Composite positive electrode active material, positive electrode comprising same, and all-solid-state secondary battery comprising same

Abstract

Disclosed are: a composite positive electrode active material including a core and a shell disposed on at least a portion of the core, wherein the core includes a composite of Li2S, a first ionic compound, and a first carbon-based material, and the shell includes an organic filler, the organic filler including a second ionic compound, a polymer, a phosphorus (P)-containing compound, or a combination thereof; a positive electrode including same; and an all-solid secondary battery including same.

Description

Composite cathode active material, cathode containing the same, and all-solid-state secondary battery

[0001] The present invention relates to a composite cathode active material, a cathode including the same, and an all-solid-state secondary battery.

[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 composite cathode active material having improved thermal stability and improved moisture stability by including an organic filler.

[0006] Another aspect is to provide a positive electrode comprising the above composite positive electrode active material.

[0007] Another aspect is to provide an all-solid-state secondary battery including the above positive electrode.

[0008] According to the implementation example

[0009] A core; and a shell disposed on at least a portion of the core,

[0010] The above core comprises a composite of Li2S, a first ionic compound, and a first carbon-based material,

[0011] The above shell contains an organic filler,

[0012] A composite cathode active material is provided, wherein the organic filler comprises a second ionic compound; and a polymer, a phosphorus (P)-containing compound, or a combination thereof.

[0013] According to the implementation example

[0014] A core; and a shell disposed on at least a portion of the core,

[0015] The above core comprises a composite of Li2S, a first ionic compound, and a first carbon-based material,

[0016] The above shell contains an organic filler,

[0017] A composite cathode active material is provided, wherein the organic filler comprises a polymer, a phosphorus (P)-containing compound, or a combination thereof.

[0018] According to another implementation example,

[0019] A cathode current collector; and a cathode active material layer disposed on one or both sides of the cathode current collector,

[0020] A positive electrode is provided, wherein the positive electrode active material layer includes the composite positive electrode active material described above and a solid electrolyte.

[0021] According to another implementation example,

[0022] A positive electrode according to the above; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode,

[0023] An all-solid-state secondary battery is provided, wherein the negative electrode includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0024] According to one aspect, it is possible to provide a composite cathode active material having improved thermal stability and moisture stability by including an organic filler.

[0025] According to another aspect, it is possible to provide an all-solid-state secondary battery providing improved capacity and initial efficiency by including a composite cathode active material having improved thermal stability and moisture stability.

[0026] Figure 1 is an XRD spectrum of pulverized Li2S, a Li2S-LiI complex which is an intermediate product of Preparation Example 1, and a Li2S-LiI-CNF complex prepared in Preparation Example 1.

[0027] Figure 2a is a scanning electron microscope image of Li2S used in Manufacturing Example 1.

[0028] Figure 2b is a scanning electron microscope image of the Li2S-LiI-CNF composite manufactured in Manufacturing Example 1.

[0029] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0030] Fig. 4 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0031] Fig. 5 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0032] Figure 6 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0033] Fig. 7 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0034] Figure 8 is a scanning electron microscope image of the side of a pellet manufactured using the composite positive electrode active material of Example 3.

[0035] Figure 9 is a scanning electron microscope image of the side of a pellet manufactured using the composite positive electrode active material of Comparative Example 1.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 can be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein can be interpreted accordingly.

[0043] "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.

[0044] In this disclosure, "particle diameter" refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter can be measured using a particle size analyzer (PSA). The "particle diameter" is, for example, the average particle diameter. The "average particle diameter" is, for example, D50, the median particle diameter.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] In the present disclosure, the “weight average molecular weight” of a polymer can be measured, for example, using gel permeation chromatography (GPC), and is a relative value to a polystyrene standard sample.

[0049] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0050] In this disclosure, “alloy” means a mixture of two or more metals.

[0051] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0052] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0053] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0054] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0055] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0056] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0057] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0058] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0059] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0060] In this disclosure, an “ionic compound” is a chemical compound composed of ions held together by electrostatic forces, referred to as ionic bonds.

[0061] 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.

[0062]

[0063] Hereinafter, composite cathode active materials and cathodes and all-solid-state secondary batteries including the composite cathode active materials according to exemplary embodiments will be described in more detail.

[0064] [Composite cathode active material]

[0065] A composite cathode active material according to one embodiment comprises a core; and a shell disposed on at least a portion of the core. The core comprises a composite of Li2S, a first ionic compound, and a first carbon-based material. The shell comprises an organic filler. The organic filler comprises a second ionic compound; and a polymer, a phosphorus (P)-containing compound, or a combination thereof.

[0066] By forming a complex of Li2S with a first ionic compound and a first carbon-based material, the ionic conductivity and electronic conductivity of Li2S can be improved simultaneously. Since the complex of Li2S, the first ionic compound, and the first carbon-based material includes the first ionic compound, the ionic conductivity of the composite cathode active material can be improved, and the internal resistance of the cathode and the all-solid-state secondary battery including the composite cathode active material can be reduced. Since the complex of Li2S, the first ionic compound, and the first carbon-based material includes the first carbon-based material, the electronic conductivity of the composite cathode active material can be improved, and the internal resistance of the cathode and the all-solid-state secondary battery including the composite cathode active material can be reduced. As a result, the charge / discharge characteristics of the all-solid-state secondary battery including the composite cathode active material can be improved.

[0067] The composite of Li2S, the first ionic compound, and the first carbon-based material is distinct from a simple mixture of Li2S, the first ionic compound, and the first carbon-based material. The simple mixture of Li2S, the first ionic compound, and the first carbon-based material fails to maintain a dense interface between Li2S, the first ionic compound, and the first carbon-based material, thereby providing high interfacial resistance, which may consequently deteriorate the life characteristics of the all-solid-state secondary battery.

[0068] The thermal stability and moisture stability of the composite cathode active material can be improved by the core including a composite of Li2S, a first ionic compound, and a first carbon-based material, and a shell including an organic filler is disposed on the core. For example, if the composite of Li2S, a first ionic compound, and a first carbon-based material includes the first carbon-based material, and the first carbon-based material having a large specific surface area comes into contact with oxygen, the first carbon-based material can generate heat of oxidation when combined with oxygen. This heat of oxidation can easily cause ignition of the first carbon-based material. By the core including a composite of Li2S, a first ionic compound, and a first carbon-based material, and a shell including an organic filler is disposed on the core, contact between the first carbon-based material and oxygen can be blocked. Oxidation of the first carbon-based material and / or generation of heat of oxidation are suppressed. The thermal stability of the composite cathode active material can be improved. In addition, since the core includes a composite of Li2S, a first ionic compound, and a first carbon-based material, and a shell including an organic filler is disposed on the core, deterioration of the core due to moisture in the air can be suppressed. The moisture stability of the composite cathode active material can be improved. Consequently, since the composite cathode active material has improved thermal stability and improved moisture stability, the charge / discharge characteristics of an all-solid-state secondary battery including the composite cathode active material can be improved.

[0069] The core comprises a composite of Li2S, a first ionic compound, and a first carbon-based material, and a shell comprising an organic filler is disposed on the core, thereby effectively blocking side reactions between the core and the solid electrolyte at the positive electrode. Deterioration of the all-solid-state secondary battery due to side reactions between the core and the solid electrolyte can be prevented. In contrast, in an all-solid-state secondary battery in which the core is in direct contact with a solid electrolyte, for example, a sulfide-based solid electrolyte, the all-solid-state secondary battery may be deteriorated due to side reactions between the core and the solid electrolyte during charge and discharge.

[0070] The composite cathode active material comprises a core, and the core comprises a composite of Li2S, a first ionic compound, and a first carbon-based material. The composite of Li2S, a first ionic compound, and a first carbon-based material is, for example, Li2S-Li a X b -C (1≤a≤5, 1≤b≤5) complex, Li2S-M1 a X b -C (1≤a≤5, 1≤b≤5) complex, Li2S-M1 a S b -C (1≤a≤5, 1≤b≤5) or a combination thereof. M1 is, for example, Mg, Ca, Sr, Ba, Al, Ga, In, V, Nb, Sc, Fe, Ru, Os or a combination thereof. X is, for example, I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2 or a combination thereof. a is, for example, 1, 2, 3, 4 or 5. b is, for example, 1, 2, 3, 4 or 5. C represents a carbonaceous material.

[0071] The first ionic compound is, for example, a first lithium salt, a first metal salt, a first metal sulfide, or a combination thereof.

[0072] The first lithium salt is, for example, a compound that does not contain sulfur (S). The first lithium salt may be, for example, a binary compound or a ternary compound. The first 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 a binary compound in the composite cathode active material, the ionic conductivity of the composite cathode active material may be further improved. By including such a composite cathode active material in the positive electrode, the internal resistance of the positive electrode having the composite cathode active material can be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode 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. By including such a ternary compound in the positive electrode, the ionic conductivity of the positive electrode can be further improved. By including such a composite cathode active material in the positive electrode, the internal resistance of the positive electrode can be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode can be further improved.

[0073] The first metal salt is, for example, a compound that does not contain lithium (Li). The first metal salt may be, for example, a compound composed of a metal other than lithium and an element from Groups 13 to 17 of the Periodic Table of Elements. The first metal salt may include, for example, AlF3, AlCl3, AlBr3, CaF2, CaCl2, CaBr2, or a combination thereof. By including such a first metal salt compound in the composite cathode active material, the ionic conductivity of the composite cathode active material may be further improved. By including such a composite cathode active material in the cathode, the internal resistance of the cathode including the composite cathode active material may be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a cathode may be further improved.

[0074] The first metal sulfide is, for example, a sulfide that does not contain lithium (Li). The first metal sulfide may be, for example, a compound composed of a metal other than lithium and an element from Groups 13 to 17 of the Periodic Table of Elements. The first metal salt may include, for example, FeS, MgS, CaS, Al2S3, V2S3FeS2, VS2, MnS, NiS, CuS, or a combination thereof. When the composite cathode active material includes such a first metal salt compound, the ionic conductivity of the composite cathode active material may be further improved. When the cathode includes such a composite cathode active material, the internal resistance of the cathode including the composite cathode active material may be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a cathode may be further improved.

[0075] The composite of Li2S, the first ionic compound, and the first carbon-based material may include, for example, a solid solution of Li2S and the first ionic compound. By including the solid solution of Li2S and the first ionic compound, the composite of Li2S, the first ionic compound, and the first carbon-based material may have increased ionic conductivity. For example, by including lithium ions arranged within Li2S crystallites in the solid solution of Li2S and the first ionic compound, the ionic conductivity of the solid solution of Li2S and the first ionic compound may be improved compared to the ionic conductivity of Li2S. As a result, the ionic conductivity of the composite of Li2S, the first ionic compound, and the first carbon-based material may be improved, and the internal resistance of the composite of Li2S, the first ionic compound, and the first carbon-based material may be reduced. By including such a composite material in a composite cathode active material, the ionic conductivity of the composite cathode active material can be further enhanced. Furthermore, by including such a composite cathode active material in the cathode, the internal resistance of the cathode comprising the composite cathode active material can be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a cathode can be further improved.

[0076] The size of Li2S crystallites obtained from the XRD spectrum of the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of Li2S crystallites obtained from the XRD spectrum of the composite of Li2S, the first ionic compound, and the first carbon-based material 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 the first ionic compound may further increase. As the contact area between Li2S and the first ionic compound further increases, the ionic conductivity of the composite of Li2S and the first ionic compound may further increase. By including such a composite, the ionic conductivity of the composite cathode active material may be further improved. By including such a composite cathode active material in the cathode, the internal resistance of the cathode comprising the composite cathode active material can be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a cathode can be further improved.

[0077] In the composite of Li2S, the first ionic compound, and the first carbon-based material, for example, the content of Li2S may be higher than the content of the first ionic compound. In the composite of Li2S, the first ionic compound, and the first carbon-based material, the molar ratio of Li2S to the first ionic compound may be, for example, 50:50 to 95:5, 55:45 to 90:10, 60:40 to 90:10, or 70:30 to 90:10. The composite of Li2S, the first ionic compound, and the first carbon-based material can simultaneously provide improved ionic conductivity and excellent ductility by having such a molar ratio of Li2S to the first ionic compound. As a result, the durability of the composite cathode active material including the composite of Li2S, the first ionic compound, and the first carbon-based material can be improved. The durability of the cathode and all-solid-state secondary battery containing the composite cathode active material can be improved. If the molar ratio of Li2S is excessively high, the ionic conductivity improvement effect by the lithium salt may be minimal. If the molar ratio of Li2S is excessively low, the energy density of the secondary battery containing the composite cathode active material may be reduced.

[0078] The composite of Li2S, a first ionic compound, and a first carbon-based material includes Li2S. Since Li2S has a high theoretical capacity, an all-solid-state secondary battery having a high energy density can be provided. Since Li2S has low ionic conductivity and / or electronic conductivity, a composite is formed with the first ionic compound and the first carbon-based material to overcome these shortcomings. The content of Li2S in the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 30 to 95 wt%, 50 to 95 wt%, 50 to 90 wt%, 50 to 80 wt%, or 50 to 70 wt% of the total weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. Alternatively, the content of Li2S in the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 10 to 95 wt%, 10 to 80 wt%, 20 to 70 wt%, 30 to 60 wt%, or 40 to 60 wt% of the total weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. When the composite of Li2S, the first ionic compound, and the first carbon-based material has a Li2S content in this range, it can simultaneously provide improved ionic conductivity and excellent ductility. As a result, the durability of the composite cathode active material including the composite of Li2S, the first ionic compound, and the first carbon-based material, and the cathode and the all-solid-state secondary battery including the same can be improved. If the content of Li2S increases excessively, it may not be easy to improve the ionic conductivity and / or electronic conductivity of Li2S. If the content of Li2S is too low, the energy density of the secondary battery may decrease.

[0079] In the composite of Li2S, the first ionic compound, and the first carbon-based material, the content of the first ionic compound may be, for example, 1 to 50 wt%, 5 to 50 wt%, 10 to 50 wt%, 20 to 50 wt%, or 30 to 50 wt% of the total weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. When the composite of Li2S, the first ionic compound, and the first carbon-based material has the content of the first ionic compound 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 composite of Li2S, the first ionic compound, and the first carbon-based material can be improved.

[0080] In the composite of Li2S, the first ionic compound, and the first carbon-based material, the content of the first carbon-based material may be, for example, 1 to 20 wt%, 5 to 20 wt%, or 10 to 20 wt% of the total weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. If the content of the first carbon-based material increases excessively, the energy density of the all-solid-state secondary battery may decrease. If the content of the first carbon-based material decreases excessively, the electronic conductivity of the composite of Li2S, the first ionic compound, and the first carbon-based material may decrease, thereby increasing the internal resistance of the composite positive electrode active material. As a result, the cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0081] For example, the composite of Li2S, the first ionic compound, and the first carbon-based material may include 10 to 80 parts by weight of Li2S, 1 to 40 parts by weight of the first ionic compound, and 1 to 20 parts by weight of the first carbon-based material, relative to 100 parts by weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. The Li2S content included in the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 10 to 80 parts by weight, 20 to 70 parts by weight, 30 to 60 parts by weight, or 40 to 60 parts by weight of Li2S, relative to 100 parts by weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. The content of the first ionic compound included in the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 1 to 40 parts by weight, 5 to 40 parts by weight, 10 to 40 parts by weight, 15 to 40 parts by weight, 20 to 40 parts by weight, or 25 to 35 parts by weight of the first ionic compound relative to 100 parts by weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. The content of the first carbon-based material included in the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 1 to 20 parts by weight, 5 to 20 parts by weight, or 10 to 20 parts by weight of the carbon-based material relative to 100 parts by weight of the composite of Li2S, the first ionic compound, and the first carbon-based material. By having a composite of Li2S, the first ionic compound, and the first carbon-based material having a composition of Li2S, the first ionic compound, and the first carbon-based material within this range, a composite cathode active material including the composite of Li2S, the first ionic compound, and the first carbon-based material can provide excellent ionic conductivity and / or electronic conductivity.

[0082] The size of the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 1 to 20 μm, 1 to 15 μm, 1 to 10 μm, 2 to 10 μm, or 3 to 10 μm. When the composite of Li2S, the first ionic compound, and the first carbon-based material has a size in this range, improved ionic conductivity and electronic conductivity can be provided simultaneously. If the size of the composite of Li2S, the first ionic compound, and the first carbon-based material is too small, it may be difficult to secure a conductive path between the composite cathode active material particles because the carbon-based material is finely divided. If the size of the composite of Li2S, the first ionic compound, and the first carbon-based material is too large, the degree of compositeness may be low. It may be difficult to secure an electronic conductive path and an ionic conductive path within the composite of Li2S, the first ionic compound, and the first carbon-based material. The size of the composite of Li2S, the first ionic compound, and the first carbon-based material can be, for example, a D50 particle size. The size of the composite of Li2S, the first ionic compound, and the first carbon-based material can be measured, for example, using a laser-assisted particle size analyzer (PSA). The size of the composite of Li2S, the first ionic compound, and the first carbon-based material can be calculated, for example, by software from a scanning electron microscope image of the composite powder.

[0083] The D10 particle size of the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 1 ㎛ or more, 1.2 ㎛ or more, 1.5 ㎛ or more, or 2 ㎛ or more. When the D10 particle size of the composite of Li2S, the first ionic compound, and the first carbon-based material is in this range, the fine particle content of the composite of Li2S, the first ionic compound, and the first carbon-based material may decrease. When the fine particle content of the composite of Li2S, the first ionic compound, and the first carbon-based material decreases, the density of the positive electrode including the composite positive electrode active material increases, so that the energy density of an all-solid-state secondary battery including the positive electrode may be improved. When the fine particle content of the composite of Li2S, the first ionic compound, and the first carbon-based material increases, the interfacial resistance between the composite particles of Li2S, the first ionic compound, and the first carbon-based material may increase, and it may become difficult to form a conductive network. As a result, the cycle characteristics of an all-solid-state secondary battery including a composite of Li2S, a first ionic compound, and a first carbon-based material may be degraded. The D10 particle size can be measured, for example, using a laser-based particle size analyzer (PSA).

[0084] The size of the Li2S particles included in the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the Li2S particles included in the composite of Li2S, the first ionic compound, and the first carbon-based material may be, for example, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm or less. Since the Li2S particles have a size in this range, the volume change during charge and discharge is suppressed, and thus the deterioration of the composite cathode active material including the composite of Li2S, the first ionic compound, and the first carbon-based material during charge and discharge can be suppressed. If the size of the Li2S particles increases excessively, the volume change of the composite of Li2S, the first ionic compound, and the first carbon-based material increases during charge and discharge, and thus the deterioration of the composite cathode active material including the composite may be accelerated. As a result, the cycle characteristics of an all-solid-state secondary battery including such a composite cathode active material may be degraded. The particle size of Li2S included in the composite of Li2S, the first ionic compound, and the first carbon-based material can be measured using, for example, a scanning electron microscope, a transmission electron microscope, etc.

[0085] The composite of Li2S, the first ionic compound, and the first carbonaceous material comprises the first carbonaceous material. The first carbonaceous material may be any material containing carbon atoms that is used as a conductive material in the art.

[0086] The first carbon-based material may include, for example, amorphous carbon, crystalline carbon, or a combination thereof. Since the first carbon-based material includes amorphous carbon, side reactions between the first carbon-based material and the solid electrolyte may be suppressed. Accordingly, the cycle characteristics of an all-solid-state secondary battery including a composite of Li2S, a first ionic compound, and the first carbon-based material may be further improved. The first carbon-based material may be, for example, a sintered product of a carbon precursor.

[0087] The first carbon-based material may include, for example, a carbon nanostructure. The carbon nanostructure may include, 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 nanofiber, a carbon nanotube, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof.

[0088] The first carbon-based material may include, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material may include, for example, periodic and regular two-dimensional or three-dimensional pores. Alternatively, the porous carbon-based material may include, for example, non-periodic and irregular two-dimensional or three-dimensional pores.

[0089] The first carbon-based material may include, for example, a fibrous carbon-based material, a particulate carbon-based material, or a combination thereof.

[0090] The first carbon-based material may include, for example, a fibrous carbon-based material. Since the composite of Li2S, the first ionic compound, and the first carbon-based material includes the fibrous carbon-based material, the electronic conductivity of the composite of Li2S, the first ionic compound, and the first carbon-based material may be further improved. Since the composite of Li2S, the first ionic compound, and the first carbon-based material includes the fibrous carbon-based material, electronic conduction may be more easily performed from the surface to the inside of the composite of Li2S, the first ionic compound, and the first carbon-based material. The internal resistance of the composite cathode active material including the composite of Li2S, the first ionic compound, and the first carbon-based material may be reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including the composite cathode active material may be further improved. The aspect ratio of the fibrous carbon-based material may be, for example, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material can be, for example, 5 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material can be, for example, 5 to 30, 5 to 20, or 5 to 10. When the fibrous carbon-based material has an aspect ratio in this range, the overall electronic conductivity of the composite is improved, and the imbalance of local electronic conductivity within the composite can be further alleviated. The fibrous carbon-based material can include, for example, a carbon nanostructure. The carbon nanostructure can include, for example, a carbon nanofiber (CNF), a carbon nanotube (CNT), a carbon nanobelt, a carbon nanorod, or a combination thereof. The carbon nanostructure can form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure in which a plurality of carbon nanostructures are aggregated. The aspect ratio of a fibrous carbon material can be measured, for example, from scanning electron microscope (SEM) or transmission electron microscope (TEM) images.

[0091] The diameter of the primary carbon nanostructure can be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure can be, for example, 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure can be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure can be measured by laser diffraction.

[0092] Secondary carbon nanostructures are, for example, structures formed by assembling primary carbon nanostructures in whole or in part to form bundles or bundle-type structures. The secondary carbon nanostructures may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or combinations thereof. The diameter of the secondary carbon nanostructures may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length of the secondary carbon nanotube structure can be, for example, 20 nm to 2 ㎛, 30 nm to 1.5 ㎛, 50 nm to 1 ㎛, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured from a scanning electron microscope (SEM) image or an optical microscope. Alternatively, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be converted into the primary carbon nanostructure by, for example, dispersing it in a solvent or the like and then used in the preparation of a composite.

[0093] The first carbon-based material may include, for example, a particulate carbon-based material. The particulate carbon-based material may include, for example, carbon black such as Ketjen Black, acetylene black, Denka Black, thermal black, channel black, or the like; graphite, activated carbon, or a combination thereof. The aspect ratio of the particulate carbon-based material may be, for example, 4 or less, 3 or less, or 2 or less. The aspect ratio of the fibrous carbon-based material may be, for example, 1 to 4, 1 to 3, or 1 to 2.

[0094]

[0095] A composite cathode active material has a core / shell structure, and the shell includes an organic filler. The organic filler includes a second ionic compound; and a polymer, a phosphorus (P)-containing compound, or a combination thereof. By including the organic filler in the shell, the thermal stability and moisture stability of the composite cathode active material can be improved. By including the second ionic compound, the organic filler can have ionic conductivity. By having ionic conductivity in the organic filler, an increase in internal resistance of the cathode and an all-solid-state secondary battery due to the introduction of the organic filler can be suppressed. By including the polymer, the phosphorus (P)-containing compound, or a combination thereof, the organic filler can effectively suppress contact between the core and moisture / air, etc., and can effectively suppress ignition and / or deterioration of the core due to moisture. Consequently, the thermal stability and / or moisture stability of the composite cathode active material can be improved. Since the organic filler has a lower elastic modulus than the core, it can more effectively accommodate changes in the core's volume during charging and discharging.

[0096] The second ionic compound may include, for example, a second lithium salt, an ionic liquid, or a combination thereof.

[0097] The second lithium salt can be any lithium salt that can be used in the art. Examples of the second lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(1≤x≤20, 1≤y≤20), LiCl, LiI, LiBr, LiF or mixtures thereof.

[0098] An ionic liquid is a salt that has a melting point below room temperature, is composed only of ions, and is liquid at room temperature or a molten salt at room temperature. Anything that can be used as an ionic liquid in the relevant technical field can be an ionic liquid. The ionic liquid may be, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may include at least one selected from compounds containing at least one anion selected from among.

[0099] The content of the second ionic compound may be, for example, 1 to 50 parts by weight, 1 to 40 parts by weight, 1 to 30 parts by weight, 1 to 20 parts by weight, or 1 to 10 parts by weight, based on 100 parts by weight of the organic filler. When the organic filler includes the second ionic compound in this range, the charge / discharge characteristics of an all-solid-state secondary battery having a composite positive electrode active material including the organic filler can be further improved.

[0100] Polymers include, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), poly(styrene-b-ethylene oxide) block copolymers (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymers, poly(styrene-ethylene oxide-styrene) block copolymers, 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-diphenylatlacene-2-sulfonate 9,10-diphenylanthracene-2-sulfonate, DPASLi +) or a combination thereof, but is not limited thereto, and any polymer capable of inhibiting the diffusion of oxygen and / or moisture in the art is possible.

[0101] The phosphorus (P)-containing compound may include, for example, a phosphate-based compound, a phosphite-based compound, or a combination thereof.

[0102] The phosphate compound can be represented, for example, by the following chemical formula 1.

[0103] <Chemical Formula 1>

[0104]

[0105] In the above formula,

[0106] R1, R2, and R3 are each independently a hydrogen atom; a fluorine atom; a halogen-substituted or unsubstituted alkyl group having 1 to 5 carbon atoms; a halogen-substituted or unsubstituted cycloalkyl group having 4 to 10 carbon atoms; a halogen-substituted or unsubstituted aryl group having 5 to 10 carbon atoms; a halogen-substituted or unsubstituted heteroaryl group having 2 to 10 carbon atoms; or a halogen-substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms.

[0107] The phosphite compound can be represented, for example, by the following chemical formula 2.

[0108] <Chemical Formula 2>

[0109]

[0110] In the above formula,

[0111] R4, R5, and R6 are each independently a hydrogen atom; a fluorine atom; a halogen-substituted or unsubstituted alkyl group having 1 to 5 carbon atoms; a halogen-substituted or unsubstituted cycloalkyl group having 4 to 10 carbon atoms; a halogen-substituted or unsubstituted aryl group having 5 to 10 carbon atoms; a halogen-substituted or unsubstituted heteroaryl group having 2 to 10 carbon atoms; or a halogen-substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms.

[0112] The phosphate compound may include, for example, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, or a combination thereof.

[0113] The phosphite compound may include, for example, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphite, or a combination thereof.

[0114]

[0115] The organic filler may comprise a phosphorus (P)-containing compound, for example, without comprising a second ionic compound.

[0116] The organic filler may be free of organic solvents. The organic filler may not contain any organic solvents intentionally added. Since the organic filler does not contain any organic solvents, unnecessary gas generation during charging and discharging of the all-solid-state secondary battery can be prevented, thereby further improving the high-temperature stability of the all-solid-state secondary battery.

[0117] The organic filler may include, for example, an organic electrolyte. The organic filler may include, for example, a polymer electrolyte, an electrolyte comprising a phosphorus (P)-containing compound, or a combination thereof.

[0118] The polymer electrolyte may include, for example, a polymer solid electrolyte, a polymer gel electrolyte, or a combination thereof.

[0119] The polymer solid electrolyte may include, for example, a mixture of a second lithium salt and a polymer, or may include a polymer having an ion-conducting functional group. The polymer solid electrolyte may be, for example, a polymer electrolyte that is solid at 25° C. and 1 atm. The polymer solid electrolyte may not include, for example, a liquid. The polymer solid electrolyte may include, for example, the polymer described above. The polymer included in the polymer solid 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 solid electrolyte may be, for example, 1,000 Dalton to 3,000,000 Dalton, 10,000 Dalton to 3,000,000 Dalton, 100,000 Dalton to 3,000,000 Dalton, or 1,000,000 Dalton to 3,000,000 Dalton.

[0120] The 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 have a gel state, for example, without containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, a mixture of an ionic liquid, a second lithium salt, and an organic solvent; a mixture of a second lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a second lithium salt and an ionic liquid. The organic solvent used in the polymer gel electrolyte may be selected from organic solvents used in liquid electrolytes. The polymer used in the polymer gel electrolyte may be selected from polymers used in a polymer solid electrolyte. The polymer solid electrolyte may 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, 1,000 Dalton to 3,000,000 Dalton, 10,000 Dalton to 3,000,000 Dalton, 100,000 Dalton to 3,000,000 Dalton, or 1,000,000 Dalton to 3,000,000 Dalton.

[0121] The content of the organic filler may be, for example, 1 to 20 wt%, 2 to 18 wt%, 3 to 17 wt%, or 5 to 15 wt% of the total weight of the composite cathode active material. By including the organic filler in this range, the oxidation resistance and / or moisture stability of the composite cathode active material may be further improved. Accordingly, the charge / discharge characteristics of an all-solid-state secondary battery including the composite cathode active material may be further improved.

[0122] A composite cathode active material includes a core and a shell disposed on the core. The thickness of the shell may be, for example, 2 μm or less, 1.5 μm or less, 1 μm or less, 800 nm or less, or 500 nm or less. The thickness of the shell may be, for example, 10 nm to 2 μm, 50 nm to 1.5 μm, 100 nm to 1 μm, 100 nm to 800 nm, or 100 nm to 500 nm. The shell thickness may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the core particle size. When the composite cathode active material has a shell thickness in this range, the oxidation resistance and / or moisture stability of the composite cathode active material may be further improved. If the shell thickness is excessively small, it may be difficult to provide the required effect. If the shell thickness is excessively thick, the energy density of the composite cathode active material may be reduced. The shell thickness can be measured, for example, using a scanning electron microscope or transmission electron microscope on a cross-section of the composite cathode active material.

[0123] The ionic conductivity of the composite cathode active material after 72 hours in an atmosphere at 25°C and 1 atm may be 0.03 mS / cm or more, 0.04 mS / cm or more, 0.05 mS / cm or more, or 0.06 mS / cm or more. The ionic conductivity of the composite cathode active material after 72 hours in an atmosphere at 25°C and 1 atm may be 0.03 to 1 mS / cm, 0.04 to 1 mS / cm, 0.05 to 1 mS / cm, or 0.06 to 1 mS / cm. Since the composite cathode active material has improved moisture stability, it is possible to suppress deterioration of the composite cathode active material due to moisture in the atmosphere during the manufacturing process of an all-solid-state secondary battery and provide excellent ionic conductivity.

[0124] The composite cathode active material may not ignite during sieving in an atmosphere of 25°C and 1 atm. The sieving time may be, for example, 72 hours or less, 48 ​​hours or less, 24 hours or less, 12 hours or less, or 1 hour or less. The composite cathode active material includes a core and a shell on the core, and since the shell includes an organic filler, the organic filler can effectively prevent frictional heat between core particles and / or oxidation heat caused by a reaction between the core and oxygen. Therefore, ignition during the sieving process of the composite cathode active material can be effectively suppressed. The composite cathode active material may have improved thermal stability. Since the composite cathode active material has improved thermal stability, the thermal stability and / or high-temperature stability of an all-solid-state secondary battery including the composite cathode active material can be improved.

[0125]

[0126] [anode]

[0127] According to one embodiment, a positive electrode includes a positive electrode current collector; and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector. The positive electrode active material layer includes the composite positive electrode active material described above and a solid electrolyte. By including the composite positive electrode active material and the solid electrolyte, the positive electrode can have further reduced internal resistance. Accordingly, the cycle characteristics of a secondary battery including the positive electrode can be further improved.

[0128] [Cathode: Composite cathode active material]

[0129] Referring to FIGS. 3 to 7, the positive electrode (10) includes a positive electrode current collector (11); and a positive electrode active material layer (12) disposed on one or both sides of the positive electrode current collector (11). The positive electrode active material layer (12) includes the composite positive electrode active material and solid electrolyte described above.

[0130] The composite cathode active material may be included in an amount of 40 to 90 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, or 50 to 70 parts by weight, based on 100 parts by weight of the cathode active material layer (12). If the content of the composite cathode active material is excessively reduced, the energy density of the secondary battery is reduced. If the content of the composite cathode active material is excessively increased, the deterioration of the cathode may be accelerated due to the change in the volume of the cathode during charge and discharge. As a result, the cycle characteristics of the secondary battery (1) may be reduced.

[0131] [Anode: Solid electrolyte]

[0132] The positive electrode active material layer (12) may include, for example, a solid electrolyte. The solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode (10) may be the same as or different from the solid electrolyte included in the electrolyte layer (30). For details on the solid electrolyte, refer to the electrolyte layer (30) section.

[0133] The solid electrolyte included in the positive electrode active material layer (12) may have a smaller average D50 particle diameter than the solid electrolyte included in the electrolyte layer (30). For example, the average D50 particle diameter of the solid electrolyte included in the positive electrode active material layer (12) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average D50 particle diameter of the solid electrolyte included in the electrolyte layer (30). The average D50 particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by, for example, a laser diffraction method.

[0134] The solid electrolyte may be included in an amount of 10 to 60 parts by weight, 10 to 50 parts by weight, 20 to 50 parts by weight, or 30 to 50 parts by weight, based on 100 parts by weight of the positive electrode active material layer (12). If the content of the solid electrolyte is excessively reduced, the internal resistance of the positive electrode may increase, thereby deteriorating the cycle characteristics of the secondary battery. If the content of the sulfide-based solid electrolyte is excessively increased, the energy density of the secondary battery (1) may be reduced.

[0135] [Polar: Challenger]

[0136] The cathode active material layer (12) may further include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited thereto, and any material used as a carbon-based conductive material in the art may be used. The metal-based conductive material may be, for example, metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material used as a metal-based conductive material in the art may be used. The content of the conductive material included in the cathode active material layer (12) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the cathode active material layer (12).

[0137] The cathode active material layer (12) may further include a second carbon-based material as a conductive material. The second carbon-based material may include, for example, a fibrous carbon-based material. The aspect ratio of the fibrous carbon-based material may be, for example, 5 or more, 10 or more, or 20 or more.

[0138] The fibrous carbon-based material may include, for example, fibrous carbon nanostructures. The fibrous carbon nanostructures may include, for example, carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or combinations thereof. The second carbon-based material is distinguished from the first carbon-based material forming part of the composite cathode active material in that it is simply mixed with the composite cathode active material.

[0139] The cathode active material layer (12) may not further include a second carbon-based material. In the cathode active material layer (12), the carbon-based material may be disposed only in the composite cathode active material. The cathode active material layer (12) may not additionally include a second carbon-based material in addition to the composite cathode active material including the first carbon-based material. Since the cathode active material layer does not additionally include a second carbon-based material, the energy density of the cathode and the secondary battery (1) can be improved and the manufacturing process can be simplified.

[0140] [Positive: Binder]

[0141] The positive electrode active material layer (12) may further include a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto, and any binder used in the relevant technical field may be used. The binder content included in the positive electrode active material layer (12) may be, for example, 0.1 wt% to 10 wt%, 0.5 to 5 wt%, or 0.5 to 2 wt% of the total weight of the positive electrode active material layer (12). The binder may be omitted.

[0142] [Positive: Other additives]

[0143] 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.

[0144] 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.

[0145] [Anode: Anode current collector]

[0146] 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.

[0147] The cathode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer can act as an electrochemical fuse and be cut off in case of overcurrent to prevent a short circuit. The limit current and the maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or the maximum current of the positive electrode current collector (11) decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added on the metal layer for connection to the outside. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and lithium battery.

[0148] [Anode: Inert member]

[0149] Referring to FIGS. 6 and 7, 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. 6, 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. 7, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and between the electrolyte layer (30) and the positive electrode current collector (11) facing the electrolyte layer (30). The inactive member (40) is not disposed on one side of the positive electrode current collector (11). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0150] By including an inert member (40), cracking of the electrolyte layer (30) is prevented during the manufacture and / or charging / discharging of the all-solid-state secondary battery (1), and as a result, the cycle characteristics of the all-solid-state secondary battery (2) are improved. In an all-solid-state secondary battery (1) that does not include an inert member (40), when the manufacture and / or charging / discharging of the all-solid-state secondary battery (1) is performed, uneven pressure is applied to the electrolyte layer (30) in contact with the positive electrode (10), which increases the possibility of cracking in the electrolyte layer (30), and thus, a short circuit may occur due to the growth of lithium metal through the crack.

[0151] In the all-solid-state secondary battery (1), the thickness of the inert member (40) is greater than or equal to the thickness of the positive electrode active material layer (12). Alternatively, in the all-solid-state secondary battery (1), the thickness of the inert member (40) is substantially equal to the thickness of the positive electrode (10). Since the thickness of the inert member (40) is equal to the thickness of the positive electrode (10), a uniform pressure is applied between the positive electrode (10) and the electrolyte layer (30), and the positive electrode (10) and the electrolyte layer (30) are sufficiently adhered to each other, so that the interfacial resistance between the positive electrode (10) and the electrolyte layer (30) can be reduced. In addition, since the electrolyte layer (30) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state secondary battery (1), the internal resistance of the electrolyte layer (30) and the all-solid-state secondary battery (1) including the same is reduced.

[0152] The inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the electrolyte layer (30). By the inert member (40) surrounding the side surface of the positive electrode (10) and being in contact with the electrolyte layer (30), cracks in the electrolyte layer (30) that occur due to a pressure difference during the pressing process in the electrolyte layer (30) that does not come into contact with the positive electrode (20) can be effectively suppressed. The inert member (40) surrounds the side surface of the positive electrode (10) and is separated from the negative electrode (20), more specifically, the first negative electrode active material layer (22). The inert member (40) surrounds the side surface of the positive electrode (10), is in contact with the electrolyte layer (30), and is separated from the negative electrode (20). Therefore, the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or a short circuit occurring due to overcharging of lithium, etc., is suppressed. For example, by placing an inert member (40) on one side of the positive electrode active material layer (12) and simultaneously on one side of the positive electrode current collector (11), the possibility of a short circuit occurring due to contact between the positive electrode current collector (11) and the negative electrode (20) is more effectively suppressed.

[0153] Referring to FIGS. 6 and 7, the inert member (40) extends from one side of the positive electrode (30) to the end of the electrolyte layer (30). By extending the inert member (40) to the end of the electrolyte layer (30), cracks occurring at the end of the electrolyte layer (30) can be suppressed. The end of the electrolyte layer (30) is the outermost part that is in contact with the side of the electrolyte layer (30). The inert member (40) extends to the outermost part that is in contact with the side of the electrolyte layer (30). The inert member (40) is separated from the negative electrode (20), more specifically, from the first negative electrode active material layer (22). The inert member (40) extends to the end of the electrolyte layer (30), but does not contact the negative electrode (20). The inert member (40) fills a space extending from, for example, one side of the anode (30) to the end of the electrolyte layer (30).

[0154] Referring to FIGS. 6 and 7, the width of the inert member (40) extending from one side of the positive electrode (10) to the end of the electrolyte layer (30) is, for example, 1 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10%, or 1 to 5% of the width between one side of the positive electrode (10) and the other side opposite to the one side. If the width of the inert member (40) is excessively large, the energy density of the all-solid-state secondary battery (1) is reduced. If the width of the inert member (40) is excessively small, the effect of arranging the inert member (40) is minimal.

[0155] The area of ​​the anode (10) is smaller than the area of ​​the electrolyte layer (30) in contact with the anode (10). An inert member (40) is arranged to surround the side of the anode (10) to compensate for the area difference between the anode (10) and the electrolyte layer (30). By compensating for the difference between the area of ​​the anode (10) and the area of ​​the electrolyte layer (30), cracks in the electrolyte layer (30) caused by the pressure difference during the pressing process are effectively suppressed. For example, the sum of the area of ​​the anode (10) and the area of ​​the inert member (40) is equal to the area of ​​the electrolyte layer (30). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0156] 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).

[0157] 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.

[0158] 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).

[0159] The area of ​​the positive electrode (10) is smaller than the area (S4) 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).

[0160] 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%.

[0161] 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).

[0162] 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.

[0163] 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.

[0164] 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).

[0165] 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.

[0166] 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).

[0167] 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.

[0168] 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).

[0169] 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).

[0170] 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.

[0171]

[0172] [All-solid-state secondary battery]

[0173] An all-solid-state secondary battery according to one embodiment includes the above-described positive electrode; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode. The negative electrode includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0174] Referring to FIGS. 3 to 7, an all-solid-state secondary battery (1) includes a positive electrode (10); a negative electrode (20); and an electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20). The negative electrode (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector.

[0175] [anode]

[0176] See the above mentioned polarities.

[0177] [cathode]

[0178] [Cathode: Cathode active material]

[0179] Referring to FIGS. 3 to 7, the negative electrode (20) includes a first negative electrode active material layer (22). The first negative electrode active material layer (22) includes, for example, a negative electrode active material and a binder.

[0180] 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.

[0181] 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.

[0182] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or semi-metal negative electrode active material.

[0183] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] The metal-based negative electrode active material supported on the carbon-based support includes, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn). The metal oxide includes, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, tellurium (Te) oxide, and zinc (Zn) oxide. The metal oxide includes, for example, Au x O y (0 <x≤2, 0<y≤3), Pt x O y (0 <x≤1, 0<y≤2), Pd x O y (0 <x≤1, 0<y≤1), Si x O y (0 <x≤1, 0<y≤2), Ag x O y (0 <x≤2, 0<y≤1), Al x O y (0 <x≤2, 0<y≤3), Bi x O y (0 <x≤2, 0<y≤3), Sn x O y (0 <x≤1, 0<y≤2), Te x O y(0 <x≤1, 0<y≤3), Zn x The y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x The y (0 <x≤2, 0<y≤3)의 복합체, Pt와 Pt x The y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x The y (0 <x≤1, 0<y≤1)의 복합체, Si와 Si x The y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x The y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x The y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x The y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x The y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x The y (0 <x≤1, 0<y≤3), Zn과 Zn x The y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0191] The carbonaceous support is, for example, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., and any material classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite carbon. Carbonaceous materials are, for example, carbonaceous negative electrode active materials.

[0192] 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.

[0193] [Cathode: Binder]

[0194] 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.

[0195] 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).

[0196] [Cathode: Other additives]

[0197] 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.

[0198] [Cathode: Solid electrolyte]

[0199] 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.

[0200] 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).

[0201] [Cathode: First negative electrode active material layer]

[0202] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer (12) is the first open circuit voltage (1 st Li / Li from open circuit voltage) + It is determined by charging up to the maximum charging voltage. The initial charging capacity of the first negative electrode active material layer (22) is determined by the second open circuit voltage (2 nd Li / Li from open circuit voltage) +It is determined by charging up to 0.01 V.

[0203] 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) to the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.45, 0.01 to 0.4, 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 multiple types of negative electrode active materials are used, the charge capacity density × mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer (22). The charge capacity density of each of the positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell using lithium metal as a counter electrode.

[0204] The initial charge capacity of each of the positive electrode active material layer (12) and the first negative electrode active material layer (22) is a constant current density, for example, 0.1 mA / cm 2 can be directly measured using an all-solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, for example, 3.0 V (vs. Li / Li + ) can be performed by charging to an operating voltage of up to 0.01 V for the negative electrode, for example, lithium metal, from a second open circuit voltage (OCV). For example, an all-solid-state half-cell having a positive electrode active material layer can be charged to an operating voltage of up to 0.1 mA / cm from a first open circuit voltage (OCV) to 3.0 V. 2 The all-solid-state half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 The all-solid-state half-cell having the positive electrode active material layer can be charged from the first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0205] 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).

[0206] 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.

[0207] [Cathode: Second negative electrode active material layer]

[0208] Referring to FIG. 5, the all-solid-state secondary battery (1) further includes, after being charged, a second negative electrode active material layer (24) disposed, for example, between the negative electrode current collector (21) and the first negative electrode active material layer (22). The second negative electrode active material layer (24) is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer (24) is a metal layer containing lithium, it functions as, for example, a lithium reservoir. The lithium alloy is, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., and any lithium alloy used in the art may be used. The second negative electrode active material layer (24) may be made of one of these alloys or lithium, or may be made of several types of alloys. The second negative electrode active material layer (24) is, for example, a plated layer. The second negative electrode active material layer (24) is deposited between the first negative electrode active material layer (22) and the negative electrode current collector (21), for example, during the charging process of an all-solid-state secondary battery (1).

[0209] 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.

[0210] 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).

[0211] 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).

[0212] [Cathode: Negative current collector]

[0213] 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.

[0214] Referring to FIG. 4, the all-solid-state secondary battery (1) may further include a thin film (23) containing an element capable of forming an alloy with lithium on one surface of the negative electrode current collector (21). The thin film (23) is disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22). The thin film (23) contains, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film (23) is composed of one of these metals or an alloy of several types of metals. By placing the thin film (23) on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (24) deposited between the thin film (23) and the first negative electrode active material layer (22) becomes flatter, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0215] 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.

[0216] 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.

[0217] [Electrolyte layer]

[0218] [Electrolyte layer: electrolyte]

[0219] Referring to FIGS. 3 to 7, the electrolyte layer (30) includes an electrolyte disposed between the positive electrode (10) and the negative electrode (20). The electrolyte may include, for example, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0220] The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0221] The solid electrolyte is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte is, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x, at least one selected from 0≤x≤2. The sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one containing sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form a solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0222] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

[0223] <Chemical Formula 1>

[0224] Li + 12-n-x A n+ X 2- 6-x Y - x

[0225] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1≤n≤5, 0≤x≤2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-xPS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0226] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the electrolyte layer by Li can be effectively suppressed.

[0227] Oxide solid electrolytes include, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. The oxide-based solid electrolyte is manufactured, for example, by a sintering method.

[0228] Oxide-based solid electrolytes include, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M doped LLZO, M=Ga, W, Nb, Ta, or Al, 0 <a<2, 0≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체전해질이다.

[0229] The polymer solid electrolyte can be selected from among polymer solid electrolytes used in composite positive electrode active materials, for example.

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

[0231] The polymer gel electrolyte may be selected from among polymer gel electrolytes used in composite positive electrode active materials, for example.

[0232] [Electrolyte layer: binder]

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

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

[0235]

[0236] As used herein, the term “alkyl” refers to a fully saturated branched or unbranched (or straight-chain or linear) hydrocarbon.

[0237] Non-limiting examples of “alkyl” include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, and the like.

[0238] One or more hydrogen atoms in "alkyl" are selected from the group consisting of a halogen atom, a C1-C20 alkyl group substituted with a halogen atom (e.g., CCF3, CHCF2, CH2CH3, CH2F, CCl3, etc.), a C1-C20 alkoxy, a C2-C20 alkoxyalkyl, a hydroxy group, a nitro group, a cyano group, an amino group, an amidino group, a hydrazine, a hydrazone, a carboxyl group or a salt thereof, a sulfonyl group, a sulfamoyl group, a sulfonic acid group or a salt thereof, a phosphoric acid or a salt thereof, or a C1-C20 alkyl group, a C2-C20 alkenyl group, a C2-C20 alkynyl group, a C1-C20 heteroalkyl group, a C6-C20 aryl group, a C6-C20 arylalkyl group, a C6-C20 heteroaryl group, a C7-C20 It may be substituted with a heteroarylalkyl group, a C6-C20 heteroaryloxy group, a C6-C20 heteroaryloxyalkyl group, or a C6-C20 heteroarylalkyl group.

[0239] As used herein, “cycloalkyl” refers to an alkyl group that forms a ring.

[0240] As used herein, the term “halogen” includes fluorine, bromine, chlorine, and iodine.

[0241] As used herein, the term "alkenyl" refers to a branched or unbranched hydrocarbon having at least one carbon-carbon double bond. Non-limiting examples of alkenyl groups include vinyl, allyl, butenyl, propenyl, isobutenyl, etc., and one or more hydrogen atoms in the alkenyl group may be replaced with the same substituents as in the case of the alkyl group described above.

[0242] As used herein, the term "alkynyl" refers to a branched or unbranched hydrocarbon having at least one carbon-carbon triple bond. Non-limiting examples of "alkynyl" include ethynyl, butynyl, isobutynyl, isopropynyl, and the like.

[0243] One or more hydrogen atoms in “alkynyl” may be replaced with the same substituents as in the case of the alkyl group described above.

[0244] As used herein, the term "aryl" also includes groups in which an aromatic ring is optionally fused to one or more carbon rings. Non-limiting examples of "aryl" include phenyl, naphthyl, tetrahydronaphthyl, and the like. Furthermore, one or more hydrogen atoms in an "aryl" group may be replaced with a substituent similar to the alkyl group described above.

[0245] The term "heteroaryl" as used herein refers to a monocyclic or bicyclic organic group containing one or more heteroatoms selected from N, O, P, or S, and the remaining ring atoms being carbon. A heteroaryl group contains, for example, 1-5 heteroatoms and 5-10 ring members. S or N can be oxidized to have various oxidation states.

[0246] Examples of heteroaryl include thienyl, furyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2,5-oxadiazolyl, 1,3,4-oxadiazolyl group, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, 1,3,4-thiadiazolyl, isothiazol-3-yl, isothiazol-4-yl, isothiazol-5-yl, oxazol-2-yl, oxazol-4-yl, oxazol-5-yl, isoxazol-3-yl, isoxazol-4-yl, isoxazol-5-yl, 1,2,4-triazol-3-yl, 1,2,4-triazol-5-yl, 1,2,3-triazol-4-yl, 1,2,3-triazol-5-yl, tetrazolyl, pyrid-2-yl, pyrid-3-yl, 2-pyrazin-2yl, pyrazin-4-yl, pyrazin-5-yl, 2-pyrimidin-2-yl, 4-pyrimidin-2-yl, or 5-pyrimidin-2-yl.

[0247] “Heteroaryl” includes heteroaromatic rings optionally fused to one or more aryl, cycloaliphatic, or heterocycles.

[0248] 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.

[0249] (composite manufacturing)

[0250] Manufacturing Example 1: Li2S-LiI-CNF composite

[0251] 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.

[0252] 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, 600 rpm, and 10 h.

[0253] A Li2S-LiI-CNF composite was used as a composite cathode active material.

[0254] Manufacturing Example 2: Li2S-LiCl-CNF composite

[0255] A Li2S-LiCl complex was prepared in the same manner as in Preparation Example 1, except that LiCl was used instead of LiI.

[0256] A Li2S-LiCl-CNF composite was used as a composite cathode active material.

[0257]

[0258] (Manufacturing of composite cathode active materials)

[0259] Example 1: Li2S-LiI-CNF / organic filler (polymer) composite, 3 wt% organic filler

[0260] Polyethylene oxide (Me = 600,000 Dalton) and LiTFSI were added to acetonitrile and mixed for more than 12 hours, and then the solvent was removed to prepare a polymer organic filler. The molar ratio of polyethylene oxide to LiTFSI was 1:20. The composite prepared in Manufacturing Example 1 and the polymer organic filler were mixed in a weight ratio of 97:3 to prepare a mixture. The mixture was mechanically milled using a ball mill to prepare a composite cathode active material. The milling conditions were 25°C and 200 rpm for 1 hour. The polymer organic filler corresponds to a solid polymer electrolyte.

[0261] The composite cathode active material has a core / shell structure in which a shell containing an organic filler is arranged on a composite core. The structure of the composite cathode active material was confirmed from a scanning electron microscope image of a cross-section of the composite cathode active material.

[0262] Example 2: Li2S-LiI-CNF / organic filler (polymer) composite, 5 wt% organic filler

[0263] A composite cathode active material was manufactured in the same manner as in Example 1, except that a mixture of the composite manufactured in Manufacturing Example 1 and a polymer organic filler was used in a weight ratio of 95:5.

[0264] Example 3: Li2S-LiI-CNF / organic filler (polymer) composite, 10 wt% organic filler

[0265] A composite cathode active material was manufactured in the same manner as in Example 1, except that a mixture of the composite manufactured in Manufacturing Example 1 and a polymer organic filler was used in a weight ratio of 90:10.

[0266] Example 4: Li2S-LiI-CNF / organic filler (polymer) composite, 15 wt% organic filler

[0267] A composite cathode active material was manufactured in the same manner as in Example 1, except that a mixture of the composite manufactured in Manufacturing Example 1 and a polymer organic filler was used in a weight ratio of 85:15.

[0268] Example 5: Li2S-LiI-CNF / organic filler (polymer) composite, 20 wt% organic filler

[0269] A composite cathode active material was manufactured in the same manner as in Example 1, except that a mixture of the composite manufactured in Manufacturing Example 1 and a polymer organic filler was used in a weight ratio of 80:20.

[0270] Example 6: Li2S-LiCl-CNF / organic filler (polymer) composite, 10 wt% organic filler

[0271] A composite cathode active material was manufactured in the same manner as in Example 1, except that a mixture of the composite manufactured in Manufacturing Example 2 and a polymer organic filler was used in a weight ratio of 90:10.

[0272] Example 7: Li2S-LiI-CNF / organic filler (P-containing compound) composite, 10 wt% organic filler

[0273] Tris(2,2,2-trifluoroethyl) phosphate and LiTFSI were added to acetonitrile and mixed for more than 12 hours, and then the solvent was removed to prepare a P-containing compound organic filler. The molar ratio of the P-containing compound and LiTFSI was 1:20. The P-containing compound organic filler corresponds to the P-containing compound electrolyte.

[0274] A mixture was prepared by mixing the composite prepared in Manufacturing Example 1 and the P-containing compound organic filler at a weight ratio of 90:10. The mixture was mechanically milled using a ball mill to prepare a composite cathode active material. The milling conditions were 25°C and 200 rpm for 1 hour.

[0275] The composite cathode active material had a core / shell structure in which a shell containing a P-containing compound organic filler was arranged on a composite core. The structure of the composite cathode active material was confirmed from a scanning electron microscope image of a cross-section of the composite cathode active material.

[0276] Reference Example 1

[0277] The mixture prepared by mixing the composite manufactured in Manufacturing Example 1 with polyethylene oxide (Me = 600,000 Dalton) and LiTFSI was used as a composite cathode active material.

[0278] The molar ratio of polyethylene oxide and LiTFSI was 1:20. The complex manufactured in Manufacturing Example 1 and the 1:20 molar ratio mixture of polyethylene oxide and LiTFSI were mixed at a weight ratio of 97:3.

[0279] Comparative Example 1: Li2S-LiI-CNF alone

[0280] The composite manufactured in Manufacturing Example 1 was used as a composite cathode active material.

[0281]

[0282] (Manufacturing of positive and secondary batteries)

[0283] Example 8

[0284] (Polar electrode manufacturing)

[0285] The composite cathode active material manufactured in Example 1 was prepared as a cathode active material. Li6PS5Cl, an argyrodite-type crystal (D50 = 1 ㎛, 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 = 60:39:1 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill.

[0286] 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.

[0287] (Cathode manufacturing)

[0288] 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.

[0289] 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.

[0290] (Manufacturing of solid electrolyte layer)

[0291] A mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of the solid electrolyte, Li6PS5Cl, which is an argyrodite-type crystal (D50=3.0 ㎛, crystalline). Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied using a bar coater onto a 15 ㎛ thick nonwoven fabric placed on a 75 ㎛ thick PET substrate, and dried in air at 80 ℃ for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 80 ℃ for 2 hours to prepare a solid electrolyte layer.

[0292] (inert absence)

[0293] 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.

[0294] 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 ㎛.

[0295] 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.

[0296] (Manufacturing of all-solid-state secondary batteries)

[0297] 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.

[0298] 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.

[0299] 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.

[0300] Examples 9 to 14

[0301] A positive electrode and an all-solid-state secondary battery were manufactured in the same manner as in Example 8, except that the composite positive electrode active materials manufactured in Examples 2 to 7 were used.

[0302] Reference Example 2

[0303] A positive electrode and an all-solid-state secondary battery were manufactured in the same manner as in Example 8, except that the composite positive electrode active material manufactured in Reference Example 1 was used.

[0304] Comparative Example 2

[0305] A positive electrode and an all-solid-state secondary battery were manufactured in the same manner as in Example 8, except that the composite positive electrode active material manufactured in Comparative Example 1 was used.

[0306]

[0307] Evaluation Example 1: XRD Analysis and Scanning Electron Microscopy Analysis

[0308] XRD spectra were measured using Cu Kα radiation for the raw material (bare) Li2S used in Manufacturing Example 1, the pulverized Li2S, the Li2S-LiI complex manufactured in the first step in Manufacturing Example 1, and the Li2S-LiI-CNF complex manufactured in Manufacturing Example 1.

[0309] Some of the measurement results are shown in Table 1 and Fig. 1 below. The Li2S crystallite size and lattice constant were derived from the first peak for the (111) crystal plane appearing at a diffraction angle of 2θ = 27° ± 2.0° in the XRD spectrum.

[0310] Crushed Li2S was prepared by milling under the same conditions as in the first step of Manufacturing Example 1, except that the 30:20 weight ratio mixture of Li2S and LiI was changed to 50 parts by weight of Li2S.

[0311] The particle sizes (D50 particle size and D10 particle size) of the composites were measured using a laser-based particle size analyzer (PSA) for the raw material Li2S used in Manufacturing Example 1, the pulverized Li2S, and the Li2S-LiI-CNF composite manufactured in Manufacturing Example 1.

[0312] Scanning electron microscope images of the raw material Li2S used in Example 1 and the Li2S-LiI-CNF composite manufactured in Example 1 are shown in FIGS. 2a and 2b, respectively.

[0313] The Li2S particle size of the composite was measured using a scanning electron microscope. The measurement results are shown in Table 1 below.

[0314] Li2S crystallite size [nm]Li2S particle size [㎛]bare Li2S658milled Li2S15-Li2S-LiI-CNF compositeless than10less than1

[0315] As shown in Table 1, the Li2S particle size and crystallite size of the Li2S-LiI-CNF composite were significantly reduced compared to that of bare Li2S. Although not shown in Table 1, the lattice constant of the Li2S-LiI-CNF composite of Preparation Example 1 was larger than that of bare Li2S. The increase in the lattice constant of the Li2S-LiI composite compared to that of bare Li2S was thought to be due to the dissolution of LiI into the Li2S crystal. Therefore, it was confirmed that the Li2S-LiI composite formed a solid solution in the Li2S-LiI-CNF composite.

[0316] The D50 particle size of the complex manufactured in Manufacturing Example 1 was about 5 ㎛, and the D10 particle size was about 1 ㎛ or more.

[0317]

[0318] Evaluation Example 2: Thermal Stability Evaluation

[0319] The composite cathode active material of Comparative Example 1 ignited during the sieving process of the manufactured composite cathode active material powder in an atmosphere at 25°C and 1 atm. The carbon-based material of the composite cathode active material ignited as it reacted with oxygen in the air.

[0320] In contrast, in the composite cathode active materials of Examples 1 to 7, no ignition occurred during the sieving process of the manufactured composite cathode active material powder in an atmosphere at 25°C and 1 atm. The thermal stability of the composite cathode active material increased by covering the carbon-based material of the composite with an organic filler. Consequently, ignition of the composite cathode active material was suppressed.

[0321] Figure 8 is a scanning electron microscope image of the side surface of a pellet prepared by pressing the composite positive electrode material of Example 3 with isostatic pressure.

[0322] Figure 9 is a scanning electron microscope image of the side of a pellet prepared by pressing the composite positive electrode material of Comparative Example 1 with isotropic pressure.

[0323] As shown in Fig. 8, the side surfaces of the pellets manufactured using the composite cathode active material of Example 3 were flat and smooth. The pellets manufactured from the composite cathode active material of Example 3 did not ignite even after being exposed to air at 25°C and 1 atm for 72 hours.

[0324] As shown in Fig. 9, the side surface of the pellet manufactured using the composite cathode active material of Comparative Example 1 contained numerous protrusions and depressions and was rough. The pellet manufactured from the composite cathode active material of Comparative Example 1 ignited when exposed to air at 25°C and 1 atm for 72 hours.

[0325] It was determined that the composite cathode active material of Example 3 had improved thermal stability, i.e., oxidation resistance, compared to the composite cathode active material of Comparative Example 1.

[0326]

[0327] Evaluation Example 3: Moisture Stability Evaluation

[0328] The composite positive electrode active materials manufactured in Examples 1 to 7 and Comparative Example 1 were pressed with isostatic pressure to prepare pellets.

[0329] Ionic conductivity was measured for each of the prepared pellets, pellets left in air for 24 hours after preparation, and pellets left in air for 72 hours after preparation.

[0330] After placing a separator layer impregnated with a liquid electrolyte (1 M LiTFSI in propylene carbonate (PC)) on both sides of the pellet, a lithium foil was placed on the separator layer to complete an electron blocking cell.

[0331] Ionic conductivity was measured using the DC polarization method at 45°C and 1 atm. After applying a DC voltage of 50 mV to the symmetric cell, the steady-state current was measured when the current change per minute decreased to less than 1 μA / g after 1 h.

[0332] The ionic resistance of the composite cathode active material was calculated from the measured current and pellet volume, and the ionic conductivity was calculated from this. Some of the obtained ionic conductivities are shown in Table 2 below.

[0333] Prepared pellet [mS / cm] Pellets left 24 hours after preparation [mS / cm] Pellets left 72 hours after preparation [mS / cm] Example 2 (organic filler 5 wt%) 0.072 0.060 0.049 Example 3 (organic filler 10 wt%) 0.084 0.074 0.062 Example 4 (organic filler 15 wt%) 0.045 0.041 0.036 Comparative Example 1 (organic filler 0 wt%) 0.052 0.036 0.021

[0334] As shown in Table 2, the composite cathode active materials of Examples 2 to 4 had ionic conductivity of at least 68% of the ionic conductivity before being left in the air for 72 hours. In contrast, the composite cathode active material of Comparative Example 1 had ionic conductivity of about 40% of the ionic conductivity before being left in the air for 72 hours.

[0335] It was determined that in the composite cathode active materials of Examples 2 to 4, the organic filler disposed on the surface of the core effectively suppressed deterioration of the composite cathode active material due to moisture, i.e., reduction in ionic conductivity, by blocking contact between the core and moisture.

[0336]

[0337] Evaluation Example 4: Charge / Discharge Test

[0338] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 8 to 14, Reference Example 2, and Comparative Example 2, which employed the composite positive electrode active materials manufactured in Examples 1 to 7, Reference Example 1, and Comparative Example 1, 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 was performed by charging for 20 hours at a constant current of 0.05 C until the battery voltage reached 2.5 V to 2.8 V. Subsequently, discharging was performed for 20 hours at a constant current of 0.05 C until the battery voltage reached 0.3 V.

[0341] The discharge capacity of the first cycle was taken as the standard capacity. The standard capacity is expressed as the specific capacity of Li2S in Table 3 below.

[0342] After the second cycle, charging and discharging were performed for up to 30 cycles under the same conditions as the first cycle. The measurement results are shown in Table 3 below. The initial efficiency is expressed by the following mathematical equation (1), and the capacity retention rate is expressed by the following mathematical equation (2).

[0343] <Mathematical Formula 1>

[0344] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0345] <Mathematical Formula 2>

[0346] Capacity retention rate [%] = [30th cycle discharge capacity / 1st cycle discharge capacity] × 100

[0347] Specific capacity [mAh / g] Initial efficiency [%] Capacity retention [%] Example 8: Li2S-LiI-CNF / organic filler (polymer) composite, organic filler 3 wt% 5007560 Example 9: Li2S-LiI-CNF / organic filler (polymer) composite, organic filler 5 wt% 6507880 Example 10: Li2S-LiI-CNF / organic filler (polymer) composite, organic filler 10 wt% 90086200 Example 11: Li2S-LiI-CNF / organic filler (polymer) composite, organic filler 15 wt% 82081180 Example 12: Li2S-LiI-CNF / organic filler (polymer) composite, organic filler 20 wt% 80078150 Example 13: Li2S-LiCl-CNF / organic filler (polymer) composite, organic filler 10 wt% 81082150 Example 14: Li2S-LiI-CNF / organic filler (P-containing compound) composite, organic filler 10 wt% 88086200 Reference Example 2: Li2S-LiI-CNF, simple mixture of polymer and lithium salt, polymer+lithium salt mixture 3 wt% 3006910 Comparative Example 2: Li2S-LiI-CNF core alone, organic filler 0 wt% 8007830

[0348] As shown in Table 3, the all-solid-state secondary batteries of Examples 8 to 14 including the composite cathode active materials of Examples 1 to 7 had improved discharge capacity, initial efficiency, and lifespan characteristics compared to the all-solid-state secondary batteries of Reference Example 2 and Comparative Example 2 including the composite cathode active materials of Reference Example 1 and Comparative Example 1. The composite cathode active material of Comparative Example 1 had lower charge-discharge characteristics compared to the composite cathode active materials of Examples 1 to 7 due to lower thermal stability and moisture stability and side reactions with the sulfide-based solid electrolyte during the charge-discharge process.

[0349] The composite cathode active material of Reference Example 1 was a simple mixture, and the organic filler was not effectively coated on the core, so the charge / discharge characteristics were lowered compared to the composite cathode active materials of Examples 1 to 7.

[0350] Although not shown in the drawing, it was confirmed that a lithium metal layer was formed between the first negative electrode active material layer and the negative electrode current collector in the all-solid-state secondary batteries of Examples 8 to 14 after initial charging. This was confirmed through a cross-sectional scanning electron microscope image of the all-solid-state secondary battery.

[0351] [Explanation of symbols]

[0352] 1 All-solid-state secondary battery 10 Cathode

[0353] 11. Cathode current collector 12. Cathode active material layer

[0354] 20 Cathode 21 Cathode current collector

[0355] 22 First negative electrode active material layer 23 Thin film

[0356] 24 Second negative electrode active material layer 30 Electrolyte layer

[0357] 40 Inert Absences

[0358] According to one aspect, it is possible to provide a composite cathode active material having improved thermal stability and moisture stability by including an organic filler.

[0359] According to another aspect, it is possible to provide an all-solid-state secondary battery providing improved capacity and initial efficiency by including a composite cathode active material having improved thermal stability and moisture stability.

Claims

1. A core; and a shell disposed on at least a portion of the core, The above core comprises a composite of Li2S, a first ionic compound, and a first carbon-based material, The above shell contains an organic filler, A composite cathode active material, wherein the organic filler comprises a second ionic compound; and a polymer, a phosphorus (P)-containing compound, or a combination thereof.

2. In the first paragraph, the complex of Li2S, the first ionic compound and the first carbon-based material Li2S-Li a X b -C (1≤a≤5, 1≤b≤5) complex, Li2S-M1 a X b -C (1≤a≤5, 1≤b≤5) complex, Li2S-M1 a S b -C (1≤a≤5, 1≤b≤5) or a combination thereof, The above M1 is Mg, Ca, Sr, Ba, Al, Ga, In, V, Nb, Sc, Fe, Ru, Os or a combination thereof, 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, a composite cathode active material.

3. In the first paragraph, the first ionic compound comprises a first lithium salt, a first metal salt, a first metal sulfide or a combination thereof, The above first lithium salt is a binary compound or a ternary compound, The above binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3 or a combination thereof, The above ternary compound comprises Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or a combination thereof, The above first metal salt comprises AlF3, AlCl3, AlBr3, CaF2, CaCl2, CaBr2 or a combination thereof, A composite cathode active material, wherein the first metal sulfide comprises FeS, MgS, CaS, Al2S3, V2S3FeS2, VS2, MnS, NiS, CuS or a combination thereof.

4. In the first paragraph, the complex of Li2S, the first ionic compound and the first carbon-based material includes a solid solution of Li2S and the first ionic compound, A composite cathode active material, wherein the size of Li2S crystallites obtained from the XRD spectrum of the composite of the above Li2S, the first ionic compound, and the first carbon-based material is 20 nm or less.

5. In the first paragraph, in the complex of Li2S, the first ionic compound, and the first carbon-based material, the molar ratio of Li2S and the first ionic compound is 50:50 to 95:5, The composite of the above Li2S, the first ionic compound and the first carbon-based material comprises 10 to 80 parts by weight of Li2S, 1 to 40 parts by weight of the first ionic compound and 1 to 20 parts by weight of the first carbon-based material, A composite cathode active material, wherein the size of the composite of the Li2S, the first ionic compound, and the first carbon-based material is 1 to 20 ㎛, and the D10 particle size of the composite of the Li2S, the first ionic compound, and the first carbon-based material is 1 ㎛ or more.

6. In the first paragraph, the first carbon-based material includes amorphous carbon, crystalline carbon, or a combination thereof, The above first carbon-based material comprises a carbon nanostructure, and the carbon nanostructure comprises carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, graphene, or a combination thereof. The first carbon-based material comprises a fibrous carbon-based material, a particulate carbon-based material, or a combination thereof, A composite cathode active material, wherein the particulate carbon-based material comprises carbon black, Ketjen black, acetylene black, Denka black, thermal black, channel black, graphite, activated carbon or a combination thereof.

7. In the first paragraph, the second ionic compound comprises a second lithium salt, an ionic liquid or a combination thereof, The above polymer is selected from the group consisting of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA), poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylatlacene-2-sulfonate 9,10-diphenylanthracene-2-sulfonate, DPASLi + ) or a combination thereof, a composite cathode active material.

8. In the first paragraph, the phosphorus (P)-containing compound comprises a phosphate compound, a phosphite compound, or a combination thereof, A composite cathode active material, wherein the phosphate compound is represented by the following chemical formula 1, and the phosphite compound is represented by the following chemical formula 2: <Chemical Formula 1> In the above formula, R1, R2, and R3 are each independently a hydrogen atom; a fluorine atom; a C1 to C5 alkyl group substituted or unsubstituted with a halogen; a C4 to C10 cycloalkyl group substituted or unsubstituted with a halogen; a C5 to C10 aryl group substituted or unsubstituted with a halogen; a C2 to C10 heteroaryl group substituted or unsubstituted with a halogen; or a C2 to C10 alkenyl group substituted or unsubstituted with a halogen, The phosphite compound can be represented, for example, by the following chemical formula 2. <Chemical Formula 2> In the above formula, R4, R5, and R6 are each independently a hydrogen atom; a fluorine atom; a C1 to C5 alkyl group substituted or unsubstituted with a halogen; a C4 to C10 cycloalkyl group substituted or unsubstituted with a halogen; a C5 to C10 aryl group substituted or unsubstituted with a halogen; a C2 to C10 heteroaryl group substituted or unsubstituted with a halogen; or a C2 to C10 alkenyl group substituted or unsubstituted with a halogen.

9. In the 8th paragraph, the phosphate compound comprises trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate or a combination thereof. The above phosphite compound includes trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphite or a combination thereof. A composite cathode active material in which an organic solvent is absent (free) in the above organic filler.

10. In the first paragraph, the organic filler comprises a polymer electrolyte, an electrolyte containing a phosphorus (P)-containing compound, or a combination thereof, The polymer electrolyte comprises a polymer solid electrolyte, a polymer gel electrolyte or a combination thereof, and the content of the organic filler is 1 to 20 wt% of the total weight of the composite cathode active material. A composite cathode active material having a shell thickness of 2 ㎛ or less.

11. In the first paragraph, the ionic conductivity of the composite cathode active material is 0.03 mS / cm or more after 72 hours in an atmosphere at 25°C and 1 atm. A composite cathode active material which does not ignite during sieving in an atmosphere at 25°C and 1 atm.

12. A cathode current collector; and a cathode active material layer disposed on one or both sides of the cathode current collector, A cathode, wherein the cathode active material layer comprises a composite cathode active material according to any one of claims 1 to 11 and a solid electrolyte.

13. In the 12th paragraph, the positive electrode active material layer further includes a second carbon-based material, The above second carbon-based material comprises a fibrous carbon-based material, The above fibrous carbon material comprises fibrous carbon nanostructures, An anode, wherein the fibrous carbon nanostructure comprises carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods or a combination thereof.

14. A positive electrode according to Article 12; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, An all-solid-state secondary battery, 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 includes a negative electrode active material and a binder, An all-solid-state secondary battery, wherein 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-based negative electrode active material capable of being alloyed with lithium. The above carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon or a combination thereof. An all-solid-state secondary battery, wherein the metal-based negative electrode active material includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

17. In the 15th paragraph, the negative electrode active material comprises a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid, 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.

18. In the 14th paragraph, a second negative electrode active material layer is further included, The second negative electrode active material layer 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 contains lithium or a lithium alloy.

19. In the 14th paragraph, the electrolyte layer includes a solid electrolyte, a gel electrolyte or a combination thereof, The above solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof. The above gel electrolyte comprises a polymer gel electrolyte, The above sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX, X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , at least one selected from 0≤x≤2, The above sulfide-based solid electrolyte includes an argyrodite-type solid electrolyte, The above argyrodite-type solid electrolyte comprises at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I, An all-solid-state secondary battery, wherein the density of the argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc.

20. In the 14th paragraph, the positive electrode includes a positive 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. The above 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. An all-solid-state secondary battery further comprising an inert member disposed on one side of the positive electrode.

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