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

Abstract

Disclosed are an all-solid-state secondary battery and a method for manufacturing same, the battery comprising a cathode layer, an anode layer, and a solid electrolyte layer disposed between the cathode layer and the anode layer, wherein: the cathode layer comprises a cathode current collector and a cathode active material layer disposed on one surface or both surfaces of the cathode current collector; the cathode active material layer comprises a composite cathode active material, a carbon-based material, and a solid electrolyte and contains a composite including M2S and molybdenum sulfide (Mo6S8), in which M is an alkali metal, the alkali metal being Li or Na; and the anode layer comprises an anode current collector and a first anode active material layer disposed on one surface of the anode current collector.

Description

All-solid-state secondary battery and its manufacturing method

[0001] It relates to an all-solid-state secondary battery and a method for manufacturing the same.

[0002] Recently, there has been active development of batteries that offer increased energy density and safety. Lithium batteries are used in information technology, communication devices, and automobiles. Because automobiles are life-threatening, safety is paramount.

[0003] Lithium batteries containing liquid electrolytes contain flammable organic solvents. Lithium batteries containing liquid electrolytes have a high risk of overheating and fire in the event of a short circuit.

[0004] Solid electrolytes offer reduced risk of overheating and fire during short circuits compared to liquid electrolytes. Lithium batteries containing solid electrolytes can offer improved safety compared to those containing liquid electrolytes.

[0005] Secondary batteries use sulfur-based materials (e.g., S) as cathode active materials to increase capacity. Since lithium is not included in the cathode during the manufacturing of secondary batteries containing sulfur-based materials, lithium metal is used for the anode. During the initial discharge process of the secondary battery, lithium metal migrates to the cathode containing the sulfur-based material, and then, during the subsequent charging process, lithium metal is deposited again between the anode current collector and the electrolyte layer. During the lithium deposition process, irregular lithium deposition can easily form lithium dendrites and / or isolated lithium. The formation of such lithium dendrites and / or isolated lithium can reduce the reversibility of the electrode reaction. A method for suppressing the uneven deposition of lithium from the anode is required.

[0006] In secondary batteries containing lithium metal, a short circuit between the lithium metal and the cathode may occur due to the growth of lithium dendrites and / or the dissolution of molten lithium during the charge / discharge process. A secondary battery capable of effectively preventing such lithium dendrites and / or lithium metal from forming a short circuit between the cathode and the cathode during the charge / discharge process is required.

[0007] In secondary batteries containing lithium metal, significant changes in the thickness of the negative electrode due to precipitation and dissolution of the lithium metal layer during charge and discharge can accelerate deterioration of the secondary battery. A secondary battery capable of suppressing significant volume changes, such as thickness changes, of the negative electrode during charge and discharge is required.

[0008] One aspect is to provide an all-solid-state secondary battery with improved high-rate characteristics and lifespan characteristics by employing a positive electrode with improved impedance characteristics including a novel composite positive electrode active material.

[0009] Another aspect is to provide a method for manufacturing the above-described all-solid-state secondary battery.

[0010] According to one embodiment, a cathode layer; a cathode layer; and a solid electrolyte layer disposed between the cathode layer and the anode layer, wherein the cathode layer includes a cathode current collector; and a cathode active material layer disposed on one or both surfaces of the cathode current collector, wherein the cathode active material layer includes a composite cathode active material, a carbon-based material, and a solid electrolyte.

[0011] M2S; and a composite comprising at least one molybdenum compound selected from molybdenum sulfide (Mo6S8) and lithiated molybdenum sulfide,

[0012] An all-solid-state secondary battery is provided, wherein the above M is an alkali metal, the alkali metal is Li or Na, and 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.

[0013] According to another aspect, a method for manufacturing an all-solid-state secondary battery is provided, comprising: a step of obtaining a composite by milling a composition including M2S and molybdenum sulfide (Mo6S8); a step of preparing a positive electrode containing a positive electrode active material layer including a positive electrode current collector and a composite positive electrode active material using a composition in which a carbon-based material and a solid electrolyte are added and mixed into the composite; a step of preparing an anode; and a step of disposing a solid electrolyte layer between the positive electrode and the anode.

[0014] According to another aspect, a composite cathode active material is provided, which contains a composite including M2S and molybdenum sulfide (Mo6S8), wherein M is an alkali metal, and the alkali metal is Li or Na.

[0015] According to another aspect, a positive electrode comprising the composite positive electrode active material described above is provided.

[0016] According to one aspect, an all-solid-state secondary battery having improved positive electrode impedance characteristics and improved energy density and high-rate characteristics can be provided by employing the same.

[0017] Figure 1 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0018] Figure 2 is a cross-sectional view of an all-solid-state secondary battery according to another embodiment.

[0019] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to another embodiment.

[0020] Figures 4 and 5 are cross-sectional views of an all-solid-state secondary battery according to another embodiment.

[0021] <Explanation of symbols for major parts of the drawing>

[0022] 1 All-solid-state secondary battery 10 Cathode layer

[0023] 11. Cathode current collector 12. Cathode active material layer

[0024] 20 Cathode layer 21 Cathode current collector

[0025] 22 Lithium host layer 30 Solid electrolyte layer

[0026] 40 Inert member 41 Second inert member

[0027] 42 First inert member

[0028] Various embodiments are illustrated in the accompanying drawings. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0029] When a component is referred to as being "on" another component, it can be understood that it is either directly on top of the other component or that other components may be intervening between them. Conversely, when a component is referred to as being "directly on" another component, no intervening components are present.

[0030] Although the terms "first," "second," "third," etc. may be used herein to describe various components, elements, regions, layers, and / or zones, these components, elements, regions, layers, and / or zones should not be limited by these terms. These terms are used only to distinguish one component, element, region, layer, or zone from another component, element, region, layer, or zone. Thus, a first component, element, region, layer, or zone described below may be referred to as a second component, element, region, layer, or zone without departing from the teachings of this specification.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms including "at least one," unless the content clearly dictates otherwise. "At least one" should not be construed as limiting to the singular. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The terms "comprises" and / or "comprising" as used in the detailed description specify the presence of stated features, regions, integers, steps, operations, components, and / or ingredients, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, ingredients, and / or groups thereof.

[0032] Spatially relative terms such as "below," "under," "bottom," "above," "above," and "top" may be used herein to readily describe the relationship of one component or feature to another. It will be understood that spatially relative terms are intended to encompass different orientations of the device when in use or operation in addition to the orientations depicted in the drawings. For example, if the device in the drawings were turned over, a component described as "below" or "below" another component or feature would then be oriented "above" the other component or feature. Thus, the exemplary term "below" can encompass both the above and below orientations. The device may be arranged in other orientations (rotated 90° or otherwise rotated), and the spatially relative terms used herein may be interpreted accordingly.

[0033] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Furthermore, it will be understood that terms defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning within the context of the relevant art and the present disclosure, and not in an idealized or overly formal sense.

[0034] Exemplary embodiments are described herein with reference to cross-sectional drawings that are schematic representations of idealized embodiments. As such, variations from the shapes depicted are to be expected, for example, as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of regions as depicted herein, but should encompass variations in shapes resulting from, for example, manufacturing. For example, regions depicted or described as flat may typically have rough and / or non-linear features. Moreover, angles depicted as sharp may be rounded. Therefore, the regions depicted in the drawings are schematic in nature, and their shapes are not intended to depict the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0035] "Group" means a group in the periodic table of elements according to the International Union of Pure and Applied Chemistry ("IUPAC") Group 1-18 classification system.

[0036] In this specification, "particle size" refers to the average diameter when the particles are spherical, and the average major axis length when the particles are non-spherical. Particle size can be measured using a particle size analyzer (PSA). "Particle size" or "particle size" is, for example, the average particle diameter. "Average particle diameter" is, for example, the median particle diameter, D50.

[0037] D50 is the size of the particle corresponding to 50% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0038] D90 is the size of the particle corresponding to 90% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0039] D10 is the size of the particle corresponding to 10% of the cumulative volume, calculated from the particle side with a small particle size in the particle size distribution measured by laser diffraction.

[0040] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0041] In this disclosure, “alloy” means a mixture of two or more metals.

[0042] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0043] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0044] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0045] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from an electrode active material.

[0046] In the present disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery, and “discharging” and “discharging” mean a process of removing electrochemical energy from a battery.

[0047] In the present disclosure, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during a discharge process, and “negative electrode” and “anode” mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0048] In the present disclosure, the aspect ratio represents the ratio (L1 / L2) of the major axis length L1 (e.g., length) and the minor axis length L2 (e.g., diameter). Here, the aspect ratio, major axis length, minor axis length, length, and diameter represent the average aspect ratio, average major axis length, average minor axis length, average length, and average diameter. The aspect ratio can be evaluated using a scanning electron microscope.

[0049] In the present disclosure, “thickness”, “length” and “width” represent average thickness, average length and average width, respectively.

[0050] In this specification, a solid solution is different from a mixture of two or more chemical species and refers to a homogeneous crystal phase containing two or more chemical species.

[0051] While specific implementations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or unforeseen may occur to the applicant or those skilled in the art. Accordingly, the appended claims, as filed and as amended, are intended to encompass all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0052] Hereinafter, an all-solid-state secondary battery according to exemplary implementation examples will be described in more detail.

[0053] Hereinafter, composite cathode active materials and cathodes and all-solid-state secondary batteries including the composite cathode active materials according to exemplary embodiments will be described in more detail.

[0054] [Composite cathode active material]

[0055] A composite cathode active material according to an embodiment of the present invention comprises a composite including M2S; and at least one molybdenum compound selected from molybdenum sulfide (Mo6S8) and lithiated molybdenum sulfide, wherein M is an alkali metal, and the alkali metal is Li or Na.

[0056] Lithiated molybdenum sulfide is, for example, Li x Mo6S8(0 <x≤4)이다.

[0057] The above composite cathode active material is, for example, a composite of lithium sulfide and molybdenum sulfide (Mo6S8) (Li2S-Mo6S8 composite), a composite of lithium sulfide and lithiated molybdenum sulfide (Li2S-Li x Mo6S8(0 <x≤4) 복합체), 또는 황화리튬과 몰리브덴 설파이드(Mo6S8)와 리튬화된 몰리브덴 설파이드의 복합체를 포함한다.

[0058] The ionic conductivity and electronic conductivity of lithium sulfide can be simultaneously improved by forming a complex with molybdenum sulfide (Mo6S8).

[0059] Molybdenum sulfide (Mo6S8) has chevrel phases, a very stable host structure, and superior ionic conductivity as well as electronic conductivity compared to MoS2.

[0060] Since the composite includes molybdenum sulfide (Mo6S8) which has excellent ionic and electronic conductivity, the electronic and ionic conductive network of lithium sulfide which has low ionic and electronic conductivity is improved, thereby improving the ionic conductivity of the composite cathode active material, and the internal resistance of the cathode and all-solid-state secondary battery including the composite cathode active material can be reduced. In addition, by using the composite containing molybdenum sulfide (Mo6S8), the content of the carbon-based conductive material can be reduced, which can suppress side reactions with the solid electrolyte and also improve the volumetric energy density. In addition, due to the synergistic effect of the intercalation reaction and the conversion reaction of lithium sulfide, the activation energy of lithium sulfide is lowered, thereby improving high-rate characteristics, initial efficiency, and cycle life characteristics.

[0061] In addition, the composite cathode active material can improve electronic conductivity by including a carbon-based material, and the internal resistance of the cathode and all-solid-state secondary battery including the composite cathode active material can be reduced.

[0062] The composite includes lithium sulfide (Li2S). Since lithium sulfide has a high theoretical capacity, it can provide a secondary battery having a high energy density. However, since lithium sulfide has low ionic conductivity and / or electronic conductivity, a composite of molybdenum sulfide (Mo6S8) is formed to overcome this drawback. The content of lithium sulfide in the composite is, for example, 60 to 99 parts by weight, 65 to 95 parts by weight, or 60 to 80 parts by weight based on 100 parts by weight of the total weight of the composite. If the content of lithium sulfide is excessively increased, it may not be easy to improve the ionic conductivity and / or electronic conductivity of lithium sulfide. If the content of lithium sulfide is excessively low, the energy density of the all-solid-state secondary battery may be reduced.

[0063] In the above composite, the size of lithium sulfide (e.g., the average particle diameter of lithium sulfide particles) is 0.1 nm to 10 μm, or 10 nm to 1 μm. By using lithium sulfide having the above-described size, the grain boundaries between a plurality of lithium sulfides can more easily accommodate the volume change of the lithium sulfide during charge and discharge, so that the volume change of the composite during charge and discharge can be alleviated, and the possibility of defects such as cracks occurring due to the volume change of the composite during charge and discharge can be reduced. By including such a composite in the composite cathode active material, the cycle characteristics of an all-solid-state secondary battery including the composite cathode active material can be improved. For example, the life characteristics of an all-solid-state secondary battery including such a composite cathode active material are improved. The size of the composite particles of Li2S and a lithium salt can be measured using, for example, laser diffraction, a scanning electron microscope, etc. The size of the complex of Li2S and lithium salt is the arithmetic mean of the particle sizes of multiple particles measured using software from, for example, scanning electron microscope images.

[0064] When the size of the lithium sulfide is within the above-described range, the contact area between lithium sulfide and molybdenum sulfide (Mo6S8) and / or carbon-based material is further increased, and thus the ionic conductivity and / or battery conductivity of the composite can be further improved by increasing the contact area between lithium sulfide and molybdenum sulfide (Mo6S8) or carbon-based material. By including such a composite in the composite cathode active material, the reversibility of the electrode reaction can be improved in an all-solid-state secondary battery including the composite cathode active material. As a result, the specific capacity of the composite cathode active material can be increased.

[0065] In the above complex, the content of a molybdenum compound such as molybdenum sulfide (Mo6S8) is 1 to 40 parts by weight, or 5 to 30 parts by weight, or 5 to 25 parts by weight, or 10 to 25 parts by weight.

[0066] The complex is composed of lithium sulfide and lithium intercalated molybdenum sulfide (Li x Mo6S8)(0 <x≤4)를 포함함에 의하여 복합체의 이온전도도가 증가할 수 있다. Li x Mo6S8 may include, for example, Li1Mo6S8, Li2Mo6S8, Li3Mo6S8, Li4Mo6S8 or a combination thereof.

[0067] The composite cathode active material according to the present invention is Li, which is lithiated Mo6S8. x Mo6S8(0 <x≤4)을 함유한다.

[0068] For example, a lithium sulfide and molybdenum sulfide (Mo6S8) complex is formed by intercalating lithium ions into molybdenum sulfide (Li x Since it includes lithium sulfide (Mo6S8), the ionic conductivity of the lithium sulfide and molybdenum sulfide (Mo6S8) composite can be improved compared to the ionic conductivity of lithium sulfide, and as a result, the internal resistance of the composite can be reduced.

[0069] By using a positive electrode containing the above-described composite, a lithium metal negative electrode can be eliminated, enabling the use of an all-solid-state secondary battery without an anode, thereby providing an all-solid-state secondary battery with improved energy density. Furthermore, by including such a composite positive electrode active material in the positive electrode, the cycle characteristics of the all-solid-state secondary battery containing the composite positive electrode active material can be improved. For example, the high-rate characteristics of the all-solid-state secondary battery containing such a composite positive electrode active material can be improved.

[0070] The composite cathode active material according to the present invention may further include a carbon-based material.

[0071] The above carbon-based material includes a fibrous carbon-based material, the fibrous carbon-based material includes a carbon nanostructure, and the carbon nanostructure includes carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof, and the content of the carbon-based material is 1 to 50 parts by weight, 5 to 50 parts by weight, or 10 to 30 parts by weight based on 100 parts by weight of the total weight of M2S and molybdenum sulfide (Mo6S8). According to another embodiment, the content of the carbon-based material is 1 to 20 parts by weight, 5 to 20 parts by weight, or 10 to 20 parts by weight based on 100 parts by weight of the total weight of M2S and molybdenum sulfide (Mo6S8). When the content of the carbon-based material is within the above range, an all-solid-state secondary battery with improved life characteristics can be manufactured without problems such as reduced energy density and side reactions.

[0072] The above complex further includes a solid electrolyte, and the content of the solid electrolyte is 1 to 50 parts by weight based on 100 parts by weight of the total weight of M2S and molybdenum sulfide (Mo6S8).

[0073] Li2S-molybdenum sulfide (Mo6S8) complexes are distinguished from simple mixtures of Li2S and molybdenum sulfide (Mo6S8). Simple mixtures of Li2S, molybdenum sulfide (Mo6S8), and carbon-based materials fail to maintain a dense interface between Li2S, molybdenum sulfide (Mo6S8), and the carbon-based material, resulting in high interfacial resistance and consequently degrading the cycle life characteristics of all-solid-state secondary batteries.

[0074] According to an embodiment, molybdenum sulfide (Mo6S8) according to a composite has a plate-like, fiber-like, or irregular shape. Using molybdenum sulfide having such a shape improves the life characteristics by enhancing the electronic and ionic conductivity network within the electrode. In addition, by reducing the conductive material content, the lithium sulfide content within the electrode relatively increases, thereby improving the initial efficiency and electrode energy density.

[0075] The specific surface area of ​​the above molybdenum sulfide is 1 to 50 m 2 / g is.

[0076] When molybdenum sulfide has a fiber shape, the average diameter of the molybdenum sulfide fiber is 1 to 50 um, and the average thickness is 5 to 50 nm. When the molybdenum sulfide has a plate-like shape, when molybdenum sulfide (Mo6S8) has a plate-like shape, for example, the plate-like molybdenum sulfide has a length in the range of 1 to 50 um, a thickness in the range of 0.01 to 10 um, and a width in the range of 1 to 30 um. Here, the length represents the size in the X-axis direction, the thickness represents the size in the Z-axis direction, and the width represents the size in the Y-axis direction.

[0077] The plate-shaped structure has a length, thickness, and width, each in the range of 0.01 to 1 um, after milling of the plate-shaped molybdenum structure contained in the positive electrode of the finally obtained all-solid-state secondary battery.

[0078] The content of molybdenum sulfide (Mo6S8) in the composite may be 1 to 40 wt%, 5 to 35 wt%, 10 to 35 wt%, 15 to 35 wt%, 20 to 35 wt%, or 25 to 35 wt% of the total weight of the composite. If the content of molybdenum sulfide (Mo6S8) increases excessively, the energy density of the all-solid-state secondary battery may decrease. If the content of molybdenum sulfide (Mo6S8) is excessively low, the ionic conductivity of the composite may decrease, which may increase the internal resistance of the composite cathode active material. As a result, the cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0079] The molar ratio of lithium sulfide to molybdenum sulfide (Mo6S8) in the complex may be, for example, 50:50 to 95:5, 60:40 to 95:5, 60:40 to 90:10, 65:35 to 90:10, 65:35 to 85:15, or 70:30 to 85:15. The molar ratio of lithium sulfide to molybdenum sulfide (Mo6S8) in the complex may be, for example, 50:50 to 95:5, 50:50 to 90:10, 50:50 to 85:15, 50:50 to 80:20, 50:50 to 75:25, or 50:50 to 70:30. By having a molar ratio of lithium sulfide and molybdenum sulfide (Mo6S8) within this range, the cycle characteristics of an all-solid-state secondary battery containing a composite cathode active material can be further improved. If the molar ratio of lithium sulfide is excessively high, the ionic conductivity enhancement effect of molybdenum sulfide (Mo6S8) may be minimal. If the molar ratio of lithium sulfide is excessively low, the energy density of the secondary battery containing the composite cathode active material may be reduced.

[0080] The particle size (e.g., average particle diameter) of the above molybdenum sulfide is larger than the size of the lithium sulfide, and the size (e.g., average particle diameter) of the lithium sulfide is 0.1 nm to 10 um, and the size (e.g., average particle diameter) of the composite is 0.1 to 50 um.

[0081] The complex further comprises at least one transition metal sulfide, wherein the transition metal sulfide comprises one or more transition metal sulfides selected from iron, copper, cobalt, nickel, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, zinc, manganese, and titanium, and wherein the transition metal sulfide is Ti4O7-MoS2, It may further include V2O5-MoS2, TiS2, NbS2, Nb3S4, or a combination thereof. A composite further including a transition metal sulfide like this can further improve the ionic conductivity of a composite cathode active material including the composite. The internal resistance of an all-solid-state secondary battery including the composite cathode active material can be reduced and the cycle characteristics can be improved. The ionic conductivity of a composite cathode active material including the composite can be further improved. The internal resistance of an all-solid-state secondary battery including the composite cathode active material can be reduced and the cycle characteristics can be improved.

[0082] In the X-ray diffraction spectrum of the above complex, the first diffraction angles of the first peaks appearing at the diffraction angles of the peaks corresponding to molybdenum sulfide (Mo6S8) at diffraction angles 2θ=31±0.5°, diffraction angles 2θ=33±0.5°, and diffraction angles 2θ=46.5±0.5° may shift to a lower angle than the second diffraction angles of the second peaks appearing at the diffraction angles 2θ=31±0.5°, diffraction angles 2θ=33±0.5°, and diffraction angles 2θ=46.5±0.5° of molybdenum sulfide (Mo6S8) used in the production of the above complex.

[0083] The peak appearing at a diffraction angle of 2θ=31±0.5° corresponding to molybdenum sulfide (Mo6S8) is for crystal plane (121), the peak appearing at a diffraction angle of 2θ=33±0.5° is for crystal plane (122), and the peak appearing at a diffraction angle of 2θ=46.5±0.5° is for crystal plane (223).

[0084] The above diffraction angle 2θ=31±0.5° appears at, for example, 30.7°, the diffraction angle 2θ=33±0.5° appears at, for example, 33.9°, and the diffraction angle 2θ=46.5±0.5° appears at, for example, 46.7°.

[0085] The first diffraction angles of the first peaks of the above complex may shift to a lower angle than the second diffraction angles of the second peaks of molybdenum sulfide (Mo6S8) used in the manufacture of the above complex. As the lithiation of Mo6S8 progresses during the milling process and is further converted to Li1Mo6S8, the shift to a lower angle occurs more frequently.

[0086] For example, the position of the first peak may shift to a low angle compared to the position of the second peak. In addition, during the milling process, Mo6S8 is lithiated, and thus, a crystal change of the Mo6S8 material may be observed on XRD. The lithium sulfide-molybdenum sulfide (Mo6S8)-carbon-based material composite may have a reduced crystallite size compared to the lithium sulfide used in the manufacture of the composite. Since the lithium sulfide-molybdenum sulfide (Mo6S8)-carbon-based material composite has a reduced crystallite size, the volume change of the crystallite during charge and discharge is reduced, and thus the volume change of the composite including a plurality of crystallites may be alleviated during charge and discharge. The occurrence of defects such as cracks during charge and discharge of the composite cathode active material including such a composite may be suppressed. As a result, the cycle characteristics of the all-solid-state secondary battery including the composite cathode active material may be improved.

[0087] The particle size of the composite cathode active material, i.e., the size of the composite particles, may be, for example, 10 μm or less, 8 μm or less, 5 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the composite particles may be, for example, 1 to 10 μm, 2 to 10 μm, 2 to 8 μm, or 3 to 8 μm.

[0088] The size of the composite particles may be, for example, 0.1 to 10 μm, 0.1 to 8 μm, 0.1 to 5 μm, 0.1 to 2 μm, 0.1 to 1.5 μm or 0.1 to 1 μm or less.

[0089] Since the composite particles have a size in this range, the volume change during charge and discharge is suppressed, thereby suppressing the deterioration of the composite cathode active material including the composite during charge and discharge. If the size of the composite particles increases excessively, the volume change of the composite during charge and discharge increases, thereby accelerating the deterioration of the composite cathode active material including the composite. As a result, the cycle characteristics of the secondary battery including such a composite cathode active material may deteriorate. The size of the M2S particles included in the composite cathode active material, that is, the size of the M2S particles included in the composite may be, for example, 2 ㎛ or less, 1.5 ㎛ or less, or 1 ㎛ or less. The size of the M2S particles may be, for example, 0.1 to 2 ㎛, 0.1 to 1.5 ㎛, or 0.1 to 1 ㎛ or less. Since the M2S particles have a size in this range, the volume change during charge and discharge is suppressed, thereby suppressing the deterioration of the composite cathode active material including the composite during charge and discharge. If the size of the M2S particles increases excessively, the volume change of the composite during charge / discharge cycles may increase, which may accelerate the deterioration of the composite cathode active material containing the composite. Consequently, the cycle characteristics of secondary batteries containing such composite cathode active materials may deteriorate.

[0090] Therefore, the cycle characteristics, such as life characteristics, of a secondary battery including a composite cathode active material can be improved. The size of the composite particles can be measured, for example, using laser diffraction, scanning electron microscopy, etc. The particle size of the composite particle is, for example, the arithmetic mean of the particle sizes of multiple particles measured using software from a scanning electron microscopy image.

[0091] The composite includes a carbon-based material, and the carbon-based material may include, for example, a fibrous carbon-based material. The inclusion of the fibrous carbon-based material in the composite can further enhance the electronic conductivity of the composite. The inclusion of the fibrous carbon-based material in the composite can facilitate electron conduction from the surface to the interior of the composite. The internal resistance of a composite cathode active material including the composite can be reduced, and the cycle characteristics of a secondary battery including the composite cathode active material can be further improved.

[0092] The aspect ratio (a ratio of width to height in an image of the fibrous carbonaceous material) of the fibrous carbonaceous material can 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 carbonaceous material can 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 carbonaceous material can be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. When the fibrous carbonaceous material has an aspect ratio in this range, the overall electronic conductivity of the composite is improved, and local electronic conductivity imbalances within the composite can be further alleviated.

[0093] The fibrous carbon-based material may include, for example, carbon nanostructures. The carbon nanostructures may include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanobelts, carbon nanorods, or combinations thereof.

[0094] The carbon nanostructure can form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure composed of a plurality of carbon nanostructures aggregated together.

[0095] The diameter of the primary carbon nanostructure (e.g., the average diameter of a plurality of primary carbon nanostructures) can 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 can 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 scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructures can be measured by laser diffraction.

[0096] A secondary carbon nanostructure is, for example, a structure formed by assembling primary carbon nanostructures in whole or in part to form a bundle or bunch shape. The secondary carbon nanostructure may include, for example, a bundle-type carbon nanostructure, a rope-type carbon nanostructure, or a combination thereof. The diameter of the secondary carbon nanostructure (for example, the average 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 structures (e.g., the average length of the secondary carbon nanotube structures) can be, for example, 20 nm to 2 ㎛, 30 nm to 1.5 ㎛, 50 nm to 1 ㎛, 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 nanostructures can be measured from a scanning electron microscope (SEM) image or an optical microscope. Alternatively, the diameter and / or length of the secondary carbon nanostructures can be measured by laser diffraction. The secondary carbon nanostructures can be converted into primary carbon nanostructures, for example, by dispersing them in a solvent or the like, and then used in the preparation of a composite.

[0097] For example, the composite may contain 10 to 80 parts by weight of lithium sulfide, 1 to 40 parts by weight of molybdenum sulfide (Mo6S8), and 1 to 20 parts by weight of a carbon-based material, relative to 100 parts by weight of the composite. The content of lithium sulfide contained in the composite 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 lithium sulfide, relative to 100 parts by weight of the composite. The content of molybdenum sulfide (Mo6S8) contained in the composite 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 molybdenum sulfide (Mo6S8), relative to 100 parts by weight of the composite. The content of the carbon-based material included in the composite 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 carbon-based material per 100 parts by weight of the composite. Since the composite has a composition of lithium sulfide, molybdenum sulfide (Mo6S8), and carbon-based material in this range, a composite cathode active material including the composite can provide excellent ionic conductivity and / or electronic conductivity.

[0098] The ionic conductivity of the complex is, for example, 1×10 at 25°C. -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 -4It can be S / cm or more. The ionic conductivity can be measured using, for example, electrochemical impedance spectroscopy, DC polarization method, etc. Since the composite has an ionic conductivity in this range, the internal resistance of the composite cathode active material including the composite can be reduced. The cycle characteristics of the secondary battery including the composite cathode active material can be improved. The electronic conductivity of the composite can be, for example, 1×10 at 25°C. -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 It can be S / cm or more. The electronic conductivity can be measured using, for example, electrochemical impedance spectroscopy, DC polarization method, etc. Since the composite has an electronic conductivity in this range, the internal resistance of the composite cathode active material including the composite can be reduced. The cycle characteristics of the secondary battery including the composite cathode active material can be improved.

[0099] [anode]

[0100] [Cathode: Cathode active material]

[0101] According to one embodiment, a positive electrode 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 contains the composite positive electrode active material described above, a carbon-based material, and a solid electrolyte.

[0102] The above-mentioned positive electrode active material layer contains a composite positive electrode active material, a carbon-based material, and a solid electrolyte according to an embodiment.

[0103] The content of the carbon-based material is 1 to 10 parts by weight, 1 to 8 parts by weight, 1 to 5 parts by weight, for example, 1 to 2 parts by weight, based on 100 parts by weight of the total weight of the positive electrode active material layer. Since the positive electrode contains Mo2S6 having high electronic conductivity and ionic conductivity, the content of the carbon conductive material as a conductive material can be reduced, thereby improving the volumetric energy density and lowering the Li2S activation energy due to the synergistic effect of the intercalation reaction and the Li2S conversion reaction, thereby manufacturing an all-solid-state secondary battery with improved rate characteristics, initial efficiency, and life characteristics.

[0104] The content of the solid electrolyte in the positive electrode active material layer is 1 to 15 parts by weight based on 100 parts by weight of the positive electrode active material layer. In addition, when the positive electrode active material layer contains a binder, the content is 1 to 10 parts by weight based on 100 parts by weight of the positive electrode active material layer.

[0105] When the positive electrode contains only a composite positive electrode active material containing Li2S and Mo6S8, the all-solid-state secondary battery exhibits cell performance at a high temperature of 60°C or higher. However, since the positive electrode contains the composite positive electrode active material, a solid electrolyte, and a carbon-based material, the positive electrode can have a further reduced internal resistance at a temperature of 45°C or lower. Accordingly, the cycle characteristics of the secondary battery including the positive electrode can be further improved.

[0106] Referring to FIGS. 1 to 5, the positive electrode (10) includes a positive electrode current collector (11); and a positive electrode active material layer (12) disposed on one or both sides of the positive electrode current collector (11). The positive electrode active material layer (12) includes the composite positive electrode active material described above or includes a composite positive electrode active material and a solid electrolyte.

[0107] The composite cathode active material may be included in an amount of 40 to 90 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, or 50 to 70 parts by weight, based on 100 parts by weight of the cathode active material layer (12). If the content of the composite cathode active material is excessively reduced, the energy density of the secondary battery is reduced. If the content of the composite cathode active material is excessively increased, the deterioration of the cathode may be accelerated due to the change in the volume of the cathode during charge and discharge. As a result, the cycle characteristics of the secondary battery (1) may be reduced.

[0108] The cathode active material layer (12) may additionally include other cathode active materials in addition to the composite cathode active material described above.

[0109] Other cathode active materials may include, for example, a Li2S-containing composite. The Li2S composite includes, for example, a composite of Li2S and a carbon-based material, a composite of Li2S and a carbon-based material and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S and a lithium salt, a composite of Li2S and a metal carbide, a composite of Li2S and a carbon-based material and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S and a carbon-based material and a metal nitride, or a combination thereof.

[0110] The composite of Li2S and a carbon-based material includes a carbon-based material. The carbon-based material refers to the carbon-based material of the composite cathode active material described above. The method for producing the composite of Li2S and a carbon-based material may be a dry method, a wet method, or a combination thereof, but is not limited thereto, and any method used in the art may be used. The method for producing the composite of Li2S and a carbon-based material includes, but is not limited to, milling, heat treatment, deposition, etc., and any method used in the art may be used.

[0111] A composite of Li2S, a carbon-based material, and a solid electrolyte includes a carbon-based material and a solid electrolyte. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The solid electrolyte can be, for example, any material used as an ion-conducting material in the relevant technical field. 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, a polymer solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte includes, for example, Li, S, and P, and may optionally further include a halogen element. The sulfide-based solid electrolyte can be selected from among the sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte has, for example, a molecular weight of 1×10 at room temperature. -5 It can have an ionic conductivity of S / cm or more. The oxide-based solid electrolyte contains, for example, Li, O, and transition metal elements, and may optionally contain other elements. The oxide-based solid electrolyte has, for example, an ionic conductivity of 1×10 at room temperature. -5 It may be a solid electrolyte having an ionic conductivity of S / cm or more. The oxide-based solid electrolyte may be selected from among oxide-based solid electrolytes used in the solid electrolyte layer.

[0112] The composite of Li2S and a solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the composite of Li2S, a carbon-based material, and a solid electrolyte described above.

[0113] The composite of Li2S and a lithium salt comprises Li2S and a lithium salt. The lithium salt refers to the lithium salt of the composite cathode active material described above. The lithium salt is particularly one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. The composite of Li2S and a lithium salt may be, for example, a composite of Li2S and a lithium halide. The composite of Li2S and a lithium salt may provide improved ionic conductivity by including a lithium halide compound. The composite of Li2S and a lithium salt is distinguished from a simple mixture of Li2S, a carbon-based material, and a lithium salt. A simple mixture of Li2S and a lithium salt may provide high interfacial resistance by failing to maintain a dense interface between Li2S and a lithium salt, which may result in reduced cycle life characteristics of an all-solid-state secondary battery.

[0114] The composite of Li2S and metal carbide includes metal carbide. The metal carbide is, for example, a two-dimensional metal carbide. The two-dimensional metal carbide is, for example, M n+1 C 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) is expressed as 2D metal carbides, 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 with O, OH and / or F.

[0115] A composite of Li2S, a carbon-based material, and a metal carbide includes a carbon-based material and a metal carbide. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The metal carbide refers to the composite of Li2S and a metal carbide described above.

[0116] The complex of Li2S and metal nitride includes 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) is expressed as The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0117] A composite of Li2S, a carbon-based material, and a metal nitride includes a carbon-based material and a metal nitride. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The metal carbide refers to the composite of Li2S and a metal nitride described above.

[0118] The cathode active material layer (12) may additionally include, for example, a sulfide-based compound that is distinct from the cathode active material described above. The sulfide-based compound may be, for example, a compound containing a metal element other than Li and the element sulfur. The sulfide-based compound may be, for example, a compound containing a metal element belonging to Groups 1 to 14 of the Periodic Table of Elements having an atomic weight of 10 or more and the element sulfur. The sulfide-based compound may be, for example, FeS2, VS2, NaS, MnS, FeS, NiS, CuS, or a combination thereof. By the cathode active material layer additionally including a sulfide-based compound, the cycle characteristics of the all-solid-state secondary battery may be further improved. The content of the sulfide-based compound included in the cathode active material layer (12) may be 10 wt% or less, 5 wt% or less, 3 wt% or less, or 1 wt% or less of the total weight of the cathode active material layer (12).

[0119] [Anode: Solid electrolyte]

[0120] The positive electrode active material layer (12) may further include, 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 (10) may be the same as or different from the solid electrolyte included in the solid electrolyte layer (30). For more details on the solid electrolyte, refer to the section on the solid electrolyte layer (30).

[0121] The solid electrolyte included in the positive electrode active material layer (12) may have a smaller average D50 particle diameter than the solid electrolyte included in the solid electrolyte layer (30). For example, the average D50 particle diameter 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 average D50 particle diameter of the solid electrolyte included in the solid electrolyte layer (30). The average D50 particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is, for example, the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by laser diffraction.

[0122] The solid electrolyte may be included in an amount of 10 to 60 parts by weight, 10 to 50 parts by weight, 20 to 50 parts by weight, or 30 to 50 parts by weight, based on 100 parts by weight of the positive electrode active material layer (12). The solid electrolyte is, for example, a sulfide-based solid electrolyte. If the content of the solid electrolyte is excessively reduced, the internal resistance of the positive electrode may increase, thereby deteriorating the cycle characteristics of the secondary battery. If the content of the sulfide-based solid electrolyte is excessively increased, the energy density of the secondary battery (1) may be reduced.

[0123] [Polar: Challenger]

[0124] The cathode 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 used as a carbon-based conductive material in the art may be used. The metal-based conductive material may be, for example, metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material used as a metal-based conductive material in the art may be used. The content of the conductive material included in the cathode 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 cathode active material layer (12).

[0125] The cathode active material layer (12) includes a carbon-based material, and the carbon-based material may be disposed only in the composite cathode active material. The cathode active material layer (12) may not additionally include a separate carbon-based material other than the composite cathode active material including the carbon-based material. Since the cathode active material layer does not include a separate carbon-based material, the energy density of the cathode and the secondary battery (1) can be improved and the manufacturing process can be simplified.

[0126] [Positive: Binder]

[0127] 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 binder used in the relevant technical field may 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 may be omitted.

[0128] [Positive: Other additives]

[0129] The cathode active material layer (12) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the cathode active material, solid electrolyte, binder, and conductive agent described above.

[0130] As fillers, coating agents, dispersants, ion conductivity aids, etc. that can be included in the positive electrode active material layer (12), known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[0131] [Anode: Anode current collector]

[0132] The positive electrode collector (11) uses a plate or foil made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode collector (11) may be omitted. The thickness of the positive electrode 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.

[0133] The cathode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may 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. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may 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 perform a short-circuit prevention function by being cut in case of overcurrent. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. When the thickness of the metal layer is reduced, the limit current and / or maximum current of the positive electrode current collector (11) decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added on the metal layer for connection to the outside. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS (stainless steel) foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this 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 less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve 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 μm. Since the metal layer has a thickness within this range, 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. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and lithium battery.

[0134] [Anode: Inert member]

[0135] Referring to FIG. 4, the positive electrode (10) (e.g., positive electrode layer) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one side of the positive electrode current collector. An inactive member (40) is disposed on one side of the positive electrode (10). Referring to FIG. 4, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and the positive electrode current collector (11). Referring to FIG. 5, the inactive member (40) may be disposed on one side of the positive electrode active material layer (12) and may have a structure in which the inactive member (40) is disposed between the solid electrolyte layer (40) and the positive electrode current collector (11) facing the solid electrolyte layer (40), and the inactive member (40) is not disposed on one side of the positive electrode current collector (11).

[0136] By including the inert member (40), cracking of the solid electrolyte layer (30) is prevented during the manufacture and / or charging and discharging of the all-solid-state secondary battery (1), and as a result, the cycle characteristics of the all-solid-state secondary battery (2) are improved. In the all-solid-state secondary battery (1) that does not include the inert member (40), when the manufacture and / or charging and discharging of the all-solid-state secondary battery (1) is performed, uneven pressure is applied to the solid electrolyte layer (30) in contact with the positive electrode (10), which increases the possibility of cracking in the solid electrolyte layer (30) and causing a short circuit due to the growth of lithium metal through the crack.

[0137] In the all-solid-state secondary battery (1), the thickness of the inert member (40) is greater than or equal to the thickness of the positive electrode active material layer (12). Alternatively, in the all-solid-state secondary battery (1), the thickness of the inert member (40) is substantially equal to the thickness of the positive electrode (10). Since the thickness of the inert member (40) is equal to the thickness of the positive electrode (10), a uniform pressure is applied between the positive electrode (10) and the solid electrolyte layer (30), and the positive electrode (10) and the solid electrolyte layer (30) are sufficiently adhered to each other, so that the interfacial resistance between the positive electrode (10) and the solid electrolyte layer (30) can be reduced. In addition, since the solid electrolyte layer (30) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state secondary battery (1), the internal resistance of the solid electrolyte layer (30) and the all-solid-state secondary battery (1) including the same is reduced.

[0138] The inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the solid electrolyte layer (30). By the inert member (40) surrounding the side surface of the positive electrode (10) and being in contact with the solid electrolyte layer (30), cracks in the solid electrolyte layer (30) that occur due to a pressure difference during the pressing process in the solid electrolyte layer (30) that does not come into contact with the positive electrode (20) can be effectively suppressed. The inert member (40) surrounds the side surface of the positive electrode (10) and is separated from the negative electrode (20), more specifically, the first negative electrode active material layer (22). The inert member (40) surrounds the side surface of the positive electrode (10), is in contact with the solid electrolyte layer (30), and is separated from the negative electrode (20). Therefore, the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or a short circuit occurring due to overcharging of lithium, etc., is suppressed. For example, by placing an inert member (40) on one side of the positive electrode active material layer (12) and simultaneously on one side of the positive electrode current collector (11), the possibility of a short circuit occurring due to contact between the positive electrode current collector (11) and the negative electrode (20) is more effectively suppressed.

[0139] Referring to FIG. 4, the inert member (40) extends from one side of the positive electrode (30) to the end of the solid electrolyte layer (30). By extending the inert member (40) to the end of the solid electrolyte layer (30), cracks occurring at the end of the solid electrolyte layer (30) can be suppressed. The end of the solid electrolyte layer (30) is the outermost part that is in contact with the side of the solid electrolyte layer (30). The inert member (40) extends to the outermost part that is in contact with the side of the solid electrolyte layer (30). The inert member (40) is separated from the negative electrode (20), more specifically, from the first negative electrode active material layer (22). The inert member (40) extends to the end of the solid electrolyte layer (30), but does not contact the negative electrode (20). The inert member (40) fills a space extending from, for example, one side of the anode (30) to the end of the solid electrolyte layer (30).

[0140] Referring to FIG. 4, the width of the inert member (40) extending from one side of the positive electrode (10) to the end of the solid electrolyte layer (30) is, for example, 1 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10%, or 1 to 5% of the width between one side of the positive electrode (10) and the other side opposite to the one side. If the width of the inert member (40) is excessively large, the energy density of the all-solid-state secondary battery (1) is reduced. If the width of the inert member (40) is excessively small, the effect of arranging the inert member (40) is minimal.

[0141] The area of ​​the anode (10) is smaller than the area of ​​the solid electrolyte layer (30) in contact with the anode (10). An inert member (40) is arranged to surround the side of the anode (10) to compensate for the area difference between the anode (10) and the solid electrolyte layer (30). By compensating for the difference between the area of ​​the anode (10) and the area of ​​the solid electrolyte layer (30), cracks in the solid electrolyte layer (30) caused by the pressure difference during the pressing process are effectively suppressed. For example, the sum of the area of ​​the anode (10) and the area of ​​the inert member (40) is equal to the area of ​​the solid electrolyte layer (30).

[0142] The area of ​​the anode (10) is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area of ​​the solid electrolyte layer (30). The area of ​​the anode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area of ​​the solid electrolyte layer (30).

[0143] If the area of ​​the positive electrode (10) is equal to or larger than the area of ​​the solid electrolyte layer (30), the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or due to overcharging of lithium increases. The area of ​​the positive electrode (10) is, for example, equal to the area of ​​the positive electrode active material layer (12). The area of ​​the positive electrode (10) is, for example, equal to the area (11) of the positive electrode current collector.

[0144] The area of ​​the inert member (40) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the area of ​​the anode (10). The area of ​​the inert member (40) is, for example, 1% to 50%, 5% to 40%, 5% to 30%, 5% to 20%, or 5% to 15% of the area of ​​the anode (10).

[0145] The area of ​​the positive electrode (10) is smaller than the area of ​​the negative electrode current collector (21). The area of ​​the positive electrode (10) is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area of ​​the negative electrode current collector (21). The area of ​​the positive electrode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area of ​​the negative electrode current collector (21). The area of ​​the negative electrode current collector (21) is, for example, the same as the area of ​​the negative electrode (20). The area of ​​the negative electrode current collector (21) is, for example, the same as the area of ​​the first negative electrode active material layer (22).

[0146] As used herein, “same” area, length, width, thickness, and / or shape includes all instances of having “substantially the same” area, length, width, thickness, and / or shape, except where the area, length, width, thickness, and / or shape are intentionally different from each other. “Same” area, length, width, and / or thickness includes a range where the unintentional difference in the area, length, width, and / or thickness of the compared objects is, for example, less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0147] The thickness of the inert member (40) is, for example, greater than the thickness of the first negative electrode active material layer (22). 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 inert member (40). 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 inert member (40).

[0148] The inert member (40) may be a gasket. By using a gasket as the inert member (40), cracks in the solid electrolyte layer (30) caused by a pressure difference during the pressing process can be effectively suppressed.

[0149] The inert member (40) has, for example, a single-layer structure. Alternatively, the inert member (40) may have a multi-layer structure. In the inert member (40) having a multi-layer structure, each layer may have a different composition. The inert member having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. The inert member (40) having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers. The adhesive layer effectively prevents, for example, a separation between the positive electrode (10) and the solid electrolyte layer (30) due to a change in the volume of the positive electrode (10) that occurs during the charge / discharge process of the all-solid-state secondary battery (10), and improves the film strength of the inert member (40) by providing a bonding force between the support layer and other layers. The support layer provides support to the inert member (40), prevents unevenness of pressure applied to the solid electrolyte layer (30) during the pressurization process or the charge / discharge process, and prevents deformation of the all-solid-state secondary battery (1) being manufactured.

[0150] The inert member (40) is, for example, a flame-retardant inert member. The flame-retardant inert member prevents thermal runaway and ignition of the all-solid-state secondary battery (1) by providing flame retardancy. Consequently, the safety of the all-solid-state secondary battery (1) is further improved. The flame-retardant inert member prevents deterioration of the all-solid-state secondary battery (1) by absorbing residual moisture within the all-solid-state secondary battery (1), thereby improving the lifespan characteristics of the all-solid-state secondary battery (1).

[0151] The flame-retardant inert member includes, for example, a matrix and a filler. The matrix includes, for example, a substrate and a reinforcing material. The matrix includes, for example, a fibrous substrate and a fibrous reinforcing material. Since the matrix includes the substrate, the matrix can have elasticity. Therefore, the matrix can effectively accommodate a change in volume during charging and discharging of the all-solid-state secondary battery (1) and can be arranged at various positions. The substrate included in the matrix includes, for example, a first fibrous material. Since the substrate includes the first fibrous material, the volume change of the positive electrode (30) occurring during the charging and discharging process of the all-solid-state secondary battery (1) can be effectively accommodated and deformation of the inert member (40) due to the change in volume of the positive electrode (30) can be effectively suppressed. The first fibrous material is, for example, a material having an aspect ratio (e.g., a ratio of length to width in an image of the first fibrous material) of 5 or more, 20 or more, or 50 or more. The first fibrous material is, for example, a material having an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. Since the first fibrous material is an insulating material, a short circuit between the positive electrode (30) and the negative electrode (20) caused by lithium dendrites, etc., generated during the charge and discharge process of the all-solid-state secondary battery (1) can be effectively prevented. The first fibrous material includes, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conductive polymer fibers. The strength of the matrix is ​​improved by including a reinforcing material in the matrix. Therefore, the matrix can prevent excessive volume change during charge and discharge of the all-solid-state secondary battery (1) and prevent deformation of the all-solid-state secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material.The reinforcing material can more uniformly increase the strength of the matrix by including a second fibrous material. The second fibrous material is, for example, a material having an aspect ratio (e.g., a ratio of length to width in an image of the second fibrous material) of 3 or more, 5 or more, or 10 or more. The first fibrous material is, for example, a material having an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame retardant material. Since the second fibrous material is a flame retardant material, ignition due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or due to external impact can be effectively suppressed. The second fibrous material is, for example, a glass fiber, a metal oxide fiber, a ceramic fiber, or the like.

[0152] The flame-retardant inert member includes a filler in addition to a matrix. The filler may be disposed within the matrix, on the surface of the matrix, or on both the interior and the surface. The filler is, for example, an inorganic material. The filler included in the flame-retardant inert member is, for example, a moisture getter. The filler removes moisture remaining in the all-solid-state secondary battery (1) by adsorbing moisture, for example, at a temperature below 100°C, thereby preventing deterioration of the all-solid-state secondary battery (1). In addition, when the temperature of the all-solid-state secondary battery (1) increases to 150°C or higher due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or an external impact, the filler releases the adsorbed moisture, thereby effectively suppressing ignition of the all-solid-state secondary battery (1). That is, the filler is, for example, 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. The content of the filler contained in the flame-retardant inert member is, for example, 10 to 80 parts by weight, 20 to 80 parts by weight, 30 to 80 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, 60 to 80 parts by weight, or 65 to 80 parts by weight, based on 100 parts by weight of the flame-retardant inert member (4).

[0153] The flame-retardant inert member may further comprise, for example, a binder. The binder may comprise, for example, a curable polymer or a non-curable polymer. A curable polymer is a polymer that cures by heat and / or pressure. A curable polymer is, for example, a solid at room temperature. The flame-retardant inert member (40) comprises, for example, a heat-pressure curable film and / or a cured product thereof. The heat-pressure curable polymer is, for example, TSA-66 from Toray.

[0154] The flame-retardant inert member may additionally include other materials in addition to the above-described substrate, reinforcing material, filler, and binder. The flame-retardant inert member may further include one or more selected from among paper, an insulating polymer, an ion-conducting polymer, an insulating inorganic material, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

[0155] The density of the substrate or reinforcing material included in the flame-retardant inert material may be, for example, 10% to 300%, 10% to 150%, 10% to 140%, 10% to 130%, or 10% to 120% of the density of the positive electrode active material included in the positive electrode active material layer (12).

[0156] The inert member (40) is a member that does not contain an electrochemically active material, for example, an electrode active material. The electrode active material is a material that absorbs / releases lithium. The inert member (40) is a member made of a material other than the electrode active material and used in the relevant technical field.

[0157]

[0158] [All-solid-state secondary battery]

[0159] An all-solid-state secondary battery according to one embodiment includes the above-described positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode. The negative electrode includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0160] Referring to FIGS. 1 to 5, an all-solid-state secondary battery (1) includes a positive electrode (10); a negative electrode (20); and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20). The negative electrode (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector.

[0161] [anode]

[0162] See the above mentioned polarities.

[0163] [cathode]

[0164] [Cathode: Cathode active material]

[0165] Referring to FIGS. 1 to 5, the negative electrode (20) includes a first negative electrode active material layer (22). The first negative electrode active material layer (22) includes, for example, a negative electrode active material and a binder.

[0166] The negative electrode active material included in the first negative electrode active material layer (22) is, for example, a negative electrode material that can form an alloy or compound with lithium.

[0167] The negative electrode active material included in the first negative electrode active material layer (22) has, for example, a particle form (for example, a plurality of particles or a particle form). The average particle diameter of the negative electrode active material having a particle form is, for example, 4 ㎛ or less, 3 ㎛ or less, 2 ㎛ or less, 1 ㎛ or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle diameter of the negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 3 ㎛, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 300 nm, or 10 nm to 100 nm. When the negative electrode active material has an average particle diameter in this range, reversible absorption and / or desorption of lithium can be facilitated during charge and discharge. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

[0168] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or metalloid negative electrode active material.

[0169] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0170] The carbon-based negative electrode active material is, in particular, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that has no crystallinity or relatively very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0171] The carbon-based negative electrode active material may be, for example, porous carbon. The porous carbon has a pore volume of, 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 porous carbon has an average pore diameter of, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The porous carbon has a BET surface area of, for example, 100 m 2 / g to 3000 m 2 / g is.

[0172] The metal or metalloid negative electrode active material includes, but is not limited to, 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), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium and therefore is not a metal negative electrode active material.

[0173] The first negative electrode active material layer (22) includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the first negative electrode active material layer (22) includes only amorphous carbon, or includes at least one selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the first negative electrode active material layer (22) includes a mixture of amorphous carbon and at least one 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 a 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 this range and is selected according to the required characteristics of the all-solid-state secondary battery (1). When the negative electrode active material has this composition, the cycle characteristics of the all-solid-state secondary battery (1) are further improved.

[0174] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid. The metal or metalloid includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the metalloid is a semiconductor. The content of the second particles is 1 to 99 wt%, 1 to 60 wt%, 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, an all-solid-state secondary battery (1) are further improved.

[0175] Alternatively, the first negative electrode active material layer (22) includes a composite negative electrode active material. The composite negative electrode active material may include, for example, a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support. Since the composite negative electrode active material has such a structure, the metal-based negative electrode active material can be prevented from being localized within the first negative electrode active material layer and a uniform distribution can be achieved. 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.

[0176] 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), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn). The metal oxide includes, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, tellurium (Te) oxide, and zinc (Zn) oxide. The metal oxide includes, 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), Si x O y (0 <x≤1, 0<y≤2), 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) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x O y (0 <x≤2, 0<y≤3)의 복합체, Pt와 Pt x O y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x O y(0 <x≤1, 0<y≤1)의 복합체, Si와 Si x O y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x O y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x O y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x O y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x O y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x O y (0 <x≤1, 0<y≤3), Zn과 Zn x O y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0177] The carbonaceous support is, for example, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., and any material classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite carbon. Carbonaceous materials are, for example, carbonaceous negative electrode active materials.

[0178] The composite negative electrode active material has, for example, a particle form (for example, a plurality of particles or a particle form). The particle size (for example, an average particle size) of the composite negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. When the composite negative electrode active material has a particle size in this range, reversible absorption and / or desorption of lithium can be facilitated during charge and discharge. The metal-based negative electrode active material supported on the support may have, for example, a particle form (for example, a plurality of particles or a particle form). The particle size (e.g., average particle size) of the metal-based negative electrode active material can 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 can have, for example, a particle shape. The particle size of the carbon-based support can be, for example, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. When the carbon-based support has a particle size in this range, it can be more uniformly arranged in the first negative electrode active material layer. The carbon-based support can be, for example, a nanoparticle 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 the median diameter (D50), for example, measured using a laser particle size distribution meter. Alternatively, the average particle size can be determined automatically using software, for example, from electron microscope images, or manually by manual means.

[0179] [Cathode: Binder]

[0180] The binder included 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 used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0181] Since the first negative electrode active material layer (22) includes a binder, the first negative electrode active material layer (22) is stabilized on the negative electrode current collector (21). In addition, cracking of the first negative electrode active material layer (22) is suppressed despite changes in the volume and / or relative position of the first negative electrode active material layer (22) during the charge and discharge process. For example, if the first negative electrode active material layer (22) does not include a binder, the first negative electrode active material layer (22) can be easily separated from the negative electrode current collector (21). As the first negative electrode active material layer (22) is detached from the negative electrode current collector (21), the possibility of a short circuit occurring increases at the exposed portion of the negative electrode current collector (21) due to the negative electrode current collector (21) coming into contact with the solid electrolyte layer (30). The first negative electrode active material layer (22) is manufactured by, for example, applying a slurry in which the material constituting the first negative electrode active material layer (22) is dispersed onto the negative electrode current collector (21) and drying the slurry. By including a binder in the first negative electrode active material layer (22), stable dispersion of the negative electrode active material in the slurry is possible. For example, when applying the slurry onto the negative electrode current collector (21) by screen printing, it is possible to suppress clogging of the screen (for example, clogging by aggregates of the negative electrode active material).

[0182] [Cathode: Other additives]

[0183] The first negative electrode active material layer (22) may further include additives used in a conventional all-solid-state secondary battery (1), such as fillers, coating agents, dispersants, and ion conductive aids.

[0184] [Cathode: Solid electrolyte]

[0185] The first negative electrode active material layer (22) may further include a solid electrolyte. The solid electrolyte may be, for example, a material selected from among the solid electrolytes included in the solid electrolyte layer (30). The solid electrolyte included in the first negative electrode active material layer (22) may act as a reaction site where lithium metal formation begins within the first negative electrode active material layer (22), as a space where the formed lithium metal is stored, or as a path for transferring lithium ions. The solid electrolyte may be omitted.

[0186] In the first negative electrode active material layer (22), the content of the solid electrolyte may be high, for example, in an area adjacent to the solid electrolyte layer (30), and low, for example, in an area adjacent to the negative electrode current collector (21). In the first negative electrode active material layer (22), the solid electrolyte may have a concentration gradient in which the concentration decreases, for example, from an area adjacent to the solid electrolyte layer (30) to an area adjacent to the negative electrode current collector (21).

[0187] [Cathode: First negative electrode active material layer]

[0188] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer (12) is the first open circuit voltage (1 st Li / Li from open circuit voltage) + The initial charge capacity of the first negative electrode active material layer (22) is determined at the maximum charging voltage. The initial charge capacity of the first negative electrode active material layer (22) is determined at the second open circuit voltage (2 nd Li / Li from open circuit voltage) + It is determined at 0.01 V.

[0189] The maximum charging voltage is determined by the type of cathode active material. The maximum charging voltage can 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 Li2S composite is Li / Li + can be 2.5 V for Li2S or Li2S complex. For example, the maximum charging voltage of Li / Li + It can be 3.0 V for. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1. The initial charge capacity (mAh) of the positive electrode active material layer (12) is obtained by multiplying the charge capacity density (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 several types of positive electrode active materials are used, the charge capacity density × 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 way. 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 several types of negative electrode active materials are used, the charge capacity density Х 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 using lithium metal as a counter electrode. The initial charge capacity of each of the positive electrode active material layer (12) and 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 value of the negative electrode active material in the first negative electrode active material layer (22). 2can be directly measured using an all-solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, for example, 3.0 V (vs. Li / Li + ) can be performed for an operating voltage of up to 0.01 V for the cathode, for example, lithium metal, from the second open circuit voltage (OCV). For example, an all-solid-state half-cell having a cathode active material layer can exhibit a current of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The all-solid-state half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 The all-solid-state half-cell having the positive electrode active material layer can be charged from the first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0190] If the initial charge capacity of the first negative electrode active material layer (22) is too small, the thickness of the first negative electrode active material layer (22) becomes very thin, so that lithium dendrites formed between the first negative electrode active material layer (22) and the negative electrode current collector (21) during repeated charge and discharge processes 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 charge capacity of the first negative electrode active material layer (22) increases excessively, the energy density of the all-solid-state secondary battery (1) decreases and the internal resistance of the all-solid-state secondary battery (1) due to the first negative electrode active material layer (22) increases, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery (1).

[0191] 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, 10% or less, or 5% 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%, 1 to 10%, or 1 to 5% 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 µm to 20 µm, 2 µm to 15 µm, or 3 µm to 10 µm. If the thickness of the first negative electrode active material layer (22) is too thin, lithium dendrites formed between the first negative electrode active material layer (22) and the negative electrode current collector (21) 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) decreases and the internal resistance of the all-solid-state secondary battery (1) due to the first negative electrode active material layer (22) increases, 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) decreases, for example, the initial charge capacity of the first negative electrode active material layer (22) also decreases.

[0192] [Cathode: Second negative electrode active material layer]

[0193] Referring to FIG. 3, the all-solid-state secondary battery (1) further includes, after being charged, 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 functions as, for example, 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 lithium alloy used in the art may be used. The second negative electrode active material layer (24) may be made of one of these alloys or lithium, or may be made of several types of 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 between the first negative electrode active material layer (22) and the negative electrode current collector (21), for example, during the charging process of an all-solid-state secondary battery (1).

[0194] The thickness of the second negative electrode active material layer (24) is not particularly limited, but is, for example, 1 ㎛ to 500 ㎛, 1 ㎛ to 200 ㎛, 1 ㎛ to 150 ㎛, 1 ㎛ to 100 ㎛, or 1 ㎛ to 50 ㎛. If the thickness of the second negative electrode active material layer (24) is too thin, it is difficult for the second negative electrode active material layer (24) to perform the role of a lithium reservoir. If the thickness of the second negative electrode active material layer (24) is too thick, the mass and volume of the all-solid-state secondary battery (1) may increase, and the cycle characteristics of the all-solid-state secondary battery (1) may rather deteriorate.

[0195] Alternatively, in the all-solid-state secondary battery (1), the second negative electrode active material layer (24) may be disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22), for example, before assembling 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 assembling the all-solid-state secondary battery (1), the second negative electrode active material layer (24) acts as a lithium reservoir because it is a metal layer containing lithium. 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 assembling the all-solid-state secondary battery (1).

[0196] When the second negative electrode active material layer (24) is precipitated by charging after assembling the all-solid-state secondary battery (1), the energy density of the all-solid-state secondary battery (1) increases because the second negative electrode active material layer (24) is not included when assembling the all-solid-state secondary battery (1). When charging the all-solid-state secondary battery (1), the charging is performed in excess of the charging 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 absorbed into 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 compound with the lithium ions that have moved from the positive electrode (10). When charging exceeds 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 (i.e., metallic lithium). This result is obtained, for example, by the negative electrode active material included in the first negative electrode active material layer (22) including a material that forms an alloy or compound with lithium. During discharge, 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 toward the positive electrode (10). Therefore, it is possible to use lithium as the negative electrode active material in an all-solid-state secondary battery (1). In addition, since the first negative electrode active material layer (22) covers the second negative electrode active material layer (24), it acts as a protective layer for the second negative electrode active material layer (24), i.e., the metal layer, and at the same time, it suppresses the precipitation and growth of lithium dendrites. Accordingly, it suppresses short circuits and capacity reduction of the all-solid-state secondary battery (1), and consequently improves the cycle characteristics of the all-solid-state secondary battery (1).In addition, when the second negative electrode active material layer (24) is placed by charging after assembling the all-solid-state secondary battery (1), the negative electrode (20), i.e., the negative electrode current collector (21) and the first negative electrode active material layer (22) and the region between them are Li-free regions that do not contain lithium (Li) in the initial state or the state after complete discharge of the all-solid-state secondary battery (1).

[0197] [Cathode: Negative current collector]

[0198] The negative electrode current collector (21) is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative electrode current collector (21) is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, 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 type of the above-described metal, or may be composed of an alloy or a coating material of two or more types of metals. The negative electrode current collector (21) is, for example, in the form of a plate or foil.

[0199] Referring to FIG. 2, the all-solid-state secondary battery (1) may further include a thin film (23) containing an element capable of forming an alloy with lithium on one surface of the negative electrode collector (21). The thin film (23) is disposed between the negative electrode collector (21) and the first negative electrode active material layer (22). The thin film (23) contains, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film (23) is composed of one of these metals or an alloy of several types of metals. By placing the thin film (23) on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (24) deposited between the thin film (23) and the first negative electrode active material layer (22) becomes flatter, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0200] 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. If the thickness of the thin film (23) is less than 1 nm, it may be difficult for the function of the thin film (23) to be exerted. If the thickness of the thin film (23) is excessively thick, the thin film (23) itself absorbs lithium, which reduces the amount of lithium precipitated from the negative electrode, thereby lowering the energy density of the all-solid-state battery and deteriorating the cycle characteristics of the all-solid-state secondary battery (1). The thin film (23) may be disposed on the negative electrode current collector (21) by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to these methods, and any method capable of forming the thin film (23) in the relevant technical field may be used.

[0201] Although not shown in the drawing, the negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may 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. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may 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 collector (21), refer to the positive electrode collector (11) described above. By having this structure, the negative electrode collector (21) can reduce the weight of the negative electrode, and consequently, improve the energy density of the negative electrode and lithium battery.

[0202]

[0203] [Solid electrolyte layer]

[0204] [Solid electrolyte layer: solid electrolyte]

[0205] Referring to FIGS. 1 to 5, the solid electrolyte layer (30) includes a solid electrolyte disposed between the positive electrode (10) and the negative electrode (20).

[0206] The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0207] The solid electrolyte is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte is, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, 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, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x, at least one selected from 0≤x≤2. The sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one containing sulfur (S), phosphorus (P), and lithium (Li) as at least 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 sulfide-based solid electrolyte material containing Li2S-P2S5 to form a solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0208] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

[0209] <Chemical Formula 1>

[0210] Li + 12-n-x A n+ X 2- 6-x Y - x

[0211] 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, and 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-xPS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0212] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since 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 is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0213] Oxide solid electrolytes include, 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), Li1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. The oxide-based solid electrolyte is manufactured, for example, by a sintering method.

[0214] Oxide-based solid electrolytes include, 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) 중에서 선택된 가넷계(Garnet-type) 고체전해질이다.

[0215] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or a polymer having ion-conducting functional groups. The polymer solid electrolyte may be, for example, a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may not, for example, comprise a liquid.The polymer solid electrolyte comprises 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), polymethyl methacrylate (PMMA, poly(methylmethacrylate), 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 (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, 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) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid 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.

[0216] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0217] A polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atm. The polymer gel electrolyte may, for example, have a gel state without containing a liquid. 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 lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature, is composed solely of ions, and is liquid at room temperature or a molten salt at room temperature. The ionic liquid may include, for example, one or more cations selected from among a) ammonium compounds, pyrrolidinium compounds, pyridinium compounds, pyrimidinium compounds, imidazolium compounds, piperidinium compounds, pyrazolium compounds, oxazolium compounds, pyridazinium compounds, phosphonium compounds, sulfonium compounds, triazolium compounds, and mixtures thereof, and b) one or more anions selected from among BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. A polymer solid electrolyte can form a polymer gel electrolyte, for example, by being impregnated into a liquid electrolyte in a secondary battery. The polymer gel electrolyte may further include inorganic particles. The polymer included 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 included 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. In the present disclosure, the weight average molecular weight of the polymer can be evaluated by gel permeation chromatography.

[0218] [Solid electrolyte layer: binder]

[0219] The solid electrolyte layer (30) may include, for example, a binder. The binder included in the solid electrolyte layer (30) is not limited to, but may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., and any binder used in the relevant technical field may be used. The binder of the solid electrolyte layer (30) may be the same as or different from the binder included in the positive electrode active material layer (12) and the negative electrode active material layer (22). The binder may be omitted.

[0220] The binder content 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).

[0221] A method for manufacturing an all-solid-state secondary battery is provided, comprising: a step of obtaining a composite including a step of milling a composition including M2S and molybdenum sulfide (Mo6S8) (M is an alkali metal, and the alkali metal is Li or Na); a step of preparing a positive electrode containing a positive electrode active material layer including a positive electrode current collector and a composite positive electrode active material using a composition in which a solid electrolyte and a binder are added and mixed into the composite; a step of preparing an anode; and a step of disposing an electrolyte between the positive electrode and the negative electrode.

[0222] An all-solid-state secondary battery according to an embodiment of the present invention is a lithium-ion battery manufactured by milling a composition containing lithium sulfide (Li2S) and molybdenum sulfide (Mo6S8) to form lithiated Mo6S8 (Li). x Mo6S8)(0 <x≤4)이 복합화된 Li2S-Mo6S8복합체를 얻는 단계; 상기 복합체에 고체 전해질 및 탄소계 재료를 부가 및 혼합한 조성물을 이용하여 양극 집전체 및 복합양극활물질을 포함하는 양극 활물질층을 함유하는 양극을 준비하는 단계; 및 상기 양극과 음극 사이에 고체 전해질층을 배치하는 단계를 포함하는 전고체 이차전지의 제조방법이 제공된다.

[0223] A binder may be further added to the above composition.

[0224] The above lithiated Mo6S8(Li x Mo6S8)(0 <x≤4)이 복합화된 Li2S-Mo6S8복합체에 탄소계 재료를 더 부가하고 밀링을 실시한다.

[0225] The step of milling a composition containing lithium sulfide (Li2S) and molybdenum sulfide (Mo6S8) can be performed in an inert atmosphere at a temperature of 15°C to 65°C and a rotation speed of 10 to 10,000 rpm, 300 to 10,000 rpm, 350 rpm to 5,000 rpm, or 370 rpm to 1,000 rpm.

[0226] Milling can combine the components of a composite by applying mechanical energy. This process applies rotational energy to the reactants, atomizing the powder and maximizing the diffusion between the powder particles, thereby inducing a chemical reaction.

[0227] Milling can be performed using a milling machine for, for example, 0.5 to 1000 hours, 0.5 to 100 hours, or 10 to 30 hours.

[0228] The milling can be performed by any known ball milling device used for high-energy ball milling, such as a vibratory mill, a Z-mill, a planetary ball-mill, an attrition mill, a SPEX mill, a vibration mill, a low-temperature crusher, a friction mill, a shaker mill, a stirred ball mill, a mixer ball mill, a vertical and horizontal attritor, etc.

[0229] An inert atmosphere may be an atmosphere substantially free of oxygen. For example, an inert atmosphere may contain nitrogen, argon, neon, or a combination thereof.

[0230] The mechanochemical reaction may be, for example, an exothermic reaction. The reaction forming the solid electrolyte represented by Chemical Formula 1 may be an exothermic reaction. The temperature of the exothermic reaction may be, for example, 100 to 500°C, 100 to 400°C, 100 to 300°C, or 100 to 200°C. The mechanical milling may be produced dry, for example, without the use of a solvent or the like. Since the mechanical milling is produced dry, a post-treatment process such as solvent removal may be omitted.

[0231] The above solid solution may include a carbon-based material. The solid solution and the carbon-based material may be milled to form a composite.

[0232] A composition containing the above lithium sulfide (Li2S) and molybdenum sulfide (Mo6S8) is milled to form a solid solution, thereby obtaining a composite as a composite positive electrode active material.

[0233] In another embodiment, a composite cathode active material is obtained by mixing the composite and a carbon-based material and milling the mixture. In this composite cathode active material, the composite and the carbon-based material are in a physical mixture state.

[0234] An organic solvent may be added during milling as needed. By performing bead milling in the presence of an organic solvent, the dissolution of lithium (Li) components in the milled material can be prevented, resulting in a finely ground product with a uniform composition.

[0235] The solvent is at least one selected from the group consisting of alcohol solvents, ketone solvents, ester solvents, glycol ether solvents, hydrocarbon solvents, ether solvents, glycol solvents and amine solvents, and for example, alcohol solvents such as isopropyl alcohol, toluene, methanol, ethanol, butanol, hexanol, benzyl alcohol and isopropyl alcohol.

[0236] Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester solvents such as methyl acetate, ethyl acetate and butyl acetate, glycol ether solvents such as propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethyl glycol monobutyl ether, 3-methoxy-3 methyl-1-butanol and diethylene glycol monobutyl ether, hydrocarbon solvents such as benzene, toluene, xylene, cyclohexane, methylcyclohexane, ethylcyclohexane, mineral oil, n-paraffin and iso-paraffin, ether solvents such as 1,3-dioxolane, 1,4-dioxane and tetrahydrofuran, glycol solvents such as ethylene glycol, diethylene glycol, propylene glycol and polyethylene glycol, monoethanolamine, diethylamine and triethanolamine, At least one selected from the group consisting of amine solvents such as n-methyl-2-pyrrolidone, 2-amino-2-methyl-1-propanol, and N,N-dimethylformamide.

[0237]

[0238] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0239] (Manufacturing of positive electrode)

[0240] Manufacturing Example 1: Anode containing composite cathode active material (70Li2S-30Mo6S8 composite) (87.8% (70Li2S-30Mo6S8 composite) + 10% SE + 1% CNF + 1.2% PTFE)

[0241] A composite cathode active material, Li2S-Mo6S8, was prepared as a cathode active material. Li6PS5Cl, an argyrodite-type crystal (D50=3.0 μm, crystalline), was prepared as a solid electrolyte. Polytetrafluoroethylene (PTFE) was prepared as a binder.

[0242] Li2S (particle size: approximately 100 nm, XRD grid size is less than 10 nm) and plate-shaped Mo6S8 were mixed in a weight ratio of 70:30. The plate-shaped Mo6S8 has a length (X direction) of approximately 30 μm, a thickness (Z direction) of 5 μm, and a width (Y direction) of approximately 15 μm (for example, Mo6S8 is a plurality of plate-shaped particles having an average length (X direction) of approximately 30 μm, an average thickness (Z direction) of 5 μm, and an average width (Y direction) of approximately 15 μm).

[0243] The mixture was mechanically milled using a ball mill to prepare a Li2S-Mo6S8 composite. The milling conditions were 25°C, 600 rpm, and 10 h in an inert atmosphere. After milling, the length, thickness, and width of Mo6S8 in the Li2S-Mo6S8 composite were each in the range of 0.01 to 1 μm.

[0244] Li6PS5Cl (D50=3.0 μm, crystalline) in the form of argyrodite was prepared as a solid electrolyte. Carbon nanofibers (CNF) were prepared as a conductive agent, and PTFE was used as a binder. The cathode mixture was prepared by mixing the composite cathode active material (Li2S-Mo6S8 composite): solid electrolyte: conductive agent: binder = 87.8:10:1:1.2 in a weight ratio. The cathode mixture was obtained by dry mixing using a ball mill. The cathode mixture obtained by ball milling formed an ionic and electronic conductive network.

[0245] The positive electrode mixture was placed on one side of a positive electrode current collector made of aluminum foil or SUS coated on one side, and plate pressed at a pressure of 200 MPa for 10 minutes to produce a positive electrode layer. The thickness of the positive electrode layer was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm. The areas of the positive electrode active material layer and the positive electrode current collector were identical.

[0246] Manufacturing Example 2: Anode containing composite cathode active material (60Li2S-40Mo6S8 composite) (87.8% (60Li2S-40Mo6S8 composite) + 10% SE + 1% CNF + 1.2% PTFE)

[0247] When manufacturing a composite cathode active material Li2S-Mo6S8 composite, the mixing weight ratio of lithium sulfide and Mo6S8 is

[0248] The positive electrode was manufactured in the same manner as in Manufacturing Example 1, except that the ratio was changed to 60:40.

[0249] Manufacturing Example 3: Anode containing composite cathode active material (70Li2S- 30Mo6S8 -10CNF composite) (87.8% (70Li2S- 30Mo6S8 -10CNF composite) + 10% SE + 1% CNF + 1.2% PTFE)

[0250] A composite cathode active material, Li2S-Mo6S8-CNF, was prepared as a cathode active material. Li6PS5Cl, an argyrodite-type crystal (D50=3.0 μm, crystalline), was prepared as a solid electrolyte. PTFE was prepared as a binder.

[0251] (Stage 1)

[0252] Li2S (particle size: approximately 100 nm, XRD grid size is less than 10 nm) and plate-shaped Mo6S8 were mixed in a weight ratio of 70:30.

[0253] The Li2S-Mo6S8 composite was prepared by mechanically milling the mixture using a ball mill. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 20 G.

[0254] The plate-shaped Mo6S8 has a length (X direction) of about 30 um, a thickness (Z direction) of 5 um, and a width (Y direction) of about 15 um (for example, Mo6S8 is a plurality of plate-shaped particles, and the average length of the plate-shaped particles is about 30 um, the average thickness is about 5 um, and the average width is about 15 um).

[0255] (Stage 2)

[0256] Li2S-Mo6S8 composite and carbon nanofiber (CNF) were mixed at a weight ratio of 100:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-Mo6S8-CNF composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was (20 G). The Li2S-Mo6S8-CNF composite was used as a composite cathode active material.

[0257] Li6PS5Cl (D50=3.0 μm, crystalline) in the form of argyrodite was prepared as a solid electrolyte, and PTFE was prepared as a binder. Ketjen black was prepared as a conductive agent. These materials were mixed in a weight ratio of composite cathode active material: solid electrolyte: binder: conductive agent = 87.8:10:1:1.2 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill. The cathode mixture obtained by ball milling formed an ionic conductive and electronic conductive network.

[0258] The positive electrode mixture was placed on one side of a positive electrode current collector made of aluminum foil or SUS coated on one side with carbon, and plate pressed at a pressure of 200 MPa for 10 minutes to produce a positive electrode layer. The thickness of the positive electrode layer was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0259] Manufacturing Example 4: Containing composite cathode active material (60Li2S- 40Mo6S8 -10CNF composite)

[0260] Anode (87.8% (60Li2S- 40Mo6S8 -10CNF composite) + 10%SE + 1%CNF + 1.2%PTFE)

[0261] When manufacturing a composite cathode active material Li2S-Mo6S8 composite, the mixing weight ratio of lithium sulfide and Mo6S8 is

[0262] The positive electrode was manufactured in the same manner as in Manufacturing Example 3, except that the ratio was changed to 60:40.

[0263] Manufacturing Example 5: Containing composite cathode active material (65Li2S- 35Mo6S8 -10CNF composite)

[0264] Anode (87.8% (65Li2S- 35Mo6S8 -10CNF composite + 10%SE + 1%CNF + 1.2%PTFE)

[0265] When manufacturing a composite cathode active material Li2S-Mo6S8 composite, the mixing weight ratio of lithium sulfide and Mo6S8 is

[0266] The positive electrode was manufactured in the same manner as in Manufacturing Example 3, except that the ratio was changed to 65:35.

[0267] Comparative Manufacturing Example 1: Anode containing only Li2S (87.8% Li2S only + 10S%E + 1%CNF +

[0268] 1.2%PTFE)

[0269] Manufacturing example, except that Li2S was used instead of the composite cathode active material in the cathode manufacturing process.

[0270] The positive electrode was manufactured in the same manner as in step 1.

[0271] Comparative Manufacturing Example 2: Anode containing Li2S-CNF (87.8% Li2S-CNF + 10% SE + 1% CNF +

[0272] 1.2% PTFE)

[0273] In the production of composite cathode active materials, Li2S was used instead of the Li2S-Mo6S8 composite, and Li2S 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-Mo6S8-CNF composite. The milling conditions were 25°C, 600 rpm, and 10 h. The Li2S-CNF composite was used as the composite cathode active material.

[0274] Comparative Manufacturing Example 3: Anode containing only sulfur (S8) (87.8% S8 only + 10% SE + 1% CNF +

[0275] 1.2% PTFE)

[0276] Except that sulfur (S8) was used instead of the composite cathode active material in the manufacture of the cathode,

[0277] The positive electrode was manufactured in the same manner as in Manufacturing Example 1.

[0278] Comparative Manufacturing Example 4: Anode containing a simple mixture of 70Li2S+30Mo6S8 (87.8% (simple mixture of 70Li2S+30Mo6S8)+10% SE+1% CNF+1.2% PTFE)

[0279] Li2S and Mo6S8 were mixed in a weight ratio of 70:30. The mixture was used as a cathode active material.

[0280] A positive electrode was manufactured using the same method as Manufacturing Example 1, except that the above positive electrode active material was used instead of the composite positive electrode active material.

[0281] Comparative Manufacturing Example 5: Anode containing 70Li2S-30MoS2 composite (87.8% (70Li2S-30MoS2 composite) + 10% SE + 1% CNF + 1.2% PTFE)

[0282] A cathode was manufactured using the same method as Manufacturing Example 1, except that MoS2 was used instead of Mo6S8 in the manufacture of the composite.

[0283] Comparative Manufacturing Example 6: Anode containing a material obtained by simultaneously ball-milling lithium sulfide, Mo6S8, and CNF (87.8% (simultaneous ball-milling of lithium sulfide, Mo6S8, and CNF) + 10% SE + 1% CNF + 1.2% PTFE)

[0284] The 70Li2S-30Mo6S8 composite and carbon nanofibers (CNF) were mixed so that the weight ratio of Li2S, Mo6S8, and carbon nanofibers (CNF) was 70:30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-Mo6S8-CNF composite. The milling conditions were 25°C, 600 rpm, and 10 h.

[0285] When the above process was performed, it was difficult to obtain the desired Li2S-Mo6S8-CNF composite.

[0286] When carried out according to Comparative Manufacturing Example 6, unlike in the case of Manufacturing Example 3, the lithiation of Mo6S8 is incomplete, so Li x The particle size of the composite was larger than that of Manufacturing Example 3 because the formation of Mo6S8 was inhibited and the particle size reduction effect was small due to the simultaneous mixing of CNF. As a result, the initial capacity, retention rate, and lifespan of the all-solid-state secondary battery were reduced.

[0287] Comparative Manufacturing Example 7: Anode containing 70Li2S-30Mo6S8 composite (97.8% (70Li2S-30Mo6S8 composite) + 1% CNF + 1.2% PTFE)

[0288] When manufacturing a positive electrode mixture, a composite positive electrode active material Li2S-Mo6S8 composite: conductive agent: binder was mixed in a weight ratio of 97.8: 1: 1.2 to prepare a positive electrode mixture. A positive electrode was manufactured by the same method as Manufacturing Example 1, except that the positive electrode mixture was obtained by dry mixing using a ball mill.

[0289] Comparative Manufacturing Example 8: Anode containing 70Li2S-30Mo6S8 composite (88.8% (70Li2S-30Mo6S8 composite) + 10% SE + 1.2% PTFE)

[0290] When manufacturing a positive electrode mixture, a composite positive electrode active material Li2S-Mo6S8 composite: electrolyte: binder was mixed in a weight ratio of 88.8: 10: 1.2 to prepare a positive electrode mixture. A positive electrode was manufactured by the same method as Manufacturing Example 1, except that the positive electrode mixture was obtained by dry mixing using a ball mill.

[0291] (Manufacturing of all-solid-state secondary batteries)

[0292] Example 1

[0293] (bipolar layer)

[0294] As the anode layer, the anode manufactured according to Manufacturing Example 1 was used.

[0295] (Cathode manufacturing)

[0296] A 10 ㎛ thick SUS foil was prepared as a negative electrode current collector. Carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials.

[0297] A mixed powder of 4 g of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of NMP (N-methyl-2-pyrrolidone) solution containing 7 wt% of PVDF (polyvinylidene fluoride) binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet 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, thereby preparing 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 approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0298] (Manufacturing of solid electrolyte layer)

[0299] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50 =3.0 um, crystalline), a mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of the solid electrolyte. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied using a bar coater onto a 15 ㎛ thick nonwoven fabric placed on a 75 ㎛ thick PET (polyethylene terephthalate) substrate, and dried in air at 80 ℃ for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 80 ℃ for 2 hours to prepare a solid electrolyte layer.

[0300] (inert absence)

[0301] A flame-retardant inert member was manufactured by forming a slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0302] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder was 20:8:70:2. The thickness of the inert material was 120 ㎛.

[0303] Before placing the manufactured flame-retardant inert material on the solid electrolyte layer, moisture, etc. of the flame-retardant inert material was removed by vacuum heat treatment at 80°C for 5 hours.

[0304] (Manufacturing of all-solid-state secondary batteries)

[0305] Referring to Fig. 1, a solid electrolyte layer was placed 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 placed on the solid electrolyte layer. A laminate was prepared by placing a gasket surrounding the positive electrode and in contact with the solid electrolyte layer. The thickness of the gasket was approximately 120 ㎛. The above-described flame-retardant inert material was used as the gasket. The gasket was placed so as to be in contact with the side surface of the positive electrode and the solid electrolyte layer. The positive electrode was placed at the center of the solid electrolyte layer, and the gasket was placed so as to surround the positive electrode and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed over the entire remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode was not placed.

[0306] The prepared laminate was plate-pressed at 85°C and 500 MPa for 30 min. This pressurization sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 μm. The density of the Li6PS5Cl solid electrolyte, 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.

[0307] The pressurized laminate was placed in a pouch and vacuum-sealed to manufacture an all-solid-state secondary battery. Portions of the positive and negative current collectors were extended outside the sealed battery to serve as positive and negative terminals.

[0308] Examples 2 to 5

[0309] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the positive electrodes of Manufacturing Examples 2 to 5 were used instead of the positive electrode of Manufacturing Example 1 as the positive electrode layer.

[0310] Comparative Examples 1 to 8

[0311] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the positive electrodes of Comparative Manufacturing Examples 1 to 8 were used instead of the positive electrode of Manufacturing Example 1 as the positive electrode layer.

[0312] Evaluation Example 1: Evaluation of anode impedance (resistance) and ionic conductivity

[0313] The impedance of the positive electrode of the all-solid-state secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 8 was evaluated by the DC polarization method.

[0314] As a result of the evaluation, it was found that the ionic and electronic conductivities of the positive electrodes of Examples 1 to 5 were higher than those of Comparative Examples 1 to 8. From these results, it can be seen that when a positive electrode containing a composite containing Mo6S8 is used, the output characteristics of an all-solid-state secondary battery having such a positive electrode can be improved due to the low interfacial resistance characteristics of the electrode and electrolyte.

[0315] The all-solid-state secondary battery of Comparative Example 5 has a positive electrode containing a complex using MoS2, and it was found that the ion conductivity characteristics were lowered and the resistance increased further compared to Example 1, which had a positive electrode containing a complex containing Mo6S8.

[0316] The all-solid-state secondary battery of Comparative Example 6 mixes Mo6S8, lithium sulfide, and carbon simultaneously.

[0317] The process resulted in poor resistance characteristics because it was difficult to manufacture the desired complex.

[0318] Evaluation Example 2: XRD Analysis

[0319] XRD spectra were measured using Cu Kα radiation for the composite cathode active materials manufactured in Examples 1 and 3 and Comparative Examples 1, 4, and 6. The XRD spectra were measured using X'pert pro (PANalytical) using Cu Kα radiation (radiation, 1.54056Å).

[0320] The diffraction angle positions at which peaks for the crystal plane (122) of Mo6S8 appear in the measured XRD spectrum are investigated and shown in Table 1 below. The peak for the crystal plane (122) of Mo6S8 appears at a diffraction angle 2θ = 33±0.5°, particularly at a diffraction angle 2θ (°) of 33.5°. In Table 2 below, the shift is indicated by ○ when the diffraction angle is shifted by 0.5° or less, particularly by 0.1-0.3°, based on the case where the diffraction angle 2θ (°) of the composite of Example 1 is 33.5°, and the case where no diffraction angle shift is observed is indicated by X.

[0321] Classification Shift (°) Example 1 (70Li2S-30Mo6S8 composite) ○ Example 3 (70Li2S-30Mo6S8-10CNF composite) ○ Comparative Example 1 (Cathode containing only Li2S) X Comparative Example 4 (Cathode containing a simple mixture of 70Li2S+30Mo6S8) X Comparative Example 6 (Simultaneous ball milling of lithium sulfide, Mo6S8 and CNF) X

[0322] As can be seen in Table 1, according to Examples 1 and 3, the diffraction angle 2θ related to lithium sulfide shifts toward a low angle. From this, lithiated Mo6S8(Li x It was found that Mo6S8) was formed.

[0323] In contrast, according to comparative examples 1 to 6, unlike in examples 1 and 3, lithiated Mo6S8(Li x It was found that Mo6S8) was not obtained. And according to Comparative Example 5 (anode containing 70Li2S-30MoS2 composite), a peak with a diffraction angle 2θ(°) of 33.9° or a peak related thereto was not observed.

[0324] Evaluation Example 3: Life Characteristics Test

[0325] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 8 were evaluated by the following charge / discharge test. The charge / discharge test was performed by placing the all-solid-state secondary batteries in a constant temperature bath at 45°C.

[0326] Charge and discharge tests were performed by placing the all-solid-state secondary battery in a constant temperature chamber at 45°C.

[0327] The first cycle involved charging for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 1.0 V.

[0328] The discharge capacity of the first cycle was taken as the standard capacity. The standard capacity is expressed as the specific capacity of Li2S in Table 3 below.

[0329] After the second cycle, charging and discharging were performed for up to 150 cycles under the same conditions as the first cycle. The measurement results are shown in Table 2 below. The initial efficiency is expressed by Equation 1 below.

[0330] <Formula 1>

[0331] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0332]

[0333] The cycle number refers to the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle. As the cycle number increases, it is considered that the all-solid-state secondary battery has excellent life characteristics. In Table 3 below, Li x The formation of Mo6S8 was confirmed by observing the peak shift toward a low angle in XRD. That is, the formation or actual formation of LixMo6S8 was indicated by ○, and the formation or actual absence of LixMo6S8 was indicated by ×.

[0334] District Li x Mo6S8 formation (electrode / active material) Capacity [mAh / g] Initial efficiency [%] Number of cycles [times] Example 1 (70Li2S-30Mo6S8 composite) + 10SE + 1CNF + 1.2PTFE) ○490 / 80085150 Example 2 (60Li2S-40Mo6S8 composite + 10SE + 1CNF + 1.2PTFE) ○481 / 90087200 Example 3 (70Li2S- 30Mo6S8-10CNF composite) + 10SE + 1CNF + 1.2PTFE ○513 / 90087.2282 Example 460Li2S-40Mo6S8-10CNF composite) + 10SE + 1CNF + 1.2PTFE)○500 / 100089.5310Example 5 (65Li2S-35Mo6S810CNF composite)+ 10SE + 1CNF + 1.2PTFE)○505 / 95088.2292Comparative Example 1 (Containing Li2S only + 10SE + 1CNF + 1.2PTFE)×○○○Comparative Example 2 (Containing Li2S-CNF + 10SE + 1CNF + 1.2PTFE)×100 / 400○○Comparative Example 3 (Containing S8 only + 10SE + 1CNF + 1.2PTFE)×○○○Comparative Example 4 (Containing a simple mixture of 70Li2S+30Mo6S8+ 10SE + 1CNF + 1.2PTFE) × 50 / 100○○Comparative Example 5 (70Li2S-30MoS2 composite + 10SE + 1CNF + 1.2PTFE○350 / 5008550Comparative Example 6 (Simultaneous ball milling of lithium sulfide, Mo6S8 and CNF + 10SE + 1CNF + 1.2PTFE) × 280 / 4008325Comparative Example 7 (70Li2S-30Mo6S8 composite + 1CNF + 1.2PTFE)○205 / 3007835Comparative Example 8 (70Li2S-30Mo6S8 composite) + 10%SE + 1.2PTFE○176 / 2808025

[0335] As shown in Table 2, the all-solid-state secondary batteries of Examples 1 to 4 employing the composite cathode active materials of Manufacturing Examples 1 to 4 showed improved discharge capacity, initial efficiency, and lifespan characteristics compared to the all-solid-state secondary batteries of Comparative Examples 1 to 8 employing the composite cathode active materials of Comparative Manufacturing Examples 1 to 6.

[0336] The all-solid-state secondary battery of Example 2 showed the best cell performance because it used an electrode with high ionic / electronic conductivity, and when an anode containing a composite containing CNF was used, the life of the all-solid-state battery was shorter than that of Example 2 due to a decrease in ionic conductivity. The result was a decrease compared to that case, and the initial efficiency due to carbon was reduced.

[0337] It was found that the all-solid-state secondary battery of Example 1 had improved initial efficiency and life characteristics, and also increased specific capacity, compared to the all-solid-state secondary battery of Comparative Example 7, which had a positive electrode non-electrolyte layer without a solid electrolyte during the manufacture of the positive electrode active material layer, and the all-solid-state secondary battery of Comparative Example 8, which had a positive electrode active material layer without a carbon-based material as a conductive agent.

[0338] Evaluation Example 4: High-rate characteristics

[0339] The high-rate characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 4 were evaluated, and the all-solid-state secondary batteries were placed in a constant-temperature bath at 60°C.

[0340] At 60°C, the battery was charged at a constant current of 0.1C and a constant voltage of 4.2V until the battery voltage reached 4.2V. Subsequently, the battery was discharged at a constant current of 0.1C until the battery voltage reached 1.0V.

[0341] Next, the battery was charged at a constant current of 0.1C until the battery voltage reached 4.2 V and a constant voltage of 4.2 V until the current value reached 0.1 C, and then discharged at a constant current of 0.33 C until the battery voltage reached 1.0 V.

[0342] The high-rate characteristics were evaluated according to Equation 2 before and after the above charging and discharging, and are shown in Table 3 below.

[0343] <Formula 2>

[0344] High rate characteristic (%) = (discharge capacity at 0.33C / discharge capacity at 0.1C) Х 100

[0345] The measurement results are shown in Table 3 below.

[0346] Classification High-rate characteristics (%) Example 1 (70Li2S-30Mo6S8 composite + 10SE + 1CNF + 1.2PTFE) 88 Example 2 (60Li2S-40Mo6S8 composite + 10SE + 1CNF + 1.2PTFE) 93 Example 3 (70Li2S-30Mo6S8-10CNF composite + 10SE + 1CNF + 1.2PTFE) 90 Example 4 (60Li2S- 40Mo6S8-10CNF composite + 10SE + 1CNF + 1.2PTFE) 96 Example 5 (65Li2S- 35Mo6S8-10CNF composite + 10SE + 1CNF + 1.2PTFE) 94 Comparative Example 1 (Li2S alone contained + 10SE + 1CNF + 1.2PTFE anode)0Comparative example 2 (Li2S-CNF containing + 10%SE + 1%CNF + 1.2PTFE anode)11Comparative example 3 (S8 containing only + 10%SE + 1%CNF + 1.2PTFE)0Comparative example 4 (70Li2S + 30Mo6S8 containing simple mixture + 10SE + 1CNF + 1.2PTFE anode)0

[0347] As shown in Table 3 below, the high-rate characteristics of the all-solid-state secondary batteries of Examples 1-5 were improved compared to those of Comparative Examples 1 to 4. In addition, it was confirmed that the high-rate characteristics of the all-solid-state secondary batteries of Comparative Examples 5 and 6 were deteriorated compared to those of Examples 1 to 4.

[0348] Evaluation Example 5: Energy Density

[0349] The all-solid-state secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 8 were operated at 0.1 C and the energy density per volume was evaluated as described below.

[0350] Energy density per volume (capacity * average voltage / volume = Ah * V / L = Wh / L) was evaluated relatively based on the difference in volume.

[0351] As a result of the energy density evaluation, the all-solid-state secondary battery of Example 1-5 was compared to Comparative Examples 1 to 8.

[0352] In this case, the energy density increased.

[0353] As described above, the all-solid-state secondary battery related to the present embodiment can be applied to various portable devices, vehicles, etc.

[0354] While exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

Claims

1. It comprises an anode layer; a cathode layer; and a solid electrolyte layer disposed between the anode layer and the cathode layer, The above positive electrode layer comprises a positive electrode current collector; and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector, The above positive electrode active material layer includes a composite positive electrode active material, a carbon-based material, and a solid electrolyte, The above composite cathode active material contains a composite including M2S; and at least one molybdenum compound selected from molybdenum sulfide (Mo6S8) and lithiated molybdenum sulfide; wherein M is an alkali metal, and the alkali metal is Li or Na, An all-solid-state secondary battery comprising a negative electrode layer and a first negative electrode active material layer disposed on one surface of the negative electrode collector.

2. An all-solid-state secondary battery comprising 60 to 99 parts by weight of M2S and 1 to 40 parts by weight of a molybdenum compound per 100 parts by weight of the composite cathode active material in the first paragraph.

3. In the first paragraph, the carbon-based material includes a fibrous carbon-based material, The above fibrous carbon material includes a carbon nanostructure, The above carbon nanostructure includes carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof, An all-solid-state secondary battery in which the content of the above carbon-based material is 0.1 to 10 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

4. In the first paragraph, the content of the solid electrolyte in the positive electrode active material layer is 1 to 15 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer. An all-solid-state secondary battery, wherein the solid electrolyte comprises a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

5. In the first paragraph, the complex further includes a carbon-based material, An all-solid-state secondary battery, wherein the content of the above carbon-based material is 1 to 20 parts by weight based on 100 parts by weight of the total weight of M2S and molybdenum compound.

6. In paragraph 5, the carbon-based material includes a fibrous carbon-based material, The above fibrous carbon material includes a carbon nanostructure, An all-solid-state secondary battery, wherein the carbon nanostructure comprises carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof.

7. In the first paragraph, the molybdenum sulfide has a plate-like shape or a fiber-like shape, and the specific surface area of ​​the molybdenum sulfide is 1 to 50 m 2 / g, When the above molybdenum sulfide has a fiber shape, the average diameter is 1 to 50 um, and the average thickness is 5 to 50 nm. When the above molybdenum sulfide has a plate-like shape, the length is 1 to 50 um, the thickness is 0.01 to 10 um, and the width is 1 to 30 um. An all-solid-state secondary battery, wherein molybdenum sulfide has a length, thickness, and width each in the range of 0.01 to 1 um after milling.

8. In the first paragraph, the M2S is lithium sulfide, the particle size of the molybdenum sulfide is larger than the size of the lithium sulfide, the size of the lithium sulfide is 0.1 nm to 10 um, and the size of the complex is 0.1 to 50 um. An all-solid-state secondary battery.

9. In the first paragraph, the M2S is lithium sulfide (Li2S), and the complex is a Li2S-Mo6S8 complex, Li2S-Li x Mo6S8(0 <x≤4) 복합체, 또는 그 조합인 전고체 이차전지.

10. In the first paragraph, the complex includes one or more transition metal sulfides selected from iron, copper, cobalt, nickel, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, zinc, manganese, and titanium. The above transition metal sulfide is Ti4O7-MoS2, An all-solid-state secondary battery further comprising V2O5-MoS2, TiS2, NbS2, Nb3S4 or a combination thereof.

11. An all-solid-state secondary battery in the first paragraph, wherein the first negative electrode active material layer includes a negative electrode active material and a binder, the negative electrode active material has a particle form, and the average particle diameter of the negative electrode active material is 4 ㎛ or less.

12. In the 11th paragraph, the negative electrode active material includes at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material, The above carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. An all-solid-state secondary battery, wherein the metal or metalloid negative electrode active material comprises gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

13. An all-solid-state secondary battery in claim 12, wherein the negative electrode active material comprises a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid, and the content of the second particles is 1 to 60 wt% based on the total weight of the mixture.

14. An all-solid-state secondary battery, further comprising a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer and between the negative electrode current collector and the solid electrolyte layer, wherein the second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

15. In the first paragraph, the electrolyte layer includes a solid electrolyte, a gel electrolyte, or a combination thereof, and the solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof. An all-solid-state secondary battery, wherein the gel electrolyte comprises a polymer gel electrolyte.

16. In the 15th paragraph, the sulfide-based solid electrolyte is 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, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , at least one selected from 0≤x≤2, An all-solid-state secondary battery, wherein the sulfide-based solid electrolyte comprises an argyrodite-type solid electrolyte, wherein the argyrodite-type solid electrolyte comprises at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I, and wherein the density of the argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc.

17. In the first paragraph, the negative electrode layer includes a negative electrode collector, 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 above base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, An all-solid-state secondary battery, 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.

18. An all-solid-state secondary battery in the first paragraph, wherein the first diffraction angle of the first peak appearing at a diffraction angle 2θ = 33.5±0.5° corresponding to the crystal plane (122) of Mo6S8 in the X-ray diffraction spectrum (XRD) of the complex is smaller than the second diffraction angle of the second peak appearing at a diffraction angle 2θ = 33.5±0.5° corresponding to the crystal plane (122) of Mo6S8 in the XRD spectrum of Mo6S8 used in the production of the complex.

19. An all-solid-state secondary battery further comprising an inert member disposed on one side of the positive electrode in accordance with claim 11. A step of obtaining a composite, including a step of milling a composition including 20.M2S and molybdenum sulfide (Mo6S8) (M is an alkali metal, and the alkali metal is Li or Na); A step of preparing a positive electrode containing a positive electrode current collector and a positive electrode active material layer including a composite positive electrode active material, a carbon-based material, and a solid electrolyte using a composition in which a solid electrolyte and a carbon-based material are added and mixed into the above complex; Step of preparing the cathode; and A method for manufacturing an all-solid-state secondary battery, comprising the step of disposing a solid electrolyte layer between the positive electrode and the negative electrode.

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