Solid electrolyte separator, all-solid secondary battery comprising same, and method for manufacturing solid electrolyte separator

Abstract

Disclosed are a solid electrolyte separator, an all-solid-state secondary battery comprising same, and a method for manufacturing a solid electrolyte separator, wherein the solid electrolyte separator comprises: a composite of Li2S and a lithium salt; and a sulfide-based solid electrolyte, wherein the composite of Li2S and a lithium salt is represented by Li2S-LiaXb (1≤a≤5, 1≤b≤5), and 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.

Description

Solid electrolyte separator, all-solid-state secondary battery including the same, and method for manufacturing the solid electrolyte separator

[0001] The present invention relates to a solid electrolyte separator, an all-solid-state secondary battery including the same, and a method for manufacturing the solid electrolyte separator.

[0002] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium batteries are used in a variety of applications, including information technology, communications devices, and automobiles. Because automobiles are life-threatening, safety is also crucial.

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

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

[0005] One aspect is to provide a solid electrolyte separator with improved durability by including a complex of Li2S and a lithium salt.

[0006] Another aspect is to provide an all-solid-state secondary battery including the above solid electrolyte separator.

[0007] Another aspect is to provide a method for manufacturing the above solid electrolyte separator.

[0008] According to the implementation example

[0009] A composite of Li2S and a lithium salt; and

[0010] Contains a sulfide-based solid electrolyte,

[0011] The above complex of Li2S and lithium salt is Li2S-Li a X b It is expressed as (1≤a≤5, 1≤b≤5),

[0012] A solid electrolyte separator is provided, 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.

[0013] According to another implementation example,

[0014] A positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode,

[0015] An all-solid-state secondary battery is provided, wherein the solid electrolyte layer includes a solid electrolyte separator according to the above.

[0016] According to another implementation example,

[0017] A step of providing a Li2S-lithium salt complex;

[0018] A step of providing a sulfide-based solid electrolyte;

[0019] A step of preparing a mixture by mixing the Li2S-lithium salt complex and the sulfide-based solid electrolyte together; and

[0020] A step of preparing a solid electrolyte separator by molding the above mixture is included.

[0021] The above complex of Li2S and lithium salt is Li2S-Li a X b It is expressed as (1≤a≤5, 1≤b≤5),

[0022] A method for manufacturing a solid electrolyte separator is provided, wherein the above 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.

[0023] According to one aspect, it is possible to provide an all-solid-state secondary battery having improved cycle characteristics by having a solid electrolyte separator including a complex of Li2S and a lithium salt.

[0024] Figure 1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0025] Figure 2 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0026] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0027] Fig. 4 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0028] Figure 5 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] "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.

[0037] In the present disclosure, "particle size" or "particle diameter" refers to the average diameter when the particles are spherical, and refers to the average major axis length when the particles are non-spherical. The particle diameter can be measured using a particle size analyzer (PSA). The "particle size" or "particle diameter" refers to, for example, the average particle diameter. The "average particle diameter" refers to, for example, the median particle diameter, D50.

[0038] D50 is the size of the particle corresponding to 50% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0039] D90 is the size of the particle corresponding to 90% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0040] D10 is the size of the particle corresponding to 10% of the cumulative volume, calculated from the particle side with a small particle size in the particle size distribution measured by laser diffraction.

[0041] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0042] In this disclosure, “alloy” means a mixture of two or more metals.

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

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

[0045] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0046] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0047] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0048] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0049] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0050] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0051] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0052] 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.

[0053]

[0054] Hereinafter, a solid electrolyte separator, an all-solid-state secondary battery including the same, and a method for manufacturing the solid electrolyte separator according to exemplary embodiments are described in more detail.

[0055] [Solid electrolyte separator]

[0056] [Solid electrolyte separator: Li2S and lithium salt complex]

[0057] A solid electrolyte separator according to an embodiment includes a composite of Li2S and a lithium salt; and a sulfide-based solid electrolyte.

[0058] Conventional solid electrolyte separators are manufactured using, for example, solid electrolyte particles. Conventional solid electrolyte separators contain pores, such as pinholes, located between the solid electrolyte particles. During the charge / discharge process of an all-solid-state secondary battery, lithium dendrites grow through these pinholes, causing defects such as cracks in the solid electrolyte separator. These defects, in turn, cause a short circuit between the positive and negative electrodes. Consequently, the cycling characteristics of the all-solid-state secondary battery deteriorate. In conventional solid electrolyte separators, pinholes act as insulators (e.g., electrical insulators), increasing the internal resistance of the solid electrolyte separator. Furthermore, they also increase the interfacial resistance between the solid electrolyte separator and the positive or negative electrode. Consequently, the high-rate characteristics of all-solid-state secondary batteries containing conventional solid electrolyte separators deteriorate.

[0059] In contrast, the durability of the solid electrolyte separator of the present disclosure is improved by including a composite of Li2S and a lithium salt. The composite of Li2S and a lithium salt has, for example, ductility. The composite of Li2S and a lithium salt acts as a kind of buffer material between sulfide-based solid electrolyte particles during the manufacturing process of the solid electrolyte separator. The composite of Li2S and a lithium salt can suppress the formation of additional cracks and pores in the sulfide-based solid electrolyte particles due to collision / friction between the sulfide-based solid electrolyte particles. The composite of Li2S and a lithium salt can easily fill the pores and / or interfaces between the sulfide-based solid electrolyte particles. In the solid electrolyte separator of the present disclosure, the formation of pores within the solid electrolyte separator is suppressed and a complex of Li2S and a lithium salt is easily provided to the formed pores, thereby suppressing the formation of pinholes in the solid electrolyte separator and suppressing or reducing the growth of lithium dendrites through these pinholes, thereby improving the durability of the solid electrolyte separator.

[0060] The ductility of the Li2S and lithium salt composite distinguishes it from other brittle conventional oxide-based solid electrolytes, such as garnet-structured oxide-based solid electrolytes. The Li2S and lithium salt composite exhibits lithium ion conductivity, distinguishing it from other conventional lithium-non-containing metal oxides, such as alumina, which do not exhibit lithium ion conductivity. The Li2S and lithium salt composite is, for example, the result of mechanical milling of Li2S and lithium salt. The Li2S and lithium salt composite is, for example, the result of a mechanochemical reaction between Li2S and lithium salt, distinguishing it from a simple mixture of Li2S and lithium salt. The simple mixture of Li2S and lithium salt can provide high interfacial resistance by failing to maintain a dense interface between Li2S and lithium salt, which can consequently increase the internal resistance of the solid electrolyte separator.

[0061] Li2S and lithium salt (Li a X b ) complex is Li2S-Li a X b (1≤a≤5, 1≤b≤5). The above 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. The variable a is, for example, 1, 2, 3, 4 or 5. The variable b is, for example, 1, 2, 3, 4 or 5.

[0062] A 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 of elements. 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. By including such binary compounds in the composite, the ionic conductivity of the composite may be further improved. By including such complexes in the solid electrolyte separator, the internal resistance of the solid electrolyte separator may be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a solid electrolyte separator can 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. When the composite includes such a ternary compound, the ionic conductivity of the composite can be further improved. When the solid electrolyte separator includes such a complex, the internal resistance of the solid electrolyte separator can be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a solid electrolyte separator can be further improved.

[0063] The complex of Li2S and a lithium salt may include, for example, a solid solution of Li2S and a lithium salt. The ionic conductivity of the complex of Li2S and a lithium salt 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 complex of Li2S and a lithium salt may be improved, and the internal resistance of the complex of Li2S and a lithium salt may be reduced. By including such a complex in the solid electrolyte separator, the internal resistance of the solid electrolyte separator may be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a solid electrolyte separator may be further improved.

[0064] The size of Li2S crystallites obtained from the XRD spectrum of the complex of Li2S and a lithium salt 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 of Li2S and a lithium salt 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. By including such a complex in a solid electrolyte separator, the internal resistance of the solid electrolyte separator may further decrease. As a result, the cycle characteristics of an all-solid-state secondary battery including such a solid electrolyte separator may further be improved.

[0065] The Mohs hardness of the complex of Li2S and a lithium salt may be lower than the Mohs hardness of the lithium salt (i.e., the Mohs hardness of the lithium salt itself). The complex of Li2S and a lithium salt may have improved ductility compared to the lithium salt. Since the complex of Li2S and a lithium salt has improved ductility, pinhole formation in the solid electrolyte separator can be more effectively suppressed during the manufacture of the solid electrolyte separator. Consequently, the durability of the solid electrolyte separator including the complex of Li2S and a lithium salt can be further improved. The Mohs hardness of the complex of Li2S and a lithium salt may be, for example, less than 2, 1.5 or less, 1 or less, or 0.7 or less, and may be, for example, 0.01 or more. If the Mohs hardness of the complex of Li2S and a lithium salt increases excessively, it may be difficult to suppress the formation of pinholes in the solid electrolyte separator due to difficulty in providing ductility. The Mohs hardness of Li2S is, for example, 0.6. 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 a lithium salt can be formed more easily. The Mohs hardness of LiI is, for example, 2.0.

[0066] Since Li2S has low ionic conductivity, a complex with a lithium salt is formed to overcome this property. The complex of Li2S and a lithium salt can provide improved ionic conductivity compared to Li2S alone. The content of Li2S in the complex of Li2S and a lithium salt can 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. When the complex of Li2S and a lithium salt has a Li2S content in this range, it can provide both improved ionic conductivity and excellent ductility. Consequently, the durability of a solid electrolyte separator including a complex of Li2S and a lithium salt can be improved. In the complex of Li2S and a lithium salt, the content of the 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. When the complex of Li2S and a lithium salt has a lithium salt content in this range, it can simultaneously provide improved ionic conductivity and excellent ductility. As a result, the durability of a solid electrolyte separator including the complex of Li2S and a lithium salt can be improved.

[0067] In the complex of Li2S and a lithium salt, for example, the content of Li2S may be higher than the content of the lithium salt. The molar ratio of Li2S to the lithium salt in the complex of Li2S and a lithium salt may be, for example, 51:49 to 95:5, 55:45 to 90:10, 60:40 to 90:10, or 70:30 to 90:10. The complex of Li2S and a lithium salt having such a molar ratio can simultaneously provide enhanced ionic conductivity and excellent ductility. Consequently, the durability of a solid electrolyte separator including the complex of Li2S and a lithium salt can be improved.

[0068] The ionic conductivity of the complex of Li2S and lithium salt is, for example, 1×10 at 25°C.-5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4 It can be more than S / cm, for example 1×10 -2 It can be less than S / cm. 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 solid electrolyte separator including the complex of Li2S and lithium salt can be further reduced. The cycle characteristics of the all-solid-state secondary battery including the solid electrolyte separator can be improved.

[0069] The content of the complex of Li2S and a lithium salt may 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 may 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 solid electrolyte separator. When the solid electrolyte separator has the content of the complex of Li2S and a lithium salt in this range, the durability of the solid electrolyte separator can be further improved and the internal resistance can be further reduced. If the content of the complex of Li2S and a lithium salt is too low, the effect may be minimal. If the content of the complex of Li2S and lithium salt increases excessively, the internal resistance of the solid electrolyte separator may increase.

[0070] The solid electrolyte separator may include, for example, composite particles of Li2S and a lithium salt and sulfide-based solid electrolyte particles. The size of the composite particles of Li2S and a lithium salt may be smaller than, for example, the size of the sulfide-based solid electrolyte particles. The size of the composite particles of Li2S and a lithium salt may be, for example, 90% or less, 80% or less, 60% or less, 40% or less, 20% or less, or 10% or less of the size of the sulfide-based solid electrolyte particles, and may be, for example, 1% or more. The composite particles of Li2S and a lithium salt may be disposed in pores between a plurality of sulfide-based solid electrolytes, for example. By disposing the composite particles of Li2S and a lithium salt in the pores between a plurality of sulfide-based solid electrolytes, pinhole formation within the solid electrolyte separator may be suppressed or reduced, and the internal resistance of the solid electrolyte separator may be reduced. As a result, the durability of the solid electrolyte separator may be improved.

[0071] The porosity of the solid electrolyte separator may be 8% or less, 7% or less, 5% or less, 3% or less, 2% or less, or 1% or less. The porosity of the solid electrolyte separator may be 0.01 to 8%, 0.05 to 7%, 0.1 to 5%, 0.1 to 3%, 0.1 to 2%, or 0.1 to 1%. When the solid electrolyte separator has a porosity of 10% or less, the internal resistance of the solid electrolyte separator is reduced and the growth of lithium dendrites can be more effectively suppressed or reduced. As a result, the durability of the solid electrolyte separator can be improved. The porosity of the solid electrolyte separator can be measured by, for example, a method of calculating the area of ​​pores from a mapping image of a cross-section of the solid electrolyte separator through ultrasonic analysis, a method of calculating the area of ​​pores from an electron microscope image of a cross-section of the solid electrolyte separator, etc.

[0072] The size of the sulfide-based solid electrolyte particles may be, for example, 1 to 10 μm, 1 to 8 μm, 1 to 6 μm, 1 to 5 μm, or 1 to 3 μm. When the sulfide-based solid electrolyte particles have a size in this range, the durability of the solid electrolyte separator may be further improved. The size of the sulfide-based solid electrolyte particles may be measured using, for example, laser diffraction, scanning electron microscopy, etc. The size of the sulfide-based solid electrolyte particles is, for example, an arithmetic mean of the particle sizes of a plurality of particles measured using software from a scanning electron microscope image.

[0073] The size of the composite particles of Li2S and a lithium salt may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the composite particles of Li2S and a lithium salt may be, for example, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm. When the composite particles of Li2S and a lithium salt have a size in this range, they can be more easily provided in the pores between a plurality of sulfide-based solid electrolytes, pinhole formation in the solid electrolyte separator can be suppressed, and the internal resistance of the solid electrolyte separator can be reduced. As a result, the durability of the solid electrolyte separator can be improved. The size of the composite particles of Li2S and a lithium salt can be measured using, for example, laser diffraction, a scanning electron microscope, etc. The size of the composite particles of Li2S and a lithium salt is, for example, an arithmetic mean value of particle sizes of a plurality of particles measured using software from a scanning electron microscope image.

[0074] The size of the Li2S particles included in the complex of Li2S and lithium salt may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the Li2S particles may be, for example, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm or less. When the Li2S particles have a size in this range, the internal resistance of the solid electrolyte separator can be further reduced.

[0075] The ratio of the size of the sulfide-based solid electrolyte particles to the size of the composite particles of Li2S and lithium salt may be, for example, 2:1 to 200:1, 2:1 to 100:1, or 2:1 to 50:1. When the ratio of the size of the sulfide-based solid electrolyte particles to the size of the composite particles of Li2S and lithium salt is within this range, the formation of defects in the solid electrolyte separator is suppressed, thereby further improving the durability of the solid electrolyte separator. If the ratio of the size of the sulfide-based solid electrolyte particles to the size of the composite particles of Li2S and lithium salt is excessively small, the porosity of the solid electrolyte separator may excessively increase, thereby reducing the durability of the solid electrolyte separator. If the ratio of the size of the sulfide-based solid electrolyte particles to the size of the composite particles of Li2S and lithium salt is excessively large, it may be difficult to uniformly disperse the composite particles of Li2S and lithium salt within the solid electrolyte separator.

[0076] [Solid electrolyte separator: sulfide-based solid electrolyte]

[0077] The solid electrolyte separator includes a sulfide-based solid electrolyte. The sulfide-based solid electrolyte includes, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x(0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x (0≤x≤2) is at least one selected from. The sulfide-based solid electrolyte can be 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 can be performed after the treatment. The sulfide-based solid electrolyte can be amorphous, crystalline, or a mixture thereof. The sulfide-based solid electrolyte can include, for example, sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. The sulfide-based solid electrolyte can include, for example, Li2S-P2S5. When using a material containing Li2S-P2S5 as a sulfide-based 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.

[0078] The sulfide-based solid electrolyte may include, for example, an argyrodite-type solid electrolyte (e.g., a compound having an argyrodite crystal structure) represented by the following chemical formula 1:

[0079] <Chemical Formula 1>

[0080] Li + 12-n-x A n+ X 2- 6-x Y - x

[0081] 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 , 0≤x≤2, may be an argyrodite-type compound (e.g., a compound having an argyrodite crystal structure) including at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I. The sulfide-based solid electrolyte may be an argyrodite-type compound (e.g., a compound having an argyrodite crystal structure) including at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0082] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. When the argyrodite-type solid electrolyte (e.g., a solid electrolyte having an argyrodite crystal structure) 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 separator by lithium can be more effectively suppressed or reduced.

[0083] [Solid electrolyte separator: binder]

[0084] The solid electrolyte separator may further include a binder. The binder included in the solid electrolyte separator may be, but is not limited to, 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 separator may be the same as or different from the binder used in the positive electrode active material layer and the negative electrode active material layer. The binder may be omitted.

[0085] The binder content included in the solid electrolyte separator is, for example, 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, or 0.1 to 2 wt% with respect to the total weight of the solid electrolyte separator.

[0086] [Solid electrolyte separator: other components]

[0087] The solid electrolyte separator may be free of carbon-based conductive materials. The solid electrolyte separator may not include carbon-based conductive materials, such as graphite, carbon black, carbon nanotubes, or carbon nanofibers. By not including a carbon-based conductive material, the solid electrolyte separator can provide high electronic insulation properties. By not including a carbon-based conductive material, the solid electrolyte separator can more effectively block or reduce the possibility of a short circuit between the anode and cathode. The solid electrolyte separator may also not include a metal-based conductive material (e.g., it may substantially not include, not include, or completely not include a metal-based conductive material).

[0088] The solid electrolyte separator may be, for example, a self-standing film or self-supporting film. The solid electrolyte separator can maintain its membrane form without a support. The solid electrolyte separator may be, for example, in the form of a sheet. Since the solid electrolyte separator is a self-supporting film, the assembly of an all-solid-state secondary battery comprising the solid electrolyte separator can be performed more easily.

[0089] The solid electrolyte separator may have, for example, a curvature greater than 0. The solid electrolyte separator may be, for example, bendable. Since the solid electrolyte separator has ductility by including a sulfide-based solid electrolyte and a complex of Li2S and a lithium salt, it can be bent or deformed. Therefore, the volume change of the positive and / or negative electrodes during the charge and discharge process of the all-solid-state secondary battery can be effectively accommodated, and the formation of cracks, etc. in the solid electrolyte separator can be effectively prevented.

[0090] In contrast, a solid electrolyte separator made of an oxide-based solid electrolyte is brittle, and thus is difficult to bend and has a curvature exceeding 0. A solid electrolyte separator made of an oxide-based solid electrolyte may not bend, but may be cut or broken by cracks due to uneven internal stress caused by volume changes of the positive and / or negative electrodes during the charge and discharge process of an all-solid-state secondary battery, for example.

[0091]

[0092] [All-solid-state secondary battery]

[0093] An all-solid-state secondary battery according to an embodiment includes a positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the solid electrolyte layer includes the above-described solid electrolyte separator.

[0094] Referring to FIGS. 1 to 5, an all-solid-state secondary battery (1) includes a positive electrode (10); a negative electrode (20); and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20). The solid electrolyte layer (30) includes a solid electrolyte separator.

[0095] [anode]

[0096] [Cathode: Cathode active material]

[0097] Referring to FIGS. 1 to 5, the positive electrode (10) includes a positive electrode current collector (11); and a positive electrode active material layer (12) disposed on one or both sides of the positive electrode current collector (11). The positive electrode active material layer (12) includes a positive electrode active material.

[0098] The cathode active material included in the cathode active material layer (12) is a cathode active material capable of reversibly absorbing and desorbing lithium ions. The cathode active material includes, for example, a sulfide-based cathode active material, an oxide-based cathode active material, or a combination thereof.

[0099] Sulfide-based cathode active materials include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof.

[0100] The oxide-based cathode active material includes, for example, a lithium transition metal oxide, a metal oxide, or a combination thereof. The lithium transition metal oxide includes, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt mangense oxide, lithium manganate, lithium iron phosphate, or a combination thereof. The metal oxide includes, for example, iron oxide, vanadium oxide, or a combination thereof.

[0101] The sulfide-based cathode active material may include, for example, a Li2S-containing complex. The Li2S-containing complex includes, for example, a complex of Li2S and carbon, a complex of Li2S and carbon and a solid electrolyte, a complex of Li2S and a solid electrolyte, a complex of Li2S and a lithium salt and carbon, a complex of Li2S and a metal carbide, a complex of Li2S and carbon and a metal carbide, a complex of Li2S and a metal nitride, a complex of Li2S and carbon and a metal nitride, or a combination thereof.

[0102] The Li2S and carbon composite comprises carbon. The carbon may be, for example, any material containing carbon atoms that is used as a conductive material (e.g., an electrically conductive material) in the art. The carbon may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon may be, for example, a sintered product of a carbon precursor. The carbon may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene balls (GB), or a combination thereof. The carbon may be, for example, porous carbon or non-porous carbon. The porous carbon may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon 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 may be, for example, particle form, sheet form, flake form, etc., but is not limited thereto, and any method used as carbon in the art may be used. The method for preparing the composite of Li2S and carbon may be, for example, a dry method, a wet method, or a combination thereof, but is not limited thereto, and the method for preparing the composite of Li2S and carbon in the art may be, for example, milling, heat treatment, deposition, etc., but is not necessarily limited thereto, and any method used in the art may be used.

[0103] The composite of Li2S, carbon, and a solid electrolyte comprises carbon and a solid electrolyte. Carbon refers to the composite of Li2S and carbon described above. The solid electrolyte may be any ion-conducting material used in the relevant technical field, for example, an amorphous solid electrolyte. The solid electrolyte is, for example, an inorganic solid electrolyte. The solid electrolyte is, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte is, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte comprises, for example, Li, S, and P, and may optionally further comprise a halogen element. The sulfide-based solid electrolyte may be selected from among the sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte may have, for example, a 1×10 -5 Ionic conductivity of more than S / cm, and for example 1×10 -2 It can have an ionic conductivity of less than S / cm. Sulfide-based solid electrolytes include, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li7-x PS 6-x I x , may include one or more selected from 0≤x≤2. The oxide-based solid electrolyte includes, for example, Li, O, and a transition metal element, and may optionally further include other elements. The oxide-based solid electrolyte may include, for example, 1×10 at room temperature. -5 It may be a solid electrolyte having an ionic conductivity of S / cm or more. The oxide-based solid electrolyte may be selected from oxide-based solid electrolytes used in the solid electrolyte layer. The solid electrolyte may be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, it may be a mixture of Li3PO4-Li2SO4 and a binary lithium salt, or a mixture of Li3PO4-Li2SO4 and a ternary lithium salt.

[0104] The composite of Li2S and a solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the composite of Li2S, carbon, and a solid electrolyte described above.

[0105] A complex of Li2S and a lithium salt and carbon comprises a lithium salt compound and carbon. The lithium salt compound does not contain, for example, a sulfur (S) atom. The lithium salt compound can 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 binary compound can include, for example, one or more selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3. The lithium salt compound can be, for example, a ternary compound composed of lithium and two elements selected from Groups 13 to 17 of the Periodic Table of Elements. The ternary compound includes, for example, one or more selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. The lithium salt compound is particularly one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. Carbon refers to the complex of Li2S and carbon described above.

[0106] The composite of Li2S and metal carbide includes metal carbide. The metal carbide is, for example, a two-dimensional metal carbide. The two-dimensional metal carbide is, for example, 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.

[0107] The complex of Li2S, carbon, and metal carbide includes carbon and metal carbide. Carbon refers to the complex of Li2S and carbon described above. Metal carbide refers to the complex of Li2S and metal carbide described above.

[0108] The complex of Li2S and metal nitride includes a metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) is expressed as The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0109] A complex of Li2S, carbon, and a metal nitride includes carbon and a metal nitride. Carbon refers to the complex of Li2S and carbon described above. Metal nitride refers to the complex of Li2S and a metal nitride described above.

[0110] The size of the sulfide-based cathode active material (e.g., the size of the sulfide-based cathode active material particles) can be, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm. The size of Li2S (e.g., the size of the Li2S particles) can be, for example, 1 nm to 10 μm, 10 nm to 5 μm, 10 nm to 3 μm, or 10 nm to 1 μm. The size of the Li2S-containing composite (e.g., the size of the Li2S-containing composite particles) can be, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm.

[0111] The oxide-based cathode active material may be, for example, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. The oxide-based cathode active material may be, for example, Li a A 1-b B' b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α(In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α' (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); LiV2O5; LiI'O2; LiNiVO4; Li (3-f)J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); may include a compound represented by any one of the chemical formulas of LiFePO4.

[0112] In the chemical formula representing the above-described compound, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of the above-described compound, or it is also possible to use a mixture of the above-described compound and the compound having a coating layer added. The coating layer added to the surface of the above-mentioned compound includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0113] The oxide-based cathode active material may include, for example, a lithium transition metal oxide represented by the following chemical formulas 1 to 8:

[0114] <Chemical Formula 1>

[0115] Li a Ni x Co y M z O 2-b A b

[0116] In the above chemical formula 1,

[0117] 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3, 및 x+y+z=1이고,

[0118] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0119] A is F, S, Cl, Br or a combination thereof,

[0120] <Chemical Formula 2>

[0121] LiNi x Co y Mn z O2

[0122] <Chemical Formula 3>

[0123] LiNi x Co y Al z O2

[0124] In the above chemical formulas 2 and 3, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며,

[0125] <Chemical Formula 4>

[0126] LiNi x Co y Mn z Al w O2

[0127] In the above chemical formula 4, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며,

[0128] <Chemical Formula 5>

[0129] Li a Co x M y O 2-b A b

[0130] In the above chemical formula 5,

[0131] 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1,

[0132] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0133] A is F, S, Cl, Br or a combination thereof,

[0134] <Chemical Formula 6>

[0135] Li a Ni x Mn y M' z O 2-b A b

[0136] In the above chemical formula 6,

[0137] 1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고,

[0138] M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof,

[0139] A is F, S, Cl, Br or a combination thereof,

[0140] <Chemical Formula 7>

[0141] Li a M1 x M2 y PO 4-b X b

[0142] In the above chemical formula 7, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며,

[0143] M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof,

[0144] M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof.

[0145] <Chemical Formula 8>

[0146] Li a M3 z PO4

[0147] In the above chemical formula 8, 0.90≤a≤1.1, 0.9≤z≤1.1,

[0148] M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0149] The oxide-based cathode active material may be covered by a covering layer. The covering layer may be any material known as a covering layer for cathode active materials of all-solid-state secondary batteries. Examples of the covering layer include Li2O-ZrO2 (LZO).

[0150] The size of the oxide-based cathode active material (e.g., the size of the oxide-based cathode active material particles) may be, for example, 0.1 to 30 μm, 0.5 to 20 μm, or 1 to 15 μm. The oxide-based cathode active material (e.g., the oxide-based cathode active material particles) may be, for example, a single-crystal particle or a polycrystalline particle.

[0151] The cathode active material may be, for example, a composite cathode active material including a core that absorbs and releases lithium and a shell disposed on the core.

[0152] The composite cathode active material includes, for example, a core that absorbs and releases lithium; and a shell provided along the surface of the core; wherein the shell has the chemical formula M a O b(0<a≤3, 0<b<4, a가 1, 2, 또는 3 이면, b는 정수가 아님)로 표시되는 1종 이상의 제1 금속산화물; 및 그래핀을 포함하며, 상기 제1 금속산화물이 그래핀 메트릭스 내에 제공되며, 상기 M은 원소주기율표 2족 내지 13족, 제15족 및 16족 중에서 선택된 하나 이상의 금속이다. 리튬을 흡장 방출하는 코어는 예를 들어 상술한 Li2S 함유 복합체를 포함할 수 있으며, Li2S 함유 복합체는 예를 들어 Li2S와 탄소의 복합체, Li2S와 탄소와 고체전해질의 복합체, Li2S와 고체전해질의 복합체, Li2S와 리튬염과 탄소의 복합체, Li2S와 금속카바이드의 복합체, Li2S와 탄소와 금속카바이드의 복합체, Li2S와 금속나이트라이드의 복합체, Li2S와 탄소와 금속나이트라이드의 복합체 또는 이들의 조합을 포함한다. 리튬을 흡장 방출하는 코어는 예를 들어 화학식 1 내지 8로 표시되는 리튬전이금속산화물을 포함할 수 있다. 리튬을 흡장 방출하는 코어는 예를 들어 Ni 함량 80 mol% 이상의 리튬전이금속산화물을 포함할 수 있다. 리튬을 흡장 방출하는 코어 상에 예를 들어 제1 금속산화물 및 그래핀을 포함하는 쉘이 배치된다. 종래의 그래핀은 응집됨에 의하여 코어 상에 균일한 코팅이 어렵다. 이에 반해, 상기 복합양극활물질은 그래핀 메트릭스에 배치된 복수의 제1 금속산화물을 포함하는 복합체를 사용함에 의하여, 그래핀의 응집을 방지하거나 또는 감소시키면서 코어 상에 균일한(예를 들어, 실질적으로 균일한) 쉘이 배치된다. 따라서, 코어와 전해액의 접촉(예를 들어 물리적 접촉)을 효과적으로 차단하거나 감소시킴에 의하여 코어와 전해질의 접촉에 의한 부반응을 방지하거나 또는 감소시킨다. 그래핀을 포함하는 쉘(shell)은 유연성을 가지므로 충방전시 복합양극활물질의 부피 변화를 용이하게 수용함에 의하여 복합양극활물질 내부의 크랙(crack) 발생이 억제되거나 또는 감소된다.Since graphene has high electron conductivity, the interfacial resistance between the composite cathode active material and the electrolyte is reduced. Therefore, the internal resistance of the lithium battery is maintained or reduced despite the introduction of a shell including graphene. In addition, since the first metal oxide has withstand voltage, deterioration of the Li2S-containing composite or lithium transition metal oxide included in the core can be prevented or reduced during charge / discharge at high voltage. Consequently, the cycle characteristics and high-temperature stability of the lithium battery including the composite cathode active material are improved. The shell may include, for example, one kind of first metal oxide or two or more different first metal oxides. The metal included in the first metal oxide may be, for example, one or more selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se. The first metal oxide may be, for example, Al2O. z (0 <z<3), NbO x (0 <x<2.5), MgO x (0 <x<1), Sc2O z (0 <z<3), TiO y (0 <y<2), ZrO y (0 <y<2), V2O z (0 <z<3), WO y (0 <y<2), MnO y (0 <y<2), Fe2O z (0 <z<3), Co3O w (0 <w<4), PdO x (0 <x<1), CuO x (0 <x<1), AgO x (0 <x<1), ZnO x (0 <x<1), Sb2O z (0 <z<3), 및 SeO y(0 <y<2) 중에서 선택된 하나 이상일 수 있다. 그래핀 메트릭스 내에 이러한 제1 금속산화물이 제공됨에 의하여 코어 상에 배치된 쉘의 균일성이 향상되고, 복합양극활물질의 내전압성이 더욱 향상된다. 예를 들어, 쉘은 제1 금속산화물로 Al2O x (0 <x<3)를 포함한다. 쉘은 화학식 M a O c (0 <a≤3, 0<c≤4, a가 1, 2, 또는 3이면, c는 정수임)로 표시되는 1종 이상의 제2 금속산화물을 더 포함할 수 있다. 상기 M은 원소주기율표 2족 내지 13족, 제15족 및 16족 중에서 선택된 하나 이상의 금속이다. 예를 들어, 제2 금속산화물은 상기 제1 금속산화물과 동일한 금속을 포함하며, 제2 금속산화물의 a 와 c의 비율인 c / a가 상기 제1 금속산화물의 a 와 b의 비율인 b / a에 비하여 더 큰 값을 가진다. 예를 들어, c / a > b / a. The second metal oxide is selected from, for example, Al2O3, NbO, NbO2, Nb2O5, MgO, Sc2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2. The first metal oxide is a reduction product of the second metal oxide. The first metal oxide is obtained by reducing part or all of the second metal oxide. Therefore, the first metal oxide has a lower oxygen content and a higher oxidation number of the metal than the second metal oxide. For example, the shell is the first metal oxide Al2O x(0<x<3) 및 제2 금속산화물인 Al2O3를 포함한다. 쉘의 두께는 예를 들어 1 nm 내지 5 um, 1 nm 내지 1 um, 1 nm 내지 500 nm, 1 nm 내지 200 nm, 1 nm 내지 100 nm, 1 nm 내지 90 nm, 1 nm 내지 80 nm, 1 nm 내지 70 nm, 1 nm 내지 60 nm, 1 nm 내지 50 nm, 1 nm 내지 40 nm, 1 nm 내지 30 nm, 1 nm 내지 20 nm, 또는 1 nm 내지 10 nm이다. 쉘이 이러한 범위의 두께를 가짐에 의하여 복합양극활물질이 포함하는 리튬전지의 내부 저항 증가가 억제되거나 또는 감소된다. 복합체가 포함하는 제1 금속산화물 및 제2 금속산화물 중에서 선택된 하나 이상의 평균입경은 1 nm 내지 1 um, 1 nm 내지 500 nm, 1 nm 내지 200 nm, 1 nm 내지 100 nm, 1 nm 내지 70 nm, 1 nm 내지 50 nm, 1 nm 내지 30 nm, 3 nm 내지 30 nm, 3 nm 내지 25 nm, 5 nm 내지 25 nm, 5 nm 내지 20 nm, 또는 7 nm 내지 20 nm일 수 있다. 제1 금속산화물 및 / 또는 제2 금속산화물이 이러한 나노 범위의 입경을 가짐에 의하여 복합체의 그래핀 메트릭스 내에 보다 균일하게 분포될 수 있다. 따라서, 이러한 복합체가 응집 없이 (예를 들어, 실질적으로 응집 없이) 코어 상에 균일하게 (예를 들어 실질적으로 균일하게) 코팅되어 쉘을 형성할 수 있다. 또한, 제1 금속산화물 및 / 또는 제2 금속산화물이 이러한 범위의 입경을 가짐에 의하여 코어 상에 보다 균일하게 배치될 수 있다. 따라서, 코어 상에 제1 금속산화물 및 / 또는 제2 금속산화물이 균일하게 배치됨(예를 들어, 실질적으로 균일하게 배치됨)에 의하여 내전압 특성을 보다 효과적으로 발휘할 수 있다. 제1 금속산화물 및 제2 금속산화물의 평균 입경은 예를 들어 레이저 회절 방식이나 동적 광산란 방식의 측정 장치를 사용하여 측정할 수 있다.Alternatively, the particle sizes of the first metal oxide and the second metal oxide can be measured from a scanning electron microscope and a transmission electron microscope.

[0153] The shape of the positive electrode active material is, for example, a particle shape such as a sphere, an ellipse, or a sphere. 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 conventional all-solid-state secondary batteries. 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 the positive electrode layer of conventional all-solid-state secondary batteries. 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).

[0154] [Polar: Challenger]

[0155] The cathode active material layer (12) may further include a conductive material (e.g., an electrical conductive material). The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited thereto, and any material used as a carbon-based conductive material in the art may be used. The metal-based conductive material may be, for example, metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material used as a metal-based conductive material in the art may be used. The content of the conductive material included in the cathode active material layer (12) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the cathode active material layer (12).

[0156] [Positive: Binder]

[0157] The positive electrode active material layer (12) may further include a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto, and any binder used in the relevant technical field may be used. The binder content included in the positive electrode active material layer (12) may be, for example, 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12). The binder may be omitted.

[0158] [Positive: Other additives]

[0159] 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.

[0160] 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.

[0161] [Anode: Anode current collector]

[0162] 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.

[0163] 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 (for example, an electrical insulator). Since the base film includes an insulating thermoplastic polymer (for example, an electrically insulating thermoplastic polymer), when a short circuit occurs, the base film softens or liquefies, thereby blocking or reducing battery operation, thereby suppressing or reducing 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 may act as an electrochemical fuse and be cut off in the event of an overcurrent to prevent or reduce a short circuit. The limit current and the maximum current can be controlled by controlling the thickness of the metal layer. The metal layer may 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 collector (11) decrease, so that the stability of the lithium battery in the event of a short circuit can be improved. A lead tab may be added on the metal layer for connection to the outside. The lead tab may be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, or the like. During welding, the base film and / or metal layer may melt, electrically connecting the metal layer to the lead tab.In order to strengthen the welding between the metal layer and the lead tab, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin piece of the same material as the metal of the metal layer. The metal chip may be, for example, a metal foil, a metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. By placing the metal chip on the metal layer and then welding it with the lead tab, the lead tab may be welded to the metal chip / metal layer laminate or the metal chip / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal chip may melt, so that the metal layer or the metal layer / metal chip laminate may be electrically connected to the lead tab. The metal chip and / or the lead tab may be added to a portion of the metal layer. The thickness of the base film may be, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, or 1 to 30 ㎛. By having a thickness of the base film in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film can be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. By having a melting point in this range, the base film can be melted during the process of welding the lead tab and easily bonded to the lead tab. A surface treatment, such as corona treatment, can be performed on the base film to improve the adhesion between the base film and the metal layer. The thickness of the metal layer can be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to 1 μm. By having a thickness of the metal layer in this range, the stability of the electrode assembly can be secured while maintaining conductivity (e.g., electrical conductivity). The thickness of the metal piece can be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. By having the metal piece in this range of thickness, the connection between the metal layer and the lead tab can be performed more easily.By having this structure, the positive electrode collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and secondary battery.

[0164] [Anode: Inert member]

[0165] Referring to FIGS. 4 and 5, the positive electrode (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one side of the positive electrode current collector. An inactive member (40) is disposed on one side of the positive electrode (10). Referring to FIG. 4, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and the positive electrode current collector (11). Referring to FIG. 5, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and between the solid electrolyte layer (30) and the positive electrode current collector (11) facing the solid electrolyte layer (30). The inactive member (40) is not disposed on one side of the positive electrode current collector (11).

[0166] By including the inert member (40), cracking of the solid 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 the all-solid-state secondary battery (1) that does not include the 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) that comes into contact (e.g., physical contact) with the positive electrode (10), and thus cracks are generated in the solid electrolyte layer (30), and the possibility of a short circuit occurring due to growth of lithium metal through the crack (e.g., growth of lithium metal dendrite through the crack) increases.

[0167] 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 (e.g., substantially 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 in close contact (e.g., in physical contact), 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.

[0168] The inert member (40) surrounds the side surface of the positive electrode (10) and contacts (e.g., physically contacts) the electrolyte layer (30). By the inert member (40) surrounding the side surface of the positive electrode (10) and contacting (e.g., physically contacting) the electrolyte layer (30), cracks in the electrolyte layer (30) that are not in contact with the positive electrode (20) due to a pressure difference during the pressing process can be effectively suppressed or reduced. 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), contacts (e.g., physically contacts) the electrolyte layer (30), and is separated from the negative electrode (20). Accordingly, the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or due to overcharging of lithium, etc., is suppressed or reduced. For example, the inert member (40) is disposed on one side of the positive electrode active material layer (12) and simultaneously disposed on one side of the positive electrode current collector (11), thereby more effectively suppressing or reducing the possibility of a short circuit occurring due to contact (e.g., physical contact) between the positive electrode current collector (11) and the negative electrode (20).

[0169] Referring to FIGS. 4 and 5, 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 or reduced. The end of the electrolyte layer (30) is the outermost portion that contacts (e.g., physically contacts) the side surface of the electrolyte layer (30). The inert member (40) extends to the outermost portion that contacts (e.g., physically contacts) the side surface of the electrolyte layer (30). The inert member (40) is physically 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 surface 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).

[0170] Referring to FIGS. 4 and 5, 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 or insufficient.

[0171] The area of ​​the anode (10) is smaller than the area of ​​the electrolyte layer (30) that is in contact (e.g., physical contact) with the anode (10). An inert member (40) surrounds the side of the anode (10) and compensates 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) that occur due to 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.

[0172] 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).

[0173] 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.

[0174] 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).

[0175] The area of ​​the positive electrode (10) is smaller than the area of ​​the negative electrode current collector (21). The area of ​​the positive electrode (10) is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area of ​​the negative electrode current collector (21). The area of ​​the positive electrode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area of ​​the negative electrode current collector (21). The area of ​​the negative electrode current collector (21) is, for example, the same as the area of ​​the negative electrode (20). The area of ​​the negative electrode current collector (21) is, for example, the same as the area of ​​the first negative electrode active material layer (22).

[0176] 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%.

[0177] 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).

[0178] 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.

[0179] 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.

[0180] 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).

[0181] 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.

[0182] 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).

[0183] 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.

[0184] 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).

[0185] 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).

[0186] 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.

[0187] [cathode]

[0188] [Cathode: Cathode active material]

[0189] Referring to FIGS. 1 to 5, the negative electrode (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector (21).

[0190] The first negative electrode active material layer (22) is, for example, a metal layer, and the metal layer may include lithium or a lithium alloy.

[0191] Alternatively, the first negative electrode active material layer (22) may include, for example, a negative electrode active material and a binder.

[0192] 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.

[0193] 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.

[0194] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or metalloid negative electrode active material.

[0195] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] The metal-based negative electrode active material supported on the carbon-based support includes, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn). The metal oxide includes, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, tellurium (Te) oxide, and zinc (Zn) oxide. The metal oxide includes, for example, Au x O y (0 <x≤2, 0<y≤3), Pt x O y (0 <x≤1, 0<y≤2), Pd x O y (0 <x≤1, 0<y≤1), Si x O y (0 <x≤1, 0<y≤2), Ag x O y (0 <x≤2, 0<y≤1), Al x O y (0 <x≤2, 0<y≤3), Bi x O y (0 <x≤2, 0<y≤3), Sn x O y (0 <x≤1, 0<y≤2), Te x O y (0 <x≤1, 0<y≤3), Zn x O y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x O y (0 <x2, 0<y3)의 복합체, Pt와 Pt x O y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x O y (0 <x≤1, 0<y≤1)의 복합체, Si와 Six O y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x O y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x O y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x O y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x O y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x O y (0 <x≤1, 0<y≤3), Zn과 Zn x O y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0203] The carbon-based 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 graphitic carbon. Carbon-based materials (e.g., carbonaceous materials) are, for example, carbon-based negative electrode active materials.

[0204] 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.

[0205] [Cathode: Binder]

[0206] The binder included in the first negative electrode active material layer (22) is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0207] 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).

[0208] [Cathode: Other additives]

[0209] 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.

[0210] [Cathode: Solid electrolyte]

[0211] 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.

[0212] 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).

[0213] [Cathode: First negative electrode active material layer]

[0214] 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 (12) 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.

[0215] 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 (12) is, for example, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1. The initial charge capacity (mAh) of the positive electrode active material layer (12) is obtained by multiplying the charge capacity density (charge specific capacity) (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer (12). When several types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the initial charge capacity of the positive electrode active material layer (12). The initial charge capacity of the first negative electrode active material layer (22) is also calculated in the same way. The initial charge capacity of the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer (22). When several types of negative electrode active materials are used, the charge capacity density Х mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer (22). The charge capacity density of each of the positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell using lithium metal as a counter electrode. The initial charge capacity of each of the positive electrode active material layer (12) and the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass value of the negative electrode active material in the first negative electrode active material layer (22). 2can be directly measured using an all-solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, for example, 3.0 V (vs. Li / Li + ) can be performed for an operating voltage of up to 0.01 V for the cathode, for example, lithium metal, from the second open circuit voltage (OCV). For example, an all-solid-state half-cell having a cathode active material layer can measure a current of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The all-solid-state half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 The all-solid-state half-cell having the positive electrode active material layer can be charged from the first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0216] 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).

[0217] 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.

[0218] [Cathode: Second negative electrode active material layer]

[0219] Referring to FIG. 3, the all-solid-state secondary battery (1) further includes, after being charged, a second negative electrode active material layer (24) disposed, for example, between the negative electrode current collector (21) and the first negative electrode active material layer (22). The second negative electrode active material layer (24) is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer (24) is a metal layer containing lithium, it functions as, for example, a lithium reservoir. The lithium alloy is, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., but is not limited thereto, and any lithium alloy used in the art may be used. The second negative electrode active material layer (24) may be made of one of these alloys or lithium, or may be made of several types of alloys. The second negative electrode active material layer (24) is, for example, a plated layer. The second negative electrode active material layer (24) is deposited between the first negative electrode active material layer (22) and the negative electrode current collector (21), for example, during the charging process of an all-solid-state secondary battery (1).

[0220] 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.

[0221] 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).

[0222] When the second negative electrode active material layer (24) is precipitated by charging after assembling the all-solid-state secondary battery (1), the energy density of the all-solid-state secondary battery (1) increases because the second negative electrode active material layer (24) is not included when assembling the all-solid-state secondary battery (1). When charging the all-solid-state secondary battery (1), the charging is performed in excess of the charging capacity of the first negative electrode active material layer (22). That is, the first negative electrode active material layer (22) is overcharged. At the initial stage of charging, lithium is absorbed into the first negative electrode active material layer (22). The negative electrode active material included in the first negative electrode active material layer (22) forms an alloy or compound with the lithium ions that have moved from the positive electrode (10). When charging exceeds the capacity of the first negative electrode active material layer (22), for example, lithium is deposited on the back surface of the first negative electrode active material layer (22), that is, between the negative electrode current collector (21) and the first negative electrode active material layer (22), and a metal layer corresponding to the second negative electrode active material layer (24) is formed by the deposited lithium. The second negative electrode active material layer (24) is a metal layer mainly composed of lithium (i.e., metallic lithium). This result is obtained, for example, by the negative electrode active material included in the first negative electrode active material layer (22) including a material that forms an alloy or compound with lithium. During discharge, lithium in the first negative electrode active material layer (22) and the second negative electrode active material layer (24), that is, the metal layer, is ionized and moves toward the positive electrode (10). Therefore, it is possible to use lithium as the negative electrode active material in an all-solid-state secondary battery (1). In addition, since the first negative electrode active material layer (22) covers the second negative electrode active material layer (24), it acts as a protective layer for the second negative electrode active material layer (24), i.e., the metal layer, and at the same time, it suppresses the precipitation and growth of lithium dendrites. Accordingly, it suppresses short circuits and capacity reduction of the all-solid-state secondary battery (1), and consequently improves the cycle characteristics of the all-solid-state secondary battery (1).In addition, when the second negative electrode active material layer (24) is placed by charging after assembling the all-solid-state secondary battery (1), the negative electrode (20), i.e., the negative electrode current collector (21) and the first negative electrode active material layer (22) and the region between them are Li-free regions that do not contain lithium (Li) in the initial state or the state after complete discharge of the all-solid-state secondary battery (1).

[0223] [Cathode: Negative current collector]

[0224] The negative electrode current collector (21) is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative electrode current collector (21) is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, and any material that can be used as an electrode current collector in the relevant technical field can be used. The negative electrode current collector (21) may be composed of one type of the above-described metal, or may be composed of an alloy or a coating material of two or more types of metals. The negative electrode current collector (21) is, for example, in the form of a plate or foil.

[0225] Referring to FIG. 2, the all-solid-state secondary battery (1) may further include a thin film (23) containing an element capable of forming an alloy with lithium on one surface of the negative electrode collector (21). The thin film (23) is disposed between the negative electrode collector (21) and the first negative electrode active material layer (22). The thin film (23) contains, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film (23) is composed of one of these metals or an alloy of several types of metals. By placing the thin film (23) on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (24) deposited between the thin film (23) and the first negative electrode active material layer (22) becomes flatter, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0226] 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.

[0227] 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.

[0228] [Solid electrolyte layer]

[0229] [Solid electrolyte layer: electrolyte]

[0230] Referring to FIGS. 1 to 5, a solid electrolyte layer (30) is disposed between the positive electrode (10) and the negative electrode (20) and includes a solid electrolyte separator. The solid electrolyte layer (30) may further include, for example, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0231] The solid electrolyte additionally included in the solid electrolyte layer (30) may include, for example, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0232] 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.

[0233] 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.

[0234] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or a polymer having ion-conducting functional groups. The polymer solid electrolyte may, for example, be a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may, for example, not comprise a liquid.The polymer solid electrolyte comprises a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), Polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0235] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0236] A polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atm. The polymer gel electrolyte may, for example, have a gel state without containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature, is composed solely of ions, and is liquid at room temperature or a molten salt at room temperature. The ionic liquid may include, for example, one or more cations selected from among a) ammonium compounds, pyrrolidinium compounds, pyridinium compounds, pyrimidinium compounds, imidazolium compounds, piperidinium compounds, pyrazolium compounds, oxazolium compounds, pyridazinium compounds, phosphonium compounds, sulfonium compounds, triazolium compounds, and mixtures thereof, and b) one or more anions selected from among BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, BF4-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. A polymer solid electrolyte can form a polymer gel electrolyte, for example, by being impregnated into a liquid electrolyte in a secondary battery. The polymer gel electrolyte may further include inorganic particles.The polymer included in the polymer gel electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0237]

[0238] [Method for manufacturing a solid electrolyte separator]

[0239] According to another embodiment, a method for manufacturing a solid electrolyte separator includes the steps of providing a Li2S-lithium salt complex; providing a sulfide-based solid electrolyte; preparing a mixture by mixing the Li2S-lithium salt complex and the sulfide-based solid electrolyte; and preparing a solid electrolyte separator by molding the mixture. The complex of Li2S and lithium salt is Li2S-Li a X b (1≤a≤5, 1≤b≤5) is expressed. 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.

[0240] A complex of Li2S and a lithium salt is provided.

[0241] A 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. A 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 1,000 rpm for 1 to 20 hours. The stirring can be performed more than once.

[0242] 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.

[0243] A sulfide-based solid electrolyte is provided. The sulfide-based solid electrolyte refers to the solid electrolyte separator section described above.

[0244] A mixture is prepared by mixing the Li2S-lithium salt complex and the above sulfide-based solid electrolyte.

[0245] The mixing ratio of the Li2S-lithium salt complex and the sulfide-based solid electrolyte may 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.

[0246] 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.

[0247] A solid electrolyte separator is prepared by molding the prepared mixture.

[0248] For example, a solid electrolyte separator in the form of a sheet can be manufactured by coating a wet mixture in the form of a slurry on a substrate and drying it. The solid electrolyte separator can be prepared by separating it from the substrate.

[0249] Alternatively, a dry mixture that does not contain a solvent can be fed into an extruder and extruded to produce a solid electrolyte separator in the form of a sheet.

[0250] 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.

[0251] (Manufacture of a complex of Li2S and lithium salt)

[0252] Manufacturing Example 1: Li2S-LiI complex

[0253] 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.

[0254] 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.

[0255] 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.

[0256] Manufacturing Example 2: Li2S-LiBr complex

[0257] A Li2S-LiBr complex was prepared in the same manner as in Preparation Example 1, except that LiBr was used instead of LiI.

[0258] Manufacturing Example 3: Li2S-LiCl complex

[0259] A Li2S-LiCl complex was prepared in the same manner as in Preparation Example 1, except that LiCl was used instead of LiI.

[0260] Comparative Manufacturing Example 1: Simple mixture of Li2S and LiBr

[0261] A mixture of Li2S and LiI with a weight ratio of 30:20 was used as is.

[0262]

[0263] (Manufacture of Li2S-LiI-CNF cathode active material)

[0264] Manufacturing Example 4: Li2S-LiI-CNF

[0265] 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.

[0266] 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.

[0267] A Li2S-LiI-CNF composite was used as a composite cathode active material.

[0268]

[0269] (Manufacturing of solid electrolyte separator)

[0270] Example 1: Solid electrolyte: Li2S-LiI complex = 99:1 weight ratio

[0271] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50 =3.0 ㎛, crystalline), and 1 part by weight of the Li2S-LiI complex prepared in the example and 1.5 parts by weight of an acrylic binder were added to 99 parts by weight of the solid electrolyte to prepare a mixture. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied onto a 15 ㎛ thick non-woven fabric placed on a PET substrate using a bar coater, and dried in air at 80 ℃ for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 80 ℃ for 2 hours and then separated from the substrate to prepare a solid electrolyte separator. The solid electrolyte separator is a self-standing film. The solid electrolyte separator can be slightly bent by applying force at both ends, and can return to its original shape when the applied force is removed. The solid electrolyte separator is used as a solid electrolyte layer as is.

[0272] Example 2: Solid electrolyte: Li2S-LiI complex = 97:3 weight ratio

[0273] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that 3 parts by weight of the Li2S-LiI complex manufactured in Example 1 and 1.5 parts by weight of an acrylic binder were used for 97 parts by weight of the solid electrolyte.

[0274] Example 3: Solid electrolyte: Li2S-LiI complex = 95:5 weight ratio

[0275] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that 5 parts by weight of the Li2S-LiI complex manufactured in Example 1 and 1.5 parts by weight of an acrylic binder were used for 95 parts by weight of the solid electrolyte.

[0276] Example 4: Solid electrolyte: Li2S-LiI complex = 90:10 weight ratio

[0277] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that 10 parts by weight of the Li2S-LiI complex manufactured in Example 1 and 1.5 parts by weight of an acrylic binder were used for 90 parts by weight of the solid electrolyte.

[0278] Example 5: Solid electrolyte: Li2S-LiBr complex = 99:1 weight ratio

[0279] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that the Li2S-LiBr complex manufactured in Manufacturing Example 2 was used instead of the Li2S-LiI complex manufactured in Manufacturing Example 1.

[0280] Example 6: Solid electrolyte: Li2S-LiCl complex = 99:1 weight ratio

[0281] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that the Li2S-LiCl complex manufactured in Manufacturing Example 3 was used instead of the Li2S-LiI complex manufactured in Manufacturing Example 1.

[0282] Comparative Example 1: Solid electrolyte alone

[0283] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that 1.5 parts by weight of an acrylic binder was used per 100 parts by weight of the solid electrolyte. The Li2S-LiI complex was not used.

[0284] Comparative Example 2: Solid electrolyte:Li2S = 99:1 weight ratio

[0285] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that Li2S was used instead of the Li2S-LiI complex manufactured in Manufacturing Example 1.

[0286] Comparative Example 3: Solid electrolyte: LiI = 99:1 weight ratio

[0287] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that LiI was used instead of the Li2S-LiI complex manufactured in Manufacturing Example 1.

[0288] Comparative Example 4: Solid electrolyte: mixture of Li2S and LiI = 99:1 weight ratio

[0289] A solid electrolyte separator was manufactured in the same manner as in Example 1, except that a simple mixture of Li2S and LiI prepared in Comparative Manufacturing Example 1 was used instead of the Li2S-LiI complex manufactured in Manufacturing Example 1.

[0290]

[0291] (Manufacturing of secondary batteries)

[0292] Example 7: Sulfide-based cathode active material (Li2S-LiI-CNF)

[0293] (Polar electrode manufacturing)

[0294] The Li2S-LiI-CNF composite manufactured in Manufacturing Example 4 was prepared as a cathode active material. Li6PS5Cl, an argyrodite-type crystal (D50=3.0 ㎛, crystalline), was prepared as a solid electrolyte. PTFE was prepared as a binder. These materials were mixed in a weight ratio of composite cathode active material: solid electrolyte: binder = 60:40:1.2 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill.

[0295] The positive electrode was manufactured by placing the positive electrode active material mixture on one side of a positive electrode current collector made of aluminum foil coated on one side and plate pressing at a pressure of 200 MPa for 10 minutes. The thickness of the positive electrode was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm. The areas of the positive electrode active material layer and the positive electrode current collector were the same.

[0296] (Cathode manufacturing)

[0297] 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.

[0298] A mixed powder of 4 g of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of an NMP solution containing 7 wt% of PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum-dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold roll pressed to flatten the surface, thereby preparing a negative electrode having a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0299] (Manufacturing of solid electrolyte layer)

[0300] The solid electrolyte separator manufactured in Example 1 was used as a solid electrolyte layer.

[0301] (inert absence)

[0302] A flame-retardant inert member was manufactured by forming a slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0303] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder was 20:8:70:2. The thickness of the inert material was 120 ㎛.

[0304] Before placing the manufactured flame-retardant inert material on the solid electrolyte layer, moisture, etc. of the flame-retardant inert material was removed by vacuum heat treatment at 80°C for 5 hours.

[0305] (Manufacturing of all-solid-state secondary batteries)

[0306] Referring to Fig. 4, a solid electrolyte layer was placed on the negative electrode such that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a positive electrode was placed on the solid electrolyte layer. A laminate was prepared by placing a gasket surrounding the positive electrode and in contact with the solid electrolyte layer. The thickness of the gasket was approximately 120 ㎛. The above-described flame-retardant inert material was used as the gasket. The gasket was placed so as to be in contact with the side surface of the positive electrode and the solid electrolyte layer. The positive electrode was placed at the center of the solid electrolyte layer, and the gasket was placed so as to surround the positive electrode and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed over the entire remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode was not placed.

[0307] 85 prepared laminates oThe solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 ㎛. The density of the Li6PS5Cl solid electrolyte, which was an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc. The area of ​​the solid electrolyte layer was the same as that of the negative electrode.

[0308] 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.

[0309] Examples 8 to 12: Sulfide-based cathode active material (Li2S-LiI-CNF)

[0310] An all-solid-state secondary battery was manufactured in the same manner as in Example 7, except that the solid electrolyte separators manufactured in Examples 2 to 6 were used.

[0311] Comparative Examples 5 to 8: Sulfide-based cathode active material (Li2S-LiI-CNF)

[0312] An all-solid-state secondary battery was manufactured in the same manner as Example 7, except that the solid electrolyte separators manufactured in Comparative Examples 1 to 4 were used.

[0313] Example 13: Oxide-based cathode active material (NCA)

[0314] (Anode layer manufacturing)

[0315] LiNi coated with Li2O-ZrO2 (LZO) as a cathode active material 0.8 Co 0.15 Al 0.05O2(NCM) was prepared. The LZO-coated cathode active material was manufactured according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. Li6PS5Cl, an argyrodite-type crystal (D50 = 0.5 μm, crystalline), was prepared as a solid electrolyte. Polytetrafluoroethylene (PTFE) binder was prepared as a binder. Carbon nanofibers (CNF) were prepared as a conductive agent. These materials were mixed with a xylene solvent at a weight ratio of cathode active material: solid electrolyte: conductive agent: binder = 84: 11.5: 3: 1.5, and the slurry was molded into a sheet shape, and then vacuum-dried at 40°C for 8 hours to manufacture a cathode sheet. The manufactured cathode sheet was placed on the carbon layer of a cathode current collector composed of aluminum foil coated with a carbon layer on one surface, and 85 o The positive electrode layer was manufactured by heated roll pressing of C. The total thickness of the positive electrode layer was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 95 μm, and the thickness of the carbon-coated aluminum foil was approximately 25 μm.

[0316] (All-solid-state secondary battery manufacturing)

[0317] A negative electrode, a solid electrolyte layer, an inert member, and an all-solid-state secondary battery were manufactured in the same manner as in Example 1, except that the positive electrode described above was used.

[0318] Comparative Example 9: Oxide-based cathode active material (NCA)

[0319] An all-solid-state secondary battery was manufactured in the same manner as Example 13, except that the solid electrolyte separator manufactured in Comparative Example 1 was used.

[0320]

[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, and the Li2S-LiI composite manufactured in Manufacturing Example 1. The measurement results are shown in Table 1 below.

[0323] The Li2S crystallite size and lattice constant were derived from the first peak for the (111) crystal plane appearing at a diffraction angle of 2θ = 27° ± 2.0° in the XRD spectrum.

[0324] Crushed Li2S was prepared by milling under the same conditions as in Manufacturing Example 1, except that the 30:20 weight ratio mixture of Li2S and LiI used was changed to 50 parts by weight of Li2S.

[0325] The particle size (i.e., D50 particle size) of the composite was measured using a laser-based particle size analyzer (PSA) for the raw material (bare) Li2S, pulverized Li2S, and the Li2S-LiI composite prepared in Manufacturing Example 1, and the Li2S particle size of the composite was measured using a scanning electron microscope. The measurement results are shown in Table 1 below.

[0326] Li2S crystallite size [nm]Li2S particle size [㎛]bare Li2S658milled Li2S15-Li2S-LiI compositeless than10less than1

[0327] As shown in Table 1, the Li2S particle size and crystallite size of the Li2S-LiI composite were significantly reduced compared to bare Li2S.

[0328] Although not shown in Table 1, the lattice constant of the Li2S-LiI complex of Preparation Example 1 was larger than that of bare Li2S. The increase in the lattice constant of the Li2S-LiI complex 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 complex formed a solid solution.

[0329] Although not shown in Table 1, the particle size of the Li2S-LiI complex of Example 1 was about 2 μm or less.

[0330]

[0331] Evaluation Example 2: Porosity Measurement

[0332] The porosity of the solid electrolyte separator manufactured in Example 1 and Comparative Example 1 was measured, and the results are shown in Table 2 below.

[0333] The porosity of solid electrolyte membranes was calculated using ultrasonic analysis. The solid electrolyte membranes were mapped using ultrasound, and ultrasonic images of the membrane cross-sections containing pores were obtained. Porosity was measured by calculating the pore area from the total cross-sectional area.

[0334] Porosity [%] Example 1 (Li2S-LiI 1 wt%) 3 Comparative Example 1 (Li2S-LiI 0 wt%) 10

[0335] As shown in Table 2, the solid electrolyte separator of Example 1 had a reduced porosity compared to the solid electrolyte separator of Comparative Example 1.

[0336]

[0337] Evaluation Example 3: Charge / Discharge Test

[0338] The charge / discharge characteristics of the all-solid-state secondary batteries of Examples 7 to 12 and Comparative Examples 5 to 8, which employed the solid electrolyte separators manufactured in Examples 1 to 6 and Comparative Examples 1 to 4, were evaluated by the following charge / discharge test.

[0339] Charge and discharge tests were performed by placing the all-solid-state secondary battery in a constant temperature chamber at 45°C.

[0340] 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.

[0341] The charge / discharge characteristics of the all-solid-state secondary battery manufactured in Example 13 were evaluated by the following charge / discharge test. The charge / discharge test was performed by placing the all-solid-state secondary battery in a constant temperature bath at 45°C.

[0342] The first cycle is 0.6 mA / cm until the battery voltage is 3.9 V to 4.25 V. 2 The battery was charged for 12.5 hours at a constant current of 0.6 mA / cm until the battery voltage reached 2.5 V. 2 Discharge was performed for 12.5 hours at a constant current.

[0343] The discharge capacity of the first cycle was taken as the standard capacity.

[0344] After the second cycle, charging and discharging were performed up to 150 cycles under the same conditions as the first cycle. The measurement results are shown in Table 3 below.

[0345] 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.

[0346] Number of Cycles [times] Example 7 (Li2S-LiI 1 wt%, Li2S active material) 250 Example 8 (Li2S-LiI 3 wt%, Li2S active material) 220 Example 9 (Li2S-LiI 5 wt%, Li2S active material) 200 Example 10 (Li2S-LiI 10 wt%, Li2S active material) 150 Example 11 (Li2S-LiBr 1 wt%, Li2S active material) 180 Example 12 (Li2S-LiCl 1 wt%, Li2S active material) 140 Example 13 (Li2S-LiI 1 wt%, NCA active material) 450 Comparative Example 5 (Li2S-LiI 0 wt%, Li2S active material) 50 Comparative Example 6 (Li2S alone 1 wt%, Li2S active material) 35 Comparative example 7 (LiI alone 1 wt%, Li2S active material) 70 Comparative example 8 (Li2S + LiI simple mixture 1 wt%, Li2S active material) 90 Comparative example 9 (Li2S-LiI 0 wt%, NCA active material) 350

[0347] As shown in Table 3, the all-solid-state secondary batteries of Examples 7 to 12 employing the solid electrolyte separators of Examples 1 to 6 showed improved life characteristics compared to the all-solid-state secondary batteries of Comparative Examples 5 to 8 employing the solid electrolyte separators of Comparative Examples 1 to 4.

[0348] The all-solid-state secondary battery of Example 13 showed improved life characteristics compared to the all-solid-state secondary battery of Comparative Example 9.

[0349] It was determined that the durability of the solid electrolyte separator was improved because the formation of pinholes was suppressed by including a Li2S-lithium salt complex in the solid electrolyte separator employed in the all-solid-state secondary batteries of Examples 7 to 13, and defects such as short circuits due to lithium dendrite growth through the pinholes were suppressed.

[0350] Although not shown in the drawing, it was confirmed that a lithium metal layer, which is a second negative electrode active material layer, was formed between the first negative electrode active material layer and the negative electrode current collector after the initial charge in the all-solid-state secondary batteries of Examples 7 to 12. This was confirmed through a cross-sectional scanning electron microscope image of the all-solid-state secondary battery. In addition, it was confirmed in a scanning electron microscope image of a cross-section of the solid electrolyte layer that a Li2S-LiI complex was arranged in the gaps between a plurality of sulfide-based solid electrolyte particles.

[0351]

[0352] Evaluation Example 4: High-Rate Characteristic Evaluation

[0353] The high-rate characteristics of the all-solid-state secondary batteries of Examples 7 to 12 and Comparative Examples 5 to 8, which employed the solid electrolyte separators manufactured in Examples 1 to 6 and Comparative Examples 1 to 4, were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the solid-state secondary batteries in a constant-temperature bath at 45°C.

[0354] The lithium batteries manufactured in Examples 7 to 12 and Comparative Examples 5 to 8 were 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 batteries were discharged at a constant current of 0.1 C rate until the voltage reached 0.3 V (vs. Li) during discharge (formation cycle).

[0355] 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) (first cycle).

[0356] 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).

[0357] 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).

[0358] 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).

[0359] In all charge / discharge cycles, a 10-minute pause was provided after each charge / discharge cycle. Some of the results of the room-temperature charge / discharge experiments are shown in Table 4 below. The high-rate characteristics are defined by the following mathematical equation (1).

[0360] <Mathematical Formula 1>

[0361] High-rate characteristic [%] = [Discharge capacity in the 4th cycle / Discharge capacity in the 1st cycle] Х 100

[0362] High rate characteristics (1C / 0.2C) [%] Example 7 (Li2S-LiI 1 wt%) 87 Example 8 (Li2S-LiI 3 wt%) 84 Example 9 (Li2S-LiI 5 wt%) 82 Example 10 (Li2S-LiI 10 wt%) 78 Example 11 (Li2S-LiBr 1 wt%) 81 Example 12 (Li2S-LiCl 1 wt%) 78 Comparative Example 5 (Li2S-LiI 0 wt%) 70 Comparative Example 6 (Li2S only 1 wt%) 65 Comparative Example 8 (LiI only 1 wt%) 73 Comparative Example 8 (Li2S + LiI simple mixture 1 wt%) 73

[0363] As shown in Table 4, the all-solid-state secondary batteries of Examples 7 to 12 employing the solid electrolyte separators manufactured in Examples 1 to 6 had improved high-rate characteristics compared to the all-solid-state secondary batteries of Comparative Examples 5 to 8 employing the solid electrolyte separators manufactured in Comparative Examples 1 to 4.

[0364] [Explanation of symbols]

[0365] 1 All-solid-state secondary battery 10 Cathode

[0366] 11. Cathode current collector 12. Cathode active material layer

[0367] 20 Cathode 21 Cathode current collector

[0368] 22 First negative electrode active material layer 23 Thin film

[0369] 24 Second negative electrode active material layer 30 Electrolyte layer

[0370] 40 Inert Absences

[0371] According to one aspect, it is possible to provide an all-solid-state secondary battery having improved cycle characteristics by having a solid electrolyte separator including a complex of Li2S and a lithium salt.

Claims

1. A composite of Li2S and a lithium salt; and Contains a sulfide-based solid electrolyte, The above complex of Li2S and lithium salt is Li2S-Li a X b It is expressed as (1≤a≤5, 1≤b≤5), A solid electrolyte separator 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.

2. In the first paragraph, the lithium salt comprises a binary compound or a ternary compound, The above binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3 or a combination thereof, A solid electrolyte separator, wherein the ternary compound comprises Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or a combination thereof.

3. In the first paragraph, the complex comprises a solid solution of Li2S and a lithium salt, A solid electrolyte separator having a Li2S crystallite size of 20 nm or less obtained from the XRD spectrum of the above complex.

4. In the first paragraph, the Mohs hardness of the complex is smaller than the Mohs hardness of the lithium salt, A solid electrolyte separator having a Mohs hardness of less than 2.

5. In the first paragraph, the Li2S content in the complex is higher than the lithium salt content, A solid electrolyte separator, wherein the molar ratio of the L2S and lithium salt in the complex is 51:49 to 95:

5.

6. A solid electrolyte separator in the first paragraph, wherein the content of the complex is 0.1 to 20 wt% of the total weight of the complex and the sulfide-based solid electrolyte.

7. In the first paragraph, the solid electrolyte separator comprises composite particles and sulfide-based solid electrolyte particles, The size of the above complex particles is smaller than the size of the above sulfide-based solid electrolyte particles, A solid electrolyte separator, wherein the above composite particles are provided in the pores between a plurality of the above sulfide-based solid electrolytes.

8. A solid electrolyte separator according to claim 1, wherein the porosity of the solid electrolyte separator is 8% or less.

9. In the 7th paragraph, the size of the sulfide-based solid electrolyte particles is 1 to 10 ㎛, The size of the above composite particles is 2 μm or less, A solid electrolyte separator having a ratio of the size of the sulfide-based solid electrolyte particles to the size of the composite particles of 2:1 to 200:

1.

10. In the first paragraph, the sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX, X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , including at least one selected from 0≤x≤2, The above sulfide-based solid electrolyte includes an argyrodite-type solid electrolyte, The above argyrodite-type solid electrolyte comprises at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I, A solid electrolyte separator having a density of the above argyrodite-type solid electrolyte of 1.5 to 2.0 g / cc.

11. In the first paragraph, the solid electrolyte separator further includes a binder, In the above solid electrolyte separator, the carbon-based conductive material is absent (free), The above solid electrolyte separator is a self-standing film, A solid electrolyte separator, wherein the solid electrolyte separator can have a curvature exceeding 0.

12. It includes an anode; a cathode; and a solid electrolyte layer disposed between the anode and the cathode, An all-solid-state secondary battery, wherein the solid electrolyte layer comprises a solid electrolyte separator according to any one of claims 1 to 11.

13. In the 12th paragraph, the positive electrode includes a positive electrode active material, The above cathode active material includes a sulfide-based cathode active material, an oxide-based cathode active material, or a combination thereof, The above sulfide-based cathode active material includes nickel sulfide, copper sulfide, Li2S, a Li2S-containing complex, or a combination thereof. An all-solid-state secondary battery, wherein the oxide-based cathode active material comprises a lithium transition metal oxide, a metal oxide, or a combination thereof, wherein the lithium transition metal oxide comprises lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt mangense oxide, lithium manganate, lithium iron phosphate, or a combination thereof, and wherein the metal oxide comprises iron oxide, vanadium oxide, or a combination thereof.

14. An all-solid-state secondary battery according to claim 12, wherein the negative electrode comprises a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

15. In the 14th paragraph, the first negative electrode active material layer is a metal layer, and the metal layer contains lithium or a lithium alloy, or An all-solid-state secondary battery, wherein the first negative electrode active material layer includes a negative electrode active material and a binder, the negative electrode active material has a particle form, and the average particle diameter of the negative electrode active material is 4 ㎛ or less.

16. In the 15th paragraph, the negative electrode active material includes at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material, The above carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. The above 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, The above negative active material comprises a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid, An all-solid-state secondary battery, wherein the content of the second particles is 1 to 60 wt% based on the total weight of the mixture.

17. In the 14th paragraph, a second negative electrode active material layer is further included, which is 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 includes lithium or a lithium alloy.

18. In the 12th paragraph, the solid electrolyte layer further includes a solid electrolyte, a gel electrolyte, or a combination thereof, The above solid electrolyte includes 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.

19. In the 12th paragraph, the positive electrode includes a positive electrode collector, and the negative electrode includes a negative electrode collector. At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, An all-solid-state secondary battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

20. A step of providing a Li2S-lithium salt complex; A step of providing a sulfide-based solid electrolyte; A step of preparing a mixture by mixing the Li2S-lithium salt complex and the sulfide-based solid electrolyte together; and A step of preparing a solid electrolyte separator by molding the above mixture is included. The above complex of Li2S and lithium salt is Li2S-Li a X b It is expressed as (1≤a≤5, 1≤b≤5), A method for manufacturing a solid electrolyte separator, 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.

Images