Positive electrode and all-solid secondary battery comprising same

Abstract

Disclosed is a positive electrode and an all-solid secondary battery comprising same, the positive electrode comprising a positive electrode current collector, and a positive active material layer disposed on one or both surfaces thereof and containing lithium sulfide-based positive active material and an inorganic filler, wherein the inorganic filler contains lithium metal oxyhalide represented by chemical formula 1. In chemical formula 1, LiaAlbMcOdCle, 0<a≤3, 0<b≤3, 0≤c<2, 0<d≤4, 0<e≤4, d<e, and M is a metal selected from groups 3-15.

Description

Anode and all-solid-state secondary battery containing the same

[0001] It relates to a cathode and an all-solid-state secondary battery including the cathode.

[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. 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 and provide improved safety by using solid electrolytes instead of liquid electrolytes.

[0005] When lithium sulfide is used as the positive electrode active material in an all-solid-state secondary battery, lithium sulfide is an insulator with virtually no electrical or ionic conductivity. Therefore, a material with high electrical and ionic conductivity is required during the manufacture of the positive electrode. Furthermore, since no solvent is used in the manufacture of the positive electrode, electrolyte layer, and negative electrode containing lithium sulfide, the solid electrolyte layer, positive electrode, and negative electrode are practically solvent-free, resulting in low electronic and lithium ion conductivity, making it difficult to secure sufficient capacity during charge and discharge. Therefore, it is important to design the interface in the positive electrode active material layer to actively promote electrochemical reactions between the positive electrode active material and other components.

[0006] One aspect is to provide a cathode with improved initial efficiency and specific capacity by strengthening the network of lithium sulfide-based cathode active material and the constituent components of the cathode active material layer and improving cathode side reactions.

[0007] Another aspect is to provide an all-solid-state secondary battery with improved capacity, lifespan, and rate characteristics by employing the above-described positive electrode.

[0008] According to one aspect

[0009] A cathode current collector; and a cathode active material layer disposed on one or both sides of the cathode current collector and containing a lithium sulfide-based cathode active material and an inorganic filler,

[0010] An anode is provided, wherein the above-mentioned inorganic filler is a compound represented by the following chemical formula 1.

[0011] <Chemical Formula 1>

[0012] Li a Al b M c O d Cl e

[0013] In chemical formula 1, 0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤4; d<e, M은

[0014] A metal selected from groups 3 to 15.

[0015] According to another aspect, an all-solid-state secondary battery is provided, which includes a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer is the positive electrode described above.

[0016] According to one aspect, a viscoelastic inorganic filler is used to enhance the ionic and electronic networks between the lithium sulfide-based cathode active material and the solid electrolyte, thereby enabling increased capacity, cycle life, and low-voltage operation. Furthermore, improved initial efficiency and specific capacity are achieved by improving high-voltage cathode side reactions. Using such a cathode, an all-solid-state secondary battery can be provided with improved rate characteristics and minimized cathode overvoltage, thereby enhancing capacity retention and charge-discharge characteristics.

[0017] Figures 1 to 10 are cross-sectional views of an all-solid-state secondary battery according to an exemplary embodiment.

[0018] <Brief description of the drawing>

[0019] 10 Anode 11 Anode current collector

[0020] 12 positive electrode active material layer 20 negative electrode

[0021] 21 Negative current collector 22 First negative electrode active material layer

[0022] 30 electrolyte layer 40 inert member

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 degrees or otherwise rotated), and the spatially relative terms used herein may be interpreted accordingly.

[0030] "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.

[0031] 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.

[0032] D50 is the particle size corresponding to 50% cumulative volume when calculated from the side of particles with small particle sizes in the size distribution of particles measured by laser diffraction, D90 is the particle size corresponding to 90% cumulative volume when calculated from the side of particles with small particle sizes in the size distribution of particles measured by laser diffraction, and D10 is the particle size corresponding to 10% cumulative volume when calculated from the side of particles with small particle sizes in the size distribution of particles measured by laser diffraction.

[0033] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states, and “alloy” means a mixture of two or more metals.

[0034] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0035] In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation, and “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0036] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from an electrode active material.

[0037] In the present disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery, and “discharging” and “discharging” mean a process of removing electrochemical energy from a battery.

[0038] In the present disclosure, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during a discharge process, and “negative electrode” and “anode” mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0039] In the present disclosure, “thickness” and “length” mean “average thickness” and “average length”, respectively.

[0040] In the present disclosure, "aspect ratio" refers to the ratio (L1 / L2) of the major axis length L1 (e.g., length) and the minor axis length L2 (e.g., diameter). Here, aspect ratio, major axis length, minor axis length, length, and diameter represent 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.

[0041] 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.

[0042] 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.

[0043] Below, the cathode and the all-solid-state secondary battery including the cathode according to exemplary implementation examples are described in more detail.

[0044] Lithium sulfide (Li2S) is an insulator with virtually no electrical conductivity. Therefore, to use it as a cathode active material, it must be composited with a highly conductive carbon material to overcome the problem of low electrical conductivity. Furthermore, in all-solid-state secondary batteries using lithium sulfide-based cathode active materials, the solid electrolyte layer, positive electrode, and negative electrode contain virtually no solvent, resulting in low electronic and lithium ion conductivity, making it difficult to secure sufficient capacity during charge and discharge. Therefore, it is important to design the interface in the cathode active material layer to actively promote the electrochemical reaction between the cathode active material and the solid electrolyte.

[0045] To achieve low-voltage operation of all-solid-state secondary batteries, simultaneous improvements in high-voltage oxidation stability and mechanical network stability at the interface between the active material and the solid electrolyte are required. To achieve this, the present disclosure utilizes an inorganic filler possessing viscoelasticity and high-voltage oxidation stability.

[0046] 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 sides of the positive electrode current collector and containing a lithium sulfide-based positive electrode active material and an inorganic filler, wherein the inorganic filler includes a compound represented by the following chemical formula 1.

[0047] <Chemical Formula 1>

[0048] Li a Al b M c O d Cl e

[0049] In chemical formula 1, 0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤4; d<e, M은 3족 내지 15족에서 선택되는 금속이다.

[0050] The positive electrode can contain the above-described inorganic filler to suppress an increase in interfacial resistance between components constituting the composite positive electrode active material, thereby improving the charge / discharge characteristics of the all-solid-state secondary battery. The inorganic filler can have elasticity. Since the inorganic filler has elasticity, the volume change of the positive electrode active material layer containing the composite positive electrode active material can be accommodated more effectively. In addition, since the inorganic filler can be easily molded into various shapes, the pores formed in the positive electrode active material layer can be easily filled. By suppressing an increase in internal resistance due to the pores of the positive electrode active material layer containing the composite positive electrode active material, an increase in internal resistance of the all-solid-state secondary battery can be suppressed. As a result, the charge / discharge characteristics of the all-solid-state secondary battery can be improved.

[0051] By including an inorganic filler in the cathode active material layer, it can provide improved durability against potential changes and temperature changes occurring during the charge / discharge process compared to a cathode active material layer including an organic filler. Inorganic fillers can suppress deterioration during the charge / discharge process of an all-solid-state secondary battery compared to organic fillers. Consequently, the charge / discharge characteristics of the all-solid-state secondary battery can be improved.

[0052] Inorganic fillers may, for example, exhibit ionic conductivity. This ionic conductivity suppresses the increase in internal resistance of the cathode active material layer caused by the inorganic filler, thereby suppressing the increase in internal resistance of the all-solid-state secondary battery. Consequently, the charge-discharge characteristics of the all-solid-state secondary battery can be improved.

[0053] The inorganic filler may be, for example, amorphous. The inorganic filler may be, for example, an amorphous lithium metal oxyhalide. The amorphous inorganic filler may be manufactured by melting the crystalline inorganic filler to produce a molten salt, which may then be cooled. Alternatively, the amorphous inorganic filler may be manufactured directly by controlling the composition during the manufacturing of the inorganic filler. The amorphous lithium metal oxyhalide may be manufactured by melting the crystalline lithium metal oxyhalide to produce a molten salt, which may then be cooled. Alternatively, the amorphous lithium metal oxyhalide may be manufactured directly by controlling the composition during the manufacturing of the lithium metal oxyhalide. The amorphous inorganic filler may have, for example, ductility. The ductility of the amorphous inorganic filler allows it to more effectively accommodate volume changes during charge and discharge of the all-solid-state secondary battery (1). In contrast, crystalline lithium metal oxyhalides may be relatively brittle compared to amorphous lithium metal halides. The amorphous nature of an inorganic filler can be confirmed using an XRD spectrum.

[0054] The inorganic filler may be, for example, glassy. The inorganic filler may be, for example, a glassy lithium metal oxyhalide having a glass transition temperature (Tg). The glassy lithium metal oxyhalide may have ductility. Since the inorganic filler has ductility, the volume change of the all-solid-state secondary battery (1) can be effectively accommodated during charge and discharge, or the all-solid-state secondary battery (1) can be easily deformed according to the volume change.

[0055] The glass transition temperature of the inorganic filler may be, for example, 20°C or lower, 10°C or lower, 0°C or lower, or -10°C or lower. Among the inorganic fillers, the compound of the above-described chemical formula 1 has a low melting point and a low glass transition temperature due to oxygen substitution, making it easy to process and transform into a continuous form without defects. Since the inorganic filler has such a low glass transition temperature, it can easily transition from a brittle crystalline metal salt state to a ductile glassy state. For example, the inorganic filler can be easily transitioned from a crystalline molten salt state to a glassy state by melting and then cooling it. Alternatively, the glassy state can be obtained during the manufacturing process of the inorganic filler. The glass transition temperature can be measured, for example, using a differential scanning calorimeter (DSC). The glass transition temperature can be measured, for example, using a dynamic mechanical analyzer (DMA).

[0056] The melting point of the inorganic filler may be, for example, 300°C or lower, 250°C or lower, 200°C or lower, or 150°C or lower. In addition, the inorganic filler has a low melting temperature of 50 to 250°C, for example, 100 to 150°C, or 110 to 130°C, so it can be applied to the all-solid-state secondary battery manufacturing process and has high mass productivity. And at room temperature (25°C), it has a melting point of 10 -5 10 inland -2 S / cm, 10 -3 10 inland -2 It has high ionic conductivity of 1.5 mS / cm or 1.5 mS / cm, which makes it highly mass-producible. Since the inorganic filler has such a low melting point, it can be easily manufactured by melting the inorganic filler into a molten salt state and then cooling it to produce an amorphous inorganic filler. The melting point of the inorganic filler can be measured using, for example, differential scanning calorimetry (DSC).

[0057] The compound of chemical formula 1, which is an inorganic filler, has a structure in which some of the chlorine (Cl) is replaced by oxygen (O), and becomes amorphous due to oxygen substitution, thereby increasing ionic conductivity and viscoelasticity. When O / Al in chemical formula 1 is 70 to 85%, 71 to 83%, 73 to 80%, for example, 75%, it is possible to produce a flexible film similar to a polymer.

[0058] The elastic modulus of the inorganic filler at 30°C may be 10 GPa or less, 5 GPa or less, 3 GPa or less, or 2 GPa or less. The elastic modulus of the inorganic filler and the first solid electrolyte can be measured using, for example, a dynamic mechanical analyzer (DMA).

[0059] Inorganic fillers can have, for example, viscoelasticity. Inorganic fillers can have, for example, viscoelastic creep. The viscoelastic creep rate of an inorganic filler can be, for example, 1×10 -4 % / s or more, 2×10 -4 % / s or more or 4×10 -4 % / s or more. % / s is the ratio of the transformed size to the initial size per unit time (second). Since the inorganic filler has viscoelasticity, it can easily accommodate the volume change during charging and discharging of the all-solid-state secondary battery (1) and the shape can be continuously transformed without defects. The creep rate is the change rate over time of the inorganic filler under stress at a constant temperature, i.e., the deformation speed. The creep rate can be measured using, for example, a universal testing machine.

[0060] The inorganic filler may have ionic conductivity. The inorganic filler may have, for example, an ionic conductivity of 0.1 mS / cm or more, 0.3 mS / cm or more, 0.5 mS / cm or more, 0.7 mS / cm or more, or 1.0 mS / cm or more at 25°C and 1 atm. The ionic conductivity may be measured by AC impedance analysis. The voltage amplitude used in the AC impedance analysis may be 5 to 10 mV, and the frequency may be 1 MHz to 1 Hz. Since the inorganic filler has ionic conductivity, an increase in the interfacial resistance between the positive electrode active material particles in the positive electrode active material layer and / or between the positive electrode active material and the first solid electrolyte may be effectively suppressed.

[0061] Applying a composite cathode active material containing inorganic fillers to the cathode active material layer enhances the electronic and ionic networks of the lithium sulfide-based cathode active material and the solid electrolyte, enabling increased capacity, cycle life, and low-voltage operation, while improving high-voltage cathode side reactions. All-solid-state secondary batteries employing such a cathode active material layer can improve specific capacity and initial efficiency, for example, by reducing capacity decline above 1.5 V or between 1.0 and 1.5 V. In particular, the infiltration characteristics with the argyrodite solid electrolyte layer reduce dendrite formation at high output and cracking in the cathode active material layer, thereby improving the cycle life characteristics of the all-solid-state secondary battery. In addition, when configuring a cathode with a thick film that realizes high energy density, the rate characteristic decline is improved, reducing the occurrence of short circuits during rapid charging, and the short circuit phenomenon is reduced due to the reduction of pinholes in the solid electrolyte layer. Therefore, the elastic sheet ratio can be reduced, so that the cell clamping pressure can be lowered to 2.5 M or less, 2 MPa or less, 0.1 to 2 MPa, or 0.15 to 1 MPa, thereby enabling the implementation of a free-standing cell.

[0062] In the above chemical formula 1, M is at least one selected from B, Al, Fe, Ga, In, As, Sb, and Mo.

[0063] The compound of Chemical Formula 1 is an inorganic filler with viscoelasticity similar to that of a polymer, has excellent processability, and decomposes into Al2O3 and MAlCl4 during high-voltage operation, acting as an anodic oxide film to improve anodic high-voltage oxidation stability, thereby enabling high-voltage charging. Thus, the inorganic filler of Chemical Formula 1 is an inorganic amorphous and / or glass inorganic filler with high viscoelasticity and high high-voltage oxidation stability. Here, high voltage means, for example, 4.3 V or higher.

[0064] The compound of the above chemical formula 1 is LiaAlbOdCle (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4;

[0065] 0 <e≤3; d<e), LiaAlbFecOdCle (0<a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e),

[0066] LiaAlbGacOdCle (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e), LiaAlbInOdCle (0<a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e), LiaAlbAscOdCle (0<a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e), LiaAlbSbcOdCle (0<a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e), LiaAlbMocOdCle (0<a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e), LiaAlbBiOdCle (0<a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e), Li a Al b B c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤3; d<e), 또는 이들의 조합을 포함한다.

[0067] Lithium metal oxyhalides are, for example, LiAl x O z Cl w(0 <x≤2; 0<z≤1; 2<w<4; z<w), LiAl x Fe y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Ga y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x In y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x As y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Sb y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Mo y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Bi y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x B y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w) 또는 이들의 조합을 포함할 수 있다.

[0068] Compounds of chemical formula 1 are, for example, LiAlO 0.75 Cl 2.5 , LiAl 1.3 O 1.1 Cl 2.7 , LiAl 1.25 As 0.09 O 1.18 Cl 2.66, or a combination thereof.

[0069] The above lithium sulfide-based cathode active material is Li2S, a Li2S complex, or a combination thereof.

[0070] The above Li2S complex is, for example, a composite of Li2S and a lithium salt, a composite of Li2S and a carbon-based material, a composite of Li2S, a carbon-based material and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S, a carbon-based material and a lithium salt, a composite of Li2S and a lithium salt, a composite of Li2S and a metal carbide, a composite of Li2S, a carbon-based material and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S, a carbon-based material and a metal nitride, or a combination thereof.

[0071] A complex of Li2S and a lithium salt is, for example, the result of mechanical milling of Li2S and a lithium salt. A complex of Li2S and a lithium salt is distinct from a simple mixture of Li2S and a lithium salt, for example, because it is the result of a mechanochemical reaction between Li2S and a lithium salt. A simple mixture of Li2S and a lithium salt can present a high interfacial resistance due to the inability to maintain a dense interface between the Li2S and the lithium salt, which can consequently increase the internal resistance of the solid electrolyte separator.

[0072] The complex of Li2S and lithium salt is Li2S-Li a X b(1≤a≤5, 1≤b≤5). Wherein X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2 or a combination thereof. a is, for example, 1, 2, 3, 4 or 5. b is, for example, 1, 2, 3, 4 or 5. The lithium salt is, for example, a compound that does not contain sulfur (S). The lithium salt may be, for example, a binary compound or a ternary compound. The lithium salt may be, for example, a binary compound composed of lithium and one element selected from Groups 13 to 17 of the Periodic Table of Elements. The lithium salt may be, for example, a ternary compound composed of lithium and two elements selected from groups 13 to 17 of the periodic table. The binary compound may include, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or a combination thereof. When the composite includes such a binary compound, the ionic conductivity of the composite may be further improved. When the positive electrode includes such a complex, the internal resistance of the positive electrode may be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode may be further improved. The ternary compound may include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or a combination thereof. The ionic conductivity of the complex may be further improved by including such ternary compounds in the complex.By including these complexes in the positive electrode, the internal resistance of the positive electrode can be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a solid electrolyte separator can be further improved.

[0073] In the above composite, the carbon-based material may be any material containing carbon atoms that is used as a conductive material in the relevant technical field. The carbon-based material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon-based material may be, for example, a sintered product of a carbon precursor. The carbon-based material may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof. The carbon-based material may be, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon-based material may be, for example, carbon black such as Ketjen Black, acetylene black, Denka Black, thermal black, channel black, etc.; graphite, activated carbon, or a combination thereof. The form of the carbon-based material may be, but is not limited to, particle form, sheet form, flake form, etc., and any form used as a carbon-based material in the relevant technical field may be used.

[0074] The complex is a complex of Li2S, a lithium salt, and a carbon-based material.

[0075] The content of the carbon-based material included in the composite of Li2S, lithium salt, and carbon-based material may be, for example, 1 to 20 wt%, 5 to 20 wt%, or 10 to 20 wt% of the total weight of the composite. If the content of the carbon-based material increases excessively, the energy density of the dry positive electrode film and the all-solid-state secondary battery may decrease. If the content of the carbon-based material decreases excessively, the electronic conductivity of the composite of Li2S, lithium salt, and carbon-based material may decrease, which may increase the internal resistance of the dry positive electrode film. As a result, the cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0076] The Mohs hardness of the lithium salt and the carbon-based material may be greater than that of Li2S. The Mohs hardness of Li2S is, for example, 0.6 or less. The Mohs hardness of the lithium salt may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. When the lithium salt has a Mohs hardness in this range, the pulverization of Li2S can be performed more easily during the milling process, and a solid solution of Li2S and the lithium salt can be formed more easily. The Mohs hardness of LiI is, for example, 2.0. The Mohs hardness of the carbon-based material may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, or 1.5 or more, respectively. Since the carbon-based material has a Mohs hardness in this range, the grinding of Li2S can be performed more easily during the milling process, and a composite of Li2S, a lithium salt, and a carbon-based material can be formed more easily. The modal hardness of carbon nanofibers (CNF) is, for example, 1.5.

[0077] The carbon-based material may include, for example, a fibrous carbon-based material. By including the fibrous carbon-based material in the composite of Li2S, a lithium salt, and a carbon-based material, the electronic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material can be further improved. By including the fibrous carbon-based material in the composite of Li2S, a lithium salt, and a carbon-based material, electronic conduction can be more easily performed from the surface to the inside of the composite of Li2S, a lithium salt, and a carbon-based material. The internal resistance of a dry cathode film including a composite of Li2S, a lithium salt, and a carbon-based material can be reduced, and the cycle characteristics of an all-solid-state secondary battery including a dry cathode film can be further improved.

[0078] The aspect ratio of the fibrous carbon-based material can be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. When the fibrous carbon-based material has an aspect ratio in this range, the overall electronic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material is improved, and the imbalance of local electronic conductivity within the composite of Li2S, a lithium salt, and a carbon-based material can be further alleviated.

[0079] The fibrous carbon-based material may include, for example, carbon nanostructures. The carbon nanostructures may include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanobelts, carbon nanorods, or combinations thereof.

[0080] The carbon nanostructure can form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure composed of a plurality of carbon nanostructures aggregated together.

[0081] The diameter of the primary carbon nanostructure can be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure can be, for example, 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure can be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure can be measured by laser diffraction.

[0082] Secondary carbon nanostructures are, for example, structures formed by assembling primary carbon nanostructures in whole or in part to form bundles or bundle-type structures. The secondary carbon nanostructures may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or combinations thereof. The diameter of the secondary carbon nanostructures may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length of the secondary carbon nanotube structure can be, for example, 20 nm to 2 ㎛, 30 nm to 1.5 ㎛, 50 nm to 1 ㎛, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured from a scanning electron microscope (SEM) image or an optical microscope. Alternatively, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be converted into a primary carbon nanostructure, for example, by dispersing it in a solvent or the like, and then used to prepare a composite of Li2S, a lithium salt, and a carbon-based material.

[0083] A composite of Li2S and a lithium salt or a composite of Li2S, a lithium salt, and a carbon-based material may include, for example, a solid solution of Li2S and a lithium salt. The ionic conductivity of the composite may increase by including the solid solution of Li2S and a lithium salt. For example, since the solid solution of Li2S and a lithium salt includes lithium ions arranged within Li2S crystallites, the ionic conductivity of the solid solution of Li2S and a lithium salt may be improved compared to the ionic conductivity of Li2S. Consequently, the ionic conductivity of the composite may be improved and the internal resistance of the composite may be reduced. By including such a composite in the positive electrode, the internal resistance of the positive electrode may be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode may be further improved.

[0084] The size of Li2S crystallites obtained from the XRD spectrum of a complex of Li2S and a lithium salt or a complex of Li2S, a lithium salt, and a carbon-based material may be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of Li2S crystallites obtained from the XRD spectrum of the complex may be, for example, 1 to 20 nm, 1 to 15 nm, or 3 to 10 nm. As the size of Li2S crystallites decreases, the contact area between Li2S and a lithium salt may further increase. As the contact area between Li2S and a lithium salt further increases, the ionic conductivity of the complex of Li2S and a lithium salt may further increase. The internal resistance of the positive electrode may further decrease when the positive electrode includes such a complex. As a result, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode may further improve.

[0085] Since Li2S has low ionic conductivity, a complex with a lithium salt is formed to overcome this drawback. A complex of Li2S and a lithium salt or a composite of Li2S and a lithium salt and a carbon-based material can provide improved ionic conductivity compared to Li2S alone. The content of Li2S in the complex may be 50 to 95 wt%, 50 to 90 wt%, 50 to 80 wt%, or 50 to 70 wt% of the total weight of the complex of Li2S and a lithium salt. By having the complex with a Li2S content in this range, a cathode with improved ionic conductivity and durability can be manufactured. The content of the lithium salt in the complex of Li2S and a lithium salt may be 5 to 50 wt%, 10 to 50 wt%, 20 to 50 wt%, or 30 to 50 wt% of the total weight of the complex of Li2S and a lithium salt.

[0086] The molar ratio of Li2S and lithium 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 Li2S and lithium 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. By having Li2S and lithium salt in this range of molar ratio, the cycle characteristics of a lithium battery including the composite cathode active material can be further improved. If the molar ratio of Li2S is excessively high, the ionic conductivity enhancement effect of lithium salt may be minimal. If the molar ratio of Li2S is excessively high, the energy density of lithium batteries containing composite cathode active materials may decrease.

[0087] In the composite of Li2S, a lithium salt, and a carbon-based material, the content of the lithium salt may be, for example, 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 of Li2S, a lithium salt, and a carbon-based material. If the content of the lithium salt is excessively increased, the energy density of the all-solid-state secondary battery may decrease. If the content of the lithium salt is excessively low, the ionic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material may decrease, which may increase the internal resistance of the dry positive electrode film. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry positive electrode film may deteriorate.

[0088] In the composite of Li2S, a lithium salt, and a carbon-based material, the molar ratio of Li2S and a 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 composite of Li2S, a lithium salt, and a carbon-based material, the molar ratio of Li2S and a 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 maintaining the molar ratio of Li2S and lithium salt within this range, the cycle characteristics of an all-solid-state lithium battery including a dry cathode film can be further improved. If the molar ratio of Li2S is excessively high, the ionic conductivity enhancement effect of the lithium salt may be minimal. If the molar ratio of Li2S is excessively high, the energy density of a lithium battery including a composite cathode active material may be reduced.

[0089] The ionic conductivity of a complex of Li2S and a lithium salt or a complex of Li2S, a lithium salt and a carbon-based material is, for example, 1×10 at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5S / 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, direct current polarization method, etc. Since the complex of Li2S and lithium salt has an ionic conductivity in this range, the internal resistance of the positive electrode including the complex of Li2S and lithium salt can be further reduced. The cycle characteristics of an all-solid-state secondary battery including the positive electrode can be improved.

[0090] The Li2S-containing composite may further comprise a solid electrolyte. The solid electrolyte may further comprise a sulfide-based solid electrolyte.

[0091] The content of the complex of Li2S and a lithium salt can be, for example, 0.1 to 20 wt%, 0.5 to 20 wt%, 0.5 to 15 wt%, 0.5 to 10 wt% or 1 to 5 wt% of the total weight of the complex of Li2S and a lithium salt and the sulfide-based solid electrolyte. The content of the complex of Li2S and a lithium salt can be, for example, 0.1 to 20 wt%, 0.5 to 20 wt%, 0.5 to 15 wt%, 0.5 to 10 wt% or 1 to 5 wt% of the total weight of the positive electrode. When the positive electrode has the content of the complex of Li2S and a lithium salt in this range, the durability of the positive electrode can be further improved and the internal resistance can be further reduced.

[0092] In the above composite, the metal carbide is, for example, a two-dimensional metal carbide. The two-dimensional metal carbide is, for example, MXene. The two-dimensional metal carbide is, for example, M n+1 C n T x(M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) is expressed as 2D metal carbides, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5 )3C2T x , Ti3CNT x , Ta4C3T x , Nb4C3T x or a combination thereof. The surface of the two-dimensional metal carbide is terminated with O, OH and / or F.

[0093] In the above complex, 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.

[0094] According to one embodiment, the positive electrode active material layer may further include one or more selected from a binder, a conductive agent, and a lithium salt.

[0095] The above-mentioned conductive material includes a carbon-based material, the carbon-based material is amorphous, the carbon-based material includes a fibrous carbon-based material, the fibrous carbon-based material includes a fibrous carbon nanostructure, and the fibrous carbon nanostructure includes carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof.

[0096] When the positive electrode active material layer contains a fibrous carbon-based material as a conductive material, the content of the conductive material is 1 to 15 wt%, 5 to 15 wt%, or 8 to 12 wt% based on 100 parts by weight of the positive electrode active material layer. When the positive electrode active material of the positive electrode active material layer contains Li2S and the compound of Chemical Formula 1 as an inorganic filler, the positive electrode active material layer includes carbon nanofibers as a fibrous carbon-based material as a conductive material, thereby producing a positive electrode having excellent ionic conductivity and electronic conductivity.

[0097] The content of inorganic filler in the positive electrode active material layer is based on the total weight of the positive electrode active material layer.

[0098] The content of the lithium sulfide-based cathode active material is 1 to 40 wt%, 5 to 40 wt%, or 20 to 40 wt%, the content of the lithium sulfide-based cathode active material is 50 to 90 wt%, 50 to 80 wt%, or 50 to 70 wt%, and the content of the binder is 1 to 10 wt%, 1 to 5 wt%, or 1 to 3 wt%. When the content of the inorganic filler is within the above range, the ion and electron network between the lithium sulfide-based cathode active material and the solid electrolyte is strengthened, thereby enabling low-voltage operation, and an all-solid-state secondary battery having improved initial efficiency and specific capacity and improved rate characteristics and life characteristics due to improved high-voltage cathode side reactions can be provided.

[0099] According to one embodiment, a positive electrode active material layer may include a lithium sulfide-based positive electrode active material, an inorganic filler, and a conductive material. As the conductive material, for example, carbon nanofibers (CNF), which are fibrous carbon-based materials, may be included. In addition, the positive electrode active material layer may further contain a lithium salt. As an example of the lithium salt, LiI may be used. According to one embodiment, in the positive electrode active material layer, the content of the lithium sulfide-based positive electrode active material is 50 to 70 wt% based on the total weight of the positive electrode active material layer, the content of the inorganic filler or the content of the inorganic filler and the lithium salt is 20 to 40 wt% based on the total weight of the positive electrode active material layer, and the content of the conductive material is 10 to 20 wt% based on the total weight of the positive electrode active material layer.

[0100] The positive electrode active material layer may further include a first solid electrolyte.

[0101] The first solid electrolyte comprises a sulfide-based solid electrolyte. The content of the first solid electrolyte is smaller than the content of the inorganic filler, and the weight ratio of the inorganic filler to the first solid electrolyte is 99:1 to 51:49.

[0102] The size of the Li2S composite particles may be, for example, 10 μm or less, 8 μm or less, 5 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the composite particles may be, for example, 1 to 10 μm, 2 to 10 μm, 2 to 8 μm, or 3 to 8 μm. The size of the composite particles may be, for example, 0.1 to 10 μm, 0.1 to 8 μm, 0.1 to 5 μm, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm or less. When the Li2S composite particles have a size in this range, they can be more easily arranged in the gaps between the plurality of sulfide-based solid electrolytes, pinhole formation within the positive electrode can be suppressed, and the internal resistance of the positive electrode can be reduced. As a result, the durability of the positive electrode can be improved. The size of Li2S complex particles can be measured using, for example, laser diffraction, scanning electron microscopy, etc. The size of the complex of Li2S and lithium salt is, for example, the arithmetic mean of the particle sizes of multiple particles measured using software from scanning electron microscopy images.

[0103] The size of the Li2S particles included in the composite cathode active material, i.e., the size of the Li2S particles included in the composite, may be, for example, 2 ㎛ or less, 1.5 ㎛ or less, or 1 ㎛ or less. The size of the Li2S particles may be, for example, 0.1 to 2 ㎛, 0.1 to 1.5 ㎛, 0.1 to 1 ㎛, or 10 to 100 nm. Since the Li2S 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 Li2S 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 an all-solid-state secondary battery including such a composite cathode active material may deteriorate.

[0104] By using a positive electrode containing the above-described composite, a lithium metal negative electrode can be eliminated, enabling the use of an all-solid-state secondary battery without an anode, thereby providing an all-solid-state secondary battery with improved energy density. Furthermore, by including such a composite positive electrode active material in the positive electrode, the cycle characteristics of the all-solid-state secondary battery containing the composite positive electrode active material can be improved. For example, the high-rate characteristics of the all-solid-state secondary battery containing such a composite positive electrode active material can be improved.

[0105] The cathode active material layer may further include a lithium salt. Including a lithium salt allows for the production of a cathode with improved ionic conductivity. The lithium salt may be the same as the lithium salt contained in the Li2S composite.

[0106] In the positive electrode active material layer, the solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode may be the same as or different from the solid electrolyte included in the electrolyte layer. The solid electrolyte included in the positive electrode active material layer may have a smaller average D50 particle size than the solid electrolyte included in the electrolyte layer. For example, the average D50 particle size of the solid electrolyte included in the positive electrode active material layer 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 size of the solid electrolyte included in the electrolyte layer. The average D50 particle size is, for example, the 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 smaller particle size in a size distribution of particles measured by, for example, laser diffraction.

[0107] Referring to FIGS. 1 to 10, an all-solid-state secondary battery (1) includes a positive electrode layer (10); a negative electrode layer (20); and a solid electrolyte layer (30) between the positive electrode layer (10) and the negative electrode layer (20). The positive electrode layer (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) on one or both surfaces of the positive electrode current collector (11). The positive electrode active material layer (12) includes a lithium sulfide-based positive electrode active material and an inorganic filler. The inorganic filler includes a lithium metal oxyhalide represented by the chemical formula 1. The negative electrode layer (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) on one surface of the negative electrode current collector (21).

[0108] [Anode layer]

[0109] Referring to FIGS. 1 to 10, 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).

[0110] [middle class]

[0111] Referring to FIGS. 2, 4, 6, 8, and 10, the positive electrode (10) further includes an interlayer (13) disposed between the positive electrode current collector (11) and the positive electrode active material layer (12). Since the inorganic filler represented by Chemical Formula 1 contained in the positive electrode active material layer can exhibit collector corrosion, further inclusion of the interlayer can prevent collector corrosion.

[0112] The intermediate layer (13) is, for example, directly disposed on one side or both sides of the positive electrode collector (11). No other layer may be disposed between the positive electrode collector (11) and the intermediate layer (13). By directly disposing the intermediate layer (13) on one side or both sides of the positive electrode collector (11), the bonding force between the positive electrode collector (11) and the positive electrode active material layer (12) can be further improved. By disposing the intermediate layer (13) between the positive electrode collector (11) and the positive electrode active material layer (12), side reactions between the inorganic filler and / or the first solid electrolyte and the positive electrode collector (11) can be more effectively suppressed. Therefore, deterioration of the all-solid-state secondary battery (1) during the charge / discharge process can be suppressed, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0113] The thickness of the intermediate layer (13) is, for example, 0.01 to 20%, 0.1 to 20%, 0.5 to 20%, 1 to 20%, 1 to 15%, 1 to 10%, 2 to 8%, or 3 to 7% of the thickness of the positive electrode current collector (11). The thickness of the intermediate layer (13) is, for example, 10 nm to 10 ㎛, 10 nm to 5 ㎛, 50 nm to 5 ㎛, 200 nm to 4 ㎛, 500 nm to 3 ㎛, 500 nm to 2 ㎛, 500 nm to 1.5 ㎛, or 700 nm to 1.3 ㎛. When the intermediate layer (13) has a thickness in this range, the bonding force between the positive electrode current collector (11) and the positive electrode active material layer (12) is further improved, and an increase in interface resistance is suppressed. The thickness of the intermediate layer can be measured, for example, from a scanning electron microscope (SEM) image of a cross-section of the intermediate layer.

[0114] The intermediate layer (13) includes, for example, a carbon-based conductive material. The carbon-based conductive material included in the intermediate layer (13) may be selected from among the carbon-based conductive materials used in the positive electrode active material layer (12). The intermediate layer (13) may include the same carbon-based conductive material as the carbon-based conductive material used in the positive electrode active material layer (12). Since the intermediate layer (13) includes a carbon-based conductive material, the intermediate layer (13) may be, for example, a conductive layer.

[0115] The above carbon-based conductive material may include, for example, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube, graphene, porous carbon, or a combination thereof.

[0116] The intermediate layer (13) may additionally include, for example, a binder. By additionally including a binder in the intermediate layer (13), the bonding strength between the positive electrode current collector (11) and the positive electrode active material layer (12) may be further improved. The binder included in the intermediate layer (13) may be, for example, a conductive binder or a non-conductive binder. The conductive binder may be, for example, an ion-conductive binder and / or an electron-conductive binder. A binder having both ion-conductive and electron-conductive properties may belong to both an ion-conductive binder and an electron-conductive binder.

[0117] The binder included in the intermediate layer (13) may be selected from among the binders used in the positive electrode active material layer (12). The intermediate layer (13) may include the same binder as the binder used in the positive electrode active material layer (12). The binder included in the intermediate layer (13) is, for example, a fluorine-based binder. The fluorine-based binder included in the intermediate layer (13) is, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or a combination thereof. The intermediate layer (13) may be, for example, a bonding layer including a binder. The intermediate layer (13) may be, for example, a conductive layer including a binder and a carbon-based conductive material.

[0118] The intermediate layer (13) can be disposed on the positive electrode collector (11) in a dry or wet manner, for example. The intermediate layer (13) can be disposed on the positive electrode collector (11) in a dry manner, for example, by deposition such as CVD or PVD. The intermediate layer (13) can be disposed on the positive electrode collector (11) in a wet manner, for example, by spin coating, dip coating, or the like. The intermediate layer (13) can be disposed on the positive electrode collector (11) in a dry manner, for example, by depositing a carbon-based conductive material on a substrate by deposition. The dry-coated intermediate layer (13) is made of a carbon-based conductive material and may not include a binder. The intermediate layer (13) can be disposed on the positive electrode collector (11) in a dry manner, for example, by coating a composition including a carbon-based conductive material, a binder, and a solvent on the surface of the electrode collector and drying it. The intermediate layer (13) can have a single-layer structure or a multi-layer structure including a plurality of layers. Multi-layer structures can be two-layer, three-layer, four-layer, etc.

[0119] Referring to FIGS. 1, 3, 5, 7, and 9, the positive electrode (10) may have a positive electrode active material layer (12) directly disposed on the positive electrode current collector (11). Another layer, for example, an intermediate layer, may not be disposed between the positive electrode current collector (11) and the positive electrode active material layer (12).

[0120] In the positive electrode layer (10) in which the positive electrode active material layer (12) is directly disposed on the positive electrode current collector (11), the positive electrode current collector (11) may be inert to the inorganic filler. The positive electrode current collector (11) may not cause a side reaction with the inorganic filler. The positive electrode current collector (11) may include, for example, tungsten (W).

[0121] [Cathode active material layer: inorganic filler]

[0122] Referring to FIGS. 1 to 10, the cathode active material layer (12) includes an inorganic filler. The inorganic filler is Li a Al b M c O d Cl e(0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 0<e≤4; d<e, M은 원소주기율표 3족 내지 15족에서 선택되는 금속) 표시되는 리튬금속옥시할라이드(lithium metal oxyhalide)를 포함한다.

[0123] The content of the inorganic filler included in the positive electrode active material layer (12) may be, for example, 0.1 to 20 wt%, 0.1 to 10 wt%, or 0.1 to 5 wt% of the total weight of the positive electrode active material layer (12).

[0124] [Cathode active material layer: Cathode active material]

[0125] The cathode active material layer (12) contains a lithium sulfide-based cathode active material.

[0126] The shape of the positive electrode active material is, for example, a particle shape such as a sphere or an ellipse. The particle size of the positive electrode active material is not particularly limited and is within a range applicable to positive electrode active materials of a conventional all-solid-state secondary battery. The content of the positive electrode active material of the positive electrode (10) is also not particularly limited and is within a range applicable to positive electrodes of a conventional all-solid-state secondary battery. The content of the positive electrode active material included in the positive electrode active material layer (12) may be, for example, 30 wt% to 99 wt%, 30 wt% to 90 wt%, 30 wt% to 80 wt%, 30 wt% to 70 wt%, or 30 wt% to 50 wt% of the total weight of the positive electrode active material layer (12).

[0127] [Cathode active material layer: first solid electrolyte]

[0128] The positive electrode active material layer (12) may include a first solid electrolyte.

[0129] Referring to FIGS. 1 to 10, the positive electrode active material layer (12) includes a first solid electrolyte. The first solid electrolyte included in the positive electrode active material layer (12) may be the same as or different from the solid electrolyte included in the solid electrolyte layer (30).

[0130] The first solid electrolyte included in the positive electrode active material layer (12) may have a smaller average D50 particle diameter than the solid electrolyte included in the solid electrolyte layer (30). For example, the average D50 particle diameter of the first solid electrolyte included in the positive electrode active material layer (12) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average D50 particle diameter of the solid electrolyte included in the solid electrolyte layer (30). The average D50 particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is, for example, the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by laser diffraction.

[0131] The content of the first solid electrolyte included in the positive electrode active material layer (12) may be, for example, 1 wt% to 40 wt%, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12).

[0132] The first solid electrolyte may be, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be, 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 PS6-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.

[0133] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 2:

[0134] <Chemical Formula 2>

[0135] Li + 12-n-x A n+ X 2- 6-x Y - x

[0136] 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-x PS 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.

[0137] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0138] [Cathode active material layer: binder]

[0139] 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, 0.1 wt% to 10 wt%, 0.5 to 5 wt%, or 0.5 to 2 wt% of the total weight of the positive electrode active material layer (12). The binder may be omitted.

[0140] [Cathode active material layer: conductive material]

[0141] The cathode active material layer (12) may further include a conductive material. The conductive material may be, for example, a carbon-based material, a metal-based material, or a combination thereof.

[0142] The conductive material content included in the positive electrode active material layer (12) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12).

[0143] The metal material may be, but is not limited to, metal powder, metal fiber, or a combination thereof, and any metal material used as a conductive material in the relevant technical field may be used.

[0144] The carbon-based material may include, for example, amorphous carbon. By including amorphous carbon in the carbon-based material, side reactions between the carbon-based material and the first solid electrolyte can be suppressed. Accordingly, the cycle characteristics of the all-solid-state secondary battery (1) including the carbon-based material can be further improved.

[0145] The carbon-based material may be, for example, a sintered product of a carbon precursor. The carbon-based material may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof. The carbon-based material may be, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon-based material may be, for example, carbon black such as Ketjen Black, acetylene black, Denka Black, thermal black, channel black, or the like; graphite, activated carbon, or a combination thereof. The form of the carbon-based material is not limited to, but may include, for example, particle form, sheet form, flake form, etc., and any form that can be used as a carbon-based material in the relevant technical field is possible.

[0146] The carbon-based material may include, for example, a fibrous carbon-based material. By including the fibrous carbon-based material in the composite, the electronic conductivity of the composite may be further improved. By including the fibrous carbon-based material in the composite, electronic conduction may be more easily performed from the surface to the interior of the composite. The internal resistance of a composite cathode active material including the composite may be reduced, and the cycle characteristics of a secondary battery including the composite cathode active material may be further improved. The aspect ratio of the fibrous carbon-based material may be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. When the fibrous carbon-based material has an aspect ratio in this range, the overall electronic conductivity of the composite is improved, and the imbalance of local electronic conductivity within the composite can be further alleviated. The fibrous carbon-based material may include, for example, a carbon nanostructure. The carbon nanostructure may include, for example, a carbon nanofiber (CNF), a carbon nanotube (CNT), a carbon nanobelt, a carbon nanorod, or a combination thereof. The carbon nanostructure may form a primary carbon nanostructure composed of a single carbon nanostructure, and a secondary carbon nanostructure in which a plurality of carbon nanostructures are aggregated.

[0147] The diameter of the primary carbon nanostructure can be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure can be, for example, 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure can be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure can be measured by laser diffraction.

[0148] Secondary carbon nanostructures are, for example, structures formed by assembling primary carbon nanostructures in whole or in part to form bundles or bundle-type structures. The secondary carbon nanostructures may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or combinations thereof. The diameter of the secondary carbon nanostructures may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length of the secondary carbon nanotube structure can be, for example, 20 nm to 2 ㎛, 30 nm to 1.5 ㎛, 50 nm to 1 ㎛, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured from a scanning electron microscope (SEM) image or an optical microscope. Alternatively, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be converted into the primary carbon nanostructure by, for example, dispersing it in a solvent or the like and then used in the preparation of a composite.

[0149] [Cathode active material layer: other additives]

[0150] 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.

[0151] As fillers, coating agents, dispersants, ion conductivity aids, etc. that the positive electrode active material layer (12) may include, known materials generally used in electrodes of all-solid-state secondary batteries may be used.

[0152] [Cathode collector]

[0153] Referring to FIGS. 1 to 10, the positive electrode layer (10) includes a positive electrode current collector (11).

[0154] 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.

[0155] 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 be cut off in case of overcurrent to prevent a short circuit. The limit current and the 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. As the thickness of the metal layer decreases, the limit current and / or the 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 current collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and the all-solid-state secondary battery.

[0156] The above cathode current collector is inert to the inorganic filler, and the above cathode current collector includes tungsten (W).

[0157] [Inert Absence]

[0158] Referring to FIGS. 7 to 9, the positive electrode (10) includes a positive electrode current collector (11), a positive electrode active material layer (12) disposed on one surface of the positive electrode current collector. Referring to FIGS. 8 to 10, the positive electrode (10) includes a positive electrode current collector (11), a positive electrode active material layer (12) disposed on one surface of the positive electrode current collector, and an intermediate layer (13) disposed between the positive electrode current collector (11) and the positive electrode active material layer (13).

[0159] An inactive member (40) is disposed on one side of the positive electrode (10). Referring to FIGS. 7 and 8, 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 FIGS. 9 and 10, 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) is not disposed on one side of the positive electrode current collector (11). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] Referring to FIGS. 7 to 10, 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).

[0164] Referring to FIGS. 7 to 10, 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.

[0165] 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.

[0166] 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).

[0167] 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.

[0168] 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).

[0169] 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).

[0170] As used herein, “same” area, length, width, thickness, and / or shape includes all instances of having “substantially the same” area, length, width, thickness, and / or shape, except where the area, length, width, thickness, and / or shape are intentionally different from each other. “Same” area, length, width, and / or thickness includes a range where the unintentional difference in the area, length, width, and / or thickness of the compared objects is, for example, less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0171] 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).

[0172] 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.

[0173] 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.

[0174] 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).

[0175] 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.

[0176] The flame-retardant inert member includes a filler in addition to a matrix. The filler may be disposed within the matrix, on the surface of the matrix, or on both the interior and the surface. The filler is, for example, an inorganic material. The filler included in the flame-retardant inert member is, for example, a moisture getter. The filler removes moisture remaining in the all-solid-state secondary battery (1) by adsorbing moisture, for example, at a temperature below 100°C, thereby preventing deterioration of the all-solid-state secondary battery (1). In addition, when the temperature of the all-solid-state secondary battery (1) increases to 150°C or higher due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or an external impact, the filler releases the adsorbed moisture, thereby effectively suppressing ignition of the all-solid-state secondary battery (1). That is, the filler is, for example, a flame retardant. The filler is, for example, a metal hydroxide having moisture adsorption properties. The metal hydroxide contained in the filler is, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, TI(OH)3, Zr(OH)4, Al(OH)3, or a combination thereof. The content of the filler contained in the flame-retardant inert member is, for example, 10 to 80 parts by weight, 20 to 80 parts by weight, 30 to 80 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, 60 to 80 parts by weight, or 65 to 80 parts by weight, based on 100 parts by weight of the flame-retardant inert member (4).

[0177] 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.

[0178] 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).

[0179] The density of the substrate or the density of the reinforcing material included in the flame-retardant inert member 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).

[0180] 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.

[0181] [Cathode layer]

[0182] [First negative electrode active material layer: negative electrode active material]

[0183] Referring to FIGS. 1 to 10, 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] [First negative electrode active material layer: binder]

[0198] The first negative electrode active material layer (22) includes a binder. The binder may be, 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.

[0199] 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).

[0200] [First negative electrode active material layer: other additives]

[0201] 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.

[0202] [First negative electrode active material layer: solid electrolyte]

[0203] 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.

[0204] 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).

[0205] [First negative electrode active material layer: charging capacity]

[0206] 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.

[0207] The maximum charging voltage is determined by the type of cathode active material. The maximum charging voltage can be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charging voltage of Li2S or Li2S composite is Li / Li + can be 2.5 V for Li2S or Li2S complex. For example, the maximum charging voltage of Li / Li + It can be 3.0 V for. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1. The initial charge capacity (mAh) of the positive electrode active material layer (12) is obtained by multiplying the charge capacity density (charge specific capacity) (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer (12). When several types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the initial charge capacity of the positive electrode active material layer (12). The initial charge capacity of the first negative electrode active material layer (22) is also calculated in the same way. The initial charge capacity of the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer (22). When several types of negative electrode active materials are used, the charge capacity density Х mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer (22). The charge capacity density of each of the positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell using lithium metal as a counter electrode.

[0208] The initial charge capacity of each of the positive electrode active material layer (12) and the first negative electrode active material layer (22) is a constant current density, for example, 0.1 mA / cm 2can be directly measured using an all-solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, for example, 3.0 V (vs. Li / Li + ) can be performed by charging to an operating voltage of up to 0.01 V for the negative electrode, for example, lithium metal, from a second open circuit voltage (OCV). For example, an all-solid-state half-cell having a positive electrode active material layer can be charged to an operating voltage of up to 0.1 mA / cm from a first open circuit voltage (OCV) to 3.0 V. 2 The all-solid-state half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 The all-solid-state half-cell having the positive electrode active material layer can be charged from the first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0209] 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).

[0210] 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.

[0211] [Second negative electrode active material layer]

[0212] Referring to FIGS. 5 and 6, 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).

[0213] 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.

[0214] 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).

[0215] 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 disposed 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).

[0216] [Cathode current collector]

[0217] The negative electrode layer (20) includes a negative electrode current collector (21). 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 is used as an electrode current collector in the relevant technical field may 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.

[0218] Referring to FIGS. 3 and 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.

[0219] The thickness of the thin film (23) is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (23) is less than 1 nm, it may be difficult for the function of the thin film (23) to be exerted. If the thickness of the thin film (23) is excessively thick, the thin film (23) itself absorbs lithium, which reduces the amount of lithium precipitated from the negative electrode, thereby lowering the energy density of the all-solid-state battery and deteriorating the cycle characteristics of the all-solid-state secondary battery (1). The thin film (23) may be disposed on the negative electrode current collector (21) by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to these methods, and any method capable of forming the thin film (23) in the relevant technical field may be used.

[0220] 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.

[0221]

[0222] [Solid electrolyte layer]

[0223] [Solid electrolyte layer: solid electrolyte]

[0224] Referring to FIGS. 1 to 10, the all-solid-state secondary battery (1) includes a solid electrolyte layer (30) disposed between a positive electrode layer (10) and a negative electrode layer (20). The solid electrolyte layer (30) includes, for example, a solid electrolyte or a combination of a solid electrolyte and a gel electrolyte.

[0225] 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.

[0226] The solid electrolyte is, for example, a sulfide-based solid electrolyte. For more specific information on the sulfide-based solid electrolyte, refer to the above-described positive electrode active material layer (12). The sulfide-based solid electrolyte of the solid electrolyte layer (20) may be selected from among the sulfide-based solid electrolytes used in the above-described positive electrode active material layer (12).

[0227] 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), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12(M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. The oxide-based solid electrolyte is manufactured, for example, by a sintering method.

[0228] 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.

[0229] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or a polymer having an ion-conducting functional group. The polymer solid electrolyte may be, for example, a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may not, for example, comprise a liquid.The polymer solid electrolyte comprises a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), Polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0230] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0231] The polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or may include 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 have a gel state, for example, 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 organic solvent is, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or a mixture thereof. The lithium salt may be selected from lithium salts used in polymer solid electrolytes. Ionic liquids are salts that have a melting point below room temperature, are composed only of ions, and are liquid at room temperature or molten 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 can further include inorganic particles. The polymer included in the polymer gel electrolyte can 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 can 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.

[0232] [Solid electrolyte layer: binder]

[0233] The solid electrolyte layer (30) may include, for example, a binder. The binder included in the solid electrolyte layer (30) is not limited to, but may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., and any binder used in the relevant technical field may be used. The binder of the solid electrolyte layer (30) may be the same as or different from the binder included in the positive electrode active material layer (12) and the negative electrode active material layer (22). The binder may be omitted.

[0234] The binder content included in the solid electrolyte layer (30) is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the solid electrolyte layer (30).

[0235] [All-solid-state secondary battery]

[0236] Referring to FIGS. 1 to 10, an all-solid-state secondary battery (1) includes a positive electrode layer (10); a negative electrode layer (20); and a solid electrolyte layer (30) between the positive electrode layer (10) and the negative electrode layer (20). The positive electrode layer (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) on one or both surfaces of the positive electrode current collector (11). The positive electrode active material layer (12) includes a lithium sulfide-based positive electrode active material and an inorganic filler, and the inorganic filler includes a lithium metal oxyhalide represented by the following chemical formula 1.

[0237] <Chemical Formula 1>

[0238] Li a Al b M c O d Cl e

[0239] In chemical formula 1, 0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 1<e≤4; d<e,

[0240] M includes lithium metal oxyhalide (a metal selected from groups 3 to 15 of the periodic table). The negative electrode layer (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) on one surface of the negative electrode current collector (21).

[0241] [Method for manufacturing an all-solid-state secondary battery]

[0242] An all-solid-state secondary battery comprises the steps of providing a positive electrode layer; providing a negative electrode layer; and disposing a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer is manufactured by: preparing a positive electrode mixture as a positive electrode active material layer composition by mixing a lithium sulfide-based positive electrode active material and at least one selected from an inorganic filler, a binder, and a conductive agent; and providing the mixture on a positive electrode current collector. The positive electrode manufacturing process using the positive electrode mixture is performed, for example, according to a dry process, and can also be performed according to a wet process.

[0243] A first solid electrolyte may be further added to the positive electrode mixture. The first solid electrolyte may be, for example, a sulfide-based solid electrolyte. In addition, a lithium salt may be further added to the positive electrode mixture.

[0244] Heat treatment may be performed during the manufacturing process of the anode. The heat treatment may be performed at a temperature of 50 to 200°C, 100 to 180°C, or 110 to 150°C. This heat treatment step can remove voids and other contaminants from the anode.

[0245] After the step of placing a solid electrolyte layer between the positive and negative electrodes, a step of obtaining a battery assembly and pressurizing it may be performed.

[0246] Pressurization is not limited to a roll press, a flat press, etc., but any pressurization method used in the relevant technical field may be used. The pressurization step may be omitted.

[0247] Pressurization is performed at a temperature of, for example, room temperature (20°C to 25°C) to 90°C. Alternatively, pressurization is performed at a high temperature of 100°C or higher. The pressurization time is, for example, 30 minutes or less, 20 minutes or less, 15 minutes or less, or 10 minutes or less. The pressurization time is 1 ms to 30 minutes, 1 ms to 20 minutes, 1 ms to 15 minutes, or 1 ms to 10 minutes. The pressurization method is, for example, isotactic press, roll press, flat press, etc., but is not necessarily limited to these methods and any pressurization method used in the art can be used. The pressure applied during pressurization is, for example, 500 MPa or less, for example, 400 MPa or less, 300 MPa or less, 200 MPa or less, 100 MPa or less, or 50 MPa. The pressure applied during pressurization is, for example, 1 to 50 MPa, 1 to 30 MPa, 1 to 20 MPa, or 1 to 10 MPa. By this pressurization, for example, the solid electrolyte powder is sintered to form a single solid electrolyte.

[0248] The pressurizing step is for example 40 to 100°C, for example 85 o Plate press treatment is performed at a pressure of 500 MPa for 30 min at C. This pressurization treatment sinteres the solid electrolyte layer, thereby improving battery characteristics.

[0249] According to another embodiment, the pressurization process described above may be omitted.

[0250] The lithium sulfide-based cathode active material is Li2S, a Li2S complex, or a combination thereof.

[0251] The Li2S complex provides a complex of Li2S and a lithium salt or a complex of Li2S, a lithium salt, and a carbon-based material. The complex of Li2S and a lithium salt can be prepared, for example, by mechanically milling Li2S and a lithium salt. The milling conditions are not particularly limited, and any conditions that can form a complex of Li2S and a lithium salt can be used. The complex of Li2S and a lithium salt can be prepared by placing Li2S particles and a lithium salt in a ball mill and stirring at a speed of 100 to 1000 rpm for 1 to 20 hours. The stirring can be performed more than once.

[0252] As lithium salts, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or combinations thereof can be used.

[0253] A composite of Li2S, a lithium salt, and a carbon-based material can be manufactured, for example, through a step of mechanically milling Li2S and a lithium salt; a step of adding a carbon-based material to the milled product, and milling the same.

[0254] A sulfide-based solid electrolyte can be used when manufacturing a Li2S complex. A mixture is prepared by mixing a Li2S-lithium salt complex and the sulfide-based solid electrolyte. The mixing ratio of the Li2S complex and the sulfide-based solid electrolyte can be, for example, a weight ratio of 50:50 to 95:5, 50:50 to 90:10, 50:50 to 80:20, or 50:50 to 70:30.

[0255] The mixture may additionally include a process solvent. By additionally including a process solvent, the mixture may take the form of a slurry. The solvent may be, for example, octyl acetate, but is not limited thereto, and any solvent used in the art may be used. Alternatively, the mixture may be prepared dry without including a process solvent.

[0256] Mechanical milling can be used in the above milling. A ball mill, etc. can be used in the mechanical milling.

[0257] According to another embodiment, the pressurization process described above may be omitted.

[0258] 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.

[0259] (Manufacture of a complex of Li2S and lithium salt)

[0260] Manufacturing Example 1: Li2S-LiI complex

[0261] 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.

[0262] The size of the Li2S-LiI complex was less than 1 μm. The size of the Li2S-LiI complex was calculated by software from scanning electron microscope images of the Li2S-LiI complex powder. The size of the Li2S-LiI complex is the average particle diameter of D50.

[0263] The Mohs hardness of Li2S was 0.6, and that of LiI was 2.0. The Mohs hardness of the Li2S-LiI composite was less than 2.

[0264] Comparative Manufacturing Example 1: Simple mixture of Li2S and LiI

[0265] A mixture of Li2S and LiI with a weight ratio of 30:20 was used as is.

[0266]

[0267] (Manufacture of Li2S-LiI-CNF cathode active material)

[0268] Manufacturing Example 2: Li2S-LiI-CNF

[0269] 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, 510 rpm, and 10 h.

[0270] Li2S-LiI composite and carbon nanofiber (CNF) were mixed at a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI-CNF composite. The milling conditions were 25°C, 510 rpm, and 10 h.

[0271] A Li2S-LiI-CNF composite was used as a composite cathode active material.

[0272] (Manufacturing of inorganic fillers)

[0273] Manufacturing Example 3: LiAlO 0.75 Cl 2.5 Manufacturing of (LACO75)

[0274] First, mill and mix LiCl and AlCl3 with a molar ratio of 1:1 evenly, then seal

[0275] The reactor was heated to 200°C and kept warm for 1 hour. After that, the reaction product was

[0276] Lithium tetrachloroaluminate (LiAlCl4) was obtained by lowering the temperature to room temperature. The prepared LiAlCl4 and Sb2O3 were uniformly mixed in a molar ratio of 4:1, heated to 300°C under an argon protective atmosphere, and kept warm for 2 hours. During this reaction, SbCl3 was removed by volatilization after the reaction due to the low vaporization point (223.5°C) of SbCl3, and LACO75 was obtained after cooling. The entire experimental process was performed under an inert atmosphere to prevent the reactants from reacting with air.

[0277] LiAlO measured at 25℃, 1 atm by AC impedance 0.75 Cl 2.5 The ionic conductivity of the (LACO) inorganic filler was approximately 1 mS / cm. The amplitude voltage used for AC impedance was 50 mV and the frequency range was 1 MHz to 1 Hz. LiAlO 0.75 Cl 2.5 The inorganic filler was amorphous and glassy with a glass transition temperature of LiAlO. 0.75 Cl 2.5 The glass transition temperature of the inorganic filler was approximately -17°C at 25°C and 1 atm. LiAlO 0.75 Cl 2.5 The elastic modulus of the inorganic filler was approximately 1.5 GPa at 30°C. LiAlO 0.75 Cl 2.5 The glass transition temperature and elastic modulus of the inorganic filler were measured using a dynamic mechanical analyzer (DMA). LiAlO 0.75 Cl 2.5 The viscoelastic creep rate of the inorganic filler is 4×10 -4 % / s. The viscoelastic creep rate was measured using a Universal Test Machine (UTM).

[0278] Manufacturing Example 4: LiAl1.3 O 1.1 Cl 2.7 Manufacturing of (LACO110)

[0279] The contents of LiCl, AlCl3 and Sb2O3 are LiAl 1.3 O 1.1 Cl 2.7 LiAl was obtained by performing the same procedure as in Manufacturing Example 1, except that the stoichiometry was changed to obtain 1.3 O 1.1 Cl 2.7 (LACO110) was manufactured.

[0280] (Manufacturing of positive and secondary batteries)

[0281] Example 1: (Li2 complex + LACO75 + binder) (60:39:1) anode / sulfide SE layer / Ag-

[0282] C silent

[0283] (Polar electrode manufacturing)

[0284] As a cathode active material, the Li2S-LiI-CNF composite manufactured in Manufacturing Example 2 was prepared. LiAlCl 2.5 O 0.75 (LACO75) was prepared. PVDF-HFP was prepared as a binder. These materials were mixed in a weight ratio of cathode active material: LACO inorganic filler: binder = 60:39:1 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill. The cathode mixture was placed on a cathode current collector made of aluminum foil coated with a carbon layer on one side, and plate pressed at 130°C and 10 MPa pressure for 10 minutes to manufacture a cathode. The total thickness of the cathode layer was approximately 120 μm. The thickness of the cathode active material layer was approximately 100 μm, the thickness of the carbon layer-coated aluminum foil was approximately 20 μm, and the thickness of the carbon layer was approximately 1 μm.

[0285] (Cathode manufacturing)

[0286] A 10 ㎛ thick SUS foil was prepared as a negative electrode 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.

[0287] 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 27 μm.

[0288] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer and the initial charge capacity (A) of the positive electrode active material layer was less than 1. The initial charge capacity of the positive electrode active material layer was less than 1 at the first open circuit voltage (1 st 4.25 V vs. Li / Li from open circuit voltage) + was determined from the charge up to . The initial charge capacity of the first negative electrode active material layer was determined from the second open circuit voltage (2 nd 0.01 V vs. Li / Li from open circuit voltage) + It was decided from the charging up to .

[0289] (Manufacturing of solid electrolyte layer)

[0290] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50=3.0 um, crystalline), a mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of the solid electrolyte. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied using a bar coater onto a 15 ㎛ thick nonwoven fabric placed on a 75 ㎛ thick PET substrate, and dried in air at 80 ℃ for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 80 ℃ for 2 hours to prepare a solid electrolyte layer.

[0291] (Inert member: elastic sheet)

[0292] A porous polyurethane foam sheet with a thickness of 50 ㎛ was prepared as an elastic sheet.

[0293] (Manufacturing of all-solid-state secondary batteries)

[0294] A solid electrolyte layer was placed on the cathode so that the first cathode active material layer was in contact with the solid electrolyte layer, and an anode was placed on the solid electrolyte layer so that the cathode active material layer was in contact with the solid electrolyte layer, thereby preparing a laminate.

[0295] 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 30 μm. The density of the Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc.

[0296] 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.

[0297] The all-solid-state secondary battery was placed between pressing jigs and pressed at a pressure of 0.5 MPa.

[0298] Example 2: (Li2S complex + LACO75 + binder)(60:39:1) cathode / LACO SE layer / Ag-C

[0299] Silent

[0300] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a LACO solid electrolyte layer obtained according to the following process was used as the solid electrolyte layer.

[0301] The LACO solid electrolyte layer is made by rolling the LACO solid electrolyte obtained according to Manufacturing Example 3 to form LiAlCl 2.5 O 0.75 (LACO75) membrane was used.

[0302] Example 3: (Li2S complex + LACO75) anode / garnet SE layer / Ag-C non-cathode

[0303] Li7La3Zr2O, a garnet oxide, as a solid electrolyte layer 12 An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a solid electrolyte layer was used.

[0304] Example 4: (Li2S complex + LACO75) anode / PE0 layer / Ag-C non-cathode

[0305] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a polyethylene oxide (PEO) solid electrolyte layer was used as the solid electrolyte layer.

[0306] Example 5: Anode: (Li2S-composite+LACO75+solid electrolyte+binder)(60:20:19:1) anode / sulfide-based SE layer / Ag-C non-cathode

[0307] (Polar electrode manufacturing)

[0308] As a cathode active material, the Li2S-LiI-CNF composite manufactured in Manufacturing Example 2 was prepared. LiAlCl 2.5 O0.75 (LACO75) was prepared, and Li6PS5Cl (D50=3.0um, crystalline), an argyrodite-type crystal, was prepared as a solid electrolyte. PVDF-HFP was prepared as a binder. These materials were mixed in a weight ratio of cathode active material: LACO solid electrolyte (SE): solid electrolyte (Li6PS5Cl): binder = 60:20:19:1.

[0309] A positive electrode mixture was prepared. The positive electrode mixture was obtained by dry mixing using a ball mill. The positive electrode mixture was placed on a positive electrode current collector made of aluminum foil coated with a carbon layer on one side, and plate pressed under pressure of 10 MPa and 130°C for 10 minutes to manufacture a positive electrode. The total thickness of the positive electrode layer was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, the thickness of the carbon-coated aluminum foil was approximately 20 μm, and the thickness of the carbon layer was approximately 1 μm.

[0310] Example 6: (Li2S complex + LACO + binder) (60:39:1) anode / sulfide SE layer / Ag-C non-cathode

[0311] LiAlCl in anode manufacturing 2.5 O 0.75 (LACO75) Instead, obtained according to Manufacturing Example 4

[0312] LiAl 1.3 Cl 2.7 O 1.1 An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that (LACO85) was used.

[0313] Comparative Example 1: (Sulphide-based SE+Li2S composite) anode / sulfide-based SE / Ag / C non-cathode

[0314] An all-solid-state secondary battery was manufactured in the same manner as Example 5, except that the positive electrode was manufactured according to the following process.

[0315] (Polar electrode manufacturing)

[0316] The Li2S-LiI-CNF composite manufactured in Manufacturing Example 2 was prepared as a cathode active material. Li6PS5Cl (D50=3.0 μm, crystalline), which is an argyrodite-type crystal, was prepared as a solid electrolyte. PVDF-HFP was prepared as a binder. These materials were mixed in a weight ratio of cathode active material: solid electrolyte (Li6PS5Cl): binder = 60:39:1 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill. The cathode mixture was placed on a cathode current collector made of aluminum foil on one side, and pressurized at 10 MPa and 130°C for 10 minutes and plate pressed for 10 minutes to manufacture a cathode. The total thickness of the cathode layer was approximately 120 μm. The thickness of the cathode active material layer was approximately 100 μm, and the thickness of the carbon layer-coated aluminum foil was approximately 20 μm.

[0317] Comparative Example 2: (Li2S complex + PEGDMA + binder) (60:39:1) anode / sulfide SE layer / Ag-C non-cathode

[0318] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that polyethylene glycol dimethacrylate (PEGDMA) was used instead of LACO in the manufacture of the positive electrode active material layer and an aluminum foil positive electrode collector without a carbon coating layer was used as the positive electrode current collector.

[0319] Comparative Example 3: (Li2S complex + LACO + binder) (60:39:1) cathode / sulfide SE layer / Ag-C non-cathode, no heat treatment during cathode manufacturing.

[0320] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the positive electrode was manufactured without a pressurized heat treatment process by placing the positive electrode mixture on a positive electrode current collector made of aluminum foil coated with a carbon layer on one side.

[0321] Evaluation Example 1: XRD Analysis and Scanning Electron Microscopy Analysis

[0322] XRD spectra were measured using Cu Kα radiation for the raw material (bare) Li2S used in Manufacturing Example 1, the pulverized Li2S, the Li2S-LiI composite manufactured in the first step of Manufacturing Example 2, and the Li2S-LiI-CNF composite manufactured in Manufacturing Example 2. The measurement results are shown in Table 1 below. The Li2S crystallite size and lattice constant were derived from the first peak for the (111) crystal plane appearing at a diffraction angle 2θ = 27°±2.0° in the XRD spectrum.

[0323] The crushed Li2S was prepared by milling under the same conditions as in the first step of Example 1, except that the 30:20 weight ratio mixture of Li2S and LiI was changed to 50 parts by weight of Li2S. The second step was not performed.

[0324] The particle size (i.e., D50 particle size) of the composites was measured using a laser-assisted particle size analyzer (PSA) and a scanning electron microscope for the raw Li2S, pulverized Li2S, the Li2S-LiI composite prepared in the first step, and the Li2S-LiI-CNF composite, and the Li2S particle size of the composites was measured using a scanning electron microscope. The measurement results are shown in Table 1 below.

[0325] Second peak position [°]Li2S crystallite size [nm]Li2S particle size [㎛]bare Li2S27.0211658First peak position [°]Li2S crystallite size [nm]Li2S particle size [㎛]crushed Li2S26.927015-Li2S-LiI composite (first stage)26.60748.81Less than Production example 2 (Li2S-LiI-CNF composite)26.70209.91Less than

[0326] As shown in Table 1, the position of the first peak for the (111) crystal plane appearing at a diffraction angle 2θ = 27°±2.0° of the Li2S-LiI-CNF composite of Preparation Example 2 shifted to a low angle compared to the position of the second peak for the (111) crystal plane appearing at a diffraction angle 2θ = 27°±2.0° of bare Li2S.

[0327] The first diffraction angle of the first peak of the Li2S-LiI-CNF composite of Example 1 was smaller than the second diffraction angle of the second peak of bare Li2S. Therefore, the crystallite size of the Li2S-LiI-CNF composite of Example 1 was significantly reduced compared to the crystallite size of bare Li2S. As shown in Table 1, the positions of the first peaks of the Li2S-LiI-CNF composite and the Li2S-LiI composite shifted to a low angle compared to the position of the first peak of the pulverized Li2S. In addition, although not shown in Table 1, the first peak of the Li2S-LiI-CNF composite had a first full width at half maximum (FWHM1), and the second peak of bare Li2S had a second full width at half maximum (FWHM2), and the first full width at half maximum was larger than the second full width at half maximum. The first full width at half maximum (FWHM1) was 1° or more.

[0328] As shown in Table 1, the particle size and crystallite size of the Li2S-LiI composite were significantly reduced compared to Li2S. Although not shown in Table 1, the lattice constant of the Li2S-LiI composite was larger than that of bare Li2S. The increase in the lattice constant of the Li2S-LiI composite compared to that of bare Li2S was thought to be due to the dissolution of LiI within the Li2S crystal. Therefore, it was confirmed that the Li2S-LiI composite formed a solid solution.

[0329] Although not shown in Table 1, the particle size of the composite of Example 1 was approximately 5 μm.

[0330] Evaluation Example 2: Charge / Discharge Test

[0331] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated by the following charge / discharge test.

[0332] Charge and discharge tests were performed by placing the all-solid-state secondary battery in a constant temperature chamber at 45°C.

[0333] 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.

[0334] 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 2 below.

[0335] 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.

[0336] <Formula 1>

[0337] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0338] 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.

[0339] Distinction Anode / SE Layer / Cathode Anode Capacity @ 0.1C (mAh / g) Initial Efficiency [%] Cycle Count (Times) Example 1 (Li2 complex + LACO75 + Binder) (60:39:1) Anode / Sulphide SE Layer / Ag-C Non-Cathode 95089480 Example 2 (Li2 complex + LACO75 + Binder) (60:39:1) Anode / LACO SE Layer / Ag-C Non-Cathode 85087280 Example 3 (Li2 complex + LACO75 + Binder) (60:39:1) Anode / Garnet SE Layer / Ag-C Non-Cathode 80088350 Example 4 (Li2 complex + LACO75 + Binder) (60:39:1) Anode / PE0 Layer / Ag-C Non-cathode 71082150Example 5 Anode: (Li2S-complex + LACO75 + solid electrolyte + binder) (60:20:19:1.0) Anode / sulfide-based SE layer / Ag-C Non-cathode 105092580Example 6 (Li2 complex + LACO110 + binder) (60:39:1) Anode / sulfide-based SE layer / Ag-C Non-cathode 89089420Comparative example 1 (Li2S complex + sulfide-based SE) Anode / sulfide-based SE / Ag / C Non-cathode 7208440Comparative example 2 (Li2 complex + PEGDMA + binder) (60:39:1) Anode / sulfide-based SE layer / Ag-C Non-cathode 7008240Comparative example 3(Li2 complex + LACO + binder)(60:39:1) cathode / sulfide SE layer / Ag-C non-cathode, no heat treatment during cathode manufacturing3507915

[0340] As shown in Table 2, the all-solid-state secondary batteries of Examples 1 to 6 showed improved cycle life and rate characteristics compared to Comparative Examples 1 to 3. The all-solid-state secondary battery of Example 1 contained LACO in the positive electrode, which reduced the interfacial resistance between the positive electrode and the solid electrolyte layer and strengthened the network of electrons and ions, thereby improving the cycle life and rate characteristics. The all-solid-state secondary battery of Examples 1 to 6, particularly the all-solid-state secondary battery manufactured according to Example 5, had a positive electrode containing LACO and an argyrodite solid electrolyte, which significantly improved ionic conductivity and electronic conductivity, thereby showing the best cycle life characteristics.

[0341] The all-solid-state secondary battery of Example 1 has a sulfide-based solid electrolyte layer, and exhibits increased life and rate characteristics compared to the all-solid-state secondary battery of Example 2 having a LACO solid electrolyte layer with low reduction stability at low voltages of 1.5 V or less, and the all-solid-state secondary battery of Example 3 having a garnet-based oxide solid electrolyte with low ionic conductivity compared to the sulfide-based solid electrolyte.

[0342] In contrast, the all-solid-state secondary battery of Comparative Example 1 had a positive electrode containing only lithium sulfide, which undergoes a large volume change during charge and discharge, and a solid electrolyte, and thus had a large interfacial resistance between the positive electrode and the solid electrolyte layer, resulting in lower life characteristics and rate characteristics compared to the all-solid-state secondary batteries of Examples 1 to 6. In addition, the all-solid-state secondary battery of Comparative Example 2 had a positive electrode containing PEGDMA, and thus the PEGDMA had poor rate characteristics and life characteristics due to a side reaction with the positive electrode active material.

[0343] In addition, the all-solid-state secondary battery of Comparative Example 3 did not perform a heat treatment process during the manufacture of the positive electrode, so it could not obtain the additional effect of LACO, and thus exhibited deteriorated rate characteristics and life characteristics.

[0344] Evaluation Example 3: Rate Characteristics

[0345] The high-rate characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1 to 3 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.

[0346] Each solid-state secondary battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.5 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 2.5 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.05 C rate until the voltage reached 0.3 V (vs. Li) during discharge (formation cycle).

[0347] Each solid-state secondary battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.5 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 2.5 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 0.3 V (vs. Li) (first cycle).

[0348] The lithium battery that had undergone the Mars cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.2 C rate until the voltage reached 0.3 V (vs. Li) (second cycle).

[0349] The lithium battery that had undergone the first cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.33 C rate until the voltage reached 0.3 V (vs. Li) (second cycle).

[0350] The lithium battery that had undergone the second cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.5 C rate until the voltage reached 0.3 V (vs. Li) (third cycle).

[0351] The lithium battery that had undergone the third cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 1.0 C rate until the voltage reached 0.3 V (vs. Li) (4th cycle).

[0352] In all charge / discharge cycles, a 10-minute pause was observed after each charge / discharge cycle. Some of the results of the room-temperature charge / discharge experiments are shown in Table 3 below. The high-rate characteristics are defined by Equation 2 below.

[0353] <Formula 2>

[0354] High-rate characteristic [%] = [Discharge capacity in the 4th cycle / Discharge capacity in the 1st cycle] × 100

[0355] Anode / SE layer / CathodeHigh rate characteristics (1C / 0.1C) [%]Example 1 (Li2 complex + LACO75 + binder) (60:39:1) Anode / Sulphide SE layer / Ag-C non-cathode 91Example 2 (Li2 complex + LACO75 + binder) (60:39:1) Anode / LACO SE layer / Ag-C non-cathode 89Example 3 (Li2 complex + LACO75 + binder) (60:39:1) Anode / Garnet SE layer / Ag-C non-cathode 87Example 4 (Li2 complex + LACO75 + binder) (60:39:1) Anode / PE0 layer / Ag-C non-cathode 82Comparative Example 1 (Li2S complex + sulfide SE) Anode / Sulphide SE / Ag / C non-cathode 75

[0356] As shown in Table 3, the all-solid-state secondary batteries of Examples 1 to 4 showed improved high-rate characteristics compared to the all-solid-state secondary battery of Comparative Example 1. In addition, although not shown in Table 2, the all-solid-state secondary batteries of Examples 5 and 6 showed high-rate characteristics that were improved or at an equivalent level compared to those of the examples.

Claims

1. A positive electrode current collector; and is disposed on one or both sides of the positive electrode current collector, It comprises a cathode active material layer containing a lithium sulfide-based cathode active material and an inorganic filler, The positive electrode, wherein the above inorganic filler is lithium metal oxyhalide represented by the following chemical formula 1: <Chemical Formula 1> Li a Al b M c O d Cl e In chemical formula 1, 0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤4; d<e, M은 3족 내지 15족에서 선택되는 금속이다.

2. In the first paragraph, the lithium metal oxyhalide is Li a Al b O d Cl e (0 <a≤3; 0<b≤3; 0<d≤2; 1<e≤4; d<e), Li a Al b Fe c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Go c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b In c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b As c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Sbc O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Mo c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Bi c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b B c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e) 또는 이들의 조합을 포함하는, 양극.

3. An all-solid-state secondary battery according to claim 1, wherein the inorganic filler is amorphous or glassy, ​​has a glass transition temperature of 20°C or lower, a melting point of the inorganic filler of 200°C or lower, and an elastic modulus of the inorganic filler at 30°C of 10 GPa or lower.

4. In the first paragraph, an intermediate layer is further included between the positive electrode current collector and the positive electrode active material layer, A cathode, wherein the intermediate layer is directly disposed on one or both sides of the cathode current collector, and the thickness of the intermediate layer is 20% or less of the thickness of the cathode current collector.

5. An anode in the fourth paragraph, wherein the intermediate layer is made of a carbon-based conductive material or the intermediate layer includes a carbon-based conductive material and a binder.

6. A positive electrode according to claim 1, wherein the positive electrode collector is inert to the inorganic filler and the positive electrode collector contains tungsten (W).

7. In the first paragraph, the lithium sulfide-based cathode active material is Li2S, a Li2S complex, or The combination of the two poles.

8. In the 7th paragraph, the Li2S complex is a composite of Li2S and a lithium salt, Li2S and A composite of a carbon-based material, a composite of Li2S, a carbon-based material, and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S, a carbon-based material, and a lithium salt, a composite of Li2S and a lithium salt, a composite of Li2S and a metal carbide, a composite of Li2S, a carbon-based material, and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S, a carbon-based material, and a metal nitride, or a combination thereof, a cathode.

9. In the 7th paragraph, the Li2S complex comprises a solid solution of Li2S and a lithium salt, A cathode having a Li2S crystallite size of 20 nm or less obtained from the XRD spectrum of the above complex.

10. In the 7th paragraph, the Li2S complex is a complex of Li2S, LiI, and a carbon-based material, the size of Li2S crystallites obtained from the XRD spectrum of the complex is less than 9.9 nm, and the composite is a cathode including a solid solution of Li2S and LiI.

11. In the first paragraph, the content of the inorganic filler in the positive electrode active material layer is A cathode, which is 1 to 40 wt% based on the total weight.

12. In the first paragraph, the positive electrode active material layer comprises a binder, a conductive agent and a lithium salt. A bipolar comprising one or more selected elements.

13. In paragraph 12, the challenge material includes a carbon-based material, The above carbon material is amorphous, The above carbon-based material includes a fibrous carbon-based material, The above fibrous carbon material comprises fibrous carbon nanostructures, An anode, wherein the fibrous carbon nanostructure comprises carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods or a combination thereof.

14. In the first paragraph, the positive electrode active material layer further includes a first solid electrolyte, The above first solid electrolyte comprises a sulfide-based solid 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, A cathode, wherein the argyrodite-type solid electrolyte comprises at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I, and the density of the argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc.

15. Comprising an anode layer; a cathode layer; and a solid electrolyte layer between the anode layer and the cathode layer, An all-solid-state secondary battery, wherein the positive electrode layer is the positive electrode of any one of claims 1 to 14.

16. In the 15th paragraph, the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector, The first negative electrode active material layer includes a negative electrode active material and a binder, The above negative electrode active material has a particle form, and the average particle diameter of the above negative electrode active material is 4 ㎛ or less. An all-solid-state secondary battery, wherein the negative electrode active material comprises at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material.

17. In the 16th paragraph, the carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon or a combination thereof. An all-solid-state secondary battery, wherein the metal or metalloid negative electrode active material includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn) or a combination thereof.

18. In the 16th paragraph, the negative electrode active material comprises a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid, The content of the second particles is 1 to 60 wt% based on the total weight of the mixture, Further comprising a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer and between the negative electrode current collector and the electrolyte layer, An all-solid-state secondary battery, wherein the second negative electrode active material layer is a metal layer, and the metal layer contains lithium or a lithium alloy.

19. In the 15th paragraph, the solid electrolyte layer includes a solid electrolyte or a combination of a solid electrolyte and a gel 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 gel electrolyte comprises a polymer gel electrolyte.

20. In the 15th 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.

Images