ b ≦ 2, 1 ≦ c ≦ 2, or 1 ≦ d ≦ 2.

[0155] The Li2S-containing composite can contain a metal halide, and the metal halide can contain, for example, one or more metals selected from Al, Mg, Ti, Sn, As, Sb, Nb, Sc, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, and Se. By the metal halide containing such metals, the cycle characteristics of all-solid-state secondary batteries containing the Li2S-containing composite can be further improved.

[0156] The Li2S-containing composite can contain a metal halide, and the metal halide can contain, for example, AlF3, AlCl3, AlBr3, AlI3, MgF2, MgCl2, MgBr2, MgI2, TiF4, TiCl4, TiBr4, TiI4, SnF4, SnCl4, SnBr4, SnI4, AsF4, AsCl4, AsBr4, AsI4, SbF4, SbCl4, SbBr4, SbI4, or a combination thereof. By the Li2S-containing composite containing such a metal halide, the cycle characteristics of all-solid-state secondary batteries containing the Li2S-containing composite can be further improved.

[0157] The Li₂S-containing composite can include, for example, a solid solution of Li₂S and a lithium salt, a solid solution of Li₂S and a metal halide, a solid solution of Li₂S, a lithium salt, and a metal halide, or a combination thereof. For example, the composite of Li₂S and a lithium salt (Li a X1 b ) and / or the composite of Li₂S, a lithium salt (Li a X1 b ), and a conductive material (C) can include a solid solution of Li₂S and a lithium salt. For example, the composite of Li₂S and a metal halide (M c X2 d ) and / or the composite of Li₂S, a metal halide (M c X2 d ), and a conductive material (C) can include a solid solution of Li₂S and a metal halide. For example, the composite of Li₂S, a lithium salt (Li a X1 b ), and a metal halide (M a X2 b ) and / or the composite of Li₂S, a lithium salt (LiₐX₁b), a metal halide (M a X2 b ), and a conductive material (C) can include a solid solution of Li₂S, a lithium salt, and a metal halide.

[0158] The Li₂S-containing composite contains a solid solution of Li₂S and a lithium salt, a solid solution of Li₂S and a metal halide, a solid solution of Li₂S, a lithium salt and a metal halide, or a combination thereof, thereby increasing the ionic conductivity of the Li₂S-containing composite. For example, when a solid solution of Li₂S and a lithium salt, a solid solution of Li₂S and a metal halide, a solid solution of Li₂S, a lithium salt and a metal halide, or a combination thereof contains lithium ions, metal ions and / or halide ions arranged in Li₂S crystallites, the ionic conductivity of the solid solution of Li₂S, a lithium salt and a metal halide can be improved compared to the ionic conductivity of Li₂S. As a result, the ionic conductivity of the Li₂S-containing composite is improved, and the internal resistance of the Li₂S-containing composite may be reduced. By including such a Li₂S-containing composite in the lithium-containing sulfide-based positive electrode active material, the cycle characteristics of all-solid-state secondary batteries containing the lithium-containing sulfide-based positive electrode active material can be further improved. For example, the high-rate characteristics of all-solid-state secondary batteries containing such a lithium-containing sulfide-based positive electrode active material can be further improved.

[0159] The composite of Li₂S, a lithium salt and a conductive material, the composite of Li₂S and a metal halide and a conductive material, and the composite of Li₂S, a lithium salt, a metal halide and a conductive material can contain a conductive material. The conductive material can include, for example, a carbon-based material, a metal-based material, or a combination thereof.

[0160] The carbon-based material can include, for example, a fibrous carbon-based material. The metal-based material can include, for example, a fibrous metal-based material.

[0161] The composite of Li2S, a metal halide, and a conductive material can further improve the electron conductivity of the composite of Li2S, a metal halide, and a conductive material by including a fibrous carbon-based material and / or a fibrous metal-based material. By including a fibrous carbon-based material and / or a fibrous metal-based material in the composite of Li2S, a metal halide, and a conductive material, electron conduction becomes easier from the surface to the interior of the composite of Li2S, a metal halide, and a conductive material. The internal resistance of the positive electrode active material layer containing the composite of Li2S, a metal halide, and a conductive material can be reduced, and the cycle characteristics of the all-solid-state secondary battery including the positive electrode active material layer can be further improved.

[0162] The aspect ratio of the fibrous carbon-based material and / or the fibrous metal-based material may be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material and / or the fibrous metal-based material may be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material and / or the fibrous metal-based material may be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. By having such an aspect ratio range for the fibrous carbon-based material and / or the fibrous metal-based material, the electron conductivity of the whole composite of Li2S, a lithium salt, and a conductive material is improved, and the variation in local electron conductivity within the composite of Li2S, a lithium salt, and a conductive material can be further alleviated.

[0163] The fibrous carbon-based material can include, for example, a carbon nanostructure. The carbon nanostructure can include, for example, carbon nanofibers (CNF), carbon nanotubes (CNT), carbon nanobelts, carbon nanorods, or a combination thereof. The fibrous metal-based material can include, for example, a metal nanostructure. The metal nanostructure can include, for example, metal nanofibers (MNF), metal nanotubes (MNT), metal nanobelts, metal nanorods, or a combination thereof.

[0164] The carbon nanostructure can include, for example, a primary carbon nanostructure consisting of one carbon nanostructure, a secondary carbon nanostructure in which a plurality of carbon nanostructures are aggregated, or a combination thereof.

[0165] The diameter of the primary carbon nanostructure may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure may be, for example, 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure can be measured from a scanning electron microscope (SEM) or transmission electron microscope (TEM) image. On the other hand, the diameter and / or length of the primary carbon nanostructure can be measured by the laser diffraction method.

[0166] The secondary carbon nanostructure is, for example, a structure formed by aggregating primary carbon nanostructures so that they are entirely or partially in a bundle type or rope type. The secondary carbon nanostructure can include, for example, a bundle-type carbon nanostructure, a rope-type carbon nanostructure, or a combination thereof. The diameter of the secondary carbon nanostructure may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length of the secondary carbon nanotube structure may be, for example, 20 nm to 2 μm, 30 nm to 1.5 μm, 50 nm to 1 μm, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured with a scanning electron microscope (SEM) image or an optical microscope. On the other hand, the diameter and / or length of the secondary carbon nanostructure can be measured by the laser diffraction method. The secondary carbon nanostructure can be used, for example, for manufacturing a composite of Li2S, a metal halide, and a conductive material after being dispersed in a solvent or the like and switched to a primary carbon nanostructure.

[0167] The particle size of the sulfide-based positive electrode active material, for example, the particle size of the Li2S-containing composite, may be, for example, 10 μm or less, 8 μm or less, 5 μm or less, 4 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less. The Li2S-containing composite particle size may be, for example, 1 to 10 μm, 2 to 10 μm, 2 to 8 μm, or 3 to 8 μm. The Li2S-containing composite particle size is, for example, 0.1 to 10 μm, 0.1 to 8 μm, 0.1 to 5 μm, 0.1 to 4 μm, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm. When the Li2S-containing composite particles have such a size range, the volume change of the sulfide-based positive electrode active material during charge and discharge is suppressed, and the deterioration of the sulfide-based positive electrode active material during charge and discharge can be more effectively suppressed. If the Li2S-containing composite particle size increases excessively, the volume change of the Li2S-containing composite during charge and discharge increases, which may accelerate the deterioration of the sulfide-based positive electrode active material. Therefore, the cycle characteristics of the all-solid-state secondary battery including such a sulfide-based positive electrode active material may deteriorate. The Li2S-containing composite particle size can be measured, for example, using a laser diffraction method, a scanning electron microscope, or the like. The size of the Li2S-containing composite is, for example, the arithmetic mean value of the particle diameters of a plurality of particles measured using software with a scanning electron microscope image.

[0168] The particle size of the Li2S particles contained in the Li2S-containing composite may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The Li2S particle size may be, for example, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm or less. When the Li2S particles have such a size range, the volume change of the Li2S-containing composite during charge and discharge is suppressed, and the deterioration of the sulfide-based positive electrode active material including the Li2S-containing composite during charge and discharge can be suppressed. If the Li2S particle size increases excessively, the volume change of the Li2S-containing composite during charge and discharge increases, which may accelerate the deterioration of the sulfide-based positive electrode active material including the Li2S-containing composite. As a result, the cycle characteristics of the secondary battery including such a sulfide-based positive electrode active material may deteriorate.

[0169] The ionic conductivity of the Li2S-containing composite can be, for example, 1×10 -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more, or 1×10 -4 S / cm or more. The ionic conductivity can be measured, for example, using electrochemical impedance spectroscopy, DC polarization method, etc. By the Li2S-containing composite having such a range of ionic conductivity, the internal resistance of the positive electrode active material layer containing the Li2S-containing composite can be further reduced. The cycle characteristics of the all-solid-state secondary battery including the positive electrode active material layer can be improved.

[0170] The electronic conductivity of the Li2S-containing composite can be, for example, 1×10 -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more, or 1×10 -4 S / cm or more. The electronic conductivity can be measured, for example, using electrochemical impedance spectroscopy, DC polarization method, etc. By the Li2S-containing composite having such a range of electronic conductivity, the internal resistance of the positive electrode active material layer containing the Li2S-containing composite can be further reduced. The cycle characteristics of the all-solid-state secondary battery including the positive electrode active material layer can be improved. For 100 parts by weight of the composite of Li2S, lithium salt, metal halide, and conductive material, for example, it can contain 40 to 80 parts by weight of Li2S, 1 to 40 parts by weight of the combination of lithium salt and metal halide, and 1 to 20 parts by weight of the conductive material. The conductive material is, for example, a carbon-based material. In the combination of lithium salt and metal halide, the molar ratio of lithium salt to metal halide can be, for example, 3:1 to 1:3, 2:1 to 1:2, or 1.5:1 to 1:1.5.

[0171] The Li2S content in the composite of Li2S, lithium salt, metal halide, and conductive material may be, for example, 10 to 80 parts by weight, 20 to 70 parts by weight, 30 to 60 parts by weight, or 40 to 60 parts by weight of Li2S with respect to 100 parts by weight of the composite of Li2S, lithium salt, metal halide, and conductive material. The conductive material is, for example, a carbon-based material.

[0172] The content of lithium salt and metal halide in the composite of Li2S, lithium salt, metal halide, and conductive material may be, for example, 10 to 40 parts by weight, 15 to 40 parts by weight, 20 to 40 parts by weight, or 25 to 35 parts by weight of the combination of lithium salt and metal halide with respect to 100 parts by weight of the composite of Li2S, lithium salt, metal halide, and conductive material. The conductive material is, for example, a carbon-based material. The molar ratio of lithium salt to metal halide is 3:1 to 1:3.

[0173] The content of the conductive material in the composite of Li2S, lithium salt, metal halide, and conductive material may be, for example, 1 to 20 parts by weight, 5 to 20 parts by weight, or 5 to 15 parts by weight of the conductive material with respect to 100 parts by weight of the composite of Li2S, lithium salt, metal halide, and conductive material. The conductive material is, for example, a carbon-based material.

[0174] By having such a composition of Li2S, lithium salt, metal halide, and conductive material in the composite of Li2S, lithium salt, metal halide, and conductive material, the sulfide-based positive electrode active material containing the composite of Li2S, lithium salt, metal halide, and conductive material can exhibit further excellent ionic conductivity and / or electronic conductivity.

[0175] The Li2S content in the positive electrode active material layer 12 may be, for example, 30 wt% to 90 wt%, 35 wt% to 90 wt%, 40 wt% to 90 wt%, 45 wt% to 80 wt%, or 50 wt% to 70 wt% of the total weight of the positive electrode active material layer 12.

[0176] The positive electrode active material layer 12 may further contain, for example, a first fibrous sulfide-based solid electrolyte (not shown). The Li2S-containing composite may further contain, for example, a second fibrous sulfide-based solid electrolyte (not shown). The Li2S-containing composite may be a composite of Li2S and the second fibrous sulfide-based solid electrolyte or a composite of Li2S, the second fibrous sulfide-based solid electrolyte, and the carbon, solid electrolyte, lithium salt, metal carbide, or metal nitride described above.

[0177] When the Li2S-containing composite further contains the second fibrous sulfide-based solid electrolyte, the deterioration of the lithium battery can be further suppressed, and the cycle characteristics of the lithium battery can be further improved. The size of the second fibrous sulfide-based solid electrolyte is smaller than the size of the first fibrous sulfide-based solid electrolyte. The length and / or thickness of the second fibrous sulfide-based solid electrolyte is 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the length and / or thickness of the first fibrous sulfide-based solid electrolyte, respectively. The length and / or thickness of the second fibrous sulfide-based solid electrolyte is 0.1 to 50%, 0.5 to 40%, 1 to 30%, 1 to 20%, or 1 to 10% of the length and / or thickness of the first fibrous sulfide-based solid electrolyte, respectively. The second fibrous sulfide-based solid electrolyte has, for example, the same form as the first fibrous sulfide-based solid electrolyte and a smaller size. Since the second fibrous sulfide-based solid electrolyte has such a reduced length and / or thickness, it can be easily distributed in the Li2S-containing composite. Since the second fibrous sulfide-based solid electrolyte has such a reduced length and / or thickness, the deterioration of the lithium battery can be further suppressed, and the cycle characteristics of the lithium battery can be further improved.

[0178] The size of the sulfide-based positive electrode active material may be, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm. The size of Li2S may be, for example, 1 nm to 10 μm, 10 nm to 5 μm, 10 nm to 3 μm, or 10 nm to 1 μm. The size of the Li2S-containing composite may be, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm.

[0179] The shape of the positive electrode active material is, for example, a particle shape such as a true spherical shape or an elliptical spherical shape. The particle size of the positive electrode active material is not particularly limited and is within a range applicable to the positive electrode active material of a conventional all-solid-state secondary battery. The content of the positive electrode active material in the positive electrode layer 10 is also not particularly limited and is within a range applicable to the positive electrode layer of a conventional all-solid-state secondary battery. The content of the positive electrode active material included in the positive electrode active material layer 12 is, for example, 10 wt% to 99 wt%, 10 wt% to 90 wt%, 10 wt% to 80 wt%, 10 wt% to 70 wt%, or 10 wt% to 50 wt% of the total weight of the positive electrode active material layer 12. On the other hand, the content of the positive electrode active material included in the positive electrode active material layer 12 is, for example, 10 wt% to 99 wt%, 10 wt% to 95 wt%, 10 wt% to 90 wt%, 20 wt% to 90 wt%, 30 wt% to 90 wt%, 40 wt% to 90 wt%, or 50 wt% to 90 wt% of the total weight of the positive electrode active material layer 12.

[0180] [Positive electrode layer: Solid electrolyte] The positive electrode active material layer 12 may further contain, for example, a solid electrolyte. The solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode layer 10 may be the same as or different from the solid electrolyte included in the solid electrolyte layer 30. For details regarding the solid electrolyte, refer to the solid electrolyte layer 30 section.

[0181] The solid electrolyte included in the positive electrode active material layer 12 has a smaller D50 average particle size than the solid electrolyte included in the solid electrolyte layer 30. For example, the D50 average particle size of the solid electrolyte included in the positive electrode active material layer 12 may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the D50 average particle size of the solid electrolyte included in the solid electrolyte layer 30. The D50 average particle size is, for example, the median particle size (D50). The median particle size (D50) is, for example, the particle size corresponding to 50% cumulative volume calculated from the side of particles having a smaller particle size to the side of particles having a larger particle size in the particle size distribution measured by the laser diffraction method.

[0182] The solid electrolyte content included in the positive electrode active material layer 12 may be, for example, 1 wt% to 40 wt%, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12.

[0183] Positive electrode layer: Conductive material The positive electrode active material layer 12 may further include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited thereto, and any material that can be used as a carbon-based conductive material in the relevant technical field can be used. The metal-based conductive material may be metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material that can be used as a metal-based conductive material in the relevant technical field can be used. The conductive material content included in the positive electrode active material layer 12 may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12.

[0184] [Positive electrode layer: Binder The positive electrode active material layer 12 may further include a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto, and any material that can be used as a binder in the relevant technical field can be used. The binder content included in the positive electrode active material layer 12 may be, for example, 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12. The binder can be omitted.

[0185] [Positive electrode layer: Other additives In addition to the positive electrode active material, solid electrolyte, binder, and conductive material described above, the positive electrode active material layer 12 may further include additives such as a filler, a coating agent, a dispersant, and an ion conductivity assisting agent.

[0186] As the filler, coating agent, dispersant, ionic conductivity auxiliary agent, etc. contained in the positive electrode active material layer 12, known materials generally used for the electrodes of all-solid-state secondary batteries can be used.

[0187] [Dry Positive Electrode: Positive Electrode Current Collector] As the positive electrode current collector 11, 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 is used. The positive electrode current collector 11 can be omitted. The thickness of the positive electrode current collector 11 is, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0188] The positive current collector 11 can include, for example, a base film and a metal layer disposed on one or both surfaces of the base film. The base film may contain, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer can include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. When the base film contains an insulating thermoplastic polymer, the base film can be softened or liquefied during a short circuit to block battery operation and suppress a rapid increase in current. The metal layer can include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer can act as an electrochemical fuse and be cut off during overcurrent to perform a short circuit prevention function. The limiting current and the maximum current may be adjusted by adjusting the thickness of the metal layer. The metal layer may be electroplated on the base film or deposited. When the thickness of the metal layer decreases, the limiting current and / or the maximum current of the positive current collector 11 decreases, so the stability of the lithium battery during a short circuit can be improved. For connection to the outside, a lead tab may be added on the metal layer. The lead tab may be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. By melting the base film and / or the metal layer during welding, the metal layer can be electrically connected to the lead tab. To further strengthen the welding between the metal layer and the lead tab, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin piece of the same material as the metal of the metal layer. The metal chip may be, for example, a metal foil, a metal mesh, etc. The metal chip may be, for example, an aluminum foil, a copper foil, a SUS foil, etc.After placing a metal piece on the metal layer and then welding it to the lead tab, the lead tab can be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. By melting the base film, metal layer, and / or metal piece during welding, the metal layer or the metal piece / metal layer laminate can be electrically connected to the lead tab. A metal piece (metal chip) and / or a lead tab may be added to a part of the metal layer. The thickness of the base film may be, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. By having the base film with a thickness in such a range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300 °C, 100 to 250 °C or lower, or 100 to 200 °C. By having the base film with a melting point in such a range, the base film can be melted and easily bonded to the lead tab during the process of welding the lead tab. For improving the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to 1 μm. By having the metal layer with a thickness in such a range, the conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. By having the metal piece with a thickness in such a range, the connection between the metal layer and the lead tab becomes even easier. By having the positive current collector 11 with such a structure, the weight of the positive electrode can be reduced, and as a result, the energy density of the positive electrode and the all-solid-state secondary battery can be improved.

[0189] [Positive electrode layer: First inert member] Referring to FIGS. 4, 5, and 8 to 12, the all-solid-state secondary battery 1 may further include first inert members 40, 40a, 40b disposed on one or more of the other surfaces of the negative current collector 21 and the other surface of the positive current collector 11.

[0190] For more specific details regarding the first inactive members 40a, 40a, and 40b, refer to the first inactive members 40, 40a, and 40b of the negative electrode layer described above.

[0191] [Positive Electrode Layer: Second Inactive Member] Referring to FIGS. 6 to 12, the positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one surface of the positive electrode current collector 11. A second inactive member 50 is disposed on one side surface of the positive electrode layer 10.

[0192] Referring to FIGS. 7, 9, and 11, the second inactive member 50 is disposed on one side surface of the positive electrode active material layer 12 and is disposed between the solid electrolyte layer 30 and the positive electrode current collector 11 facing the solid electrolyte layer 30. The second inactive member 50 is not disposed on one side surface of the positive electrode current collector 11. Referring to FIGS. 6, 8, 10, and 12, the second inactive member 50 is disposed on one side surfaces of the positive electrode active material layer 12 and the positive electrode current collector 11. By including the second inactive member 50, cracks in the solid electrolyte layer 30 are prevented during the manufacture of the all-solid-state secondary battery 1 and / or during charge and discharge. As a result, the cycle characteristics of the all-solid-state secondary battery 1 are improved. In the all-solid-state secondary battery 1 that does not include the second inactive member 50, non-uniform pressure is applied to the solid electrolyte layer 30 that contacts the positive electrode layer 10 during the manufacture of the all-solid-state secondary battery 1 and / or during charge and discharge, causing cracks to occur in the solid electrolyte layer 30, and the possibility of short circuit due to the growth of lithium metal increases.

[0193] Referring to FIGS. 6 to 12, in the all-solid-state secondary battery 1, the thickness of the second inactive member 50 is, for example, even thicker than the thickness of the first negative electrode active material layer 22. The thickness of the second inactive member 50 is, for example, even larger than the thickness of the solid electrolyte layer 30.

[0194] Referring to FIGS. 6 to 12, the second inert member 50 surrounds the side surface of the positive electrode layer 10 and contacts the solid electrolyte layer 30. By surrounding the side surface of the positive electrode layer 10 and contacting the solid electrolyte layer 30, cracks in the solid electrolyte layer 30 generated by the pressure difference during the pressing process in the solid electrolyte layer 30 that does not contact the positive electrode layer 20 can be effectively suppressed. The second inert member 50 surrounds the side surface of the positive electrode layer 10 and is separated from the negative electrode layer 20, specifically, the first negative electrode active material layer 22. The second inert member 50 surrounds the side surface of the positive electrode layer 10, contacts the solid electrolyte layer 30, and is separated from the negative electrode layer 20. Therefore, the possibility of a short circuit due to physical contact between the positive electrode layer 10 and the first negative electrode active material layer 22, or a short circuit caused by overcharging of lithium, etc. is suppressed. By arranging the second inert member 50 on one side surface of the positive electrode active material layer 12 and the positive electrode current collector 11 at the same time, a short circuit due to contact between the positive electrode current collector 11 and the negative electrode layer 20 can be more effectively suppressed.

[0195] Referring to FIGS. 6 to 12, the second inert members 41, 41a, 41b extend from one side surface of the positive electrode layer 30 to the end portion of the solid electrolyte layer 30. By extending the second inert member 50 to the end portion of the solid electrolyte layer 30, cracks generated at the end portion of the solid electrolyte layer 30 can be suppressed. The end portion of the solid electrolyte layer 30 is the outermost portion in contact with the side surface of the solid electrolyte layer 30. The second inert member 50 extends to the outermost portion in contact with the side surface of the solid electrolyte layer 30. The second inert member 50 is separated from the negative electrode layer 20, specifically, the first negative electrode active material layer 22. The second inert member 50 extends to the end portion of the solid electrolyte layer 30 but does not contact the negative electrode layer 20. The second inert member 50 fills, for example, the space extending from one side surface of the positive electrode layer 30 to the end portion of the solid electrolyte layer 30.

[0196] The area of the positive electrode active material layer 12 or the positive electrode layer 10 (e.g., the surface area of the positive electrode active material layer 12 or the positive electrode layer 10 facing the solid electrolyte layer 30) is even smaller than the area of the first negative electrode active material layer 22 or the negative electrode layer 20 (e.g., the surface area of the first negative electrode active material layer 22 or the negative electrode layer 20 facing the solid electrolyte layer 30). The area of the positive electrode active material layer 12 or the positive electrode layer 10 is even smaller than the area of the solid electrolyte layer 30.

[0197] The second inert member 50 is also, for example, a gasket. By using a gasket as the second inert member 50, cracks in the solid electrolyte layer 30 generated by the pressure difference during the press process can be effectively suppressed.

[0198] The second inert member 50 has, for example, a single-layer structure. On the other hand, although not shown, the second inert member 50 has a multilayer structure. The multilayer structure has, for example, a two-layer, three-layer, or four-layer structure, and by having a multilayer structure, the physical properties of the second inert member 50 can be adjusted more precisely.

[0199] Although not shown, part or all of the second inert member 50 can be arranged separated from the side surface of the positive electrode active material layer 12. By arranging part or all of the second inert member 50 separated from the side surface of the positive electrode active material layer 12, the manufacturing process of the all-solid-state secondary battery 1 becomes easier, and the manufacturing speed of the all-solid-state secondary battery 1 can be increased. By arranging part or all of the second inert member 50 separated from the side surface of the positive electrode active material layer 12, the volume change in the side surface direction of the positive electrode active material layer 12 during charge and discharge can be received more effectively, and the life characteristics of the all-solid-state secondary battery 1 can be further improved. The distance between the side surfaces of the second inert member 50 and the positive electrode active material layer 12 is independent of each other and is, for example, 0.1 μm to 10 mm, 1 μm to 1 mm, 1 μm to 500 μm, 1 μm to 100 μm, 1 μm to 50 μm, or 1 μm to 10 μm.

[0200] Referring to FIGS. 1 to 12, the second inert member 50 may be selected, for example, from the materials used for the aforementioned first inert members 40, 40a, and 40b. The second inert member 50 does not contain, for example, a positive electrode active material. The second inert member 50 may be, for example, a flame-retardant inert member, an electron-insulating inert member, an ion-insulating inert member, or an elastic inert member.

[0201] [Solid electrolyte layer] [Solid electrolyte layer: Solid electrolyte]

[0202] Referring to FIGS. 1 to 12, the solid electrolyte layer 30 includes a solid electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20. The solid electrolyte layer 30 includes, for example, a solid electrolyte or a combination of a solid electrolyte and a gel electrolyte.

[0203] The solid electrolyte can include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0204] The solid electrolyte is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte is, for example, Li2S-P2S5, Li2S-P2S5-LiX (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, 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 Li7-x PS 6-x I x (0 ≦ x ≦ 2) and is one or more selected therefrom. The sulfide-based solid electrolyte is produced, for example, by treating starting materials such as Li2S and P2S5 by a melt quenching method or a mechanical milling method. Further, after such treatment, heat treatment may be performed. The solid electrolyte may be in an amorphous, crystalline, or mixed state thereof. Further, the solid electrolyte may contain, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a material containing Li2S-P2S5 in the sulfide-based solid electrolyte material forming the solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of about Li2S:P2S5 = 20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0205] The sulfide-based solid electrolyte may contain, for example, an argyrodite type solid electrolyte represented by the following chemical formula SE.

[0206] <Chemical formula SE> Li + 12-n-x A n+ X 2- 6-x Y - x

[0207] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, 1 ≦ n ≦ 5, 0 ≦ x ≦ 2. The sulfide-based solid electrolyte is, 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 PS6-x I x It may be an Argyrodite-type compound containing one or more selected from (0≦x≦2). The sulfide-based solid electrolyte may be an Argyrodite-type compound containing one or more selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0208] The density of the Argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. When the Argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state secondary battery can be reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0209] The oxide-based solid electrolyte is, for example, Li 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) (0≦x<1, 0≦y<1), PB(Mg3Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, 0 < z < 3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≦x≦10≦y≦1), Li xLa 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, 0 ≤ x ≤ 10), or a combination thereof may be used. The oxide-based solid electrolyte is produced, for example, by a sintering method or the like.

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

[0211] The polymer solid electrolyte can include, for example, a mixture of a lithium salt and a polymer, or a polymer having an ion-conductive functional group. The polymer solid electrolyte may be, for example, a polymer electrolyte that is in a solid state at 25 °C and 1 atm. The polymer solid electrolyte does not contain, for example, a liquid.The polymer solid electrolyte contains a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride - hexafluoropropylene (PVDF - HFP), polyethylene oxide (PEO), poly(styrene - b - ethylene oxide) block copolymer (PS - PEO), poly(styrene - butadiene), poly(styrene - isoprene - styrene), poly(styrene - b - divinylbenzene) block copolymer, poly(styrene - ethylene oxide - styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), poly(methyl methacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10 - diphenylanthracene - 2 - sulfonate (DPASLi). +) or a combination thereof, and is not limited thereto. Any material can be used as long as it is used for polymer electrolytes in the relevant technical field. Any lithium salt can be used as long as it is used as a lithium salt in the relevant technical field. Examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(where x and y are each from 1 to 20), LiCl, LiI, or a mixture thereof. The polymer contained in the solid polymer electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight average molecular weight of the polymer contained in the solid polymer electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0212] The gel electrolyte is, for example, a polymer gel electrolyte. The gel electrolyte may, for example, not contain a polymer and have a gel state.

[0213] A polymer gel electrolyte can include, for example, a liquid electrolyte and a polymer, or a polymer having an organic solvent and an ion-conductive functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte in a gel state at 25°C and 1 atm. The polymer gel electrolyte may, for example, not contain a liquid and have a gel state. The liquid electrolyte used in the polymer gel electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The organic solvent is, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or a mixture thereof, etc. The lithium salt can be selected from the lithium salts used in polymer solid electrolytes. An ionic liquid has a melting point below room temperature, consists only of ions, and refers to a salt in a liquid state at room temperature or a room-temperature molten salt. The ionic liquid is, for example, a) one or more cations selected from ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolinium-based, piperidinium-based, pyrazolinium-based, oxazolinium-based, pyridazinium-based, phosphonium-based, sulfonium-based, triazolinium-based, and mixtures thereof, and b) 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 - It can include one or more selected from compounds containing one or more anions selected from - to - . The polymer solid electrolyte can form a polymer gel electrolyte, for example, by being impregnated with a liquid electrolyte in a secondary battery. The polymer gel electrolyte may further contain inorganic particles. The polymer contained in the polymer gel electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight average molecular weight of the polymer contained in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0214] [Solid electrolyte layer: Binder] The solid electrolyte layer 30 can contain, for example, a binder. The binder contained in the solid electrolyte layer 30 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto, and any binder that can be used in the technical field can be used. The binder of the solid electrolyte layer 30 may be the same as or different from the binders contained in the positive electrode active material layer 12 and the negative electrode active material layer 22. The binder can be omitted.

[0215] The content of the binder included in the solid electrolyte layer 30 is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the solid electrolyte layer 30.

Example

[0216] The inventive concept will be further specifically described through the following examples and comparative examples. However, the examples are for illustrating the inventive concept and do not limit the scope of the inventive concept thereby.

[0217] (Preparation of Sulfide-Based Composite Cathode Active Material) Production Example 1: Li 2 S-LiI-CNF Composite Cathode Active Material

[0218] Li2S and LiI were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI composite. The milling conditions were 25 °C, 510 rpm for 10 hours.

[0219] The Li2S-LiI composite and carbon nanofibers (CNF) were mixed at a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI-CNF composite. The milling conditions were 25 °C, 510 rpm for 10 hours. The Li2S-LiI-CNF composite was used as the composite cathode active material.

[0220] Production Example 2: Li 2 S-LiI-AlI 3 -CNF Composite (First Stage) A first mixture was prepared by mixing LiI and AlI3 at a molar ratio of 1:1.

[0221] Li2S and the first mixture were mixed at a weight ratio of 40:20 to prepare a second mixture. The second mixture was mechanically milled using a ball mill to produce a Li2S-LiI-AlI3 composite. The milling conditions were 25 °C, 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G.

[0222] (Second stage) The Li2S-LiI-AlI3 composite and carbon nanofibers (CNF) were mixed at a weight ratio of 60:10 to prepare a third mixture. The third mixture was mechanically milled using a ball mill to produce a Li2S-LiI-AlI3-CNF composite. The milling conditions were 25 °C, 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G. The Li2S-LiI-AlI3-CNF composite was used as a sulfide-based positive electrode active material.

[0223] The weight ratio of each component of the Li2S-LiI-AlI3-CNF composite was 40:15:5:10.

[0224] Reference Production Example 1: A mixture of Li 2 S, LiI, AlI 3 and CNF LiI and AlI3 were mixed at a 1:1 molar ratio to prepare a first mixture.

[0225] Li2S and the first mixture were mixed at a weight ratio of 40:20, and this mixture of Li2S, LiI, and AlI3 was further mixed with carbon nanofibers (CNF) at a weight ratio of 60:10 and used as a sulfide-based positive electrode active material.

[0226] (Fabrication of all-solid-state secondary battery) Example 1: Elastic Sheet (50 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (37 μm, Si particles:CNT:Binder = 3:1:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) (Fabrication of positive electrode layer)

[0227] As the positive electrode active material, LiNi coated with Li2O-ZrO2 (LZO) 0.8 Co 0.15 Al 0.05O2(NCA) was prepared. The LZO-coated cathode active material was prepared by the method disclosed in Korean Patent Publication No. 10-2016-0064942. As the solid electrolyte, Li6PS5Cl (D50 = 0.5 μm, crystalline), which is an argyrodite-type crystal, was prepared. As the binder, a polytetrafluoroethylene (PTFE) binder was prepared. As the conductive material, carbon nanofibers (CNF) were prepared. These materials were mixed with a xylene solvent in a weight ratio of cathode active material:solid electrolyte:conductive material:binder = 84:11:3:2 to form a slurry, which was then formed into a sheet and vacuum dried at 40 °C for 8 hours to produce a cathode sheet. The produced cathode sheet was placed on the carbon layer of a cathode current collector made of aluminum foil coated with a carbon layer on one side, and a cathode layer was produced by heated roll pressing at 85 °C. The total thickness of the cathode layer was about 112 μm. The thickness of the cathode active material layer was about 92 μm, and the thickness of the carbon-coated aluminum foil was about 20 μm.

[0228] The initial charge capacity of the cathode was measured by the above-described half-cell. The initial charge capacity of the cathode active material layer was 25 mAh.

[0229] (Anode Fabrication) As the negative electrode current collector, a SUS foil with a thickness of 10 μm was prepared. As the first negative electrode active material, silicon (Si) particles with a primary particle size of 1 μm were prepared. As the second negative electrode active material, a 3:1 weight ratio mixture of carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle size of about 60 nm was prepared. As the fibrous carbon-based material, carbon nanotubes were prepared. The carbon nanotubes contained a carbon nanotube primary structure and a carbon nanotube secondary structure. The carbon nanotube primary structure consisted of one carbon nanotube unit. The length of the carbon nanotube unit was 200 nm to 300 nm, and the diameter of the carbon nanotube unit was about 5 to 10 nm. The carbon nanotube secondary structure was formed by aggregating a plurality of carbon nanotube units. The length of the carbon nanotube secondary structure was about 5 μm, and the diameter was about 40 nm.

[0230] 3 g of a 3:1 weight ratio mixture of silicon (Si) particles and carbon nanotubes and 1 g of a 3:1 weight ratio mixture of carbon black (CB) and silver (Ag) were placed in a container, and 4 g of an NMP solution containing 7 wt% of a PVDF binder (#9300 from Kuraray Co., Ltd.) was added thereto to prepare a mixed solution. While adding NMP little by little to the prepared mixed solution, the mixed solution was stirred to prepare a slurry. The prepared slurry was applied to a SUS substrate using a bar coater, dried in air at 80 °C for 10 minutes, and then vacuum dried at 40 °C for 10 hours to prepare a laminate. The prepared laminate was cold roll pressed to flatten the surface to prepare a negative electrode having a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was about 27 μm.

[0231] The initial charge capacity of the negative electrode was measured by the above-described half-cell. The initial charge capacity of the first negative electrode active material layer was 9.0 mAh.

[0232] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer was 0.36. The initial charge capacity of the positive electrode active material layer was determined during charging from the first open circuit voltage (1 st open circuit voltage) to 4.25 V (vs. Li / Li + ). The initial charge capacity of the first negative electrode active material layer was determined during charging from the second open circuit voltage (2 nd open circuit voltage) to 0.01 V (vs. Li / Li + ).

[0233] In Examples 2 to 5 and Comparative Example 1, the ratios (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer, measured under the same conditions as in Example 1, were 0.23 to 0.44, respectively.

[0234] (Fabrication of Solid Electrolyte Layer) To Li6PS5Cl solid electrolyte (D 50 = 3.0 μm, crystalline), which is an argyrodite-type crystal, 1.5 parts by weight of an acrylic binder was added to 98.5 parts by weight of the solid electrolyte to prepare a mixture. While stirring, octyl acetate was added to the prepared mixture to prepare a slurry. The prepared slurry was applied onto a nonwoven fabric placed on a PET substrate using a bar coater and dried in air at 80 °C for 10 minutes to prepare a laminate. The prepared laminate was vacuum dried at 80 °C for 2 hours to fabricate a solid electrolyte layer.

[0235] (Inert Member: Elastic Sheet) A porous polyurethane foam sheet with a thickness of 50 μm was prepared as the elastic sheet.

[0236] (Fabrication of All-Solid-State Secondary Battery) A solid electrolyte layer was disposed on the negative electrode such that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a positive electrode was disposed on the solid electrolyte layer such that the positive electrode active material layer was in contact with the solid electrolyte layer to prepare a laminate.

[0237] The prepared laminate was subjected to a plate press treatment at 85°C under a pressure of 500 MPa for 30 minutes. By this pressing treatment, the solid electrolyte layer was sintered and the battery characteristics were improved. The thickness of the sintered solid electrolyte layer was about 30 μm. The density of the Li6PS5Cl solid electrolyte, which is an Argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc. The area of the solid electrolyte layer was the same as that of the negative electrode. An elastic sheet was further disposed on the positive electrode current collector of the pressed laminate.

[0238] The laminate further including the elastic sheet was put into a pouch and vacuum-sealed to fabricate an all-solid-state secondary battery. A part of the positive electrode current collector and the negative electrode current collector was extended to the outside of the sealed battery and used as a positive electrode terminal and a negative electrode terminal.

[0239] Example 2: Elastic Sheet (50 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (37 μm, Si particles:CNT:Binder = 3.2:0.8:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) An all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the composition ratio of the negative electrode active material and the fibrous carbon-based material was changed to 3.2:0.8 (4:1).

[0240] Example 3: Elastic Sheet (50 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (37 μm, Si particles:CNT:Binder = 3.5:0.5:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) An all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the composition ratio of the negative electrode active material and the fibrous carbon-based material was changed to 3.5:0.5 (7:1).

[0241] Example 4: Elastic Sheet (50 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (37 μm, Si particles:CNT:Binder = 3.6:0.4:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) An all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the composition ratio of the negative electrode active material and the fibrous carbon-based material was changed to 3.6:0.4 (9:1).

[0242] Example 5: Elastic Sheet (50 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (37 μm, Si particles:CNT:Binder = 2:2:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) An all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the composition ratio of the negative electrode active material and the fibrous carbon-based material was changed to 2:2 (1:1).

[0243] Example 6: Elastic Sheet (50 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (37 μm, Si particles:CNT:Binder = 3:1:0.28): (Si-CNT:Ag-supported Carbon = 3:1 weight ratio) A full solid-state secondary battery was fabricated in the same manner as in Example 1, except that 1 g of carbon black on which the following silver particles were supported was used instead of 1 g of a 3:1 weight ratio mixture of carbon black and silver particles as the second negative electrode active material.

[0244] (Preparation of Carbon Black Supported with Silver Particles) Carbon black was dispersed in a 1.0 M sulfuric acid solution, stirred for 2 hours, and then filtered and dried to prepare acid-treated carbon black.

[0245] 10 g of the acid-treated carbon black was added to a mixed solvent of 1500 g of distilled water, 1500 g of ethyl alcohol, and 30 g of glycerol, stirred, and then 2 g of AgNO3 was added and stirred to prepare a mixed solution. The particle size of the carbon black was 80 nm. A reducing agent was added to the mixed solution to reduce and support silver ions on the carbon black. The carbon black supported with silver-containing particles was filtered, washed, and dried to prepare a composite negative electrode active material. As a result of scanning electron microscope and XPS measurements, it was confirmed that a plurality of silver-containing particles were supported on the carbon black particles. The silver-containing particles were silver particles, silver oxide (Ag2O) particles, and composite particles of silver (Ag) and silver oxide (Ag2O). The content of the silver-containing particles in the composite negative electrode active material (carbon black supported with silver-containing particles) was 5 wt%. The average particle size of the silver particles was 10 nm.

[0246] Comparative Example 1: Elastic Sheet (50 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (37 μm, Si particles:CNT:Binder = 3.6:0.4:0): (Si-CNT:Ag-C = 4:0 weight ratio) A full solid-state secondary battery was fabricated in the same manner as in Example 4, except that 4 g of a 3:1 weight ratio mixture of silicon (Si) particles and carbon nanotubes was used instead of a 3:1 weight ratio mixture of carbon black (CB) and silver (Ag), and no binder was used.

[0247] Reference Example 1: Elastic Sheet (100 μm) / Cathode Layer (112 μm, NCA) / Solid Electrolyte Layer (30 μm) / Anode Layer (17 μm, Ag-C + Binder): (Si-CNT:Ag-C = 0:4 weight ratio) A all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that a 3:1 weight ratio mixture of carbon black (CB) and silver (Ag) (4 g) was used instead of a 3:1 weight ratio mixture of silicon (Si) particles and carbon nanotubes, the thickness of the negative electrode active material layer was changed to 7 μm, and the thickness of the elastic sheet was changed to 100 μm. The thickness of the negative electrode layer is the total thickness of the negative electrode current collector and the negative electrode active material layer.

[0248] Example 7: Cathode Layer (113.8 μm, Li 2 (S-LiI-CNF) / Solid electrolyte layer (30 μm) / Negative electrode layer (37 μm, Si particles: CNT: Binder = 3:1:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) A all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that a positive electrode containing a sulfide-based positive electrode active material was used and the elastic sheet was omitted.

[0249] (Positive electrode fabrication) The Li2S-LiI-CNF composite prepared in Production Example 1 was prepared as a positive electrode active material. As a solid electrolyte, Li6PS5Cl, which is an argyrodite-type crystal (D50 = 3.0 μm, crystalline), was prepared. PTFE was prepared as a binder. These materials were mixed at a weight ratio of composite positive electrode active material:solid electrolyte:binder = 60:40:1.2 to prepare a positive electrode mixture. The positive electrode mixture was obtained by mixing using a ball mill.

[0250] The positive electrode mixture was placed on one surface of a positive electrode current collector made of aluminum foil coated with carbon on one side, and plate pressed at a pressure of 200 MPa for 10 minutes to fabricate a positive electrode. The total thickness of the positive electrode layer was about 113.8 μm. The thickness of the positive electrode active material layer was about 93.8 μm, and the thickness of the aluminum foil coated with carbon was about 20 μm.

[0251] In Example 7, the ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer was 0.35. The initial charge capacity of the positive electrode active material layer was from the first open circuit voltage (1 st open circuit voltage) to 2.8 V (vs. Li / Li +) was determined during the charging up to. The initial charging capacity of the first negative electrode active material layer is from the second open circuit voltage (2 nd open circuit voltage) to 0.01 V (vs. Li / Li + ) and was determined during the charging up to.

[0252] Comparative Example 2: Positive electrode layer (113.8 μm, Li 2 (S-LiI-CNF) / Solid electrolyte layer (30 μm) / Negative electrode layer (37 μm, Si particles: CNT: Binder = 3.6:0.4:0): (Si-CNT:Ag-C = 4:0 weight ratio) A all-solid-state secondary battery was fabricated in the same manner as in Example 4, except that the positive electrode of Example 7 was used, 4 g of a mixture of silicon (Si) particles and carbon nanotubes with a weight ratio of 9:1 was used, a mixture of carbon black (CB) and silver (Ag) with a weight ratio of 3:1 was not used, no binder was used, and the elastic sheet was omitted.

[0253] Reference Example 2: Elastic sheet (50 μm) / Positive electrode layer (113.8 μm, Li 2 (S-LiI-CNF) / Solid electrolyte layer (30 μm) / Negative electrode layer (17 μm, Ag-C + Binder): (Si-CNT:Ag-C = 0:4 weight ratio) A all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 7 was used, a mixture of silicon (Si) particles and carbon nanotubes with a weight ratio of 3:1 was not used, 4 g of a mixture of carbon black (CB) and silver (Ag) with a weight ratio of 3:1 was used, and the thickness of the negative electrode active material layer was changed to 7 μm. The thickness of the negative electrode layer is the total thickness of the negative electrode current collector and the negative electrode active material layer.

[0254] Example 8: Positive electrode layer (113.8 μm, Li 2 (S-LiI-AlI 3 (-CNF composite) / Solid electrolyte layer (30 μm) / Negative electrode layer (37 μm, Si particles: CNT: Binder = 3:1:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) A all-solid-state secondary battery was fabricated in the same manner as in Example 7, except that the Li2S-LiI-AlI3-CNF composite prepared in Production Example 2 was used as the positive electrode active material instead of the Li2S-LiI-CNF composite.

[0255] Reference Example 3: Positive electrode layer (113.8 μm, Li 2 (S-LiI-AlI 3 (-CNF mixture) / Solid electrolyte layer (30 μm) / Negative electrode layer (37 μm, Si particles: CNT: Binder = 3:1:0.28): (Si-CNT:Ag-C = 3:1 weight ratio) A all-solid-state secondary battery was fabricated in the same manner as in Example 7, except that a simple mixture of Li2S, LiI, AlI3, and CNF prepared in Reference Production Example 1 was used as the positive electrode active material instead of the Li2S-LiI-CNF composite.

[0256] Evaluation Example 1-1: Evaluation of volume change during charge and discharge (NCA positive electrode active material) For all-solid-state secondary batteries manufactured in Example 1 and Reference Example 1, after performing only the charging stage of the first cycle in the charge-discharge experiment of Evaluation Example 3 below, a scanning electron microscope image of the cross-section of the all-solid-state secondary battery was measured to observe the thickness change.

[0257] A lithium metal layer was formed between the first negative electrode active material layer and the negative electrode current collector after the first cycle charging.

[0258] In the all-solid-state secondary battery of Example 1, the thickness of the lithium metal layer formed between the first negative electrode active material layer and the negative electrode current collector after the initial charging was about 8 μm, which was smaller than the thickness (34 μm) of the first negative electrode active material layer after charging.

[0259] The increase in the thickness of the all-solid-state secondary battery of Example 1 after the initial charging was 10% or less of the initial thickness of the all-solid-state secondary battery. As a result, the volume change was suppressed during the charge-discharge process of the all-solid-state secondary battery of Example 1.

[0260] In the all-solid-state secondary battery of Example 1, a 50-μm-thick elastic member was used to accommodate the volume change during charge and discharge. As a result, including the 50-μm-thick elastic member caused a partial decrease in the energy density of the all-solid-state secondary battery.

[0261] The thickness of the lithium metal layer formed between the first negative electrode active material layer and the negative electrode current collector after the initial charging of the all-solid-state secondary battery of Reference Example 1 was about 30 μm, which was larger than the thickness (7 μm) of the first negative electrode active material layer after charging.

[0262] The increase in the thickness of the all-solid-state secondary battery of Reference Example 1 after the initial charging exceeded 15% of the initial thickness of the all-solid-state secondary battery. As a result, the volume change was significant during the charge-discharge process of the all-solid-state secondary battery of Reference Example 1.

[0263] In the all-solid-state secondary battery of Reference Example 1, in order to accommodate the volume change during charge and discharge, an elastic member with a thickness of 100 μm was used. As a result, including the elastic member with a thickness of 100 μm further decreased the energy density of the all-solid-state secondary battery.

[0264] Evaluation Example 1-2: Evaluation of volume change during charge and discharge (Li 2 (S-LiI-CNF positive electrode active material) For the all-solid-state secondary batteries manufactured in Example 7 and Reference Example 2, after performing only the charging stage of the first cycle in the charge-discharge experiment of Evaluation Example 3 below, a scanning electron microscope image of the cross-section of the all-solid-state secondary battery was measured to observe the thickness change.

[0265] After the first cycle charging, a lithium metal layer was formed between the first negative electrode active material layer and the negative electrode current collector.

[0266] In the all-solid-state secondary battery of Example 7, the thickness of the lithium metal layer formed between the first negative electrode active material layer and the negative electrode current collector after the initial charging was about 8 μm, which was smaller than the thickness of the first negative electrode active material layer (34 μm) after charging.

[0267] The increase in the thickness of the all-solid-state secondary battery of Example 7 after the initial charging was 5% or less of the initial thickness of the all-solid-state secondary battery. As a result, the volume change during the charge-discharge process of the all-solid-state secondary battery of Example 7 was negligible.

[0268] In the all-solid-state secondary battery of Example 7, an elastic member for accommodating the volume change during charge and discharge was not used. As a result, there was no decrease in the energy density of the all-solid-state secondary battery due to the elastic member.

[0269] The thickness of the lithium metal layer formed between the first negative electrode active material layer and the negative electrode current collector after the initial charging of the all-solid-state secondary battery manufactured in Reference Example 2 was about 30 μm, which was larger than the thickness of the first negative electrode active material layer (7 μm).

[0270] The increase in the thickness of the all-solid-state secondary battery after the initial charging in Reference Example 2 exceeded 10% of the initial thickness of the all-solid-state secondary battery. As a result, during the charge-discharge process of the all-solid-state secondary battery in Reference Example 2, the volume change was remarkable.

[0271] In order to accommodate the increased volume change during charge and discharge in the all-solid-state secondary battery of Reference Example 2, an elastic member with a thickness of 50 μm was used. As a result, including the elastic member with a thickness of 50 μm caused a partial decrease in the energy density of the all-solid-state secondary battery.

[0272] Evaluation Example 2: XRD analysis and scanning electron microscope analysis For the raw (bare) Li2S, pulverized Li2S, and Li2S-LiI-AlI3-CNF composite prepared in Production Example 2, XRD spectra were measured using CuKα radiation. The measurement results are shown in Table 1 below. From the first peak of the (111) crystal plane of Li2S shown in the XRD spectrum, the size of the Li2S crystallite and the lattice constant were derived.

[0273] The pulverized Li2S was prepared by milling under the same conditions except that in the first stage of Production Example 2, the mixture of Li2S and the first mixture (a 1:1 molar ratio mixture of LiI and AlI3) with a weight ratio of 40:20 was changed to 50 parts by weight of Li2S. The second stage was not carried out.

[0274] For the raw Li2S, pulverized Li2S, and Li2S-LiI-AlI3-CNF composite used in Production Example 2, the particle size of the composite (i.e., D50 particle size) and the particle size of Li2S particles in the composite were measured using a particle size analyzer (PSA) using a laser and a scanning electron microscope. The measurement results are shown in Table 1 below.

[0275]

Table 1

[0276] As shown in Table 1, the Li2S particle size and Li2S crystallite size in the Li2S-LiI-AlI3-CNF composite of Production Example 2 were significantly reduced compared to bare Li2S.

[0277] Although not shown in Table 1, the Li2S lattice constant of the Li2S-LiI-AlI3-CNF composite of Production Example 2 was even larger than the lattice constant of bare Li2S.

[0278] Compared to the lattice constant of bare Li2S, the Li2 S The increase in the lattice constant was determined to be due to the dissolution of LiI and / or AlI3 in the Li2S crystal. Therefore, it was confirmed that Li2S and LiI and / or AlI3 form a solid solution in the Li2S-LiI-AlI3-CNF composite.

[0279] Although not shown in Table 1, the D50 particle size of the Li2S-LiI-AlI3-CNF composite produced in Production Example 2 exceeded 8 μm, the D10 particle size exceeded 2.0 μm, and the D90 particle size was 25 μm.

[0280] Evaluation Example 3: Charge and discharge test The charge-discharge characteristics of all-solid-state secondary batteries fabricated in Examples 1 to 6, Comparative Example 1, and Reference Example 1 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state secondary battery in a thermostat at 45°C.

[0281] In the first cycle, it was charged at a constant current of 0.5 mA / cm 2 until the battery voltage reached 3.9 V to 4.25 V for 12.5 hours. Then, it was discharged at a constant current of 0.5 mA / cm 2 until the battery voltage reached 2.5 V for 12.5 hours.

[0282] On the other hand, the charge-discharge characteristics of all-solid-state secondary batteries fabricated in Examples 7 and 8, Comparative Example 2, and Reference Examples 2 and 3 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state secondary battery in a thermostat at 45°C.

[0283] In the first cycle, charging was performed at a constant current of 0.1C for 12.5 hours until the battery voltage reached 2.5V to 2.8V. Subsequently, discharging was carried out at a constant current of 0.1C for 12.5 hours until the battery voltage reached 0.3V.

[0284] The discharge capacity of the first cycle was taken as the standard capacity.

[0285] After the second cycle, charging and discharging were carried out under the same conditions as the first cycle up to a certain number of cycles (for example, 500 cycles or more). The measurement results are shown in Table 2 below.

[0286] The number of cycles means the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle. The more the number of cycles increases, the better the life characteristics are considered.

[0287]

Table 2

[0288] As shown in Table 2, all-solid-state secondary batteries of Examples 1 to 5 exhibited excellent life characteristics by suppressing volume change during charge and discharge and suppressing an increase in internal resistance.

[0289] The all-solid-state secondary batteries of Examples 1 to 6 had improved life characteristics compared to the all-solid-state secondary battery of Comparative Example 1 that did not contain the second negative electrode active material and binder.

[0290] In the all-solid-state secondary battery of Comparative Example 1, it was determined that the life characteristics of the all-solid-state secondary battery deteriorated due to electrode detachment and / or disconnection of the conductive path due to detachment of the negative electrode active material and the fibrous carbon-based material during the charge and discharge process.

[0291] The all-solid-state secondary batteries of Examples 7 and 8 exhibited excellent life characteristics by suppressing volume change during charge and discharge and suppressing an increase in internal resistance.

[0292] The all-solid-state secondary batteries of Examples 7 and 8 had improved life characteristics compared to the all-solid-state secondary battery of Comparative Example 2 that did not contain the second negative electrode active material and the binder.

[0293] In the all-solid-state secondary battery of Comparative Example 2, it was determined that the life characteristics of the all-solid-state secondary battery deteriorated due to an increase in the interfacial resistance between the first negative electrode active material layer and the solid electrolyte or between the first negative electrode active material layer and the negative electrode current collector during the charge and discharge process due to electrode detachment.

[0294] Although not shown in Table 2, the life characteristics of the all-solid-state secondary battery of Reference Example 3 were lower than those of the all-solid-state secondary battery of Example 8.

[0295] Evaluation Example 4: High rate performance evaluation The high-rate characteristics of the all-solid-state secondary batteries of Examples 1 to 6, Comparative Example 1, and Reference Example 1 were evaluated by the following charge and discharge test. The charge and discharge test was performed by placing the solid-state secondary battery in a constant temperature bath at 45°C.

[0296] The all-solid-state secondary batteries of Examples 1 to 6, Comparative Example 1, and Reference Example 1 were charged at a constant current of 0.1 C rate until the voltage reached 3.9 V (vs. Li) at 45°C, and then cut off at a current of 0.05 C rate while maintaining 3.9 V in the constant voltage mode. Then, it was discharged at a constant current of 0.1 C rate until the voltage reached 2.5 V (vs. Li) during discharge (formation cycle).

[0297] The all-solid-state secondary battery that had undergone the formation cycle was charged at a constant current of 0.2 C rate until the voltage reached 3.9 V (vs. Li) at 45°C. Then, it was discharged at a constant current of 0.2 C rate until the voltage reached 2.5 V (vs. Li) during discharge (first cycle).

[0298] The all-solid-state secondary battery that had undergone the first cycle was charged at a constant current of 0.2 C rate until the voltage reached 3.9 V (vs. Li) at 45°C. Then, it was discharged at a constant current of 0.33 C rate until the voltage reached 2.5 V (vs. Li) during discharge (second cycle).

[0299] The all-solid-state secondary battery after the second cycle was subjected to constant-current charging at 45 °C with a current of 0.2 C rate until the voltage reached 3.9 V (vs. Li). Subsequently, it was discharged at a constant current of 0.5 C rate until the voltage reached 2.5 V (vs. Li) during discharge (the third cycle).

[0300] The all-solid-state secondary battery after the third cycle was subjected to constant-current charging at 45 °C with a current of 0.2 C rate until the voltage reached 3.9 V (vs. Li). Subsequently, it was discharged at a constant current of 1.0 C rate until the voltage reached 2.5 V (vs. Li) during discharge (the fourth cycle).

[0301] After each charge-discharge cycle in all charge-discharge cycles, a rest period of 10 minutes was provided. A part of the room-temperature charge-discharge experiment results is shown in Table 2 below. The high-rate characteristics are defined by the following mathematical formula 1.

[0302] The high-rate characteristics of the all-solid-state secondary batteries of Example 7, Comparative Example 2, and Reference Example 2 were evaluated by the following charge-discharge test. The charge-discharge test was carried out by placing the solid-state secondary battery in a constant-temperature bath at 45 °C.

[0303] The all-solid-state secondary batteries of Example 7, Comparative Example 2, and Reference Example 2 were subjected to constant-current charging at 45 °C with a current of 0.1 C rate until the voltage reached 2.5 V (vs. Li), and then, while maintaining 2.5 V in the constant-voltage mode, it was cut off with a current of 0.05 C rate. Subsequently, during discharge, it was discharged at a constant current of 0.1 C rate until the voltage reached 0.3 V (vs. Li) (formation cycle).

[0304] The all-solid-state secondary battery after the formation cycle was subjected to constant-current charging at 45 °C with a current of 0.2 C rate until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.2 C rate until the voltage reached 0.3 V (vs. Li) during discharge (the first cycle).

[0305] The all-solid-state secondary battery after the first cycle was charged at a constant current of 0.2 C rate at 45 °C until the voltage reached 2.5 V (vs. Li). Then, it was discharged at a constant current of 0.33 C rate until the voltage reached 0.3 V (vs. Li) during discharge (the second cycle).

[0306] The all-solid-state secondary battery after the second cycle was charged at a constant current of 0.2 C rate at 45 °C until the voltage reached 2.5 V (vs. Li). Then, it was discharged at a constant current of 0.5 C rate until the voltage reached 0.3 V (vs. Li) during discharge (the third cycle).

[0307] The all-solid-state secondary battery after the third cycle was charged at a constant current of 0.2 C rate at 45 °C until the voltage reached 2.5 V (vs. Li). Then, it was discharged at a constant current of 1.0 C rate until the voltage reached 0.3 V (vs. Li) during discharge (the fourth cycle).

[0308] After each charge-discharge cycle in all charge-discharge cycles, a rest time of 10 minutes was provided. A part of the room-temperature charge-discharge experiment results is shown in Table 2 below. The high-rate characteristics are defined by the following Equation 1.

[0309] <Equation 1> High-rate characteristics [%] = [Discharge capacity in the fourth cycle / Discharge capacity in the formation cycle] × 100

[0310]

Table 3

[0311] As shown in Table 3, the all-solid-state secondary batteries of Examples 1 to 6 had improved high-rate characteristics compared to the all-solid-state secondary battery of Comparative Example 1.

[0312] In all-solid-state secondary batteries of Examples 1 to 6, since the first negative electrode active material layer simultaneously contains the first negative electrode active material, the second negative electrode active material, and the fibrous carbon-based material, despite the volume change of the first negative electrode active material layer during charge and discharge, the increase in the internal resistance of the first negative electrode active material layer is suppressed, and the uniformity of the electrode reaction is improved, thereby improving the high-rate characteristics as compared with the all-solid-state secondary battery of Comparative Example 1.

[0313] The all-solid-state secondary battery of Example 7 had improved high-rate characteristics as compared with the all-solid-state secondary battery of Comparative Example 2.

[0314] In the all-solid-state secondary battery of Example 7, since the first negative electrode active material layer simultaneously contains the first negative electrode active material, the second negative electrode active material, and the fibrous carbon-based material, despite the volume change of the first negative electrode active material layer during charge and discharge, the increase in the internal resistance of the first negative electrode active material layer is suppressed, and the uniformity of the electrode reaction is improved, thereby improving the high-rate characteristics as compared with the all-solid-state secondary battery of Comparative Example 2.

Explanation of Reference Numerals

[0315] 1 All-solid-state secondary battery 10 Positive electrode 11 Positive electrode current collector 12 Positive electrode active material layer 20 Negative electrode 21 Negative electrode current collector 22 First negative electrode active material layer 23 Thin film 24 Second negative electrode active material layer 30 Solid electrolyte layer 40, 40a, 40b First inert member 50 Second inert member

Claims

1. a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer; the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on one surface of the positive electrode current collector, the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector, the first negative electrode active material layer includes a first negative electrode active material capable of forming an alloy or compound with lithium, a second negative electrode active material, and a fibrous carbon-based material; a ratio (B / A) of an initial charge capacity (B) of the first negative electrode active material layer to an initial charge capacity (A) of the positive electrode active material layer is 0.01 to 0.75; The initial charge capacity of the positive electrode active material layer is a first open circuit voltage (1 st is determined by charging from the open circuit voltage to a maximum charging voltage based on Li / Li+, The initial charge capacity of the first negative electrode active material layer is a second open circuit voltage (2 nd An all-solid-state secondary battery determined by charging from a voltage (open circuit voltage) to 0.01 V based on Li / Li+.

2. 2. The all-solid-state secondary battery according to claim 1, wherein the first negative electrode active material is in a particulate form, the size of the first negative electrode active material is 2 μm or less, and the aspect ratio of the first negative electrode active material is 5 or less.

3. the first negative electrode active material comprises a first metallic negative electrode active material, 3. The all-solid-state secondary battery according to claim 2, wherein the first metal-based negative electrode active material comprises silicon (Si), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

4. The size of the first negative electrode active material is smaller than the length of the fibrous carbon-based material, 2. The all-solid-state secondary battery according to claim 1, wherein a ratio of a size of the first negative electrode active material or a size of the second negative electrode active material to a length of the fibrous carbon-based material is 1:10 to 1:2000.

5. the fibrous carbon-based material is a conductive carbon-based material, The aspect ratio of the fibrous carbon-based material is 10 or more; 2. The all-solid-state secondary battery according to claim 1, wherein the fibrous carbon-based material comprises an amorphous fibrous carbon-based material, a crystalline fibrous carbon-based material, or a combination thereof.

6. The fibrous carbon-based material includes a fibrous carbon nanostructure, 2. The all-solid-state secondary battery of claim 1, wherein the fibrous carbon nanostructures comprise carbon nanotubes, carbon nanofibers, carbon nanobelts, or combinations thereof.

7. the carbon nanotube comprises a carbon nanotube primary structure, a carbon nanotube secondary structure comprising a plurality of carbon nanotube primary particles, or a combination thereof; The all-solid-state secondary battery according to claim 6 , wherein the carbon nanotube primary structure is one carbon nanotube unit.

8. The carbon nanotube primary structure includes a single-walled carbon nanotube (SWCNT), a double-walled carbon nanotube (DWCNT), a multi-walled carbon nanotube (MWCNT), or a combination thereof; The carbon nanotube primary structure has a diameter of 1 nm to 20 nm and a length of 100 nm to 2 μm; The carbon nanotube secondary structure comprises a bundle-type carbon nanotube, a rope-type carbon nanotube, or a combination thereof; 8. The all-solid-state secondary battery according to claim 7, wherein the diameter of the carbon nanotube secondary structure is 2 nm to 50 nm, and the length of the carbon nanotube secondary structure is 500 nm to 1000 μm.

9. the second negative electrode active material is particulate, the size of the second negative electrode active material is less than 1 μm, and the aspect ratio of the second negative electrode active material is 5 or less; the second negative electrode active material comprises a carbon-based negative electrode active material, a second metal-based negative electrode active material distinct from the first negative electrode active material, or a combination thereof; The carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof; 2. The all-solid-state secondary battery according to claim 1, wherein the second metal-based negative electrode active material comprises gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

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

11. the second negative electrode active material comprises a composite negative electrode active material; the composite negative electrode active material includes a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support, The metal-based negative electrode active material includes a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof; The metal-based negative electrode active material has a particulate shape, and the particle size of the metal-based negative electrode active material is 1 nm to 200 nm; 2. The all-solid-state secondary battery according to claim 1, wherein the carbon-based support has a particulate shape, and the particle size of the carbon-based support material is 10 nm to 2 μm.

12. the first negative electrode active material layer includes a binder, 2. The all-solid-state secondary battery of claim 1, wherein the binder comprises a polymer binder, the binder comprises a fluorine-based binder, and a content of the binder is 0.1 to 20 parts by weight based on 100 parts by weight of a mixture of the first negative electrode active material and the second negative electrode active material.

13. the thickness of the first negative electrode active material layer is 50% or less of the thickness of the positive electrode active material layer, 2. The all-solid-state secondary battery according to claim 1, wherein the thickness of the first negative electrode active material layer is 1 to 50 μm.

14. a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer, or between the negative electrode current collector and an electrolyte layer; the second negative electrode active material layer is a metal layer, the metal layer containing lithium or a lithium alloy, The all-solid-state secondary battery according to claim 1 , wherein a thickness of the second negative electrode active material layer is smaller than a thickness of the first negative electrode active material layer.

15. the positive electrode active material layer contains a positive electrode active material, The positive electrode active material includes a sulfide-based positive electrode active material, an oxide-based positive electrode active material, or a combination thereof; The sulfide-based positive electrode active material is nickel sulfide, copper sulfide, Li ２ S., Li. ２ S-containing complexes, or combinations thereof, 2. The all-solid-state secondary battery according to claim 1, wherein the oxide-based positive electrode active material comprises a lithium transition metal oxide, a metal oxide, or a combination thereof, the lithium transition metal oxide comprises lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminium oxide, lithium nickel cobalt manganese oxide, lithium manganate, lithium iron phosphate, or a combination thereof, and the lithium transition metal oxide comprises iron oxide, vanadium oxide, or a combination thereof.

16. The Li ２ The S-containing complex is Li ２ A complex of S and a lithium salt, Li ２ A composite of S, a lithium salt, and a conductive material, Li ２ Complex of S and metal halide, Li ２ A composite of S, a metal halide and a conductive material, Li ２ A complex of S, a lithium salt and a metal halide, Li ２ A complex of S, a lithium salt, a metal halide, and a conductive material, or a combination thereof; The Li ２ The complex of S and a lithium salt is Li ２ S-Li ａ X1 ｂ (1≦a≦5, 1≦b≦5), The Li ２ A complex of S, a lithium salt, a metal halide, and a conductive material is Li ２ S-Li ａ X1 ｂ -C (1≦a≦5, 1≦b≦5) The Li ２ The complex of S and metal halide is Li ２ S-M ｃ X2 ｄ (1≦c≦5, 1≦d≦5), The Li ２ The composite of S, metal halide and conductive material is Li ２ S-M ｃ X2 ｄ -C (1≦c≦5, 1≦d≦5), The Li ２ A complex of S, a lithium salt, and a metal halide is Li ２ S-Li ａ X1 ｂ -M ｃ X2 ｄ (1≦a≦5, 1≦b≦5, 1≦c≦5, 1≦d≦5), The Li ２ A complex of S, a lithium salt, a metal halide, and a conductive material is Li ２ S-Li ａ X1 ｂ -M ｃ X2 ｄ -C (1≦a≦5, 1≦b≦5, 1≦c≦5, 1≦d≦5), The X1 is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF ６ , B.F. ４ , SbF, AsF ６ , ClO ４ , AlO ２ , AlCl ４ , NO ３ , CO ３ , B.H. ４ , S.O. ４ , B.O. ３ , P.O. ４ , NCl, NCl ２ , B.N. ２ or a combination thereof, M is one or more metals selected from Groups 2 to 15 of the Periodic Table of Elements; The all-solid-state secondary battery according to claim 1 , wherein X2 is I, Br, Cl, F, or a combination thereof.

17. The positive electrode active material layer further includes at least one selected from a solid electrolyte, a conductive material, and a binder, the solid electrolyte includes a sulfide-based solid electrolyte, the conductive material includes a carbon-based conductive material, and the solid electrolyte layer includes a solid electrolyte or a combination of a solid electrolyte and a gel electrolyte; The solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof; The all-solid-state secondary battery according to claim 1 , wherein the gel electrolyte comprises a polymer gel electrolyte.

18. The sulfide-based solid electrolyte is Li ２ S-P ２ S ５ , Li ２ S-P ２ S ５ -LiX (X is a halogen element), Li ２ S-P ２ S ５ -Li ２ O., Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ , Li ２ S-SiS ２ - LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ - LiI, Li ２ S-SiS ２ -P ２ S ５ - LiI, Li ２ S-B ２ S ３ , Li ２ S-P ２ S ５ -Z ｍ S ｎ (m and n are positive numbers, Z is one of Ge, Zn and Ga), Li ２ S-GeS ２ , Li ２ S-SiS ２ -Li ３ P.O. ４ , Li ２ S-SiS ２ -Li ｐ M.O. ｑ (p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In), Li ７－ｘ P.S. ６－ｘ C ｘ (0≦x≦2), Li ７－ｘ P.S. ６－ｘ B ｘ (0≦x≦2), and Li ７－ｘ P.S. ６－ｘ I ｘ (0≦x≦2), The sulfide-based solid electrolyte includes an Argyrodite-type solid electrolyte, The Argyrodite-type solid electrolyte is Li ６ P.S. ５ Cl, Li ６ P.S. ５ Br and Li ６ P.S. ５ I, The all-solid-state secondary battery according to claim 17, wherein the density of the Argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc.

19. At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, the base film comprises a polymer, the polymer comprising polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof; 2. The all-solid-state secondary battery according to claim 1, wherein the metal layer comprises 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.

20. The positive electrode current collector and the negative electrode current collector may further include a first inactive member disposed on at least one of the other surface of the positive electrode current collector and the other surface of the negative electrode current collector, The all-solid-state secondary battery according to claim 1 , wherein the first inactive member is an elastic member.

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