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 all-solid-state secondary battery comprising a positive electrode layer, a negative electrode layer and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer, wherein: the positive electrode layer comprises a positive electrode current collector and a positive electrode active material layer arranged on one surface or both surfaces of the positive electrode current collector; the positive electrode active material layer comprises a composite positive electrode active material; the composite positive electrode active material comprises a composite of M2S, an alkali metal salt, an inorganic electronically conductive structure and a metal conductive material, wherein M is an alkali metal, the alkali metal is Li or Na, and the electronic conductivity of the inorganic electronically conductive structure is 1 X 10-3S / cm or higher; the composite comprises a solid solution of M2S and the alkali metal salt; and the length / thickness ratio of the metal conductive material is at least 2.

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] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium batteries are used in a variety of applications, including information technology, communications devices, and automobiles. Because automobiles are life-threatening, safety is also crucial.

[0003] Lithium batteries using liquid electrolytes may have an increased risk of fire and / or explosion in the event of a short circuit. All-solid-state secondary batteries using solid electrolytes instead of liquid electrolytes are being proposed. Solid electrolytes are less likely to catch fire than liquid electrolytes.

[0004] All-solid-state secondary batteries can reduce the risk of fire or explosion by using solid electrolytes instead of liquid electrolytes. All-solid-state secondary batteries can offer improved safety.

[0005] When lithium sulfide is used as a cathode active material in an all-solid-state secondary battery, lithium sulfide is an insulator with little electrical and ionic conductivity, so a composite with a material with high electrical and ionic conductivity is required.

[0006] One aspect is to provide an all-solid-state secondary battery having improved initial efficiency, high-rate characteristics and energy density by having an anode with an enhanced electronic conduction network.

[0007] Another aspect is to provide a method for manufacturing the above-described all-solid-state secondary battery.

[0008] According to one embodiment, a battery comprising: a cathode layer; a cathode layer; and a solid electrolyte layer disposed between the cathode layer and the cathode layer, wherein the cathode layer comprises 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 comprises a composite cathode active material, wherein the composite cathode active material comprises a composite of M2S, an alkali metal salt, an inorganic electronically conductive structure, and a metal conductive material, wherein M is an alkali metal, the alkali metal is Li or Na, and the electronic conductivity of the inorganic electronically conductive structure is 1 X 10 -3 An all-solid-state secondary battery is provided, wherein the metal conductive material has a length / thickness ratio of 2 or more.

[0009] The content of the metal conductive material is 0.1 to 40 parts by weight based on 100 parts by weight of the composite, the content of the inorganic electronic conductive structure is 1 to 30 parts by weight based on 100 parts by weight of the composite, and the mixing weight ratio of the inorganic electronic conductive structure and the metal conductive material is 1:1 to 10:1.

[0010] The particle size of the composite of the above M2S, alkali metal salt, inorganic electronic conductive structure, and metal conductive material is 2 μm or less. In addition, the composite of the above M2S, alkali metal salt, two-dimensional inorganic electronic conductive structure, and metal conductive material further includes a carbon-based material.

[0011] A step of first milling M2S and alkali metal salt on the other side;

[0012] A method for manufacturing an all-solid-state secondary battery is provided, comprising: a step of obtaining a composite, including a step of adding an inorganic electronically conductive structure and a metal conductive material to a first milled product and performing a second milling; a step of manufacturing a positive electrode using a composition obtained by adding and mixing a binder to the composite; a step of preparing an anode; and a step of disposing an electrolyte between the positive electrode and the negative electrode.

[0013] In the step of obtaining the above complex, a carbon-based material may be further added to the composition.

[0014] According to one aspect, it is possible to provide an all-solid-state secondary battery having improved initial efficiency and high-rate characteristics as well as improved volumetric energy density by providing an anode with an improved electronic conduction network using a composite of an inorganic electronically conductive structure and a metal conductive material.

[0015] Figure 1 is a drawing showing a positive electrode active material layer according to an embodiment.

[0016] Figures 2 to 7 are cross-sectional views of an all-solid-state secondary battery according to an exemplary embodiment.

[0017] <Brief explanation of symbols in the drawing>

[0018] 1 All-solid-state secondary battery 10 Cathode

[0019] 11. Cathode current collector 12. Cathode active material layer

[0020] 20 Cathode 21 Cathode current collector

[0021] 22 First negative electrode active material layer 30 Electrolyte layer

[0022] 40 Inert member 41: First inert member

[0023] 41: Second inert member

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used in this disclosure have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure pertains. Furthermore, terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0025] Exemplary embodiments are described in this disclosure 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 in this disclosure should not be construed as limited to the specific shapes of regions as depicted in this disclosure, 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.

[0026] This creative idea may be embodied in many different forms and should not be construed as limited to the embodiments described in this disclosure. These embodiments are provided so that this disclosure will be thorough and complete, and so that it will fully convey the scope of the creative idea to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0027] 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.

[0028] Although terms such as "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 only used 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 disclosure.

[0029] 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.

[0030] Spatially relative terms such as "below," "under," "lower," "above," "upper," and the like 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.

[0031] "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.

[0032] In this disclosure, "particle diameter" refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter can be measured using a particle size analyzer (PSA). The "particle diameter" is, for example, the average particle diameter. The "average particle diameter" is, for example, D50, the median particle diameter.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0037] In this disclosure, “alloy” means a mixture of two or more metals.

[0038] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0039] In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation, and in the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0040] In the present disclosure, “lithiation” and “lithiating” refer to a process of adding lithium to an electrode active material. And in the present disclosure, “delithiation” and “delithiating” refer to a process of removing lithium from an electrode active material.

[0041] In the present disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery, and “discharging” and “discharging” in the present disclosure mean a process of removing electrochemical energy from a battery.

[0042] In the present disclosure, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during a discharge process, and in the present disclosure, “negative electrode” and “anode” mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0043] In the present disclosure, “thickness” and “length” represent “average thickness” and “average length”.

[0044] 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.

[0045] In this specification, “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.

[0046] 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.

[0047] 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.

[0048] [Composite cathode active material]

[0049] A composite cathode active material according to an embodiment includes a composite of M2S, an alkali metal salt, an inorganic electronically conductive structure, and a metal conductive agent, wherein M is an alkali metal, the alkali metal is Li or Na, and the electronic conductivity of the inorganic electronically conductive structure is 1×10 -3 S / cm or more, or 1×10 -2 S / cm or more, and the length / diameter ratio of the metal conductive material has a range of 2 or more. In the present disclosure, the length represents the size in the X direction.

[0050] When the composite cathode active material includes a composite of M2S, an alkali metal salt, and an inorganic electronically conductive structure, further improvement of the electronically conductive network is required depending on the shape of the inorganic electronically conductive structure.

[0051] Figure 1 schematically illustrates the structure of a positive electrode active material layer according to an embodiment. In Figure 1, Li2S is used as an example of M2S, and LiI is used as an example of an alkali metal salt.

[0052] Referring to this, the positive electrode active material layer contains Li2S (1), LiI (2), an inorganic electronically conductive material (3), and a solid electrolyte (4).

[0053] The inorganic electronically conductive conductive agent (3) forms a network that imparts electronic conductivity between lithium sulfide, which is an insulator, as shown in Fig. 1, but it is required to further strengthen the electronically conductive network depending on the shape of the inorganic electronically conductive conductive agent (3).

[0054] When adding more carbon conductive material during the manufacture of the positive electrode active material layer, the carbon conductive material may react with the solid electrolyte, which may lower the initial efficiency.

[0055] In the present disclosure, by adding a metal conductive material (5) having a length / diameter ratio of 2 or more, the electron conductivity network within the electrode can be effectively strengthened due to the long path network effect, as shown in Fig. 1. When the electron conductivity network is strengthened in this way, the electrode energy density is improved, and an all-solid-state secondary battery with improved rate characteristics and lifespan characteristics can be manufactured. In addition, unlike carbon conductive materials such as carbon nanotubes, this metal conductive material does not undergo side reactions with a solid electrolyte, and thus an all-solid-state secondary battery with improved initial efficiency and lifespan characteristics can be manufactured.

[0056] The above metal conductive material is, for example, SUS, Ti, Ni, Al, Ag, Au, V, Cr, Mn, Fe, Co, Cu, Zn, Nb, Ta, Mo, W, or a combination thereof. Here, "the combination" includes alloys of the metals listed above, and examples thereof include Al-Fe, Al-Cr-Fe, etc. Such metal conductive material has corrosion resistance to hydrogen sulfide gas.

[0057] The content of the metal conductive material is 0.1 to 30 parts by weight, 0.1 to 2 parts by weight, 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, or 0.1 to 1 part by weight, based on 100 parts by weight of the composite positive electrode active material. The length of the metal conductive material is 1 to 50 um, 1 to 40 um, 1 to 30 um, 1 to 20 um, 1 to 10 um, or 1 to 5 um, and the diameter is 0.01 to 10 um, 0.01 to 5 um, 0.01 to 3 um, 0.01 to 2 um, or 0.01 to 1 um. When the metal conductive material has the length and diameter ranges described above, the overall electronic conductivity of the composite is improved, and local electronic conductivity imbalances within the composite can be further alleviated. When the length and / or diameter of the metal conductive material has these ranges, the ion conduction path within a lithium battery including the metal conductive material is extended, and the volume change of the positive electrode active material during charge and discharge of the all-solid-state secondary battery can be more effectively accommodated, and the ion conduction path within the all-solid-state secondary battery can be maintained despite the volume change of the positive electrode active material. Consequently, deterioration of the all-solid-state secondary battery can be suppressed, and the cycle characteristics of the all-solid-state secondary battery can be improved.

[0058] The length / diameter ratio (aspect ratio) of the metal conductive material can be, for example, 2 or more, 3 or more, 5 or more, 8 or more, 10 or more, or 20 or more. The aspect ratio of the metal conductive material can be, for example, 5 to 50, 10 to 40, 10 to 45, or 20 to 40. The aspect ratio of the fibrous metal conductive material can be, for example, 5 to 50, 10 to 40, 10 to 45, or 20 to 40. When the metal conductive material has an aspect ratio in this range, the electronic conductive network of the composite is strengthened, thereby improving the overall electronic conductivity of the composite, and further alleviating local electronic conductivity imbalances within the composite.

[0059] The metal conductive material may include, for example, a rod structure, a tube structure, a needle structure, a wire structure, or a combination thereof, but is not necessarily limited to these forms, and any fibrous structure used in the relevant technical field may be used. Since the metal conductive material has a rod structure, a tube structure, a needle structure, a wire structure, or the like, the ion conduction path is extended in an all-solid-state secondary battery including a fibrous carbon-based material, and the volume change of the positive electrode active material during charge and discharge of the all-solid-state secondary battery can be accommodated more effectively, and the ion conduction path in the all-solid-state secondary battery can be maintained despite the volume change of the positive electrode active material. As a result, deterioration of the all-solid-state secondary battery can be suppressed, and the cycle characteristics of the all-solid-state secondary battery can be improved.

[0060] The cross-section perpendicular to the longitudinal direction of the metal conductive material, that is, the side surface of the fibrous carbon-based material, may have, for example, an irregular, circular, or polygonal shape. The side surface shape of the metal conductive material is, for example, a shape determined by a plane view viewed in the longitudinal direction (z direction) of the metal conductive material. The polygonal shape includes, but is not necessarily limited to, a triangle, a square, a pentagon, a hexagon, a heptagon, an octagon, a nonagon, or a decagon, and any polygonal shape used in the art may be used. The circular shape may include, but is not limited to, a perfect circle or an oval, and any shape that has an overall circular shape may be used. The circularity of the cross-section perpendicular to the longitudinal direction of the metal conductive material, that is, the circularity of the side surface of the metal conductive material, may be, for example, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. The sphericity is, for example, 4πA / P 2 It is calculated by, where A is the area of ​​the side or cross-section of the fibrous carbon material and P is the perimeter of the side or cross-section.

[0061] In the present disclosure, the content of the inorganic electronically conductive structure is 1 to 40 parts by weight, 1 to 30 parts by weight, 2 to 20 parts by weight, 3 to 15 parts by weight, or 5 to 10 parts by weight based on 100 parts by weight of the composite. And the mixing weight ratio of the inorganic electronically conductive structure and the metal conductive agent is 1:1 to 10:1, 3:1 to 10:1, or 5:1 to 9:1. When the mixing weight ratio of the inorganic electronically conductive structure and the metal conductive agent is within the above range, the rate characteristics, life characteristics, and electrode density can be improved due to the enhancement of the electronic conductivity network within the electrode.

[0062] Electronic conductivity can be measured, for example, using electrochemical impedance spectroscopy, direct current polarization, etc. Since the composite containing the metal conductive material and the inorganic electronic conductive structure has an electronic conductivity within this range, the internal resistance of the composite cathode active material including the composite can be reduced. The initial efficiency, electrode energy density, and cycle life characteristics of the all-solid-state secondary battery including the composite cathode active material can be improved.

[0063] The size of the M2S crystallite obtained from the XRD spectrum of the above complex is less than 10 nm, and the above complex contains a solid solution of M2S and an alkali metal salt.

[0064] Inorganic electronically conductive structures are inorganic structures that exhibit electronic conductivity and minimal ionic conductivity. Their small particle size and uniform dispersion within the composite facilitate the formation of conductive networks. Inorganic electronically conductive structures can be zero-dimensional, one-dimensional, two-dimensional, three-dimensional, or a combination thereof.

[0065] The zero-dimensional form can be a particle shape, the one-dimensional form can be, for example, a fiber shape, and the two-dimensional form can be, for example, a plate shape. When a composite using such an inorganic electronically conductive structure is used to manufacture a cathode and an all-solid-state secondary battery, the initial efficiency (specific capacity) is improved by reducing the side reaction characteristics with the solid electrolyte. Here, the side reaction refers to an increase in resistance due to the reaction between the hydroxyl group (H2O) present in the carbon-based material layer and the solid electrolyte, and an increase in resistance due to the reaction of carbon with lithium polysulfide (Li2S4< Li2S6). Carbon-based materials refer to graphene and carbon nanofibers (CNF), which are used as conductive materials.

[0066] The content of the inorganic electronic conductive structure in the complex is 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 15 parts by weight, or 5 to 15 parts by weight based on 100 parts by weight of the complex.

[0067] The length of the above-mentioned inorganic electron-conducting structure is 1 to 50 μm, the thickness is 0.01 to 10 μm, and the size of the M2S is 0.1 nm to 10 μm. By using a composite using a two-dimensional carbon nanostructure having such a length and thickness, an all-solid-state secondary battery with improved life characteristics can be manufactured by improving the electron-conducting network within the positive electrode. In addition, the energy density within the electrode can be improved by reducing the conductive material content within the positive electrode by strengthening the electron-conducting network. In addition, by reducing the conductive material content within the positive electrode, the content of lithium sulfide can be relatively increased, thereby improving the initial efficiency.

[0068] Any material that has a two-dimensional structure, a chalcogenide material, and electronic conductivity can be used as the inorganic electronic conductive structure.

[0069] The inorganic electronically conductive structure may have a zero-dimensional, one-dimensional, or two-dimensional structure form. For example, the zero-dimensional structure is in the form of a spherical particle, the one-dimensional structure is in the form of a fiber, and the two-dimensional structure is in the form of a plate, for example. Using an inorganic electronically conductive structure having a one-dimensional structure can produce an anode with improved film and electrode stability, and using an inorganic electronically conductive structure having a two-dimensional structure can improve the effect of suppressing volume expansion of the anode.

[0070] The inorganic electronically conductive conductive material comprises a transition metal sulfide, at least one metal sulfide of a group 3 to 5 metal, or a combination thereof, and the inorganic electronically conductive conductive material is titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, niobium, tantalum, molybdenum, tungsten, or a combination thereof.

[0071] Metal sulfides, such as transition metal sulfides, are one or more metal substances selected from ZrS2, FeS, FeS2, CuS, Cu2S, CuS2, Cu9S8, Cu7S4, CoS, CoS2, Co3S4, Co9S8, NiS, NiS2, Ni9S8, Ni3S2, VS, VS2, V2S3, V2S5, VS4, NbS2, NbS3, NbS4, NbS5, Nb2S3, Nb2S5, TaS2, TaS3, TaS4, TaS5, Ta2S3, Ta2S5, Cr2S3, CrS3, MoS2, MoS3, MoS4, WS2, WS3, WS4, WS5, MnS, Mn2S3, TiS2, NiNb3S6, Cu2MoS4 and Cu4Mo6S8. For example, at least one metal sulfide can be selected from the group consisting of FeS2, CuS2, CoS2, Co3S4, NiS2, VS2, VS4, NbS2, NbS3, NbS4, NbS5, TaS2, TaS3, TaS4, TaS5, CrS3, MoS2, MoS3, MoS4, WS2, WS3, WS4, WS5. Such transition metal sulfides can have, for example, a two-dimensional plate-like form.

[0072] According to another embodiment, the inorganic electronic conductive material is, for example, VO2, ReO2, CrO2, TiOx(0.75≤x≤1.45), Ti n O 2n-1 (4 <n<10), ReO2, VO2, SnO2, TiO2, ZrO2, Al2O3 및 TeN 중에서 선택된 하나 이상의 금속 산화물, 또는 그 조합이다.

[0073] The inorganic electronically conductive material may be, for example, alumina fibers, zirconia fibers, titania fibers, TeN fibers, SnO2 fibers, or a combination thereof. When having such a fiber shape, the inorganic electronically conductive structure has a length of 0.1 to 5 μm, a diameter of 0.01 to 0.5 μm, and an aspect ratio of 10 or more.

[0074] When the inorganic electronic conductive structure has a two-dimensional plate shape, the length is 1 to 50 um and the thickness is 0.01 to 10 um, and the size of the M2S is 0.1 nm to 10 um. The size of the alkali metal salt (LiI) is 1 nm to 10 um.

[0075] According to one embodiment, the size ratio of the inorganic electronic conductive structure and LiI is, for example, 3:1 to 0.5:1, and the size ratio of the inorganic electronic conductive structure and Li2S is, for example, 2:1 to 0.5:1.

[0076] In another embodiment, the size of the inorganic electron-conductive structure is larger than the size of lithium sulfide and the alkali metal salt (LiI), and the particle size may gradually decrease in the order of the inorganic electron-conductive structure, the alkali metal salt (LiI), and M2S. Here, the size is, for example, an arithmetic mean of the particle diameters of a plurality of particles measured using software from a scanning electron microscope image.

[0077] The size of the above M2S is equal to or smaller than the size of the alkali metal salt, the size of the above inorganic electron-conductive structure is larger than the sizes of lithium sulfide and the alkali metal salt, and the particle size gradually decreases in the order of the above inorganic electron-conductive structure, alkali metal salt, and M2S.

[0078] The size ratio of the inorganic electronic conductive structure and LiI is, for example, 3:1 to 1.5:1, and the size ratio of the inorganic electronic conductive structure and Li2S is, for example, 2:1 to 1.5:1.

[0079] The above M is an alkali metal, and the alkali metal is Li or Na. M2S is, for example, Li2S or Na2S. The complex includes a solid solution of M2S and an alkali metal salt.

[0080] By forming a complex of M2S with an alkali metal salt and an inorganic electron-conducting structure, both the ionic conductivity and the electronic conductivity of M2S can be improved simultaneously. Since the complex includes an alkali metal salt, the ionic conductivity of the composite cathode active material can be improved, and the internal resistance of the cathode and lithium battery including the composite cathode active material can be reduced. Since the complex includes an inorganic electron-conducting structure, the electronic conductivity of the composite cathode active material can be improved, and the internal resistance of the cathode and all-solid-state secondary battery including the composite cathode active material can be reduced.

[0081] The composite includes M2S crystallites, and as the size of the M2S crystallites is reduced to 10 nm or less, the volume change of the M2S crystallites during charge and discharge can be alleviated. For example, as the size of the M2S crystallites is reduced, the volume change due to a single M2S crystallite is reduced, so the overall volume change of the composite during charge and discharge can be alleviated. For example, as the size of the M2S crystallites is reduced, the grain boundaries between a plurality of M2S crystallites can more easily accommodate the volume change of the M2S crystallites during charge and discharge, so the volume change of the composite during charge and discharge can be alleviated. The possibility of defects such as cracks occurring due to the volume change of the composite during charge and discharge can be reduced. When the composite cathode active material includes such a composite, the cycle characteristics of a secondary battery including the composite cathode active material can be improved. For example, the cycle characteristics of a lithium battery including such a composite cathode active material are improved.

[0082] The composite includes M2S crystallites, and as the size of the M2S crystallites is reduced to 10 nm or less, the contact area between the M2S crystallites and the alkali metal salt and / or the carbon-based material can be further increased. As the contact area between the M2S crystallites and the alkali metal salt and / or the carbon-based material increases, the ionic conductivity and / or battery conductivity of the composite can be further improved. As the composite cathode active material includes such a composite, the reversibility of the electrode reaction can be improved in a secondary battery including the composite cathode active material. As a result, the specific capacity of the composite cathode active material can be increased.

[0083] The ionic conductivity of the composite may increase when the composite includes a solid solution of M2S and an alkali metal salt. For example, since the solid solution of M2S and an alkali metal salt includes alkali metal ions arranged within the M2S crystallites, the ionic conductivity of the solid solution of M2S and an alkali metal salt may be improved compared to the ionic conductivity of M2S. Consequently, the ionic conductivity of the composite may be improved and the internal resistance of the composite may be reduced. When the composite cathode active material includes such a composite, the cycle characteristics of a secondary battery including the composite cathode active material may be improved. For example, the high-rate characteristics of a secondary battery including such a composite cathode active material may be improved.

[0084] The Li2S-alkali metal salt-inorganic electron-conducting structure composite is distinguished from a simple mixture of Li2S, alkali metal salt, and carbon-based structure. The simple mixture of Li2S, alkali metal salt, and inorganic electron-conducting structure provides high interfacial resistance due to the inability to maintain a dense interface between Li2S, alkali metal salt, and carbon-based structure, which may result in a deterioration of the life characteristics of all-solid-state secondary batteries. The Li2S-alkali metal salt-inorganic electron-conducting structure composite is distinguished from a simple mixture of Li2S, alkali metal salt, and carbon-based structure. The simple mixture of Li2S, alkali metal salt, and inorganic electron-conducting structure provides high interfacial resistance due to the inability to maintain a dense interface between Li2S, alkali metal salt, and carbon-based structure, which may result in a deterioration of the life characteristics of all-solid-state secondary batteries.

[0085] The composite includes M2S. Since M2S has a high theoretical capacity, a secondary battery having a high energy density can be provided. However, since M2S has low ionic conductivity and / or electronic conductivity, a composite is formed with an alkali metal salt and a carbon-based material to overcome this drawback. The content of M2S in the composite may be, for example, 10 to 80 wt%, 20 to 70 wt%, 30 to 60 wt%, or 40 to 60 wt% of the total weight of the composite. If the content of M2S is excessively increased, it may not be easy to improve the ionic conductivity and / or electronic conductivity of M2S. If the content of M2S is excessively low, the energy density of the secondary battery may be reduced.

[0086] The complex comprises an alkali metal salt. An alkali metal salt is, for example, a compound that does not contain sulfur (S). The alkali metal salt may be, for example, a binary compound or a ternary compound. The alkali metal salt may be, for example, a binary compound composed of an alkali metal and one element selected from Groups 13 to 17 of the Periodic Table of the Elements. The alkali metal salt may be, for example, a ternary compound composed of an alkali metal and two elements selected from Groups 13 to 17 of the Periodic Table of the Elements.

[0087] The alkali metal salt may be, for example, a lithium salt. The lithium salt binary compound may include, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or combinations thereof. The lithium salt ternary compound may include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or combinations thereof.

[0088] The alkali metal salt may be, for example, a sodium salt. The sodium salt binary compound may include, for example, NaI, NaBr, NaCl, NaF, Na2O, Na2Se, Na3N, Na3P, Na3As, Na3Sb, Na3Al2, NaB3, or a combination thereof. The sodium salt ternary compound may include, for example, Na3OCl, NaBF4, NaPF6, NaAsF6, NaClO4, NaNO3, NaAlO2, NaAlCl4, NaNO3, Na2CO3, NaBH4, Na2SO4, Na3BO3, Na3PO4, Na4NCl, Na5NCl2, Na3BN2, or a combination thereof. The ionic conductivity of the complex may be further improved by including the above-described lithium salt or sodium salt in the complex. Such a lithium salt or sodium salt can more easily form a solid solution with, for example, Li2S or Na2S in the complex.

[0089] The content of the alkali metal salt 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 the alkali metal salt is excessively increased, the energy density of the secondary battery may decrease. If the content of the alkali metal salt 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 secondary battery may deteriorate.

[0090] The molar ratio of M2S and the alkali metal salt in the composite 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 M2S and the alkali metal salt in the composite 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. When M2S and the alkali metal salt have a molar ratio in this range, the cycle characteristics of a secondary battery including the composite positive electrode active material can be further improved. If the molar ratio of M2S is excessively high, the ionic conductivity enhancement effect of the alkali metal salt may be minimal. If the molar ratio of M2S is excessively high, the energy density of the secondary battery containing the composite cathode active material may be reduced.

[0091] In the complex, the molar ratio of Li2S or Na2S and the lithium salt 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. In the complex, the molar ratio of Li2S or Na2S and the lithium salt 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 Li2S or Na2S and a lithium salt within this range, the cycle characteristics of a lithium battery including a composite cathode active material can be further improved. If the molar ratio of Li2S or Na2S is excessively high, the effect of improving ionic conductivity by the lithium salt may be minimal. If the molar ratio of Li2S or Na2S is excessively high, the energy density of an all-solid-state secondary battery including a composite cathode active material may be reduced.

[0092] The content of the inorganic electronically conductive structure included in the composite may be, for example, 1 to 30 wt%, 1 to 20 wt%, 5 to 20 wt%, or 5 to 15 wt% of the total weight of the composite. If the content of the inorganic electronically conductive structure increases excessively, the energy density of the secondary battery may decrease. If the content of the inorganic electronically conductive structure decreases excessively, the electronic 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 secondary battery may deteriorate.

[0093] In the XRD spectrum of the composite cathode active material according to an embodiment, peaks appear at diffraction angles 2θ = 14.5±0.5, diffraction angle 2θ = 32.5±0.5°, and diffraction angle 2θ = 58.5±0.5° in relation to the crystal plane of molybdenum sulfide (MoS2).

[0094] The peak appearing at the diffraction angle 2θ = 14.5±0.5° is for the molybdenum sulfide (MoS2) (002) crystal plane, so the diffraction angle 2θ is, for example, 14.1°. And the peak appearing at the diffraction angle 2θ = 32.5±0.5° is for the molybdenum sulfide (MoS2) (100) crystal plane, so the diffraction angle 2θ is, for example, 32.9°. The peak appearing at the diffraction angle 2θ = 58.5±0.5° is for the molybdenum sulfide (MoS2) (110) crystal plane, so the diffraction angle 2θ is, for example, 58.8°.

[0095] In the X-ray diffraction spectrum (XRD) of the composite cathode active material, the first diffraction angle of the first peak appearing at a diffraction angle 2θ = 14.5±0.5°, the second peak appearing at a diffraction angle 2θ = 32.5±0.5°, and the third peak appearing at a diffraction angle 2θ = 58.5±0.5° of the composite may shift to a lower angle than the second diffraction angle of the fourth peak appearing at a diffraction angle 2θ = 14.5±0.5°, the fifth peak appearing at a diffraction angle 2θ = 32.5±0.5°, and the sixth peak appearing at a diffraction angle 2θ = 58.5±0.5° in the XRD spectrum of MoS2 used in the manufacture of the composite. The shift to a lower angle occurs more as the composite is formed during the milling process.

[0096] For example, the position of the first peak may shift to a lower angle compared to the position of the second peak. Additionally, the intensity of the first peak appearing at the diffraction angle 2θ = 14.5±0.5° is reduced compared to the intensity of the second peak appearing at the diffraction angle 2θ = 14.5±0.5° in the XRD spectrum of MoS2 used in the preparation of the composite.

[0097] In addition, crystal changes of the MoS2 material can be observed in the XRD during the milling process. The lithium sulfide-MoS2-SUS wire-molybdenum sulfide (MoS2) composite can have a reduced crystallite size compared to the lithium sulfide used in the manufacture of the composite. Since the lithium sulfide-MoS2-SUS wire-molybdenum sulfide (MoS2) composite has a reduced crystallite size, the volume change of the crystallite during charge and discharge is reduced, so the volume change of the composite including multiple crystallites can 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 can be suppressed. As a result, the cycle characteristics of the all-solid-state secondary battery including the composite cathode active material can be improved.

[0098] In the XRD spectrum of the composite, the first lattice constant (d1) derived from the seventh peak corresponding to the (111) crystal plane of M2S at a diffraction angle of 2θ = 27° ± 2.0° may be larger than the second lattice constant (d2) derived from the eighth peak corresponding to the (111) crystal plane of M2S at a diffraction angle of 2θ = 27° ± 2.0° in the XRD spectrum of M2S used in the preparation of the composite. Since the M2S-alkali metal salt-inorganic electron conductive structure composite has a larger lattice constant (d) than the M2S used in the preparation of the composite, alkali metal ions may be more easily transported within the M2S crystal structure of the composite. The ionic conductivity of the composite cathode active material including the composite may be further improved. The internal resistance of a secondary battery including the composite cathode active material may be reduced and the cycle characteristics may be improved. The difference between the first lattice constant (d1) and the second lattice constant (d2) may be 0.05 Å or more, 0.1 Å or more, 0.15 Å or more, 0.2 Å or more, or 0.25 Å or more. The size of the first lattice constant (d1) may be, for example, 5.78 Å or more, 5.80 Å or more, 5.82 Å or more, 5.85 Å or more, 5.90 Å or more, 5.95 Å or more, or 6.0 Å or more. Since the composite has such a size of the first lattice constant (d1), the ionic conductivity of the composite cathode active material including the composite may be further improved. The internal resistance of a secondary battery including the composite cathode active material may be reduced and the cycle characteristics may be improved.

[0099] In the XRD spectrum of the composite, for example, the seventh peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has the seventh diffraction angle, and in the XRD spectrum of M2S used in the preparation of the composite, the eighth peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has the eighth diffraction angle, and the seventh diffraction angle may be smaller than the eighth diffraction angle. For example, the position of the seventh peak may shift to a low angle compared to the position of the eighth peak. Therefore, the M2S-alkali metal salt-inorganic electron conductive structure composite may have a reduced crystallite size compared to M2S used in the preparation of the composite. Since the M2S-alkali metal salt-carbon material composite has a reduced crystallite size, the volume change of the crystallites during charge and discharge is reduced, so the volume change of the composite containing multiple crystallites during charge and discharge can be alleviated. The occurrence of defects such as cracks during charge and discharge of the composite cathode active material containing such a composite can be suppressed. Consequently, the cycle characteristics of the secondary battery containing the composite cathode active material can be improved.

[0100] In the XRD spectrum of the composite, for example, the seventh peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has a first full width at half maximum (FWHM1), and in the XRD spectrum of M2S used in the preparation of the composite, the eighth peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has a second full width at half maximum (FWHM2), and the first full width may be larger than the second full width. Accordingly, the M2S-alkali metal salt-inorganic electron conductive structure composite may have an increased lattice strain compared to the M2S used in the preparation of the composite. For example, the M2S-alkali metal salt-inorganic electron conductive structure composite may have an increased lattice strain when M2S and the alkali metal salt form a solid solution. Since the M2S-alkali metal salt-inorganic electron conducting structure composite has an increased full width at half maximum (FWHM) compared to the M2S used in the composite preparation, 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.

[0101] The first half-width (FWHM1) may be, for example, 1° or more, 1.05° or more, 1.10° or more, or 1.15° or more. When the composite has a first half-width (FWHM1) in this range, the ionic conductivity of the composite cathode active material including the composite can be further improved. The internal resistance of the secondary battery including the composite cathode active material can be reduced and the cycle characteristics can be improved.

[0102] According to an embodiment, based on 100 parts by weight of the complex, the content of M2S is 30 to 80 parts by weight, the content of the alkali metal salt is 1 to 40 parts by weight, the content of the inorganic electronically conductive material is 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 10 parts by weight, or 1 to 4 parts by weight, and the content of the metal conductive material is 1 to 40 parts by weight, 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 10 parts by weight, or 1 to 4 parts by weight.

[0103] The particle size of the composite cathode active material, i.e., the size of the composite particles, may be, for example, 2 ㎛ or less, 1.5 ㎛ or less, or 1 ㎛ or less. The size of the composite particles may be, for example, 0.1 to 2 ㎛, 0.1 to 1.5 ㎛, or 0.1 to 1 ㎛ or less. Since the composite particles have a size in this range, the volume change during charge and discharge is suppressed, and thus the deterioration of the composite cathode active material including the composite during charge and discharge can be suppressed. If the size of the composite particles increases excessively, the volume change of the composite during charge and discharge may increase, and thus the deterioration of the composite cathode active material including the composite may be accelerated. As a result, the cycle characteristics of a secondary battery including such a composite cathode active material may deteriorate.

[0104] Therefore, the cycle characteristics, such as life characteristics, of an all-solid-state 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, a scanning electron microscope, 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 microscope image.

[0105] The composite includes an ion-conducting alkali metal salt, an electron-conducting inorganic electron-conducting structure, and a metal conductive material added to lithium sulfide particles, so that electron conduction can be more easily performed from the surface to the interior of the composite. The internal resistance of the composite cathode active material including the composite is reduced, and the cycle characteristics of an all-solid-state secondary battery including the composite cathode active material can be further improved.

[0106] In this specification, the length and diameter of the metal conductive material and the length and thickness of the inorganic electronic conductive structure can be measured from a scanning electron microscope (SEM) image or an optical microscope.

[0107] For example, the composite may contain 10 to 80 parts by weight of M2S, 1 to 40 parts by weight of an alkali metal salt, 1 to 20 parts by weight of an inorganic electronically conductive structure, and 0.1 to 3 parts by weight of a metal conductive material, relative to 100 parts by weight of the composite. The M2S content included 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 M2S, relative to 100 parts by weight of the composite. The alkali metal salt content included 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 the alkali metal salt, relative to 100 parts by weight of the composite.

[0108] The content of the metal conductive material included in the composite is 0.1 to 40 parts by weight, 0.1 to 30 parts by weight, 0.1 to 20 parts by weight, 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.1 to 3 parts by weight, based on 100 parts by weight of the composite. And the content of the inorganic electron conductive structure may be 1 to 30 parts by weight, 1 to 20 parts by weight, 5 to 20 parts by weight, or 5 to 15 parts by weight, based on 100 parts by weight of the composite. Since the composite has M2S, an alkali metal salt, a metal conductive material, and an inorganic electron conductive structure in these ranges, a composite cathode active material including the composite can provide excellent ionic conductivity and / or electronic conductivity.

[0109] The composite of the above M2S, alkali metal salt, and two-dimensional inorganic electronically conductive structure may further include a carbon-based material.

[0110] 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 -4 It 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 -5S / 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 initial efficiency, electrode energy density, and cycle life characteristics of the all-solid-state secondary battery including the composite cathode active material can be improved.

[0111] [anode]

[0112] [Cathode: Cathode active material]

[0113] 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 includes the composite positive electrode active material described above and may further include a solid electrolyte. By including the composite positive electrode active material and the solid electrolyte, the positive electrode can have a further reduced internal resistance. Accordingly, the cycle characteristics of a secondary battery including the positive electrode can be further improved.

[0114] Figure 1 schematically illustrates the structure of a positive electrode active material layer according to an embodiment. In Figure 1, Li2S is used as an example of M2S, and LiI is used as an example of an alkali metal salt.

[0115] Referring to this, the positive electrode active material layer contains Li2S (1), LiI (2), an inorganic electronically conductive agent (3), and a metal conductive agent (5). The metal conductive agent (5) can strengthen the electronically conductive network by connecting Li2S (1), LiI (2), and the inorganic electronically conductive agent (3). As shown in Fig. 1, the sizes of the inorganic electronically conductive agent (3), LiI (2), and Li2S (1) are 1≤2<3. When they have these sizes, the inorganic electronically conductive agent can well form a network that imparts electronic conductivity between lithium sulfide, which is an insulator. The size of the inorganic electronically conductive agent refers to the average size.

[0116] Referring to FIGS. 2 to 7, 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 and solid electrolyte described above.

[0117] 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.

[0118] The cathode active material layer (12) may additionally include other cathode active materials in addition to the composite cathode active material described above.

[0119] 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.

[0120] 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.

[0121] 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, 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 electrolyte layer. The sulfide-based solid electrolyte has, for example, a molecular weight of 1×10 at room temperature. -5It 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 electrolyte layer.

[0122] 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.

[0123] 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 Li2 and a lithium halide. The composite of Li2 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.

[0124] 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 , Nb0.5 )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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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).

[0129] [Anode: Solid electrolyte]

[0130] 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 electrolyte layer (30). For more details on the solid electrolyte, refer to the electrolyte layer (30) section.

[0131] 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 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 electrolyte layer (30). The average D50 particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is 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, for example, a laser diffraction method.

[0132] 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). 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.

[0133] [Polar: Challenger]

[0134] 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).

[0135] 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.

[0136] [Positive: Binder]

[0137] 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.

[0138] [Positive: Other additives]

[0139] 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.

[0140] 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.

[0141] [Anode: Anode current collector]

[0142] 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.

[0143] 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 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.

[0144] [Anode: Inert member]

[0145] Referring to FIGS. 5 and 6, the positive electrode (10) 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. 5, 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. 6, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and between the electrolyte layer (30) and the positive electrode current collector (11) facing the electrolyte layer (30). The inactive member (40) may not be disposed on one side of the positive electrode current collector (11). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0146] By including an inert member (40), cracking of the electrolyte layer (30) is prevented during the manufacture and / or charging / 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 an all-solid-state secondary battery (1) that does not include an inert member (40), when the manufacture and / or charging / discharging of the all-solid-state secondary battery (1) is performed, uneven pressure is applied to the electrolyte layer (30) in contact with the positive electrode (10), which increases the possibility of cracking in the electrolyte layer (30), and thus, a short circuit may occur due to the growth of lithium metal through the crack.

[0147] The inert member may be an elastic member.

[0148] 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 electrolyte layer (30), and the positive electrode (10) and the electrolyte layer (30) are sufficiently adhered to each other, so that the interfacial resistance between the positive electrode (10) and the electrolyte layer (30) can be reduced. In addition, since the electrolyte layer (30) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state secondary battery (1), the internal resistance of the electrolyte layer (30) and the all-solid-state secondary battery (1) including the same is reduced.

[0149] The inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the electrolyte layer (30). By the inert member (40) surrounding the side surface of the positive electrode (10) and being in contact with the electrolyte layer (30), cracks in the electrolyte layer (30) that occur due to a pressure difference during the pressing process in the 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 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.

[0150] Referring to FIGS. 6 and 7, the inert member (40) extends from one side of the positive electrode (30) to the end of the electrolyte layer (30). By extending the inert member (40) to the end of the electrolyte layer (30), cracks occurring at the end of the electrolyte layer (30) can be suppressed. The end of the electrolyte layer (30) is the outermost part that is in contact with the side of the electrolyte layer (30). The inert member (40) extends to the outermost part that is in contact with the side of the 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 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 electrolyte layer (30).

[0151] Referring to FIGS. 6 and 7, the width of the inert member (40) extending from one side of the positive electrode (10) to the end of the 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.

[0152] The area of ​​the anode (10) is smaller than the area of ​​the 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 electrolyte layer (30). By compensating for the difference between the area of ​​the anode (10) and the area of ​​the electrolyte layer (30), cracks in the 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 electrolyte layer (30). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0153] 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 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 electrolyte layer (30).

[0154] If the area of ​​the positive electrode (10) is equal to or larger than the area of ​​the 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 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.

[0155] 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).

[0156] The area (S1) of the positive electrode (10) is smaller than the area (S4) of the negative electrode current collector (21). The area (S1) 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 (S4) of the negative electrode current collector (21). The area (S1) 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 (S4) of the negative electrode current collector (21). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the negative electrode (20). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the first negative electrode active material layer (22).

[0157] As used herein, “same” area, length, width, diameter, thickness, and / or shape includes all instances of having “substantially the same” area, length, width, diameter, thickness, and / or shape, except where the area, length, width, diameter, thickness, and / or shape are intentionally different from each other. “Same” area, length, width, diameter, and / or thickness includes a range where the unintentional difference in the area, length, width, diameter, 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%.

[0158] 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).

[0159] The inert member (40) may be a gasket. By using a gasket as the inert member (40), cracks in the electrolyte layer (30) caused by a pressure difference during the pressing process can be effectively suppressed.

[0160] The inert member (40) has, for example, a single-layer structure. Alternatively, although not shown in the drawing, 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 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 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.

[0161] 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).

[0162] 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 volume changes during charge and discharge 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 changes of the positive electrode (30) occurring during charge and discharge of the all-solid-state secondary battery (1) can be effectively accommodated and deformation of the inert member (40) due to the volume changes of the positive electrode (30) can be effectively suppressed. The first fibrous material is, for example, a material having an aspect ratio 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 the inclusion of 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 deformation of the all-solid-state secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material. Since the reinforcing material includes the second fibrous material, the strength of the matrix can be increased more uniformly. The second fibrous material is, for example, a material having an aspect ratio 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, glass fiber, metal oxide fiber, ceramic fiber, etc.

[0163] 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.

[0164] 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.

[0165] 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).

[0166] 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).

[0167] 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.

[0168] [All-solid-state secondary battery]

[0169] An all-solid-state secondary battery according to one embodiment includes the above-described positive electrode layer; a negative electrode layer; and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer. 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.

[0170] The negative electrode layer includes a negative electrode current collector and a lithium host layer disposed on one surface of the negative electrode current collector, the lithium host layer includes a lithium host structure, the lithium host structure includes one or more lithium hosts, the lithium hosts include a carbon-based lithium host, a metal-based lithium host, a polymer-based lithium host, or a combination thereof, and includes a first inactive member disposed on one surface of the negative electrode layer.

[0171] All-solid-state secondary batteries include lithium-containing sulfide-based cathode active materials as their cathode active materials. Therefore, the disruption of ion and / or electron transport pathways due to volume increase during initial discharge of non-lithium-containing sulfide-based cathode active materials, such as sulfur (S), is prevented. By preventing such disruption of ion and / or electron transport pathways, the cycle characteristics of all-solid-state secondary batteries are improved.

[0172] Since the all-solid-state secondary battery includes a lithium host layer in its anode layer, the lithium host layer acts as a support during the deposition of lithium metal in the anode layer, thereby suppressing the non-uniformity of lithium deposition. Furthermore, the formation and growth of lithium dendrites and / or isolated lithium (dead lithium) during the charge / discharge process of the all-solid-state secondary battery can be suppressed. Consequently, deterioration of the all-solid-state secondary battery is suppressed and cycle characteristics are improved.

[0173] By including a lithium host layer in the anode layer of an all-solid-state secondary battery, rapid volume changes in the anode layer during the charge / discharge process of the all-solid-state secondary battery can be suppressed. By suppressing rapid volume changes in the anode layer, deterioration of the all-solid-state secondary battery due to volume changes during the charge / discharge process of the all-solid-state secondary battery is suppressed, and cycle characteristics are improved.

[0174] Since the all-solid-state secondary battery includes a solid electrolyte layer, the migration of polysulfides generated during charging and discharging of the lithium-containing sulfide-based positive electrode active material to the negative electrode layer is blocked. Consequently, side reactions between polysulfides and the negative electrode active material are suppressed.

[0175] By arranging an inert material on one side of the cathode layer, short circuits between the lithium dendrites generated and grown during charging and discharging of the all-solid-state secondary battery and the anode and / or the lithium metal melting at high temperatures are more effectively suppressed. Consequently, short circuits in the all-solid-state secondary battery are prevented and the life characteristics are improved.

[0176] Referring to FIGS. 3 to 7, an all-solid-state secondary battery (1) includes a positive electrode layer (10); a negative electrode layer (20); and an electrolyte layer (30) disposed between the positive electrode layer (10) and the negative electrode layer (20). The negative electrode layer (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.

[0177] [anode]

[0178] See the above mentioned polarities.

[0179] [cathode]

[0180] [Cathode: Cathode active material]

[0181] Referring to FIGS. 3 to 7, 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.

[0182] 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.

[0183] The negative electrode active material included in the first negative electrode active material layer (22) has, for example, 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.

[0184] 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 semi-metal negative electrode active material.

[0185] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0186] The carbon-based negative electrode 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), and graphene, and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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 The y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x The y (0 <x≤2, 0<y≤3)의 복합체, Pt와 Pt x The y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x The y (0 <x≤1, 0<y≤1)의 복합체, Si와 Si x The y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x The y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x The y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x The y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x The y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x The y (0 <x≤1, 0<y≤3), Zn과 Zn x The y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0193] 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.

[0194] The composite negative electrode active material may have, for example, a particle form. The 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 may be facilitated during charge and discharge. The metal-based negative electrode active material supported on the support may have, for example, a particle form. The particle size of the metal-based negative electrode active material may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 5 nm to 100 nm, or 10 nm to 50 nm. The carbon-based support may have, for example, a particle form. The particle size of the carbon-based support may 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. By having a particle size in this range, the carbon-based support can be more uniformly arranged within the first negative electrode active material layer. The carbon-based support may be, for example, nanoparticles having a particle size of 500 nm or less. The particle sizes of the composite negative electrode active material, the particle sizes of the metal-based negative electrode active material, and the particle sizes of the carbon-based support are, for example, average particle sizes. The average particle size is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer. Alternatively, the average particle size may be determined automatically using software, for example, from an electron microscope image, or manually by a manual method.

[0195] [Cathode: Binder]

[0196] 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.

[0197] 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 separated from the negative electrode current collector (21), the possibility of a short circuit occurring increases as the negative electrode current collector (21) comes into contact with the electrolyte layer (30) at the exposed portion of the negative electrode current collector (21). 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).

[0198] [Cathode: Other additives]

[0199] 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.

[0200] [Cathode: Solid electrolyte]

[0201] 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 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), a space where the formed lithium metal is stored, or a path for transferring lithium ions. The solid electrolyte may be omitted.

[0202] 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 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 electrolyte layer (30) to an area adjacent to the negative electrode current collector (21).

[0203] [Cathode: First negative electrode active material layer]

[0204] 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.

[0205] 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 × 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 a solid 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 of the negative electrode active material in the first negative electrode active material layer (22). 2can be directly measured using a solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, e.g., 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, a solid-state half-cell having a cathode active material layer can have an operating voltage of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The solid 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 A solid-state battery having a positive electrode active material layer can be charged from a 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.

[0206] 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).

[0207] 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.

[0208] [Cathode: Second negative electrode active material layer]

[0209] Referring to FIG. 5, 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, but is not limited to, 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., 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).

[0210] 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.

[0211] 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).

[0212] 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).

[0213] [Cathode: Negative current collector]

[0214] 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.

[0215] Referring to FIG. 4, 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 current collector (21). The thin film (23) is disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22). The thin film (23) contains, for example, an element 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.

[0216] 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 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.

[0217] 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.

[0218]

[0219] [Electrolyte layer]

[0220] [Electrolyte layer: electrolyte]

[0221] Referring to FIGS. 1 to 6, the electrolyte layer (30) includes an electrolyte disposed between the positive electrode (10) and the negative electrode (20). The electrolyte may include, for example, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0222] 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.

[0223] 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.

[0224] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

[0225] <Chemical Formula 1>

[0226] Li + 12-n-x A n+ X 2- 6-x Y - x

[0227] 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.

[0228] 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 electrolyte layer by Li can be effectively suppressed.

[0229] 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.

[0230] 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.

[0231] 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, for example, be a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may, for example, not 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), 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, Li(FSO2)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.

[0232] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0233] 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.

[0234] [Electrolyte layer: binder]

[0235] The electrolyte layer (30) may include, for example, a binder. The binder included in the 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 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.

[0236] The binder content included in the 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 electrolyte layer (30).

[0237] Referring to Fig. 7, the negative electrode layer (20) includes a negative electrode current collector (21) and a lithium host layer (22) disposed on one side of the negative electrode current collector (21). A first inactive member (41) is disposed on one side of the positive electrode layer (10). A second inactive member (42) is disposed on one side of the negative electrode layer (20).

[0238] The second inert member (42) is disposed on one side of the lithium host layer (22) and between the solid electrolyte layer (40) and the negative electrode current collector (21) facing the solid electrolyte layer (40). The second inert member (42) is not disposed on one side of the negative electrode current collector (21). Referring to FIG. 7, the second inert member (42) is disposed on one side of the lithium host layer (22) and the negative electrode current collector (21). By including the second inert member (42), a short circuit between the lithium metal deposited on the lithium host layer (22) and the positive electrode layer (10) during charge and discharge of the all-solid-state secondary battery (1) is more effectively prevented, thereby improving the cycle characteristics of the all-solid-state secondary battery (2). By including the second inert member (42), 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 (1) are improved. In the all-solid-state secondary battery (1) that does not include the second inert member (42), 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 negative electrode layer (20), which causes cracking of the solid electrolyte layer (30), and the possibility of a short circuit occurring due to the growth of lithium metal through the cracking increases.

[0239] Referring to FIGS. 3 to 7, in the all-solid-state secondary battery (1), the thickness (T2) of the second inactive member (42) is substantially the same as the thickness (T1) of the lithium host layer (22). Since the sum of the thickness (T2) of the second inactive member (42) and the thickness (T4) of the negative electrode current collector (21) is substantially the same as the thickness (T3) of the negative electrode layer (20), a uniform pressure is applied between the negative electrode layer (20) and the solid electrolyte layer (30), and the negative electrode layer (20) and the solid electrolyte layer (30) are sufficiently adhered to each other, thereby reducing the interfacial resistance between the negative electrode layer (20) and the solid electrolyte layer (30). 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.

[0240] The manufacturing method of an all-solid-state secondary battery according to an embodiment is as follows.

[0241] An all-solid-state secondary battery according to an embodiment of the present invention comprises a first milling step of M2S and an alkali metal salt;

[0242] The method can be manufactured by including the steps of: adding an inorganic electronic conductive structure and a metal conductive material to a milled product and milling them a second time to obtain a composite; manufacturing an anode using a composition in which a binder is added and mixed into the composite; preparing an anode; and disposing an electrolyte between the anode and the cathode.

[0243] During the first and second milling, the material is crushed and energy is applied. The second milling time is adjusted to be shorter than the first milling time to control the size of the inorganic electronically conductive structure and metallic conductive material.

[0244] In the step of obtaining the above complex, a carbon-based material may be further added to the composition.

[0245] The mixing weight ratio of the inorganic electronically conductive structure and the metal conductive material is in the range of 1:1 to 10:1, 1:1 to 5:1, 3:1 to 10:1, or 5:1 to 9:1. When the mixing weight ratio of the inorganic electronically conductive structure and the metal conductive material is in the above range, an all-solid-state secondary battery with improved rate characteristics, life characteristics, and electrode density can be manufactured due to an improvement in the electronic conductivity network within the electrode.

[0246] A solid electrolyte may be added to the above composition.

[0247] The above solid electrolyte is a sulfide-based solid electrolyte. The size of the sulfide-based solid electrolyte is 0.1 nm to 10 um, for example, 100 nm to 3 um.

[0248] The above 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 , 0≤x≤2, and the sulfide-based solid electrolyte comprises an argyrodite-type solid electrolyte, and the argyrodite-type solid electrolyte comprises at least one selected from among Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0249] The density of the above argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc.

[0250] In the step of obtaining the above complex, a carbon-based material may be further added to the composition. The carbon-based material may be carbon nanofibers, etc.

[0251] 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.

[0252] In the examples below, SE represents the solid electrolyte and its content used in the positive electrode mixture described below, and % represents weight%.

[0253] (Manufacturing of composite cathode active materials)

[0254] Example 1: 30% Li2S-20% LiI-(0.75% SUS wire + 6.75% MoS2) + 42.5% SE, 2 steps

[0255] (Stage 1)

[0256] Li2S and LiI were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm, and 10 h.

[0257] (Stage 2)

[0258] Li2S-LiI composite, plate-like MoS2 (Sigma Aldrich), and SUS wire were mixed in a weight ratio of 50:6.75:0.75. The SUS wire had a length (X direction) of 4 μm, a diameter of 100 nm (0.1 μm), and a length / diameter ratio of 40. In addition, the MoS2 had a plate-like shape, and the plate-like MoS2 had a length (X direction) of about 30 μm, a thickness (Z direction) of 5 μm, and a width (Y direction) of about 15 μm. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-MoS2 composite. The milling conditions were 25 ℃, 600 rpm, and 5 h. The Li2S-LiI-MoS2-SuS wire composite was used as a composite cathode active material. And 42.5% SE represents the content of the solid electrolyte in the positive electrode mixture described below. The same applies to the following examples and comparative examples.

[0259] Example 2: 30% Li2S-20% LiI-(0.75% Ti wire + 6.75 % MoS2)+ 42.5% SE,

[0260] Step 2

[0261] A composite cathode active material was manufactured in the same manner as in Example 1, except that Ti wire was used instead of SUS wire.

[0262] Example 3: 30% Li2S-20% LiI-(3.75% SUS wire + 3.75% MoS2) + 42.5% SE,

[0263] Step 2

[0264] In the second step, a composite cathode active material was manufactured in the same manner as in Example 1, except that the weight ratio of the Li2S-LiI composite, the plate-shaped MoS2 (Sigma Aldrich), and the SUS wire was changed from 50:6.75:0.75 to 50:3.75:3.75.

[0265] Example 4: 30% Li2S-20% LiI-(3.75% Ti wire + 3.75% MoS2) + 42.5% SE, 2-step

[0266] In the second step, a composite cathode active material was manufactured in the same manner as in Example 2, except that the weight ratio of the Li2S-LiI composite and the plate-shaped MoS2 (Sigma Aldrich) and the Tu wire was changed from 50:6.75:0.75 to 50:3.75:3.75.

[0267] Example 5: 30% Li2S-20% LiI-(0.75% SUS wire + 6.75% VO2) + 42.5% SE,

[0268] Step 2

[0269] A Li2S-LiI- SUS wire+VO2 fiber composite was manufactured in the same manner as in Example 1, except that VO2 in the form of fibers was used instead of plate-shaped WS2.

[0270] Comparative Example 1: 30% Li2S-20% LiI-7.5% CNF + 42.5% SE (Li2S-LiI-CNF, 510 rpm, 10 hr, 2 stages, 20G

[0271] (Stage 1)

[0272] A first mixture was prepared by mixing Li2S and LiI in a weight ratio of 30:20. The first mixture was mechanically milled using a ball mill to prepare a Li2S-LiI complex.

[0273] Milling conditions were 25 ℃, 510 rpm for 10 h. The milling energy applied to the sample during milling was 20 G.

[0274] (Stage 2)

[0275] A second mixture was prepared by mixing the Li2S-LiI complex and carbon nanofibers (CNF) at a weight ratio of 50:10. The second mixture was mechanically milled using a ball mill to produce a Li2S-LiI-CNF complex.

[0276] The milling conditions were 25°C, 510 rpm for 10 h. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-CNF composite was used as the composite cathode active material.

[0277] Comparative Example 2: 30% Li2S-20% LiI-7.5% MoS2 + 42.5% SE

[0278] In the second step, a composite cathode active material was manufactured in the same manner as in Example 1, except that instead of mixing the Li2S-LiI complex and the plate-shaped MoS2 (Sigma Aldrich) and SUS wire in a weight ratio of 50:6.75:0.75, the Li2S-LiI complex and MoS2 were mixed in a weight ratio of 50:7.5.

[0279] Comparative Example 3: 30% Li2S- 20% LiI-(0.75% CNF + 6.75% MoS2) + 42.5% SE, 2-stage

[0280] A composite cathode active material was manufactured using the same method as Example 1, except that CNF was used instead of SUS wire.

[0281] Comparative Example 4: 30% Li2S + 20% LiI + 0.75% SUS wire + 6.75% MoS2 simple blend, 1 step

[0282] Li2S, LiI, SUS wire, and MoS2 were mixed in a weight ratio of 30:20:0.75:6.75. The mixture was used as a cathode active material.

[0283] Comparative Example 5: (Li2S-MoS2)-(LiI+SUS wire composite)+ 42.5% SE)

[0284] (Stage 1)

[0285] Li2S and MoS2 were mixed at a weight ratio of 30:7.5. The mixture was mechanically milled using a ball mill to prepare a Li2S-MoS2 composite. The milling conditions were 25°C, 600 rpm, and 5 h.

[0286] (Stage 2)

[0287] Li2S-MoS2 composite and LiI and SUS wire were mixed in a weight ratio of 36.75:20:6.75. The mixture was mechanically milled using a ball mill to prepare a Li2S-MoS2-LiI+ SUS wire composite. The milling conditions were 25°C, 600 rpm, and 10 h. The Li2S-MoS2-LiI+ SUS wire composite was used as a composite cathode active material.

[0288] Comparative Example 6: 30% Li2S-20% LiI + (0.75% SUS wire + 7.5% MoS2) simple blend, 2-stage

[0289] Li2S and LiI were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm, and 10 h.

[0290] Li2S-LiI complex, SUS wire, and MoS2 were mixed in a weight ratio of 50:0.75:6.75. The mixture was used as a cathode active material.

[0291] Comparative Example 6A

[0292] The same procedure as in Example 1 was followed, except that a structure having a length (X direction) of 4 μm, a diameter of 4 μm, and a length / diameter ratio of 1 was used instead of the SUS wire in the second stage Li2S-LiI complex and plate-like MoS2 (Sigma Aldrich) and SUS wire.

[0293] Comparative Example 6B

[0294] The same procedure as in Example 1 was followed, except that the Li2S-LiI complex in the second step and SiO2 instead of the plate-like MoS2 in the plate-like MoS2 (Sigma Aldrich) and SUS wire were used.

[0295] (Manufacturing of positive and secondary batteries)

[0296] Example 6

[0297] (Polar electrode manufacturing)

[0298] The composite manufactured in Example 1 was prepared as a cathode active material. Li6PS5Cl (D50=3.0 μm, crystalline) in the form of argyrodite was prepared as a solid electrolyte. PTFE was prepared as a binder. These materials were physically mixed in a mortar at a weight ratio of composite cathode active material: solid electrolyte: binder = 57.5:42.5:1.2 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill.

[0299] The positive electrode was manufactured by placing the positive electrode active material mixture on one side of a positive electrode current collector made of aluminum foil coated on one side and plate pressing at a pressure of 200 MPa for 10 minutes. The thickness of the positive electrode 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 the same.

[0300] (Cathode manufacturing)

[0301] 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.

[0302] 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 an NMP solution containing 7 wt% of PVDF 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.

[0303] (Manufacturing of solid electrolyte layer)

[0304] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50 =3.0 (m, crystalline), a mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of a 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 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, and dried in air at 80°C for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 80°C for 2 hours to prepare a solid electrolyte layer.

[0305] (inert absence)

[0306] 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.

[0307] 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 ㎛.

[0308] 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.

[0309] (Manufacturing of all-solid-state secondary batteries)

[0310] Referring to Fig. 6, 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 on the entire remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode was not placed.

[0311] 85 prepared laminates oThe solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 ㎛. The density of the Li6PS5Cl solid electrolyte, which was 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.

[0312] 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.

[0313] Examples 7 to 10

[0314] A positive electrode and an all-solid-state secondary battery were manufactured in the same manner as in Example 6, except that the composite positive electrode active materials manufactured in Examples 2 to 5 were used.

[0315] Comparative Examples 7 to 12

[0316] A positive electrode and an all-solid-state secondary battery were manufactured in the same manner as in Example 6, except that the composite positive electrode active materials manufactured in Comparative Examples 1 to 6 were used.

[0317] Comparative Examples 12A and 12B

[0318] A positive electrode and an all-solid-state secondary battery were manufactured in the same manner as in Example 6, except that the composite positive electrode active materials manufactured in Comparative Examples 6A and 6B were used, respectively.

[0319] Example 11: Use of sulfide-based positive electrode active material (Li2S-C composite), first negative electrode active material layer (Ag-supported carbon), and first and second flame-retardant inert members

[0320] (Cathode layer manufacturing)

[0321] A 10 ㎛ thick SUS foil was prepared as a negative electrode current collector. In addition, carbon black (CB) particles 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.

[0322] 4 g of a mixed powder containing carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of an NMP solution containing 7 wt% PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. Then, a slurry was prepared by stirring the mixed solution while adding NMP little by little to the mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater and dried in the air at 80°C for 10 minutes. The laminate thus obtained was vacuum-dried at 40°C for 10 hours. The dried laminate was dried at 5 ton·f / cm 2 The surface of the first negative electrode active material layer of the laminate was flattened by cold roll pressing at a pressure of 5 m / sec. The negative electrode layer was manufactured by the above process. The thickness of the first negative electrode active material layer included in the negative electrode layer was approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0323] (Anode layer manufacturing)

[0324] As a cathode active material, a composite cathode active material manufactured in Example 1 was prepared.

[0325] Li6PS5Cl (D50=3.0 μm, crystalline) in the form of argyrodite was prepared as a solid electrolyte. Ketjen black was prepared as a conductive agent. These materials were mixed in a weight ratio of positive electrode active material: solid electrolyte: conductive agent = 40:50:10 to prepare a positive electrode mixture. The positive electrode mixture was obtained by dry mixing using a ball mill. The positive electrode mixture obtained by ball milling formed an ionic and electronic conductive network.

[0326] 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.

[0327] (Manufacturing of solid electrolyte layer)

[0328] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50 =3.0 mm, 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 mm thick nonwoven fabric placed on a 75 mm thick PET substrate, and dried in air at 80°C for 10 minutes to obtain a laminate. The obtained laminate was vacuum-dried at 80°C for 2 hours. A solid electrolyte layer was prepared by the above process.

[0329] (flame retardant inert material)

[0330] A flame-retardant inert member was manufactured by forming a slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), titanium dioxide (TiO2), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0331] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), titanium dioxide (TiO2), and acrylic binder was 20:8:60:10:2. The thickness of the inert material was 120 ㎛.

[0332] 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.

[0333] (Manufacturing of all-solid-state secondary batteries)

[0334] Referring to Fig. 6, a solid electrolyte layer was placed on the negative electrode layer such that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a positive electrode layer was placed on the solid electrolyte layer. A laminate was prepared by placing a first gasket around the negative electrode layer to surround the negative electrode layer and to contact the solid electrolyte layer. The thickness of the first gasket was approximately 120 ㎛. The flame-retardant inert member (first inert member) was used as the first gasket. The negative electrode layer was placed at the center of the solid electrolyte layer, and the first gasket was placed to surround the negative electrode layer and extend to the end of the solid electrolyte layer. The area of ​​the negative electrode layer was approximately 90% of the area of ​​the solid electrolyte layer, and the first gasket was placed on the entire remaining 10% of the area of ​​the solid electrolyte layer where the negative electrode layer was not placed.

[0335] A laminate was prepared by placing a second gasket around the anode layer and contacting the solid electrolyte layer. The thickness of the second gasket was approximately 120 μm. The flame-retardant inert member (second inert member) was used as the second gasket. The anode layer was placed at the center of the solid electrolyte layer, and the second gasket was placed so as to surround the anode layer and extend to the end of the solid electrolyte layer. The area of ​​the anode layer was approximately 80% of the area of ​​the solid electrolyte layer, and the second gasket was placed over the entire remaining 20% ​​of the area of ​​the solid electrolyte layer where the anode layer was not placed.

[0336] 85 prepared laminates o The solid electrolyte layer was plate-pressed at a pressure of 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 μm.

[0337] 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 electrode collectors were extended outside the sealed battery to serve as positive and negative electrode terminals.

[0338] Example 12: Mono-cell all-solid-state secondary battery, sulfide-based cathode active material (Li2S-C-solid electrolyte composite), lithium host layer, flame-retardant first and second inert members

[0339] (Cathode layer manufacturing)

[0340] A 10 μm thick SUS foil was prepared as a negative electrode collector. In addition, a carbonized cotton sheet was prepared as a lithium host. The carbonized cotton sheet was manufactured according to the method disclosed in Joule 2017, 1, 563.

[0341] The prepared carbonized cotton sheet was placed on a SUS foil to prepare a laminate. The prepared laminate was vacuum dried at 40°C for 10 hours. The dried laminate was dried at 5 ton·f / cm 2 The surface of the first negative electrode active material layer of the laminate was flattened by cold roll pressing at a speed of 5 m / sec under a pressure of . The negative electrode layer was manufactured by the above process. The thickness of the carbonized cotton sheet included in the negative electrode layer, i.e., the lithium host layer, was approximately 120 ㎛.

[0342] (Anode layer manufacturing)

[0343] The composite cathode active material of Example 1 was prepared as a cathode active material.

[0344] Li6PS5Cl (D50=3.0 μm, crystalline) in the form of argyrodite was prepared as a solid electrolyte. Ketjen black was prepared as a conductive agent. These materials were mixed in a weight ratio of positive electrode active material: solid electrolyte: conductive agent = 40:50:10 to prepare a positive electrode mixture. The positive electrode mixture was obtained by dry mixing using a ball mill. The positive electrode mixture obtained by ball milling formed an ionic and electronic conductive network.

[0345] 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.

[0346] (Manufacturing of solid electrolyte layer)

[0347] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50 =3.0 mm, 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 mm thick nonwoven fabric placed on a 75 mm thick PET substrate, and dried in air at 80°C for 10 minutes to obtain a laminate. The obtained laminate was vacuum-dried at 80°C for 2 hours. A solid electrolyte layer was prepared by the above process.

[0348] (flame retardant inert material)

[0349] A flame-retardant inert member was manufactured by forming a slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), titanium dioxide (TiO2), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0350] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), titanium dioxide (TiO2), and acrylic binder was 20:8:60:10:2. The thickness of the inert material was 120 ㎛.

[0351] 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.

[0352] (Manufacturing of all-solid-state secondary batteries)

[0353] Referring to Fig. 7, a solid electrolyte layer was placed on the negative electrode layer such that the lithium host layer was in contact with the solid electrolyte layer, and a positive electrode layer was placed on the solid electrolyte layer. A laminate was prepared by placing a first gasket around the negative electrode layer and in contact with the solid electrolyte layer. The thickness of the first gasket was approximately 120 ㎛. The flame-retardant inert member (the first flame-retardant inert member) was used as the first gasket. The negative electrode layer was placed at the center of the solid electrolyte layer, and the first gasket was placed so as to surround the negative electrode layer and extend to the end of the solid electrolyte layer. The area of ​​the negative electrode layer was approximately 90% of the area of ​​the solid electrolyte layer, and the first gasket was placed on the entire remaining 10% of the area of ​​the solid electrolyte layer where the negative electrode layer was not placed.

[0354] A laminate was prepared by placing a second gasket around the anode layer and contacting the solid electrolyte layer. The thickness of the second gasket was approximately 120 μm. The flame-retardant inert material (second flame-retardant inert material) was used as the second gasket. The anode layer was placed at the center of the solid electrolyte layer, and the second gasket was placed so as to surround the anode layer and extend to the end of the solid electrolyte layer. The area of ​​the anode layer was approximately 90% of the area of ​​the solid electrolyte layer, and the second gasket was placed over the entire remaining 10% of the area of ​​the solid electrolyte layer where the anode layer was not placed.

[0355] 85 prepared laminates o The solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process 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, which is an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc.

[0356] 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 electrode collectors were extended outside the sealed battery to serve as positive and negative electrode terminals.

[0357] Comparative Example 13: Sulfide-based cathode active material (Li2S-C-solid electrolyte composite), no lithium host layer used (free), no flame-retardant first and second inert members used (free)

[0358] An all-solid-state secondary battery was manufactured in the same manner as Example 11, except that the second flame-retardant inert member (second gasket) was not used in the positive electrode layer, only the negative electrode current collector was used in the negative electrode layer, and the lithium host layer and the first flame-retardant inert member (first gasket) were not used.

[0359] Comparative Example 14: Sulfide-based cathode active material (Li2S-C-solid electrolyte composite), no lithium host layer used (free), no flame-retardant first inert member used (free)

[0360] An all-solid-state secondary battery was manufactured in the same manner as Example 12, except that a second flame-retardant inert member (second gasket) was used in the positive electrode layer, only a negative electrode current collector was used in the negative electrode layer, and the lithium host layer and the first flame-retardant inert member (first gasket) were not used.

[0361] Evaluation Example 1: XRD Analysis and Scanning Electron Microscopy Analysis

[0362] XRD spectra were measured using Cu Kα radiation for the composite cathode active materials (i.e., composites) manufactured in the examples and comparative examples. The Li2S crystallite sizes calculated from the first peak for the (111) crystal plane appearing at a diffraction angle of 2θ = 27° ± 2.0° in the measured XRD spectra are shown in Table 2 below. The crystallite sizes were calculated using the Sherrer Equation.

[0363] The Li2S particle size (D50 particle size) of the composite cathode active materials manufactured in Example 1 and Comparative Examples 2 to 5 was measured using a laser-based particle size analyzer (PSA) and a scanning electron microscope. The Li2S particle size of the composite cathode active material is the arithmetic mean of the particle sizes of multiple Li2S particles measured using software from scanning electron microscope images. The measurement results are shown in Table 1 below.

[0364] Classification 1st stage milling 2nd stage milling Solid solution formation Li2S crystallite size [nm] Li2S particle size [㎛] Example 1 30%Li2S-20%LiI-(0.75% SUS wire + 6.75% MoS2) + 42.5% SE 600 rpm, 28 G, 10 hr 600 rpm, 28 G, 5 hr ○ Less than 9.61 Example 2 30%Li2S-20%LiI-(0.75% Ti wire + 6.75% MoS2) + 42.5% SE 600 rpm, 28 G, 10 hr 600 rpm, 28 G, 5 hr ○ Less than 9.81 Example 3 30%Li2S-20%LiI-(3.75% SUS wire + 3.75% MoS2) + 42.5% SE600 rpm, 28 G, 10 hr600 rpm, 28 G, 5 hr○9.81 Less than Example 430%Li2S-20%LiI-(3.75% Ti wire + 3.75% MoS2) + 42.5%SE, 2nd stage600 rpm, 28 G, 10 hr600 rpm, 28 G, 5 hr○10.01 Less than Example 530%Li2S-20%LiI-(0.75% SUS wire + 6.75% VO2) + 42.5%SE600 rpm, 28 G, 10 hr600 rpm, 28 G, 5 hr○9.81 Less than Comparative Example 130%Li2S-20%LiI-7.5%CNF + 42.5%SE Tatsumi Sago 600 rpm, 28 G, 10 hr 600 rpm, 28 G, 10 hr ○9.81 Less than comparative example 230%Li2S-20%LiI-7.5% MoS2+ 42.5% SE 600 rpm, 28 G, 10 hr 600 rpm, 28 G, 5 hr ○10.11 Less than comparative example 330%Li2S-20%LiI-(0.75% CNF + 6.75 % MoS2) + 42.5% SE 600 rpm, 28 G, 10 hr 600 rpm, 28 G, 5 hr ○10.21 Less than comparative example 430% Li2S + 20% LiI + 0.75% SUS wire + 6.75% MoS2 Simple blend, 1 step--X678 Comparative example 5(Li2S-MoS2)-(LiI+SUS wire composite)600 rpm,28 G, 10 hr600 rpm,28 G, 5 hrX10.Comparative example below 41 630% Li2S-20% LiI + (SUS wire 0.75% + 7.5% MoS2) simple blend, 2-stage 600 rpm, 28 G, 10 hr-○304.

[0365] As shown in Table 1, the (Li2S-LiI-SUS wire + MoS2) composite of Example 1 contained a Li2S-LiI solid solution, the size of the Li2S crystallites was 9.6 nm, and the Li2S particle size of the composite was less than 1 μm. This composite simultaneously improved electrical and ionic conductivities through ball milling, thereby reducing the relative content of the solid electrolyte and increasing the relative content of Li2S, thereby improving the electrode energy density. In contrast, as shown in Table 1, the simple mixture of Li2S, LiI, SUS wire, and MoS2 of Comparative Example 4 did not form a solid solution.

[0366] In addition, in the composite of Comparative Example 4, the Li2S-LiI solid solution and the Li2S-LiI-MoS2 composite containing it were not properly formed when milling was performed to manufacture the composite.

[0367] In Comparative Example 5, the (Li2S-MoS2-LiI+ SUS wire) composite was not properly formed as the Li2S-LiI solid solution was not formed properly because the Li2S-MoS2-LiI composite was manufactured in the first step and then the composite was manufactured in the second step.

[0368] According to Comparative Example 6, the Li2S-LiI solid solution was formed, and then the SUS wire and MoS2 were simply blended to form the composite of Example 1.

[0369] Evaluation Example 2: Charge / Discharge Test

[0370] The charge / discharge characteristics of the all-solid-state secondary batteries of Examples 6 to 10 and Comparative Examples 7 to 12, Comparative Example 12A, and Comparative Example 12B, which employed the composite positive electrode active materials manufactured in Examples 1 to 5, Comparative Examples 1 to 6, Comparative Example 6A, and Comparative Example 6B, were evaluated by the following charge / discharge test.

[0371] Charge and discharge tests were performed by placing the solid secondary battery in a constant temperature bath at 45°C.

[0372] The first cycle involved charging for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 2.5 V to 2.8 V. Subsequently, discharging was performed for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 0.3 V.

[0373] 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 1 below.

[0374] 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.

[0375] <Formula 1>

[0376] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0377] The cycle count is the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle. A higher cycle count is considered to indicate better life characteristics.

[0378] Electrode capacity [mAh / g] Electrode density (g / cm3) Electrode capacity (mAh / g) Initial efficiency [%] Lifespan (SOH80@) Example 6 30% Li2S-20% LiI-(0.75% SUS wire + 6.75% MoS2) + 42.5% SE11601.8234890800 Example 7 30% Li2S-20% LiI-(0.75% Ti wire + 6.75% MoS2) + 42.5% SE11601.8034890770 Example 8 30% Li2S-20% LiI-(3.75% SUS wire + 3.75% MoS2) + 42.5% SE10502.1231589720 Example 930%Li2S-20%LiI-(3.75%Ti wire + 3.75% MoS2) + 42.5%SE, 2-stage 10502.1031588690 Example 1030%Li2S-20%LiI-(0.75% SUS wire + 6.75 % VO2) + 42.5% SE 10801.7732489700 Comparative Example 7 (tatsumisago) 30%Li2S-20%LiI-7.5%CNF + 42.5% SE 7001.52106510 Comparative Example 830%Li2S-20%LiI-7.5% MoS2+ 42.5% SE 10101.7334888550 Comparative Example 930%Li2S-20%LiI-(0.75% CNF + 6.75% MoS2) + 42.5% SE9501.733087630Comparative Example 1030% Li2S + 20% LiI + 0.75% SUS wire + 6.75% MoS2Simple blend, Step 1501.830--Comparative Example 11(Li2S-MoS2)-(LiI+SUS wire composite)3001.8906120Comparative Example 1230% Li2S-20% LiI + (SUS wire 0.75% + 6.75% MoS2)Simple blend, Step 21701.851--

[0379] In the above Table 2, - indicates that it is so poor that it cannot be measured. As shown in Table 2, the all-solid-state secondary batteries of Examples 6 to 10 employing the composite cathode active materials of Examples 1 to 5 showed improved discharge capacity, initial efficiency, and lifespan characteristics compared to the all-solid-state secondary batteries of Comparative Examples 7 to 12 employing the composite cathode active materials of Comparative Examples 1 to 6.

[0380] The all-solid-state secondary battery of Comparative Example 7, which employed the Li2S-LiI-CNF composite cathode active material, also had a reduced electrode capacity compared to Example 6, which employed the composite cathode active material of Example 1.

[0381] The all-solid-state secondary batteries of Comparative Examples 8 to 12, which employed the composite cathode active materials of Comparative Examples 2 to 6, exhibited poor initial efficiency and lifespan characteristics in at least one case. In addition, the all-solid-state secondary battery of Comparative Example 12A, which employed the composite cathode active material of Comparative Example 6A, exhibited poor characteristics, such as discharge capacity, initial capacity, and lifespan characteristics at the same level as those of the all-solid-state secondary battery of Comparative Example 8. In addition, the all-solid-state secondary battery of Comparative Example 12B, which employed the composite cathode active material of Comparative Example 6B using SiO2 having no electron conductivity, exhibited very poor initial efficiency and lifespan characteristics, similar to those of the all-solid-state secondary battery of Comparative Example 12.

[0382] Evaluation Example 3: Rate Characteristic Evaluation

[0383] The rate characteristics of the all-solid-state secondary batteries of Examples 6 to 10 and Comparative Examples 7 to 12, which employed the composite positive electrode active materials manufactured in Examples 1 to 5 and Comparative Examples 1 to 6, 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.

[0384] The all-solid-state secondary batteries manufactured in Examples 6 to 10 and Comparative Examples 6 to 9 were charged at 45°C with a constant current of 0.1 C and a constant voltage of 4.2 V until the battery voltage reached 4.2 V, and then discharged at a constant current of 0.1 C until the battery voltage reached 2.5 V.

[0385] 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 2.5 V.

[0386] The rate characteristics were evaluated according to Equation 3 below before and after the above charging and discharging, and are shown in Table 3 below.

[0387] <Formula 2>

[0388] Rate characteristic (%) = (discharge capacity at 0.33C / discharge capacity at 0.1C) Х 100

[0389] Classification Rate Characteristics (0.33C / 0.1C) [%] Example 6 30%Li2S-20%LiI-(0.75% SUS wire + 6.75% MoS2) + 42.5% SE97 Example 7 30%Li2S-20%LiI-(0.75% Ti wire + 6.75% MoS2) + 42.5% SE95 Example 8 30%Li2S-20%LiI-(3.75% SUS wire + 3.75% MoS2) + 42.5% SE96 Example 9 30%Li2S-20%LiI-(3.75% Ti wire + 3.75% MoS2) + 42.5% SE94 Example 10 30%Li2S-20%LiI-(0.75% SUS wire + 6.75 % VO2) + 42.5 % SE95Comparative Example 7 (tatsumisago)30 % Li2S-20 % LiI-7.5 % CNF + 42.5 % SE89Comparative Example 830 % Li2S-20 % LiI-7.5 % MoS-2 + 42.5 % SE91Comparative Example 930 % Li2S-20 % LiI-(0.75 % CNF + 6.75 % MoS2) + 42.5 % SE90Comparative Example 1030 % Li2S+20 % LiI+0.75 % SUS wire+6.75 % MoS2Simple Blend0Comparative Example 11 (Li2S-MoS2)-(LiI+ SUS wire) Composite0Comparative Example 1230 % Li2S-20 % LiI + (SUS wire 0.75 % + 7.5 % MoS2) Simple Blend 0

[0390] As shown in Table 3, the all-solid-state secondary batteries of Examples 6 to 10 had improved rate characteristics compared to the all-solid-state secondary batteries of Comparative Examples 7 to 12. As shown in Table 3, the rate characteristics of the all-solid-state secondary batteries of Comparative Examples 7 to 12 could not be measured.

[0391] Evaluation Example 4: High-temperature life characteristics test

[0392] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Example 11 and Comparative Example 13 were evaluated by the following charge / discharge test. The charge / discharge test was performed by placing the solid-state secondary batteries in a constant temperature bath at 45°C.

[0393] The first cycle is 0.3 mA / cm until the battery voltage reaches 2.5 V to 2.8 V. 2 The battery was charged for 12.5 hours at a constant current of 0.3 mA / cm until the battery voltage reached 0.5 V. 2 Discharge was performed for 12.5 hours at a constant current.

[0394] The discharge capacity of the first cycle was used as the standard capacity. From the second cycle onward, charging and discharging were performed up to 200 cycles under the same conditions as the first cycle. The measurement results are shown in Table 4 below.

[0395] The higher the number of cycles required for the discharge capacity to decrease to 95% of the standard capacity after the second cycle, the better the life characteristics were considered to be.

[0396] In the all-solid-state secondary battery of Comparative Example 11, a short circuit occurred before the first cycle was completed, making it impossible to measure the life characteristics.

[0397] Number of cycles [times] Example 11 (mono-cell / composite cathode active material / flame-retardant cathode gasket / carbonized cotton sheet / flame-retardant cathode gasket) 172 Comparative example 13 (mono-cell / Li2S-C-solid electrolyte composite / - / - / -) Not measurable

[0398] As shown in Table 4, the all-solid-state secondary battery of Example 11 had improved life characteristics compared to the all-solid-state secondary battery of Comparative Example 13.

[0399] It was determined that the all-solid-state secondary battery of Example 11 including lithium hosts had improved life characteristics compared to the all-solid-state secondary battery of Comparative Example 13 not including lithium hosts, as the growth of lithium dendrites was suppressed, short circuits were suppressed, and volume changes in the negative electrode layer were suppressed.

[0400] Although not shown in the drawing, it was confirmed that a lithium metal layer was formed between the first negative electrode active material layer and the negative electrode current collector in the all-solid-state secondary batteries of Examples 7 to 12 after initial charging. This was confirmed through a cross-sectional scanning electron microscope image of the all-solid-state secondary battery.

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, The above composite cathode active material comprises a composite of M2S, an alkali metal salt, an inorganic electronically conductive structure, and a metal conductive material, wherein M is an alkali metal, and the alkali metal is Li or Na. The electronic conductivity of the above inorganic electronic conductive structure is 1 X 10 -3 S / cm or more, An all-solid-state secondary battery, wherein the length / diameter ratio of the above metal conductive material is 2 or more.

2. In paragraph 1, the metal conductive material is SUS, Ti, Ni, Al, Ag, Au, V, Cr, Mn, Fe, Co, Cu, Zn, Nb, Ta, Mo, W, or a combination thereof. An all-solid-state secondary battery, wherein the length of the metal conductive material is 1 to 50 um and the diameter of the metal conductive material is 0.01 to 10 um.

3. In paragraph 1, the content of the metal conductive material is 0.1 to 40 parts by weight based on 100 parts by weight of the composite. The content of the above inorganic electronic conductive structure is 1 to 30 parts by weight based on 100 parts by weight of the composite. An all-solid-state secondary battery, wherein the mixing weight ratio of the above-mentioned inorganic electronic conductive structure and the metal conductive material is 1:1 to 10:

1.

4. An all-solid-state secondary battery in accordance with claim 1, wherein the size of M2S crystallites obtained from the XRD spectrum of the complex is less than 10 nm, and the complex includes a solid solution of M2S and an alkali metal salt.

5. In the first paragraph, the inorganic electronic conductive structure has a zero-dimensional, one-dimensional, or two-dimensional structure form, An all-solid-state secondary battery, wherein the length of the above-mentioned inorganic electronic conductive structure is 1 to 50 um, the thickness is 0.01 to 10 um, and the size of the M2S is 0.1 nm to 10 um.

6. In the first paragraph, the inorganic electronic conductive structure comprises a transition metal sulfide, at least one metal sulfide among group 3 to group 5 metals, or a combination thereof, The above inorganic electronically conductive structure is one or more metals selected from titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, niobium, tantalum, molybdenum, and tungsten, or a combination thereof, The above inorganic electronic conductive structure is VO2, ReO2, CrO2, ReO2, VO2, SnO2, TiO2, ZrO2, Al2O3, TeN, TiN, TiO, TiOx (0.75≤x≤1.45), Ti n O 2n-1 (4 <n<10), ReO3, CrO2, VO2 중에서 선택된 하나 이상의 금속 산화물, ZrS2, FeS, FeS2, CuS, Cu2S, CuS2, Cu9S8, Cu7S4, CoS, CoS2, Co3S4, Co9S8, NiS, NiS2, Ni9S8, Ni3S2, VS, VS2, V2S3, V2S5, VS4, NbS2, NbS3, NbS4, NbS5, Nb2S3, Nb2S5, TaS2, TaS3, TaS4, TaS5, Ta2S3, Ta2S5, Cr2S3, CrS3, MoS2, MoS3, MoS4, WS2, WS3, WS4, WS5, MnS, Mn2S3, TiS2, NiNb3S6, Cu2MoS4 및 Cu4Mo6S8 중에서 선택된 하나 이상의 금속 물질, 또는 그 조합인 전고체 이차전지.

7. In the first paragraph, the first lattice constant (d1) derived from the seventh peak appearing at a diffraction angle 2θ = 27°±2.0° corresponding to the (111) crystal plane of M2S in the XRD spectrum of the complex is greater than the second lattice constant (d2) derived from the eighth peak appearing at a diffraction angle 2θ = 27°±2.0° corresponding to the (111) crystal plane of M2S in the XRD spectrum of M2S used in the production of the complex. An all-solid-state secondary battery having a first lattice constant (d1) size of 5.78 Å or more.

8. In the first paragraph, the size of the M2S is equal to or smaller than the size of the alkali metal salt, and the size of the inorganic electronic conductive structure is equal to or smaller than the size of the lithium sulfide and the alkali metal salt. An all-solid-state secondary battery, in which the particle size is gradually reduced in the order of the inorganic electron-conductive structure, alkali metal salt and M2S.

9. In the first paragraph, the positive electrode active material layer further includes a solid electrolyte, The above 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 content of the solid electrolyte is 10 to 60 parts by weight based on 100 parts by weight of the positive electrode active material layer.

10. In paragraph 1, the alkali metal salt is a lithium salt or a sodium salt, The above alkali metal salt is a binary compound or a ternary compound, The above binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3 or a combination thereof, or comprises NaI, NaBr, NaCl, NaF, Na2O, Na2Se, Na3N, Na3P, Na3As, Na3Sb, Na3Al2, NaB3 or a combination thereof, The above ternary compound comprises Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or a combination thereof, or comprises Na3OCl, NaBF4, NaPF6, NaAsF6, NaClO4, NaNO3, NaAlO2, NaAlCl4, NaNO3, Na2CO3, NaBH4, Na2SO4, Na3BO3, Na3PO4, Na4NCl, Na5NCl2, Na3BN2 or a combination thereof, An all-solid-state secondary battery, wherein the molar ratio of the M2S and the alkali metal salt in the above complex is 50:50 to 95:

5.

11. An all-solid-state secondary battery in the first paragraph, wherein the particle size of the composite of the M2S, the alkali metal salt, and the inorganic electronic conductive structure is 2 ㎛ or less.

12. In the first paragraph, the composite of the M2S, the alkali metal salt, and the two-dimensional inorganic electronic conductive structure further includes a carbon-based material.

13. An all-solid-state secondary battery according to claim 1, wherein the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on the negative electrode current collector.

14. In the 13th paragraph, the negative electrode active material of the first negative electrode active material layer includes at least one selected from a carbon-based negative electrode active material and a metal-based negative electrode active material, The above carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. The above metal-based negative electrode active material includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn) or a combination thereof. In the first paragraph, the negative electrode active material of the first negative electrode active material layer is an all-solid-state secondary battery including a mixture of a metal-based negative electrode active material and a carbon-based material, a metal-based negative electrode active material supported on a carbon-based material, or a combination thereof.

15. In the first paragraph, the negative electrode layer includes a negative electrode current collector and a lithium host layer disposed on one surface of the negative electrode current collector, The above lithium host layer includes a lithium host structure, The lithium host structure comprises one or more lithium hosts, wherein the lithium host comprises a carbon-based lithium host, a metal-based lithium host, a polymer-based lithium host, or a combination thereof, An all-solid-state secondary battery including a first inactive member disposed on one side of the cathode layer, 16. In the first paragraph, the negative electrode current collector is disposed between the first negative electrode active material layer. It further includes a second negative electrode active material layer, wherein the second negative electrode active material layer is a metal layer including lithium or a lithium alloy, The above second negative electrode active material layer is a plated layer, The thickness of the first negative electrode active material layer is greater than the thickness of the second negative electrode active material layer. Large, all-solid-state secondary battery.

17. An all-solid-state secondary battery further comprising an inert elastic member disposed on one surface of the positive electrode layer or the negative electrode layer in the first paragraph.

18. In the first paragraph, the electrolyte layer includes a solid electrolyte, a gel electrolyte, or a combination thereof, The above solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof, The above gel electrolyte comprises a polymer gel electrolyte, The above 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, The above sulfide-based solid electrolyte includes an argyrodite-type solid electrolyte, The above argyrodite-type solid electrolyte comprises at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I, An all-solid-state secondary battery, wherein the density of the above argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc.

19. 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.

20. Step of first milling M2S and alkali metal salt; A step of adding an inorganic electronic conductive structure and a metal conductive material to a first milled product and performing a second milling to obtain a composite; A step of manufacturing an anode using a composition in which a binder is added and mixed into the above complex; Step of preparing the cathode; and A method for manufacturing an all-solid-state secondary battery, including a step of placing an electrolyte between the positive electrode and the negative electrode, for manufacturing the all-solid-state secondary battery of claim 1.

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