Positive electrode active material, positive electrode including the same, solid-state secondary battery including the positive electrode, and method for preparing positive electrode active material

Abstract

Disclosed are a positive electrode active material, a positive electrode including the positive electrode active material, a solid-state secondary battery including the positive electrode, and a method for producing the positive electrode active material, in which the positive electrode active material includes secondary particles, the secondary particles are aggregated from primary particles including a composite containing Li2S, and a D10 size of the secondary particles is 5 μm or more.

Description

Technical Field

[0001] One or more embodiments of this disclosure relate to a positive electrode active material, a positive electrode including the positive electrode active material, a solid-state secondary battery including the positive electrode, and a method for preparing the positive electrode active material. Background Technology

[0002] Based on recent industry developments and market demands, there is an active search for and development of batteries with relatively high energy density and stability. For example, lithium batteries are used for one or more suitable purposes in information devices, communication devices, automobiles, etc. In automobiles, safety is given paramount importance because it directly impacts human well-being.

[0003] Lithium-ion batteries using liquid electrolytes are more prone to catching fire and / or exploding due to short circuits. Solid-state secondary batteries using solid electrolytes instead of liquid electrolytes have been proposed. Compared to liquid electrolytes, solid electrolytes are likely less likely to cause fires.

[0004] Therefore, by using a solid electrolyte instead of a liquid electrolyte, solid-state secondary batteries can reduce the risk of fire or explosion. Solid-state batteries offer improved safety. Summary of the Invention

[0005] Technical issues One or more aspects of this disclosure relate to a positive electrode active material having a reduced proportion of fine particles of small particle size, a positive electrode including the positive electrode active material, and a solid-state secondary battery.

[0006] One or more aspects of this disclosure relate to a method for preparing a positive electrode active material in which the proportion of fine particles having a small particle size is reduced.

[0007] Technical solution According to one or more embodiments of this disclosure, the positive electrode active material includes: secondary particles, which are aggregated from primary particles comprising (e.g., all comprising) a Li2S-containing complex, wherein the D10 size (e.g., diameter or major axis) of the secondary particles is 5 μm or greater.

[0008] According to one or more embodiments of the present disclosure, the positive electrode for a solid-state secondary battery includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector and including the positive electrode active material.

[0009] According to one or more embodiments of the present disclosure, a solid-state secondary battery includes: a positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the positive electrode includes the aforementioned positive electrode for a solid-state secondary battery.

[0010] According to one or more embodiments of this disclosure, a method for preparing a composite positive electrode active material includes: preparing primary particles comprising a Li2S-containing composite by ball milling a composition containing Li2S; and preparing secondary particles (e.g., each of the secondary particles) by granulation of the primary particles, wherein the D10 size of the secondary particles is 5 μm or greater.

[0011] Beneficial effects of the invention According to one or more embodiments of this disclosure, the positive electrode active material can reduce side reactions caused by such fine particles due to having a relatively low proportion of fine particles with small particle size, and has excellent or suitable ionic conductivity and electronic conductivity, thus providing a solid-state secondary battery with improved charge-discharge characteristics. Attached Figure Description

[0012] Figure 1 This is a schematic cross-sectional view of a solid-state secondary battery according to one or more embodiments of the present disclosure.

[0013] Figure 2 This is a schematic cross-sectional view of a solid-state secondary battery according to one or more embodiments of the present disclosure.

[0014] Figure 3 This is a schematic cross-sectional view of a solid-state secondary battery according to one or more embodiments of the present disclosure.

[0015] Figure 4 This is a schematic cross-sectional view of a solid-state secondary battery according to one or more embodiments of the present disclosure.

[0016] Figure 5 This is a schematic cross-sectional view of a solid-state secondary battery according to one or more embodiments of the present disclosure. Detailed Implementation

[0017] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will also be understood that terms (such as those defined in common dictionaries) shall be interpreted as having the same meaning as they have in the context of the specification and / or the relevant field, and shall not be interpreted in an idealized or overly formal sense, unless expressly defined herein.

[0018] Embodiments are described herein with reference to schematic cross-sectional views as idealized examples. Thus, variations in the shapes shown will be expected due to, for example, manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions shown herein, but rather include, for example, shape deviations caused by manufacturing processes. For example, regions shown or described as flat may generally have rough and / or non-linear characteristics. Furthermore, angles shown as sharp may be rounded (or chamfered). Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shapes of the regions, nor are they intended to limit the scope of this disclosure.

[0019] However, this disclosure may be embodied in various different forms and should not be construed as being limited to the embodiments shown herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete and will fully convey to those skilled in the art the aspects and features of this disclosure. The same reference numerals may be used for the same components.

[0020] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, "connected to" another element, or "on" another element, the element may be directly on, directly connected to, or directly on the other element, or one or more intermediary elements may be present. Conversely, when an element is referred to as being "directly on" another element or "directly on" another element, no intermediary element is present.

[0021] It will be understood that although the terms “first,” “second,” “third,” etc., may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. For example, without departing from the spirit and scope of this disclosure, the first element, first component, first region, first layer, or first part described below may be referred to as a second element, second component, second region, second layer, or second part.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are also intended to include the plural forms that include “at least one.” The term “at least one” should not be construed as limited to the singular form. It will also be understood that when the terms “comprising” or “including,” “having,” and / or variations thereof are used in this specification, it indicates the presence of the stated features, regions, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0023] Furthermore, for ease of explanation, spatial relative terms such as “lower,” “bottom,” “below,” “upper,” “top,” “above,” etc., are used herein to describe the relationship between one element or feature and another element(s) as shown in the accompanying drawings. It will be understood that, in addition to the orientations depicted in the drawings, the spatial relative terms are intended to cover different orientations of the device while it is being used or operated. For example, if one of the devices in the drawings is flipped, the element described as being “lower” or “bottom” on the other element will subsequently be oriented to be “upper” or “top” on the other element. Thus, example terms such as “lower” can therefore cover both “lower” and “upper” orientations. The device may be placed in other orientations (it may be rotated 90 degrees or in different directions), and the spatial relative terms used herein can be interpreted accordingly.

[0024] "Group" refers to a group in the periodic table of elements according to the group numbering system of the International Union of Pure and Applied Chemistry ("IUPAC"), from group 1 to group 18.

[0025] Unless the context clearly indicates otherwise, the terms “diameter,” “particle size,” or “particle diameter” as used herein refer to the average particle size when the particles are spherical, and to the average major axis length when the particles are non-spherical. Particle size can be measured using a particle size analyzer (PSA). The terms “particle size” or “particle diameter” refer to, for example, the average particle size. As used herein, the term “average particle diameter” refers to, for example, the median particle size (D50).

[0026] D50 (e.g., D50 size) can refer to the average diameter (or size) of 50% of the particles in a particle size distribution (e.g., a cumulative distribution), and refers to the value corresponding to 50% of the particle size from the smallest particle in a cumulative distribution curve accumulated in order from the smallest to the largest particle size, such as by laser diffraction, when the total number of particles is 100%.

[0027] D90 (e.g., D90 size) can refer to the average diameter (or size) of 90% of the particles in a particle size distribution (e.g., a cumulative distribution), and refers to the value corresponding to 90% of the particle size from the smallest particle in a cumulative distribution curve, such as that measured by laser diffraction, in order from the smallest to the largest particle size, when the total number of particles is 100%.

[0028] D10 (e.g., D10 size) can refer to the average diameter (or size) of 10% of the particles in a particle size distribution (e.g., a cumulative distribution), and refers to the value corresponding to 10% of the particle size from the smallest particle in a cumulative distribution curve, such as that measured by laser diffraction, in order from the smallest to the largest particle size, when the total number of particles is 100%.

[0029] As used herein, the term "metal" refers to metals and metalloids (such as silicon and germanium) that exist in elemental or ionic states.

[0030] As used herein, the term "alloy" refers to a mixture of two or more metals.

[0031] As used herein, the term "electrode active material" refers to electrode materials capable of undergoing lithiation and delithiation.

[0032] As used herein, the term "composite cathode active material" refers to cathode materials capable of undergoing lithiation and delithiation.

[0033] As used herein, the term "negative electrode active material" refers to a negative electrode material capable of lithiation and delithiation.

[0034] As used herein, the terms “lithiation” and “carrying lithiation” refer to the process of adding lithium to an electrode active material.

[0035] As used herein, the terms “delithiation” and “performing delithiation” refer to the process of removing lithium from the electrode active material.

[0036] As used here, the terms “charging” and “performing a charge” refer to the process by which a battery provides electrochemical energy.

[0037] As used herein, the terms “discharge” and “perform a discharge” refer to the process of removing electrochemical energy from a battery.

[0038] As used herein, the terms "positive electrode" and "positive electrode" refer to the electrode that undergoes electrochemical reduction and lithiation during the discharge process.

[0039] As used herein, the terms “negative electrode” and “negative electrode” refer to the electrode that undergoes electrochemical oxidation and delithiation during the discharge process.

[0040] While specific examples are described herein, alternatives, modifications, variations, improvements, and substantial equivalents (including those not currently foreseen or understood) of the examples disclosed herein may exist that can be recognized by the applicant or a person skilled in the art. Therefore, the appended claims, as filed and as they may be modified, are intended to cover all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0041] The following describes in more detail a positive electrode active material according to one or more embodiments, a positive electrode including the positive electrode active material, a solid-state secondary battery including the positive electrode, and a method for preparing the positive electrode active material.

[0042] [Positive electrode active material] The positive electrode active material according to one or more embodiments may include secondary particles formed by the aggregation of primary particles containing a Li2S-containing complex, and the D10 of the secondary particles may be 5 μm or larger.

[0043] For example, adjusting the D10 of the secondary particles to 5 μm or larger results in a reduced proportion of fine particles, which can suppress or reduce side reactions caused by such fine particles. The composite cathode active material can also exhibit improved ionic and electronic conductivity due to the enhanced contact between Li₂S-containing complexes. For instance, by preparing primary particles comprising Li₂S-containing complexes and then aggregating such primary particles to prepare secondary particles, the cathode active material can have a reduced proportion of fine particles included within it; therefore, the D10 of the secondary particles can be 5 μm or larger.

[0044] For example, although there are no restrictions on the methods for aggregating primary particles into secondary particles, secondary particles can be manufactured by granulating primary particles containing Li2S-containing complexes using a mixer (such as the NOBILTA MINI from Hosokawa Micron, the NARA hybridization system from NARA, etc.).

[0045] According to one or more embodiments, the D10 of the secondary particles can be from about 5 μm to about 10 μm, the D50 of the secondary particles can be from about 9 μm to about 20 μm, and the D90 of the secondary particles can be from about 16 μm to about 55 μm. For example, the D10 of the secondary particles can be from about 5 μm to about 9 μm. For example, the D50 of the secondary particles can be from about 10 μm to about 20 μm. For example, the D90 of the secondary particles can be from about 20 μm to about 55 μm, from about 30 μm to about 55 μm, from about 32 μm to about 55 μm, or from about 32 μm to about 51 μm.

[0046] For example, D10, D50, and D90 particle sizes can be measured using measuring devices that utilize laser diffraction or dynamic light scattering techniques. For instance, the D10 particle size can be the median particle size (D10) measured as a cumulative percentage of 10% from the smallest volume-based particle size, as measured by a laser scattering particle size distribution analyzer (e.g., the LA-920 manufactured by HORIBA). Similarly, the D50 particle size can be the median particle size (D50) measured as a cumulative percentage of 50% from the smallest volume-based particle size, as measured by a laser scattering particle size distribution analyzer (e.g., the LA-920 manufactured by HORIBA). And the D90 particle size can be the median particle size (D90) measured as a cumulative percentage of 90% from the smallest volume-based particle size, as measured by a laser scattering particle size distribution analyzer (e.g., the LA-920 manufactured by HORIBA).

[0047] According to one or more embodiments, the Li2S-containing complex may include a complex of Li2S and a lithium salt.

[0048] For example, Li₂S and lithium salt complexes are malleable and therefore differ from comparable or related art brittle oxide-based solid electrolytes, such as oxide-based solid electrolytes with garnet structures. Li₂S and lithium salt complexes can thus be distinguished from comparable or related art lithium-free metal oxides (e.g., alumina) that lack lithium-ion conductivity due to their lithium-ion conductivity. Li₂S and lithium salt complexes can be, for example, mechanically ground products of Li₂S and lithium salts. Li₂S and lithium salt complexes can be, for example, products of a mechanochemical reaction between Li₂S and lithium salts, and are therefore distinguishable from simple mixtures of Li₂S and lithium salts. Simple mixtures of Li₂S and lithium salts may provide relatively high interfacial resistance due to the inability to maintain a dense interface, which can result in increased internal resistance of the solid electrolyte membrane.

[0049] The complex of Li₂S and lithium salt can be represented as Li₂S-Li a X b (1≤a≤5, 1≤b≤5). In this formula, X can be 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 and / or any suitable combination thereof, a can be, for example, 1, 2, 3, 4 or 5, and b can be, for example, 1, 2, 3, 4 or 5. The lithium salt can be, for example, a sulfur-free (S) compound.

[0050] According to one or more embodiments, the lithium salt can be a binary compound or a ternary compound. The lithium salt can be, for example, a binary compound consisting of lithium and one element from groups 13 to 17 of the periodic table (e.g., selected from groups 13 to 17). The lithium salt can be, for example, a ternary compound consisting of lithium and two elements from groups 13 to 17 of the periodic table (e.g., selected from groups 13 to 17). The binary compound can include, for example, LiI, LiBr, LiCl, LiF, LiH, Li₂O, Li₂Se, Li₂Te, Li₃N, Li₃P, Li₃As, Li₃Sb, Li₃Al₂, LiB₃ and / or any suitable combination thereof. Because the composite includes such a binary compound, the ionic conductivity of the composite can be further improved. Using a solid electrolyte membrane comprising this composite, the internal resistance of the positive electrode can be further reduced. As a result, the cycle performance of the solid-state secondary battery comprising this positive electrode can be further improved.

[0051] Ternary compounds can include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, and / or any suitable combination thereof. Because the composite includes such ternary compounds, the ionic conductivity of the composite can be further improved. Because the composite positive electrode active material includes such a composite, the internal resistance of the positive electrode can be further reduced. As a result, the cycle performance of the solid-state secondary battery, including the solid electrolyte membrane, can be further improved.

[0052] According to one or more embodiments, the molar ratio of Li2S to lithium salt in the Li2S-containing composite can be, for example, about 50:50 to about 95:5, about 60:40 to about 95:5, about 60:40 to about 90:10, about 65:35 to about 90:10, about 65:35 to about 85:15, or about 70:30 to about 85:15. The molar ratio of Li2S to lithium salt in the Li2S-containing composite can be, for example, about 50:50 to about 95:5, about 50:50 to about 90:10, about 50:50 to about 85:15, about 50:50 to about 80:20, about 50:50 to about 75:25, or about 50:50 to about 70:30. If (for example, when) the molar ratio of Li2S to lithium salt is within the aforementioned ranges, the cycle performance of the solid-state secondary battery including the composite positive electrode active material can be further improved. If (for example, when) the molar fraction of Li2S is too high (or relatively high), the effect of the lithium salt on improving ionic conductivity may be negligible. If (for example, when) the molar fraction of Li2S is excessively high (or relatively high), the energy density of the lithium battery including this composite cathode active material may be reduced.

[0053] Li2S-containing complexes can also include carbon-based materials. A Li2S-containing complex can be a combination of Li2S, lithium salts, and carbon-based materials.

[0054] Carbon-based materials can be, for example, any carbon-containing material that can be used as a conductive material in the art. Carbon-based materials can be, for example, crystalline carbon, amorphous carbon, and / or any suitable combination thereof. Carbon-based materials can be, for example, sintered products of carbon precursors. Carbon-based materials can be, for example, carbon nanostructures (e.g., nanoscale structures). Examples of carbon nanostructures can include one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, and / or any suitable combination thereof. Examples of carbon nanostructures can include carbon nanotubes, carbon nanofibers, carbon nanotubes, carbon nanorods, graphene, and / or any suitable combination thereof. Carbon-based materials can be, for example, porous carbon materials or non-porous carbon materials. Porous carbon materials can contain, for example, periodic and regular two-dimensional or three-dimensional pores. Examples of porous carbon materials can include carbon black (such as Ketjen black, acetylene black, Denka black, thermal black, and channel black), and graphite, activated carbon, and / or any suitable combination thereof. Carbon-based materials can be in the form of granules, flakes, sheets, etc., but are not limited thereto, and any suitable material commonly available in the art and / or commonly used as a carbon-based material can be used.

[0055] Carbon-based materials can include, for example, fibrous carbon materials. Because the composite of Li₂S, lithium salt, and carbon materials includes fibrous carbon materials, the electronic conductivity of the composite can be further improved. Because the composite of Li₂S, lithium salt, and carbon materials includes fibrous carbon materials, electronic conduction from the surface of the composite to its interior can be facilitated (and can occur more readily). The internal resistance of the dry cathode film including the Li₂S, lithium salt, and carbon material composite can be reduced, and the cycle performance of the all-solid-state secondary battery including this dry cathode film can be further improved.

[0056] For example, fibrous carbon materials can have an aspect ratio of 2 or greater, 3 or greater, 4 or greater, 5 or greater, 10 or greater, or 20 or greater (e.g., the length-to-width ratio in an image of carbon materials). For example, fibrous carbon materials can have an aspect ratio of about 2 to about 30, about 3 to about 30, about 4 to about 30, about 5 to about 30, about 10 to about 30, or about 20 to about 30. For example, fibrous carbon materials can have an aspect ratio of about 2 to about 30, about 2 to about 20, about 2 to about 10, about 2 to about 8, about 2 to about 5, or about 2 to about 4. Because fibrous carbon materials have aspect ratios within the aforementioned ranges, the overall electronic conductivity of the Li2S, lithium salt, and carbon material composite can be improved, and the local irregularities in electronic conductivity within the Li2S, lithium salt, and carbon material composite can be further mitigated.

[0057] Fibrous carbon materials can include, for example, carbon nanostructures (e.g., nanoscale structures). Carbon nanostructures can include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanoribbons, carbon nanorods, and / or any suitable combination thereof.

[0058] Carbon nanostructures can form primary carbon nanostructures, which consist of a single carbon nanostructure (e.g., composed of a single carbon nanostructure) and secondary carbon nanostructures, which are formed by the aggregation (e.g., agglomeration) of multiple carbon nanostructures.

[0059] The diameter of the primary carbon nanostructure can be, for example, about 1 nm to about 200 nm, about 1 nm to about 150 nm, about 1 nm to about 100 nm, about 1 nm to about 50 nm, about 1 nm to about 30 nm, or about 1 nm to about 20 nm. The length of the primary carbon nanostructure can be, for example, about 10 nm to about 2 μm, about 10 nm to about 1.5 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 400 nm, about 10 nm to about 300 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. The diameter and / or major axis length of the primary carbon nanostructure can be measured from scanning electron microscopy (SEM) images or transmission electron microscopy (TEM) images. In one or more embodiments, the diameter and / or major axis length of the primary carbon nanostructure can be measured by laser diffraction.

[0060] Secondary carbon nanostructures can be structures formed by assembling primary carbon nanostructures to integrally or partially form bundle-like (or rope-like) or rope-like (or rope-like) structures. Secondary carbon nanostructures can be, for example, bundle-like (or rope-like) carbon nanostructures, rope-like (or rope-like) carbon nanostructures, and / or any suitable combination thereof. The diameter of the secondary carbon nanostructure can be, for example, about 2 nm to about 200 nm, about 3 nm to about 150 nm, about 5 nm to about 100 nm, about 5 nm to about 50 nm, about 5 nm to about 30 nm, or about 5 nm to about 20 nm. The length of the secondary carbon nanostructure can be, for example, about 20 nm to about 2 μm, about 30 nm to about 1.5 μm, about 50 nm to about 1 μm, about 50 nm to about 500 nm, about 50 nm to about 400 nm, about 50 nm to about 300 nm, about 50 nm to about 200 nm, or about 50 nm to about 100 nm or greater. The diameter and length of the secondary carbon nanostructure can be measured from SEM images or optical microscope images. In one or more embodiments, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. For example, the secondary carbon nanostructure can be dispersed in a solvent or the like to transform it into a primary carbon nanostructure, which can then be used to prepare composites of Li₂S, lithium salts, and carbon-based materials.

[0061] In a composite of Li₂S, lithium salt, and carbon materials, the content (e.g., amount) of lithium salt relative to the total weight of the composite can be, for example, about 1 wt% to about 40 wt%, about 5 wt% to about 35 wt%, about 10 wt% to about 35 wt%, about 15 wt% to about 35 wt%, about 20 wt% to about 35 wt%, or about 25 wt% to about 35 wt%. If (e.g., when) the content (e.g., amount) of lithium salt is excessively (or significantly) increased, the energy density of the all-solid-state secondary battery may decrease. If (e.g., when) the content (e.g., amount) of lithium salt is too low, the ionic conductivity of the composite of Li₂S, lithium salt, and carbon materials may deteriorate, increasing the internal resistance of the dry cathode film. As a result, the cycle performance of the all-solid-state secondary battery including this dry cathode film may deteriorate.

[0062] In the composite of Li₂S, lithium salt, and carbon-based materials, the molar ratio of Li₂S to lithium salt can be, for example, about 50:50 to about 95:5, about 60:40 to about 95:5, about 60:40 to about 90:10, about 65:35 to about 90:10, about 65:35 to about 85:15, or about 70:30 to about 85:15. In the composite of Li₂S, lithium salt, and carbon-based materials, the molar ratio of Li₂S to lithium salt can be, for example, about 50:50 to about 95:5, about 50:50 to about 90:10, about 50:50 to about 85:15, about 50:50 to about 80:20, about 50:50 to about 75:25, or about 50:50 to about 70:30. Because the molar ratio of Li₂S to lithium salt is within the aforementioned range, the cycle performance of the all-solid-state secondary battery including this dry cathode film can be further improved. If (for example) the molar fraction of Li2S is excessively (or relatively) high, the effect of lithium salt on improving ionic conductivity may be negligible. If (for example) the molar fraction of Li2S is excessively (or relatively) high, the energy density of lithium batteries including composite cathode active materials may be reduced.

[0063] According to one or more embodiments, the content (e.g., amount) of carbon materials included in the composite of Li2S, lithium salt, and carbon materials can be, for example, about 1 wt% to about 20 wt%, about 5 wt% to about 20 wt%, or about 10 wt% to about 20 wt%, relative to the total weight of the composite. If the amount of carbon materials is excessively (or significantly) increased, the energy density of the dry cathode film and the all-solid-state secondary battery may deteriorate. If the content (e.g., amount) of carbon materials is excessively (or significantly) decreased, the electronic conductivity of the composite of Li2S, lithium salt, and carbon materials may decrease, thus increasing the internal resistance of the dry cathode film. As a result, the cycle performance of the all-solid-state secondary battery may deteriorate.

[0064] According to one or more embodiments, the composite of Li2S and lithium salt, or the composite of Li2S, lithium salt, and carbon-based materials, may include, for example, a solid solution of Li2S and lithium salt. Because the composite includes a solid solution of Li2S and lithium salt, the ionic conductivity of the composite can be increased. For example, because the solid solution of Li2S and lithium salt includes lithium ions disposed within Li2S microcrystals, the ionic conductivity of the solid solution of Li2S and lithium salt can be improved relative to the ionic conductivity of Li2S. As a result, the ionic conductivity of the composite can be improved, and the internal resistance of the composite can be reduced. Because the positive electrode includes the composite, the internal resistance of the positive electrode can be further reduced. As a result, the cycle performance of the solid-state secondary battery including the positive electrode can be further improved.

[0065] According to one or more embodiments, the size of Li2S crystallites obtained from the XRD spectra of Li2S and lithium salt composites or Li2S, lithium salt, and carbon-based materials can be, for example, 30 nm or less, 25 nm or less, or 20 nm or less. The size of the Li2S crystallites obtained from the XRD spectra of the composite can be, for example, about 1 nm to about 20 nm, about 1 nm to about 15 nm, or about 3 nm to about 10 nm. Reducing the size of the Li2S crystallites allows for a further increase in the contact surface between Li2S and the lithium salt. This further increase in the contact surface between Li2S and the lithium salt allows for a further increase in the ionic conductivity of the Li2S and lithium salt composite. Because the cathode includes this composite, the internal resistance of the cathode can be further reduced. As a result, the cycle performance of the solid-state secondary battery including this cathode can be further improved.

[0066] For example, to address the relatively low ionic conductivity of Li₂S, it can be formed into a complex with a lithium salt. Compared to Li₂S used alone, the complex of Li₂S and a lithium salt, or the complex of Li₂S, a lithium salt, and a carbon-based material, can provide improved ionic conductivity. The content (e.g., amount) of Li₂S in the Li₂S-containing complex can be from about 50 wt% to about 95 wt%, from about 50 wt% to about 90 wt%, from about 50 wt% to about 80 wt%, or from about 50 wt% to about 70 wt%, relative to the total weight of the Li₂S-containing complex. Using a complex having a Li₂S content (e.g., amount) within the aforementioned range, a cathode with improved ionic conductivity and durability can be prepared. In the Li₂S and lithium salt complex, the content (e.g., amount) of lithium salt relative to the total weight of the Li₂S-containing complex can be from about 5 wt% to about 50 wt%, from about 10 wt% to about 50 wt%, from about 20 wt% to about 50 wt%, or from about 30 wt% to about 50 wt%.

[0067] The Mohs hardness of lithium salts and carbonaceous materials can both be greater than that of Li₂S. The Mohs hardness of Li₂S can be, for example, 0.6 or less. The Mohs hardness of lithium salts can be 0.7 or greater, 0.8 or greater, 0.9 or greater, 1.0 or greater, 1.5 or greater, or 2.0 or greater. Because lithium salts have Mohs hardness within the aforementioned ranges, Li₂S can be more easily pulverized during the grinding process, and solid solutions of Li₂S and lithium salts can be formed more easily. The Mohs hardness of LiI can be, for example, 2.0. The Mohs hardness of carbonaceous materials can all be 0.7 or greater, 0.8 or greater, 0.9 or greater, 1.0 or greater, 1.2 or greater, or 1.5 or greater. Because carbonaceous materials have Mohs hardness within the aforementioned ranges, Li₂S can be more easily pulverized during the grinding process, and solid solutions of Li₂S, lithium salts, and carbonaceous materials can be formed more easily. The Mohs hardness of carbon nanofibers (CNFs) can be, for example, 1.5.

[0068] The ionic conductivity of Li₂S and lithium salt complexes, or Li₂S, lithium salts, and carbon materials, at 25°C can be, for example, 1 × 10⁻⁶. -5 S / cm or greater, 2×10 -5 S / cm or greater, 4×10 -5 S / cm or greater, 6×10 -5 S / cm or greater, 8×10 -5 S / cm or greater, or 1×10 -4 S / cm or greater. Ionic conductivity can be measured, for example, using electrochemical impedance spectroscopy, DC polarization methods, etc. Because the Li₂S and lithium salt complex has ionic conductivity within the aforementioned range, the internal resistance of the cathode including the Li₂S and lithium salt complex can be further reduced. This can improve the cycle performance of the solid-state secondary battery including this cathode.

[0069] [positive electrode] The positive electrode according to one or more embodiments may include: a positive electrode current collector; and a positive electrode active material layer located on the positive electrode current collector and comprising the aforementioned composite positive electrode active material.

[0070] For example, the positive electrode active material layer may include a composite positive electrode active material comprising a Li₂S-containing composite having a reduced content (e.g., amount) of fine particles (fine powder) and a D₁₀ of 5 μm or larger. In one or more embodiments, the lifetime characteristics of the solid-state secondary battery including this positive electrode active material layer can be improved because side reactions caused by the fine particles are suppressed or reduced. Furthermore, since the positive electrode active material layer improves ionic and electronic conductivity, the charge-discharge efficiency of the solid-state secondary battery including this positive electrode active material layer can be excellent or suitable.

[0071] [Positive electrode: Positive electrode active material layer] The positive electrode according to one or more embodiments may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer may include the above-described composite positive electrode active material.

[0072] According to one or more embodiments, the positive electrode active material layer may further include a solid electrolyte. For example, by including the composite positive electrode active material and the solid electrolyte, the positive electrode can have a further reduced internal resistance. Therefore, the cycle performance of the secondary battery in which this positive electrode is provided can be further improved.

[0073] Reference Figures 1 to 5 The positive electrode 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on the positive electrode current collector 11. The positive electrode active material layer 12 may include a composite positive electrode active material.

[0074] According to one or more embodiments, the content (e.g., amount) of the composite positive electrode active material relative to the total weight of the positive electrode active material layer 12 can be about 40 wt% to about 90 wt%, about 40 wt% to about 80 wt%, about 50 wt% to about 80 wt%, or about 50 wt% to about 70 wt%. If (e.g., when) the amount of the composite positive electrode active material is excessively (or significantly) reduced, the energy density of the secondary battery may deteriorate. If (e.g., when) the amount of the composite positive electrode active material is excessively (or significantly) increased, it may accelerate the degradation of the positive electrode caused by volume changes during charge and discharge. As a result, the cycle performance of the secondary battery 1 may deteriorate.

[0075] In addition to the aforementioned composite positive electrode active material, the positive electrode active material layer 12 may also include other suitable composite positive electrode active materials.

[0076] Other composite cathode active materials may include, for example, Li2S-containing complexes. Li2S complexes may include, for example, complexes of Li2S and carbon-based materials, complexes of Li2S, carbon-based materials and solid electrolytes, complexes of Li2S and solid electrolytes, complexes of Li2S and lithium salts, complexes of Li2S and metal carbides, complexes of Li2S, carbon-based materials and metal carbides, complexes of Li2S and metal nitrides, complexes of Li2S, carbon-based materials and metal nitrides, and / or any suitable combination thereof.

[0077] The Li2S and carbon-based composite material may include the carbon-based material. For details on the carbon-based material, refer to the section on carbon-based materials in the composite cathode active material above. The method for preparing the Li2S and carbon-based composite material may be dry, wet, and / or any suitable combination thereof; however, the method is not limited thereto and may be any suitable method generally available and / or commonly used in the art. For example, the method for preparing the Li2S and carbon-based composite material may be grinding, heat treatment, deposition, etc.; however, the method is not necessarily limited thereto and may be any suitable method generally available and / or commonly used in the art.

[0078] The composite of Li₂S, carbonaceous materials, and solid electrolytes may include carbonaceous materials and solid electrolytes. For details regarding carbonaceous materials, refer to the above description of composites of Li₂S and carbonaceous materials. The solid electrolyte may be any suitable material, such as those commonly available in the art and / or commonly used as ion-conducting materials. The solid electrolyte may be, for example, an inorganic solid electrolyte. The solid electrolyte may be, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, and / or any suitable combination thereof. The solid electrolyte may be, for example, a sulfide solid electrolyte, an oxide solid electrolyte, and / or any suitable combination thereof. Sulfide solid electrolytes may contain, for example, Li, S, and P, and may optionally also include halogen elements. Sulfide solid electrolytes may be (e.g., may be selected from) sulfide solid electrolytes used in the electrolyte layer. For example, a sulfide solid electrolyte may have a concentration of 1 × 10⁻⁶ at room temperature. -5 Oxide solid electrolytes may contain, for example, Li, O, and transition metals, and may optionally also contain other elements. For example, oxide solid electrolytes may have an ionic conductivity of 1 × 10⁻⁶ S / cm or greater at room temperature. -5 Solid electrolytes with an ionic conductivity of S / cm or greater. Oxide-based solid electrolytes can be (e.g., selected from) oxide-based solid electrolytes used in the electrolyte layer.

[0079] Complexes of Li₂S and solid electrolytes may include solid electrolytes. For details on solid electrolytes, refer to the section on complexes of Li₂S, carbon-based materials, and solid electrolytes.

[0080] The Li2S and lithium salt complex may include Li2S and a lithium salt. For details of the lithium salt, refer to the lithium salt of the composite cathode active material described above. In one or more embodiments, the lithium salt may be (e.g., selected from) at least one lithium halide compound from LiF, LiCl, LiBr, and / or LiI. For example, the Li2S and lithium salt complex may be a complex of Li2S and lithium halides. Because the Li2S and lithium halide complex includes a lithium halide compound, it can provide further improved ionic conductivity. The Li2S and lithium salt complex may differ from a simple mixture of Li2S and lithium salt. Because a simple mixture of Li2S and lithium salt cannot maintain a dense interface between Li2S and the lithium salt, it may provide a relatively high interfacial resistance and potentially lead to deterioration of the lifetime characteristics of the all-solid-state secondary battery.

[0081] Complexes of Li₂S and metal carbides may include metal carbides. The metal carbides may be, for example, two-dimensional metal carbides. Two-dimensional metal carbides may be composed of, for example, M… n+1 C n T x (M is a transition metal, T is an end group, T is O, OH and / or F, n = 1, 2 or 3, and x is the number of end groups) Two-dimensional metal carbides can be, for example, Ti₂CT. x 、(Ti 0.5 ,Nb 0.5 )2CT x Nb2CT x V2CT x Ti3C2T x 、(V 0.5 ,Cr 0.5 3C2T x Ti3CNT x Ta4C3T x Nb4C3T x and / or any suitable combination thereof. The surface of two-dimensional metal carbides can be capped by O, OH and / or F.

[0082] Complexes of Li₂S, carbonaceous materials, and metal carbides may include both carbonaceous materials and metal carbides. For details regarding carbonaceous materials, refer to the section on complexes of Li₂S and carbonaceous materials. For details regarding metal carbides, refer to the section on complexes of Li₂S and metal carbides.

[0083] Complexes of Li₂S and metal nitrides can include metal nitrides. Metal nitrides can be, for example, two-dimensional metal nitrides. Two-dimensional metal nitrides can be formed from, for example, M... n+1 N n T x(M is a transition metal, T is an end group, T is O, OH and / or F, n=1, 2 or 3, and x is the number of end groups) represents the two-dimensional metal nitride. The surface of the two-dimensional metal nitride can be capped by O, OH and / or F.

[0084] Complexes of Li₂S, carbonaceous materials, and metal nitrides may include both carbonaceous materials and metal nitrides. For details regarding carbonaceous materials, refer to the section on complexes of Li₂S and carbonaceous materials. For details regarding metal nitrides, refer to the section on complexes of Li₂S and metal nitrides.

[0085] The positive electrode active material layer 12 may also include, for example, sulfide compounds different from the composite positive electrode active material described above. Sulfide compounds may be, for example, compounds comprising sulfur and metallic elements other than Li. Sulfide compounds may be, for example, compounds comprising sulfur and metallic elements belonging to groups 1 to 14 of the periodic table with an atomic weight of 10 or greater. Sulfide compounds may be, for example, FeS2, VS2, NaS, MnS, FeS, NiS, CuS, and / or any suitable combination thereof. When the positive electrode active material layer also includes sulfide compounds, the cycle performance of the all-solid-state secondary battery can be further improved. The amount of such sulfide compounds included in the positive electrode active material layer 12 relative to the total weight of the positive electrode active material layer 12 may be 10 wt% or less, 5 wt% or less, 3 wt% or less, or 1 wt% or less.

[0086] [Positive electrode: Solid electrolyte] The positive electrode active material layer 12 may also include, for example, a solid electrolyte. For example, the solid electrolyte may be a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode 10 may be substantially the same as or different from the solid electrolyte included in the electrolyte layer 30. For details regarding the solid electrolyte, refer to the description of solid electrolytes provided above.

[0087] The solid electrolyte included in the positive electrode active material layer 12 may have a median particle size D50 smaller than that of the solid electrolyte included in the electrolyte layer 30. For example, the median particle size D50 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 relative to the median particle size D50 of the solid electrolyte included in the electrolyte layer 30. The average particle size of D50 may be, for example, the median particle size (D50). The median particle size (D50) may refer to the particle size corresponding to 50% of the cumulative volume counted from the smallest particle size in a particle size distribution measured by laser diffraction.

[0088] The solid electrolyte may be included in amounts of about 10 parts by weight to about 60 parts by weight, about 10 parts by weight to about 50 parts by weight, about 20 parts by weight to about 50 parts by weight, or about 30 parts by weight to about 50 parts by weight, relative to 100 parts by weight of the positive electrode active material layer 12. If the content (e.g., amount) of the solid electrolyte is excessively (or significantly) reduced, the internal resistance of the positive electrode may increase, leading to a deterioration in the cycle performance of the secondary battery. If the amount of the sulfide-based solid electrolyte is excessively (or significantly) increased, the energy density of the secondary battery 1 may decrease.

[0089] [Positive electrode: Conductive material] The positive electrode active material layer 12 may also include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metallic conductive material, and / or any suitable combination thereof. Examples of carbon-based conductive materials may include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and / or any suitable combination thereof. However, carbon-based conductive materials are not limited to the foregoing examples and may be any suitable material commonly available in the art and / or commonly used as a carbon-based conductive material. Metallic conductive materials may be, but are not limited to, metal powders, metal fibers, and / or any suitable combination thereof, and may be any suitable metallic conductive material commonly available in the art and / or commonly used. For example, the content (e.g., amount) of the conductive material included in the positive electrode active material layer 12 relative to the total weight of the positive electrode active material layer 12 may be from about 1 wt% to about 30 wt%, from about 1 wt% to about 20 wt%, or from about 1 wt% to about 10 wt%.

[0090] The positive electrode active material layer may include carbon-based materials, and the carbon-based materials may be disposed solely in the composite positive electrode active material. Apart from providing a composite positive electrode active material containing carbon-based materials, the positive electrode active material layer 12 may not contain any other carbon-based materials. Because the positive electrode active material layer does not contain any other carbon-based materials, the positive electrode and the secondary battery 1 can have improved energy density, and the manufacturing process of the positive electrode and the secondary battery can be simplified.

[0091] [Positive electrode: binder] The positive electrode active material layer 12 may also include a binder. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to the foregoing examples; any suitable material commonly available in the art and / or commonly used as a binder may be used. The content (e.g., amount) of the binder included in the positive electrode active material layer 12 may be, for example, from about 1 wt% to about 10 wt% relative to the total weight of the positive electrode active material layer 12. In one or more embodiments, a binder may not be provided.

[0092] [Positive electrode: Other additives] In addition to the aforementioned composite positive electrode active material, solid electrolyte, binder and conductive material, the positive electrode active material layer 12 may also include, for example, additives (such as fillers, coating agents, dispersants and ionic conductive agents).

[0093] For fillers, coatings, dispersants, and ion-conducting additives that may be included in the positive electrode active material layer 12, any suitable materials that are typically available and / or commonly used in the electrodes of all-solid-state secondary batteries may be used.

[0094] [Positive electrode: Positive current collector] For example, the positive current collector 11 can be a plate, foil, etc., formed of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li) and / or alloys thereof (or including indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li) and / or alloys thereof). In one or more embodiments, the positive current collector 11 may not be provided. The positive current collector 11 may have a thickness of, for example, about 1 μm to about 100 μm, about 1 μm to about 50 μm, about 5 μm to about 25 μm, or about 10 μm to about 20 μm.

[0095] For example, the positive current collector 11 may include a substrate film and metal layers disposed on one or both sides (e.g., opposite sides) of the substrate film. For example, the substrate film may include a polymer. For example, the polymer may be a thermoplastic polymer. For example, the polymer may include polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), and / or any suitable combination thereof. For example, the substrate film may be an insulator. Because the substrate film comprises an insulating thermoplastic polymer, in the event of a short circuit, the substrate film softens or liquefies, preventing the operation of the battery, thereby preventing or reducing a rapid increase in current. For example, the metal layers may include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), and / or alloys thereof. In the event of an overcurrent, the metal layers can disconnect, thus acting as an electrochemical fuse to provide protection against short circuits. The limiting current and maximum current can be controlled or selected by controlling the thickness of the metal layers. The metal layer can be plated or deposited on the substrate film. As the thickness of the metal layer decreases, the limiting current and / or maximum current of the positive electrode current collector 11 decreases, thus improving the stability of the lithium battery during short circuits. Lead tabs can be added to the metal layer for external connection. The lead tabs can be welded to the metal layer or metal layer / substrate film laminate by ultrasonic welding, laser welding, spot welding, etc. When the substrate film and / or metal layer melts during welding, the metal layer can be electrically connected to the lead tabs. For stronger welding between the metal layer and the lead tabs, a metal sheet can be added between the metal layer and the lead tabs. The metal sheet can be a thin sheet of material substantially the same as the metal of the metal layer. For example, the metal sheet can be a metal foil, metal mesh, etc. For example, the metal sheet can be aluminum foil, copper foil, SUS foil, etc. By welding the metal layer to the lead tabs after placing the metal sheet on the metal layer, the lead tabs can be welded to the metal sheet / metal layer laminate or the metal sheet / metal layer / substrate film laminate. When the substrate film, metal layer, and / or metal sheet melt during soldering, the metal layer or metal layer / metal sheet laminate can be electrically connected to the lead patch. Metal sheets and / or lead patches can be further added to a portion of the metal layer. For example, the thickness of the substrate film can be about 1 μm to about 50 μm, about 1.5 μm to about 50 μm, about 1.5 μm to about 40 μm, or about 1 μm to about 30 μm. Using a substrate film with a thickness within the aforementioned ranges allows for a more effective reduction in the weight of the electrode assembly. For example, the substrate film can have a melting point of about 100°C to about 300°C, about 100°C to about 250°C or lower, or about 100°C to about 200°C. If, for example, the substrate film has a melting point within the aforementioned ranges, the substrate film can be readily melted and bonded to the lead patch during soldering.To improve the adhesion between the substrate film and the metal layer, the substrate film can be surface-treated, such as by corona treatment. For example, the metal layer can have a thickness of about 0.01 μm to about 3 μm, about 0.1 μm to about 3 μm, about 0.1 μm to about 2 μm, or about 0.1 μm to about 1 μm. Using a metal layer with a thickness within the aforementioned range, the electrode assembly can provide stability while maintaining conductivity. For example, the metal sheet can have a thickness of about 2 μm to about 10 μm, about 2 μm to about 7 μm, or about 4 μm to about 6 μm. Using a metal sheet with a thickness within the aforementioned range, the metal layer and lead terminals can be more easily connected. If (for example, when) the positive current collector 11 has the above structure, the weight of the positive electrode can be reduced, resulting in improved energy density of the positive electrode and the lithium battery.

[0096] [Positive electrode: Inactive component] Reference Figure 4 and Figure 5 The positive electrode 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on the positive electrode current collector 11. An inactive component 40 may be disposed on one side surface of the positive electrode 10. (See reference...) Figure 4 The inactive component 40 can be arranged on one side surface of the positive electrode current collector 11 and one side surface of the positive electrode active material layer 12. (Refer to...) Figure 5 The inactive component 40 may be disposed on one side surface of the positive electrode active material layer 12 and between the electrolyte layer 30 and the positive electrode current collector 11 opposite to the electrolyte layer 30. The inactive component 40 may not be disposed on one side surface of the positive electrode current collector 11. The electrolyte layer 30 may be, for example, a solid electrolyte layer.

[0097] Because the inclusion of the inactive component 40 prevents crack formation in the electrolyte layer 30 during the manufacture of the all-solid-state secondary battery 1 and / or during the charge-discharge cycle of the all-solid-state secondary battery 1, the cycle performance of the all-solid-state secondary battery 1 can be improved. In an all-solid-state secondary battery 1 without the inactive component 40, when uneven (substantially uneven) pressure is applied to the electrolyte layer 30 in contact with the positive electrode 10 during the manufacture and / or charge-discharge cycle of the all-solid-state secondary battery 1, cracks may form in the electrolyte layer 30, and the likelihood of a short circuit may increase due to the subsequent growth of lithium metal.

[0098] In the all-solid-state secondary battery 1, the thickness of the inactive component 40 can be greater than or equal to the thickness of the positive electrode active material layer 12. In one or more embodiments, the thickness of the inactive component 40 in the all-solid-state secondary battery 1 can be substantially the same as the thickness of the positive electrode 10. Since the thickness of the inactive component 40 is equal to the thickness of the positive electrode 10, a substantially uniform pressure can be applied between the positive electrode 10 and the electrolyte layer 30, and since the positive electrode 10 and the electrolyte layer 30 can be sufficiently flush with each other, the interfacial resistance between the positive electrode 10 and the electrolyte layer 30 can be reduced. Furthermore, since the electrolyte layer 30 is sufficiently sintered during the pressing process of the all-solid-state secondary battery 1, the electrolyte layer 30 and the all-solid-state secondary battery 1 including it can have reduced internal resistance.

[0099] The inactive component 40 can contact the electrolyte layer 30 while located around the side surface of the positive electrode 10 (e.g., surrounding the side surface of the positive electrode 10). Because the inactive component 40 is in contact with the electrolyte layer 30 while located around the side surface of the positive electrode 10 (e.g., surrounding the side surface of the positive electrode 10), crack formation in the electrolyte layer 30, which is not in contact with the positive electrode 20, can be effectively suppressed or reduced. This crack formation may be caused by pressure differences during the pressing process. The inactive component 40 can surround the side surface of the positive electrode 10 while being spaced apart from the negative electrode 20 (e.g., from the first negative electrode active material layer 22). The inactive component 40 can contact the electrolyte layer 30 while located around the side surface of the positive electrode 10 (e.g., surrounding the side surface of the positive electrode 10) and can be spaced apart from the negative electrode 20. In one or more embodiments, the possibility of a short circuit due to physical contact between the positive electrode 10 and the first negative electrode active material layer 22 and / or due to overcharging of lithium can be suppressed or reduced. For example, because the inactive components 40 are arranged in parallel (e.g., simultaneously) on one side surface of the positive electrode active material layer 12 and one side surface of the positive electrode current collector 11, the risk of short circuit due to contact between the positive electrode current collector 11 and the negative electrode 20 can be effectively suppressed or reduced.

[0100] Reference Figure 4 and Figure 5The inactive member 40 can extend from one side surface of the positive electrode 10 to the end of the electrolyte layer 30. Because the inactive member 40 extends to the end of the electrolyte layer 30, crack formation in the end of the electrolyte layer 30 can be suppressed or reduced. The end of the electrolyte layer 30 can be the outermost portion in contact with the side surface of the electrolyte layer 30. The inactive member 40 can extend to the outermost portion in contact with the side surface of the electrolyte layer 30. The inactive member 40 can be spaced apart from the negative electrode 20 (e.g., from the first negative electrode active material layer 22). The inactive member 40 can extend to the end of the electrolyte layer 30, but may not be in contact with the negative electrode 20. The inactive member 40 can, for example, fill the space extending from one side surface of the positive electrode 10 to the end of the electrolyte layer 30.

[0101] Reference Figure 4 and Figure 5 The width of the inactive member 40 extending from one side surface of the positive electrode 10 to the end of the electrolyte layer 30 can be, for example, about 1% to about 30%, about 1% to about 25%, about 1% to about 20%, about 1% to about 20%, about 1% to about 15%, about 1% to about 10%, or about 1% to about 5% of the width relative to one side surface of the positive electrode 10 and the other side surface opposite to said one side surface. If (for example) the width of the inactive member 40 is excessively (or relatively) large, the energy density of the all-solid-state secondary battery 1 can be reduced. If (for example) the width of the inactive member 40 is too small, the effect of placing the inactive member 40 may be negligible.

[0102] The surface area of ​​the positive electrode 10 can be smaller than the surface area of ​​the electrolyte layer 30 in contact with the positive electrode 10. The inactive component 40 compensates for the difference in surface area between the positive electrode 10 and the electrolyte layer 30 by being arranged around the side surface of the positive electrode 10. Because the surface area of ​​the inactive component 40 compensates for the difference between the surface areas of the positive electrode 10 and the electrolyte layer 30, crack formation in the electrolyte layer 30 caused by pressure difference during the pressing process can be effectively suppressed or reduced. For example, the sum of the surface areas of the positive electrode 10 and the inactive component 40 can be equal to the surface area of ​​the electrolyte layer 30. The electrolyte layer 30 can be, for example, a solid electrolyte layer.

[0103] For example, the surface area of ​​the positive electrode 10 may be less than 100%, 99%, 98%, 97%, 96%, or 95% of the surface area of ​​the electrolyte layer 30. For example, the surface area of ​​the positive electrode 10 may be about 50% to less than 100%, about 50% to about 99%, about 55% to about 98%, about 60% to about 97%, about 70% to about 96%, about 80% to about 95%, or about 85% to about 95% of the surface area of ​​the electrolyte layer 30.

[0104] If the surface area of ​​the positive electrode 10 is equal to or greater than the surface area of ​​the electrolyte layer 30, the possibility of a short circuit due to physical contact between the positive electrode 10 and the first negative electrode active material layer 22, or due to lithium overcharging, may increase. For example, the surface area of ​​the positive electrode 10 may be equal to the surface area of ​​the positive electrode active material layer 12. For example, the surface area of ​​the positive electrode 10 may be equal to the surface area of ​​the positive electrode current collector 11.

[0105] For example, the surface area of ​​the inactive component 40 may be 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less relative to the surface area of ​​the positive electrode 10. For example, the surface area of ​​the inactive component 40 may be about 1% to about 50%, about 5% to about 40%, about 5% to about 30%, about 5% to about 20%, or about 5% to about 15% relative to the surface area of ​​the positive electrode 10.

[0106] The surface area (S1) of the positive electrode 10 is smaller than the surface area (S4) of the negative electrode current collector 21. For example, the surface area (S1) of the positive electrode 10 may be less than 100%, 99%, 98%, 97%, 96%, or 95% of the surface area (S4) of the negative electrode current collector 21. For example, the surface area (S1) of the positive electrode 10 may be less than 50% to 100%, about 50% to about 99%, about 55% to about 98%, about 60% to about 97%, about 70% to about 96%, about 80% to about 95%, or about 85% to about 95% of the surface area (S4) of the negative electrode current collector 21. For example, the surface area (S4) of the negative electrode current collector 21 may be equal to the surface area of ​​the negative electrode 20. For example, the surface area (S4) of the negative electrode current collector 21 may be equal to the surface area of ​​the first negative electrode active material layer 22.

[0107] As used herein, unless otherwise specified, the area, length, width, thickness, and / or shape or form is intentionally altered to be different from each other; otherwise, “equivalent” and / or “identical” area, length, width, thickness, and / or shape or form can include “substantially equivalent” and “substantially identical” area, length, width, thickness, and / or shape or form. For example, “equivalent” and / or “identical” area, length, width, thickness, and / or shape or form can include unintended differences in area, length, width, thickness, and / or shape or form within the range of less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0108] The thickness of the inactive component 40 may, for example, be greater than the thickness of the first negative electrode active material layer 22. For instance, the thickness of the first negative electrode active material layer 22 may be 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less relative to the thickness of the inactive component 40. The thickness of the first negative electrode active material layer 22 may, for example, be about 1% to about 50%, about 1% to about 40%, about 1% to about 30%, about 1% to about 20%, or about 1% to about 10% relative to the thickness of the inactive component 40.

[0109] The inactive component 40 can be a gasket. If (for example, when) a gasket is used as the inactive component 40, crack formation in the electrolyte layer 30 that may occur due to pressure differences during the pressing process can be effectively suppressed or reduced.

[0110] The inactive component 40 may have, for example, a single-layer structure. In one or more embodiments, the inactive component 40 may have a multi-layer structure. In the inactive component 40 with a multi-layer structure, each layer may have a different composition. The inactive component 40 with 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 inactive component 40 with a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers. For example, the adhesive layer can effectively prevent or reduce separation between the positive electrode 10 and the electrolyte layer 30 that may occur due to volume changes of the positive electrode 10 during the charging and discharging of the all-solid-state secondary battery 1, and can improve the film strength of the inactive component 40 by providing adhesion between the support layer and other layers. The support layer can provide support to the inactive component 40, prevent or reduce non-uniformity of pressure applied to the electrolyte layer 30 during the pressing process or the charging and discharging process, and prevent or reduce deformation of the shape of the manufactured all-solid-state secondary battery 1.

[0111] The inactive component 40 can be, for example, a flame-retardant inactive component. The flame retardancy provided by the flame-retardant inactive component can reduce the risk of thermal runaway and explosion of the all-solid-state secondary battery 1. Therefore, the safety of the all-solid-state secondary battery 1 can be further improved. Because the flame-retardant inactive component absorbs residual moisture inside the all-solid-state secondary battery 1, it can prevent or reduce the degradation of the all-solid-state secondary battery 1, which leads to an improvement in the lifespan characteristics of the all-solid-state secondary battery 1.

[0112] The flame-retardant inactive component may include, for example, a matrix and a filler. For example, the matrix may include a substrate and a reinforcing material. For example, the matrix may include a fibrous substrate and a fibrous reinforcing material. If (for example, when) the matrix includes a substrate, the matrix may be elastic. The matrix may be placed in one or more suitable locations and effectively accommodate volume changes of the all-solid-state secondary battery 1 during charging and discharging. The substrate included in the matrix may include, for example, a first fibrous material. When the substrate includes a first fibrous material, it can effectively accommodate volume changes of the positive electrode 10 during charging and discharging of the all-solid-state secondary battery 1 and can effectively suppress or reduce deformation of the inactive component 40 that may be caused by volume changes of the positive electrode 10. For example, the first fibrous material may be a material having an aspect ratio of 5 or greater, 20 or greater, or 50 or greater (e.g., the length-to-width ratio in an image of the material). For example, the first fibrous material may be a material having an aspect ratio of about 5 to about 1,000, about 20 to about 1,000, or about 50 to about 1,000. The first fibrous material may be, for example, an insulating material. Because the first fibrous material is an insulating material, it can effectively prevent or reduce short circuits that may occur between the positive electrode 10 and the negative electrode 20 due to lithium dendrites or the like during the charging and discharging of the all-solid-state secondary battery 1. The first fibrous material may include one or more of, for example, pulp fibers, insulating polymer fibers, and / or ion-conducting polymer fibers (e.g., selected from one or more of these). If (e.g., when) the matrix includes a reinforcing material, the strength of the matrix can be improved. The matrix can be used to prevent or reduce the possibility of excessive volume changes in the all-solid-state secondary battery 1 during charging and discharging, and to protect the all-solid-state secondary battery 1 from deformation. The reinforcing material included in the matrix may include, for example, a second fibrous material. When the reinforcing material includes a second fibrous material, a more uniform (e.g., substantially more uniform) increase in the strength of the matrix can be achieved. For example, the second fibrous material may be a material with an aspect ratio of 3 or greater, 5 or greater, or 10 or greater. For example, the first fibrous material may be a material having an aspect ratio of about 3 to about 100, about 5 to about 100, or about 10 to about 100. The second fibrous material may be, for example, a flame-retardant material. Because the second fibrous material is a flame-retardant material, it can effectively suppress or reduce ignition that may be caused by external impact or thermal runaway during the charging and discharging of the all-solid-state secondary battery 1. The second fibrous material can be, for example, glass fiber, metal oxide fiber, ceramic fiber, etc.

[0113] In addition to the matrix, the flame-retardant inactive component may also include a filler. The filler may be disposed within the matrix, on the surface of the matrix, or both. Examples of fillers may include inorganic materials. The filler included in the flame-retardant inactive component may be, for example, a hygroscopic agent. For example, by adsorbing moisture at temperatures below 100°C, the filler can remove residual moisture from the all-solid-state secondary battery 1, thereby preventing or reducing the degradation of the all-solid-state secondary battery 1. Furthermore, if (e.g., when) the temperature of the all-solid-state secondary battery 1 rises to 150°C or higher during charging and discharging or due to thermal runaway caused by an external impact, the filler can release the adsorbed moisture, thereby effectively preventing or reducing ignition of the all-solid-state secondary battery 1. For example, the filler may be a flame retardant. For example, the filler may be a hygroscopic metal hydroxide. The metal hydroxide included in the filler can be, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, Ti(OH)3, Zr(OH)4, Al(OH)3 and / or any suitable combination thereof. The amount of filler included in the flame-retardant inactive component 40 relative to 100 parts by weight can be, for example, about 10 parts by weight to about 80 parts by weight, about 20 parts by weight to about 80 parts by weight, about 30 parts by weight to about 80 parts by weight, about 40 parts by weight to about 80 parts by weight, about 50 parts by weight to about 80 parts by weight, about 60 parts by weight to about 80 parts by weight, or about 65 parts by weight to about 80 parts by weight.

[0114] For example, a flame-retardant inactive component may include an adhesive. The adhesive may include, for example, a curable polymer or a non-curable polymer. The curable polymer may be a polymer that cures by heat and / or pressure. For example, the curable polymer may be solid at room temperature. Examples of the flame-retardant inactive component 40 may include a heat-curable film and / or its cured product. The heat-curable polymer of the heat-curable film may be, for example, Toray's TSA-66.

[0115] In addition to the substrate, reinforcing material, filler, and binder described above, the flame-retardant inactive component may also include other materials. For example, the flame-retardant inactive component may also include at least one of paper, insulating polymer, ion-conducting polymer, insulating inorganic material, oxide solid electrolyte, and / or sulfide solid electrolyte (e.g., selected from at least one of them). The insulating polymer may be an olefin polymer, such as polypropylene (PP), polyethylene (PE), etc.

[0116] The density of the substrate or reinforcing material included in the flame-retardant inactive component may be, for example, about 10% to about 300%, about 10% to about 150%, about 10% to about 140%, about 10% to about 130%, or about 10% to about 120% of the density of the composite positive electrode active material included in the positive electrode active material layer 12.

[0117] The inactive component 40 may be a component that does not contain any electrochemically active material (i.e., electrode active material). The electrode active material may be a material that absorbs / desorbs lithium. The inactive component 40 may be a component made of a material other than the electrode active material used in the art.

[0118] [All-solid-state rechargeable battery] An all-solid-state secondary battery according to one or more embodiments may include: a positive electrode; a negative electrode; and an electrolyte layer disposed between the positive and negative electrodes. The negative electrode layer may include a negative electrode current collector and a first negative electrode active material layer disposed on one side of the negative electrode current collector.

[0119] Reference Figures 1 to 5 The all-solid-state secondary battery 1 may include: 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 may include a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on one side of the negative electrode current collector.

[0120] [positive electrode] For details regarding the positive electrode, please refer to the positive electrode section above.

[0121] [negative electrode] [Negative electrode: Negative electrode active material] Reference Figures 1 to 5 The negative electrode 20 may include a first negative electrode active material layer 22. The first negative electrode active material layer 22 may include, for example, a negative electrode active material and a binder.

[0122] The negative electrode active material included in the first negative electrode active material layer 22 can be, for example, a negative electrode material capable of forming an alloy or compound with lithium.

[0123] The negative electrode active material included in the first negative electrode active material layer 22 can be, for example, in particulate form (in the form of particles). The negative electrode active material in particulate form can have, for example, an average particle size of 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, 300 nm or less, or 100 nm or less. The negative electrode active material in particulate form can have, for example, an average particle size of about 10 nm to about 4 μm, about 10 nm to about 3 μm, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 300 nm, or about 10 nm to about 100 nm. If (for example, when) the negative electrode active material has an average particle size within the aforementioned range, it can further promote the reversible absorption and / or desorption of lithium during charge and discharge. The average particle size of the negative electrode active material can be, for example, the median particle size (D50) measured by a laser-type (or similar) particle size analyzer.

[0124] The negative electrode active material included in the first negative electrode active material layer 22 may include at least one of, for example, carbon-based negative electrode active materials and / or metal or quasi-metal negative electrode active materials (e.g., at least one selected from them).

[0125] Carbon-based anode active materials may include, for example, amorphous carbon, crystalline carbon, porous carbon, and / or any suitable combination thereof.

[0126] Carbon-based anode active materials can be, for example, amorphous carbon. Examples of amorphous carbon can include carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, etc.; however, carbon-based anode active materials are not limited to the foregoing examples and can be any suitable material classified as amorphous carbon in the art. Amorphous carbon is carbon that does not have a crystalline structure or has a relatively very low degree of crystallinity, and therefore can be different from crystalline carbon or graphitic carbon.

[0127] For example, carbon-based anode active materials can be porous carbon. For example, the pores included in the porous carbon can have a pore volume of about 0.1 cc / g to about 10.0 cc / g, about 0.5 cc / g to about 5 cc / g, or about 0.1 cc / g to about 1 cc / g. For example, the pores included in the porous carbon can have an average pore size of about 1 nm to about 50 nm, about 1 nm to about 30 nm, or about 1 nm to about 10 nm. The Brunauer-Emmett-Teller (BET) specific surface area of ​​the porous carbon can be, for example, about 100 m². 2 / g to approximately 3,000m 2 / g.

[0128] Metallic or quasi-metallic anode active materials may include at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and / or zinc (Zn) (e.g., selected from at least one of them), but are not limited to the aforementioned materials. Any suitable metallic or quasi-metallic anode active material that can form alloys or compounds with lithium and is generally available and / or commonly used in the art may be used. For example, nickel (Ni) does not form alloys with lithium and is therefore not considered a metallic anode active material.

[0129] Among these negative electrode active materials, the first negative electrode active material layer 22 may include a single negative electrode active material, or may include a mixture of multiple different types (classes) of negative electrode active materials. For example, the first negative electrode active material layer 22 may include only amorphous carbon, or may include one or more of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn) (e.g., selected from one or more of them). In one or more embodiments, the first negative electrode active material layer 22 may include amorphous carbon and a mixture of one or more of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn) (e.g., selected from one or more of them). In such a mixture, the mixing ratio of amorphous carbon to metal (such as gold (Au)) described herein, by weight, can be approximately 99:1 to approximately 1:99, approximately 10:1 to approximately 1:2, approximately 5:1 to approximately 1:1, or approximately 4:1 to approximately 2:1, but is not limited thereto. The mixing ratio can be selected according to the desired or required characteristics of the all-solid-state secondary battery 1. If (for example, when) the negative electrode active material has the above composition, the cycle performance of the all-solid-state secondary battery 1 can be further improved.

[0130] The negative electrode active material included in the first negative electrode active material layer 22 may include, for example, a mixture of first particles made of amorphous carbon and second particles made of metal or metalloid. Examples of metal or metalloid may include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), etc. In one or more embodiments, the metalloid may be a semiconductor. The content (e.g., amount) of the second particles relative to the total weight of the mixture may be about 1 wt% to about 99 wt%, about 1 wt% to about 60 wt%, about 8 wt% to about 60 wt%, about 10 wt% to about 50 wt%, about 15 wt% to about 40 wt%, or about 20 wt% to about 30 wt%. If (e.g., when) the content (e.g., amount) of the second particles is within the aforementioned range, the cycle performance of the all-solid-state secondary battery 1 may be further improved.

[0131] In one or more embodiments, the first negative electrode active material layer 22 may include 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. If (for example, when) the composite negative electrode active material has the above structure, it is possible to prevent or reduce uneven distribution of the metal-based negative electrode active material within the first negative electrode active material layer, and to achieve a substantially uniform distribution of the metal-based negative electrode active material. As a result, the cycle performance of the all-solid-state secondary battery 1 including the first negative electrode active material layer 22 can be further improved.

[0132] Examples of metal-based anode active materials supported on carbon-based supports can include metals, metal oxides, metal-metal oxide complexes, and / or any suitable combination thereof. Metals can include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), zinc (Zn), etc. Metal oxides can include, 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, zinc (Zn) oxide, etc. For example, metal oxides can include Au... x O y (0) <x≤2,0<y≤3)、Pt x O y (0) <x≤1,0<y≤2)、Pd x O y (0) <x≤1,0<y≤1)、Si x O y (0) <x≤1,0<y≤2)、Ag x O y(0 < x ≤ 2, 0 < y ≤ 1), Al x O y (0 < x ≤ 2, 0 < y ≤ 3), Bi x O y (0 < x ≤ 2, 0 < y ≤ 3), Sn x O y (0 < x ≤ 1, 0 < y ≤ 2), Te x O y (0 < x ≤ 1, 0 < y ≤ 3), Zn x O y (0 < x ≤ 1, 0 < y ≤ 1) and / or any suitable combination thereof. Examples of the metal-metal oxide composite may include the composite of Au and Au x O y (0 < x ≤ 2, 0 < y ≤ 3), the composite of Pt and Pt x O y (0 < x ≤ 1, 0 < y ≤ 2), the composite of Pd and Pd x O y (0 < x ≤ 1, 0 < y ≤ 1), the composite of Si and Si x O y (0 < x ≤ 1, 0 < y ≤ 2), the composite of Ag and Ag x O y (0 < x ≤ 2, 0 < y ≤ 1), the composite of Al and Al x O y (0 < x ≤ 2, 0 < y ≤ 3), the composite of Bi and Bi x O y (0 < x ≤ 2, 0 < y ≤ 3), the composite of Sn and Sn x O y (0 < x ≤ 1, 0 < y ≤ 2), the composite of Te and Te x O y (0 < x ≤ 1, 0 < y ≤ 3), the composite of Zn and Zn x O y (0 < x ≤ 1, 0 < y ≤ 1) and / or any suitable combination thereof.

[0133] The carbonaceous carrier may be, for example, amorphous carbon. The amorphous carbon may be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., but is not limited thereto, and any suitable material classified as amorphous carbon in the art may be used. Amorphous carbon is carbon that does not have a crystal structure or has a relatively low crystallinity, and thus may be different from crystalline carbon or graphite carbon. The carbonaceous material may be, for example, a carbonaceous negative electrode active material.

[0134] Composite anode active materials can be, for example, in particulate form (in the form of particles). Composite anode active materials in particulate form can have particle sizes, for example, from about 10 nm to about 4 μm, from about 10 nm to about 1 μm, from about 10 nm to about 500 nm, from about 10 nm to about 200 nm, or from about 10 nm to about 100 nm. If (for example, when) the composite anode active material has a particle size within the aforementioned range, it can further promote the reversible absorption and / or desorption of lithium during charge and discharge. Metallic anode active materials supported on a support can be, for example, in particulate form. Metallic anode active materials can have particle sizes, for example, from about 1 nm to about 200 nm, from about 1 nm to about 150 nm, from about 5 nm to about 100 nm, or from about 10 nm to about 50 nm. Carbon-based supports can be, for example, in particulate form. For example, carbon-based supports can have particle sizes of about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 500 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. Using carbon-based supports with particle sizes within the aforementioned ranges allows for a more uniform (e.g., substantially more uniform) distribution within the first anode active material layer. For example, the carbon-based support can be nanoparticles with a particle size of 500 nm or smaller (in the nanometer scale). The particle sizes of the composite anode active material, the metal-based anode active material, and the carbon-based support can be, for example, the average particle size. The average particle size can be, for example, the median particle size (D50) measured by a laser-type (or laser-like) particle size analyzer. In one or more embodiments, the average particle size can be determined automatically using software or manually from electron microscope images.

[0135] [Negative electrode: binder] The binder included in the first negative electrode active material layer 22 can be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc. However, the binder is not limited to the foregoing examples and can be any suitable material commonly available in the art and / or commonly used as a binder. The binder can consist of a single type (class) of binder or multiple types (classes) of binders.

[0136] Because the first negative electrode active material layer 22 includes a binder, it can be stabilized on the negative electrode current collector 21. Furthermore, despite volume changes and / or displacements of the first negative electrode active material layer 22 during charge and discharge processes, crack formation in the first negative electrode active material layer 22 can be suppressed or reduced. For example, if (e.g., when) the first negative electrode active material layer 22 does not contain any binder, it may delaminate from the negative electrode current collector 21 (e.g., easily). Since the first negative electrode active material layer 22 delaminates from the negative electrode current collector 21, the negative electrode current collector 21 and the electrolyte layer 30 come into contact with each other in the exposed area of ​​the negative electrode current collector 21, potentially increasing the likelihood of a short circuit. For example, the first negative electrode active material layer 22 can be prepared by coating and drying a slurry containing a material that forms (or provides) the first negative electrode active material layer 22 on the negative electrode current collector 21. By including a binder in the first negative electrode active material layer 22, stable dispersion of the negative electrode active material in the slurry can be achieved. For example, if (e.g., when) the paste is applied to the negative electrode current collector 21 by screen printing, it is possible to prevent or reduce screen clogging (e.g., clogging by agglomerates of the negative electrode active material).

[0137] [Anode: Other additives] The first negative electrode active material layer 22 may also include other additives used in comparable all-solid-state secondary batteries in the relevant field, such as fillers, coating agents, dispersants, ion-conducting agents, etc.

[0138] [Negative electrode: Solid electrolyte] The first negative electrode active material layer 22 may also include a solid electrolyte. The solid electrolyte may be, for example, a material included in the electrolyte layer 30 (e.g., selected from materials included in the electrolyte layer 30). The solid electrolyte included in the first negative electrode active material layer 22 may serve as a reaction site for initiating lithium metal formation, as a space for storing the formed lithium metal, or as a pathway for transferring lithium ions within the first negative electrode active material layer 22. In one or more embodiments, a solid electrolyte may not be provided.

[0139] In the first negative electrode active material layer 22, the concentration of the solid electrolyte can be relatively high in the region adjacent to the electrolyte layer 30 and relatively low in the region adjacent to the negative electrode current collector 21. For example, the solid electrolyte in the first negative electrode active material layer 22 can have a concentration gradient in which the concentration of the solid electrolyte gradually decreases from the region adjacent to the electrolyte layer 30 to the region adjacent to the negative electrode current collector 21.

[0140] [Negative Electrode: First Negative Electrode Active Material Layer] The ratio 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, B / A, can be from approximately 0.005 to approximately 0.45. The initial charge capacity of the positive electrode active material layer 12 can be determined from the first open-circuit voltage relative to Li / Li + The initial charging capacity of the first negative electrode active material layer 22 can be determined at the maximum charging voltage relative to the second open-circuit voltage. + Determined at 0.01V.

[0141] The maximum charging voltage can be determined by the type (or kind) of the composite positive electrode active material. The maximum charging voltage can be, for example, 1.5V, 2.0V, 2.5V, 3.0V, 3.5V, 4.0V, 4.2V, or 4.3V. For example, the maximum charging voltage of Li₂S or a Li₂S composite can be relative to Li / Li + 2.5V. For example, the maximum charging voltage of Li2S or Li2S complexes can be relative to Li / Li + 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 (B / A) can be, for example, about 0.01 to about 0.3, about 0.01 to about 0.2, or about 0.05 to about 0.1. The initial charge capacity (mAh) of the positive electrode active material layer 12 can be obtained by multiplying the specific charge capacity (mAh / g) of the composite positive electrode active material by the mass (g) of the composite positive electrode active material in the positive electrode active material layer 12. If (for example, when) multiple types (species) of composite positive electrode active materials are used, the product of specific charge density × mass can be calculated for each composite positive electrode active material, and the sum of these products can be defined as 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 can also be calculated in substantially the same manner. The initial charge capacity of the first negative electrode active material layer 22 can be obtained by multiplying the specific charge 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. If (e.g., when) multiple types (variety) of negative electrode active materials are used, the product of specific charge density × mass can be calculated for each negative electrode active material, and the sum of these products can be defined as the initial charge capacity of the first negative electrode active material layer 22. The specific charge density of the composite positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell using lithium metal as the counter electrode. The initial charge capacity of each of the positive electrode active material layer 12 and the first negative electrode active material layer 22 can be obtained using an all-solid-state half-cell at a constant current density (e.g., at 0.1 mA / cm²). 2 (Below) Direct measurement. For the positive electrode, measurements can be taken from the first open-circuit voltage (OCV) to the maximum charging voltage (e.g., 3.0V relative to Li / Li).+ This measurement is performed on the operating voltage of the electrode. For the negative electrode, this measurement can be performed on the operating voltage relative to the negative electrode (e.g., lithium metal) from the second OCV to 0.01V. For example, an all-solid-state half-cell with a positive electrode active material layer can be measured at 0.1mA / cm. 2 A constant current is applied from the first OCV to 3.0V, and the all-solid-state half-cell with the first negative electrode active material layer can be charged at 0.1mA / cm. 2 A constant current charges the device from the second OCV to 0.01V. For example, the current density during constant current charging could be 0.2mA / cm². 2 or 0.5mA / cm 2 All-solid-state half-cells with a positive electrode active material layer can be charged from the first OCV to, for example, 2.5V, 2.0V, 3.5V, or 4.0V. The maximum charging voltage of the positive electrode active material layer can be determined based on the maximum voltage of a battery that meets the safety conditions described in JISC 8712:2015 of the Japanese Standards Institute.

[0142] If (for example, when) the initial charge capacity of the first negative electrode active material layer 22 is excessively (or relatively) small, the thickness of the first negative electrode active material layer 22 becomes extremely small. As a result, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 during repeated charge-discharge processes may cause the first negative electrode active material layer 22 to disintegrate, making it difficult to achieve improved cycle performance of the all-solid-state secondary battery 1. If (for example, when) the charge capacity of the first negative electrode active material layer 22 is excessively (or relatively) large, the energy density of the all-solid-state secondary battery 1 may decrease, and the internal resistance of the all-solid-state secondary battery 1 may increase due to the first negative electrode active material layer 22, making it difficult to achieve improved cycle performance of the all-solid-state secondary battery 1.

[0143] For example, the thickness of the first negative electrode active material layer 22 can be 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. For example, the thickness of the first negative electrode active material layer 22 can be about 1% to about 50%, about 1% to about 40%, about 1% to about 30%, about 1% to about 20%, about 1% to about 10%, or about 1% to about 5% relative to the thickness of the positive electrode active material layer 12. The first negative electrode active material layer 22 can have a thickness of, for example, about 1 μm to about 20 μm, about 2 μm to about 15 μm, or about 3 μm to about 10 μm. If (for example, when) the first negative electrode active material layer 22 is excessively (or relatively) thin, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 may cause the first negative electrode active material layer 22 to disintegrate, making it difficult to achieve improved cycle performance of the all-solid-state secondary battery 1. If (for example, when) the thickness of the first negative electrode active material layer 22 is excessively (or significantly) increased, the energy density of the all-solid-state secondary battery 1 may decrease, and the internal resistance of the all-solid-state secondary battery 1 may increase due to the first negative electrode active material layer 22, thus making it difficult to achieve improved cycle performance of the all-solid-state secondary battery 1. As 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 may also decrease.

[0144] [Negative electrode: Second negative electrode active material layer] Reference Figure 3 The all-solid-state secondary battery 1, after charging, may further include, for example, a second negative electrode active material layer 24 disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The second negative electrode active material layer 24 may be a metal layer comprising lithium or a lithium alloy. In one or more embodiments, because the second negative electrode active material layer 24 is a lithium-containing metal layer, it can be used, for example, as a lithium storage device. The lithium alloy may include, but is not limited to, Li-Al alloys, Li-Sn alloys, Li-In alloys, Li-Ag alloys, Li-Au alloys, Li-Zn alloys, Li-Ge alloys, Li-Si alloys, etc., and may be any suitable material commonly available in the art and / or commonly used as a lithium alloy. The second negative electrode active material layer 24 may be composed of one of these alloys or lithium, or may be composed of one (or more) suitable alloys. The second negative electrode active material layer 24 may be, for example, a plating. For example, the second negative electrode active material layer 24 may be plated between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charging process of the all-solid-state secondary battery 1.

[0145] The thickness of the second negative electrode active material layer 24 is not limited, but can be, for example, about 1 μm to about 500 μm, about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 1 μm to about 100 μm, or about 1 μm to about 50 μm. If the thickness of the second negative electrode active material layer 24 is excessively (or relatively) small, the second negative electrode active material layer 24 may not be able to function adequately as a lithium storage device. If, for example, the thickness of the second negative electrode active material layer 24 is excessively (or relatively) large, the mass and volume of the all-solid-state secondary battery 1 may increase, and the cycle performance of the all-solid-state secondary battery 1 may be more likely to deteriorate.

[0146] In one or more embodiments, in the all-solid-state secondary battery 1, before assembling the all-solid-state secondary battery 1, a second negative electrode active material layer 24 may be arranged, for example, between the negative electrode current collector 21 and the first negative electrode active material layer 22. In embodiments where the second negative electrode active material layer 24 is arranged 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, since the second negative electrode active material layer 24 is a lithium-containing metal layer, it can act as a lithium storage device. For example, before assembling the all-solid-state secondary battery 1, a lithium foil may be arranged between the negative electrode current collector 21 and the first negative electrode active material layer 22.

[0147] In cases where a second negative electrode active material layer 24 is deposited during charging after assembling the all-solid-state secondary battery 1, the all-solid-state secondary battery 1 can have an increased energy density because the second negative electrode active material layer 24 is not included during the assembly of the all-solid-state secondary battery 1. If (e.g., when) the all-solid-state secondary battery 1 is charged, a charge exceeding the charging capacity of the first negative electrode active material layer 22 can be performed. The first negative electrode active material layer 22 can then be overcharged. At the start of charging, lithium can be 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 can form an alloy or compound with lithium ions moving from the positive electrode 10. If (e.g., when) a charge exceeding the capacity of the first negative electrode active material layer 22 is performed, lithium can be deposited on, for example, the back surface of the first negative electrode active material layer 22 (e.g., between the negative electrode current collector 21 and the first negative electrode active material layer 22), and the deposited lithium can then form a metal layer corresponding to the second negative electrode active material layer 24. The second negative electrode active material layer 24 can be a metal layer mainly composed of lithium (i.e., metallic lithium). This result can be attributed to the fact that the negative electrode active material included in the first negative electrode active material layer 22 comprises materials that form alloys or compounds with lithium. During discharge, lithium in the metal layers (e.g., in the first negative electrode active material layer 22 and the second negative electrode active material layer 24) can be ionized and migrate toward the positive electrode 10. In one or more embodiments, lithium can be used as the negative electrode active material in the all-solid-state secondary battery 1. In one or more embodiments, the first negative electrode active material layer 22 covers the second negative electrode active material layer 24, thus acting as a protective layer for the metal layers (e.g., the second negative electrode active material layer 24) while suppressing or reducing the precipitation and growth of lithium dendrites. In one or more embodiments, short circuits and capacity decay in the all-solid-state secondary battery 1 can be suppressed or reduced, thereby improving the cycle performance of the all-solid-state secondary battery 1. In one or more embodiments, where the second negative electrode active material layer 24 is arranged by charging after the all-solid-state secondary battery 1 is assembled, the negative electrode 20 (e.g., the negative electrode current collector 21, the first negative electrode active material layer 22, and the region therebetween) can be a Li-free region while the all-solid-state secondary battery 1 is in its initial state or fully discharged state.

[0148] [Negative electrode: Negative electrode current collector] The negative electrode current collector 21 can be formed of a material that does not react with lithium (e.g., does not form an alloy or compound with lithium). The material providing the negative electrode current collector 21 can be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), etc., but is not limited to these, and can be any suitable material commonly available in the art and / or commonly used as an electrode current collector. The negative electrode current collector 21 can be formed of one type (or class) of the aforementioned metals, an alloy of two or more types (classes) of such metals, or a covering material. The negative electrode current collector 21 can be, for example, plate-type (or foil-type) or foil-type (or foil-type).

[0149] Reference Figure 2 The all-solid-state secondary battery 1 may further include a thin film 23 on one side of the negative electrode current collector 21, comprising elements capable of forming an alloy with lithium. The thin film 23 may be located between the negative electrode current collector 21 and the first negative electrode active material layer 22. The thin film 23 may include, for example, elements capable of forming an alloy with lithium. Examples of elements capable of forming an alloy with lithium include gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but are not limited thereto; any suitable element commonly available and / or commonly used in the art capable of forming an alloy with lithium may be used. The thin film 23 may be composed of one of the aforementioned metals, or may be composed of an alloy of one or more suitable types of metals. If (for example, when) the thin film 23 is arranged on the negative electrode current collector 21, the second negative electrode active material layer 24 deposited between the thin film 23 and the first negative electrode active material layer 22 may have a further planarized form, and may further improve the cycle performance of the all-solid-state secondary battery 1.

[0150] For example, the thin film 23 may have a thickness of about 1 nm to about 800 nm, about 10 nm to about 700 nm, about 50 nm to about 600 nm, or about 100 nm to about 500 nm. If (for example, when) the thickness of the thin film 23 is less than 1 nm, it may be difficult to achieve the functions attributable to the thin film 23. If (for example, when) the thickness of the thin film 23 is excessively (or relatively) large, the thin film 23 may absorb lithium itself, resulting in a reduction in the amount of lithium deposited at the negative electrode. As a result, the all-solid-state secondary battery 1 may have a reduced energy density and degraded cycle performance. The thin film 23 may be located on the negative electrode current collector 21 by vacuum deposition, sputtering, plating, etc., but is not limited to the foregoing methods, and may be any suitable method generally available and / or commonly used in the art capable of forming (or providing) the thin film 23.

[0151] In one or more embodiments, the negative electrode current collector 21 may include a substrate film and a metal layer disposed on one or both sides (e.g., opposite sides) of the substrate film. For example, the substrate film may include a polymer. For example, the polymer may be a thermoplastic polymer. For example, the polymer may include polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), and / or any suitable combination thereof. The polymer may be an insulating polymer. Because the substrate film includes an insulating thermoplastic polymer, in the event of a short circuit, the substrate film softens or liquefies, preventing battery operation and thus preventing or reducing a rapid increase in current. For example, the metal layer may include copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The negative electrode current collector 21 may also include a metal sheet and / or lead terminals. For a detailed description of the substrate film, metal layer, metal sheet, and lead terminals of the negative electrode current collector 21, refer to the positive electrode current collector 11 described above. If (for example, when) the negative electrode current collector 21 has the above structure, the weight of the negative electrode can be reduced, which in turn can improve the energy density of the negative electrode and the lithium battery.

[0152] [Electrolyte layer] [Electrolyte layer: Electrolyte] Reference Figures 1 to 5 The electrolyte layer 30 may include an electrolyte disposed between the positive electrode 10 and the negative electrode 20. For example, the electrolyte may include a solid electrolyte, a gel electrolyte, and / or any suitable combination thereof.

[0153] Examples of solid electrolytes may include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes and / or any suitable combination thereof.

[0154] Solid electrolytes can be, for example, sulfide-based solid electrolytes. Sulfide-based solid electrolytes can be one or more of the following (e.g., selected from one or more of the following): 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 Where m and n are both positive numbers, and Z is Ge, Zn, or Ga; Li2S-GeS2; Li2S-SiS2-Li3PO4; Li2S-SiS2-Lip MO q Where p and q are both positive numbers, and M is P, Si, Ge, B, Al, Ga, or In; Li 7-x PS 6-x Cl x Where 0 ≤ x ≤ 2; Li 7-x PS 6-x Br x Where 0 ≤ x ≤ 2; and / or Li 7-x PS 6-x I x Where 0 ≤ x ≤ 2. Sulfide-based solid electrolytes can be prepared by treating starting materials such as Li₂S and P₂S₅ using methods such as melt quenching, mechanical grinding, etc. In one or more embodiments, heat treatment may be performed after such treatment. Sulfide-based solid electrolytes can be amorphous or crystalline, or can be a mixture thereof. In one or more embodiments, among the sulfide-based solid electrolyte materials described herein, the solid electrolyte can be a material containing at least sulfur (S), phosphorus (P), and lithium (Li) as its constituent elements. For example, the solid electrolyte can be a material comprising Li₂S-P₂S₅. If (e.g., when) the sulfide-based solid electrolyte material used to form (or provide) the solid electrolyte comprises Li₂S-P₂S₅, the mixing molar ratio of Li₂S:P₂S₅ can be in the range of, for example, about 20:80 to about 90:10, about 25:75 to about 90:10, about 30:70 to about 70:30, or about 40:60 to about 60:40.

[0155] For example, sulfide solid electrolytes may include sulfide-germanium ore type (or similar) solid electrolytes represented by Formula 1: <Formula 1> Li + 12-n-x A n+ X 2- 6-x Y - x .

[0156] In Formula 1, A can be P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; X can be S, Se, or Te; Y can be Cl, Br, I, F, CN, OCN, SCN, or N3, and can satisfy 1 ≤ n ≤ 5 and 0 ≤ x ≤ 2. For example, sulfide solid electrolytes can be sulfide-germanium ore type (or similar) compounds including one or more of the following (e.g., selected from one or more of the following): Li 7-x PS 6-x Cl x Where 0 ≤ x ≤ 2; Li7-x PS 6-x Br x , where 0 ≤ x ≤ 2; and Li 7- x PS 6-x I x , where 0 ≤ x ≤ 2. For example, the sulfide-based solid electrolyte may be a thiogermanate-type (or analogous) compound including at least one of Li6PS5Cl, Li6PS5Br, and Li6PS5I (e.g., at least one selected from the following).

[0157] The thiogermanate-type (or analogous) solid electrolyte may have a density of about 1.5 g / cc to about 2.0 g / cc. If (e.g., when) the thiogermanate-type (or analogous) solid electrolyte has a density of 1.5 g / cc or greater, the internal resistance of the all-solid-state secondary battery can be reduced, and the penetration of Li into the electrolyte layer can be more effectively suppressed or reduced.

[0158] The oxide-based solid electrolyte may be, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 < x < 2, and 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (0 ≤ x < 1, and 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, and 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, and 0 < z < 3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0 ≤ x ≤ 1, and 0 ≤ y ≤ 1), Li x La yTiO3 (0 < x < 2, and 0 < y < 3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, and 0 ≤ x ≤ 10) and / or any suitable combination thereof. Oxide - based solid electrolytes are manufactured, for example, by a sintering method or the like.

[0159] For example, a polymer solid electrolyte may include a mixture of a lithium salt and a polymer, or may include a polymer having an ion - conductive functional group. For example, a polymer solid electrolyte may be a polymer electrolyte in a solid state at 25 °C and 1 atm. For example, a polymer solid electrolyte may not contain a liquid. A polymer solid electrolyte may include a polymer, and the polymer may be, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride - hexafluoropropylene (PVDF - HFP), polyethylene oxide (PEO), poly(styrene - b - ethylene oxide) block copolymer (PS - PEO), poly(styrene - butadiene), poly(styrene - isoprene - styrene), poly(styrene - b - divinylbenzene) block copolymer, poly(styrene - ethylene oxide - styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), poly(methyl methacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), poly(ethylenedioxythiophene) (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(benzimidazole - benzoisoquinolinone)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10 - diphenylanthracene - 2 - sulfonate (DPASLi + ) and / or any suitable combination thereof. However, the polymer is not limited to the foregoing examples and may be any material commonly available in the art and / or commonly used in polymer electrolytes. The lithium salt may be any lithium salt available in the art. The lithium salt may be, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1SO2 (where x and y are integers from 1 to 20), LiCl, LiI, and / or any suitable mixture thereof. For example, the polymer included in the polymeric solid electrolyte may be a compound containing 10 or more repeating units, 20 or more repeating units, 50 or more repeating units, or 100 or more repeating units. For example, the polymer included in the polymeric solid electrolyte may have a weight-average molecular weight of 1,000 Daltons or greater, 10,000 Daltons or greater, 100,000 Daltons or greater, or 1,000,000 Daltons or greater.

[0160] For example, a gel electrolyte can be a polymeric gel electrolyte. Alternatively, a gel electrolyte can have a gel state without containing a polymer.

[0161] For example, a polymeric gel electrolyte may comprise a liquid electrolyte and a polymer, or an organic solvent and a polymer having ionicly conductive functional groups. For example, a polymeric gel electrolyte may be a polymeric electrolyte in a gel state at 25°C and 1 atm. For example, a polymeric gel electrolyte may have a gel state without containing a liquid. The liquid electrolyte used for the polymeric gel electrolyte may be, for example, a mixture of an ionic liquid, a lithium salt, and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; and / or any suitable mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used for the polymeric gel electrolyte may be a polymer used for solid polymeric electrolytes (e.g., selected from polymers used for solid polymeric electrolytes). The organic solvent may be an organic solvent used for liquid electrolytes (e.g., selected from organic solvents used for liquid electrolytes). The lithium salt may be a lithium salt used for polymeric solid electrolytes (e.g., selected from lithium salts used for polymeric solid electrolytes). An ionic liquid may refer to a room-temperature molten salt that comprises only ions (e.g., consists only of ions) and has a melting point at room temperature or lower, or a salt that is liquid at room temperature. For example, an ionic liquid may be at least one of the following compounds (e.g., selected from at least one of the following compounds): a) at least one cation of ammonium, pyrrolidineonium, pyridinium, pyrimidineonium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazineonium, phosphonium, sulfonium, triazolium and / or any suitable mixture thereof (e.g., selected from among them); 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 - At least one anion (e.g., selected from among them). For example, a polymeric solid electrolyte can be formed (or provided) by impregnating a liquid electrolyte in a secondary battery. The polymeric gel electrolyte may also include inorganic particles. For example, the polymer included in the polymeric gel electrolyte may be a compound comprising 10 or more repeating units, 20 or more repeating units, 50 or more repeating units, or 100 or more repeating units. For example, the polymer included in the polymeric gel electrolyte may have a weight-average molecular weight of 500 Daltons or greater, 1,000 Daltons or greater, 10,000 Daltons or greater, 100,000 Daltons or greater, or 1,000,000 Daltons or greater.

[0162] [Electrolyte layer: binder] The electrolyte layer 30 may also include, for example, an adhesive. The adhesive included in the electrolyte layer 30 may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to the foregoing examples, and any suitable adhesive commonly available and / or commonly used in the art may be used. The adhesive in the electrolyte layer 30 may be the same as or different from the adhesive included in the positive electrode active material layer 12 and the negative electrode active material layer 22. In one or more embodiments, an adhesive may not be provided.

[0163] The amount (e.g., quantity) of the binder included in the electrolyte layer 30 relative to the total weight of the electrolyte layer 30 may be about 0.1 wt% to about 10 wt%, about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 1 wt%, about 0 wt% to about 0.5 wt%, or about 0 wt% to about 0.1 wt%.

[0164] [Methods for preparing composite positive electrode active materials] To prepare composite positive electrode active materials, Li2S-containing compositions can be ball-milled to produce primary particles comprising Li2S-containing composites.

[0165] Once primary particles are prepared, they can be granulated to produce secondary particles, thereby creating a composite positive electrode active material. Because secondary particles are prepared by granulating primary particles, the D10 of the secondary particles can be 5 μm or larger.

[0166] According to one or more embodiments, primary particles comprising a Li2S-containing complex can be prepared as follows: firstly, a first composition is prepared by first ball milling a composition comprising Li2S and a lithium salt; and after injecting a carbon-based material into the first composition, the first composition is ball milled a second time to thereby prepare primary particles comprising a Li2S-containing complex.

[0167] For details on Li2S-containing complexes, Li2S, lithium salts, and carbon-based materials, please refer to the description above.

[0168] According to one or more embodiments, the first ball mill and the second ball mill can each be performed independently at about 100 rpm to about 1,000 rpm for about 1 hour to about 20 hours. For example, the first ball mill and the second ball mill can each be performed independently at about 200 rpm to about 800 rpm, about 300 rpm to about 700 rpm, or about 400 rpm to about 600 rpm. For example, the first ball mill and the second ball mill can each be performed independently for about 1 hour to about 16 hours, about 2 hours to about 12 hours, or about 3 hours to about 10 hours.

[0169] The preparation of secondary particles can be achieved by granulating primary particles. For example, granulation can be performed by loading primary particles into a mixer (such as the NOBILTA MINI or NARA Hybridization System from Hosokawa Micron).

[0170] For example, granulation can be performed by loading primary particles into a mixer (such as Hosokawa Micron's NOBILTAMINI, NARA Hybridization System, etc.) and then granulating at approximately 1,000 rpm to approximately 9,000 rpm for approximately 1 minute to approximately 30 minutes.

[0171] For example, granulation can be carried out by loading primary particles into a container of Hosokawa Micron's NOBILTA MINI, and the loading amount of primary particles before granulation can be about 20% to about 80% of the total volume of the container, about 30% to about 70% of the total volume, about 30% to about 60% of the total volume, or about 30% to about 50% of the total volume of the container.

[0172] For example, granulation can be carried out for about 2 minutes to about 25 minutes, about 3 minutes to about 20 minutes, about 5 minutes to about 20 minutes, or about 10 minutes to about 20 minutes. For example, granulation can be carried out at about 1,000 rpm to about 9,000 rpm, about 2,000 rpm to about 8,000 rpm, about 3,000 rpm to about 7,000 rpm, or about 4,000 rpm to about 6,000 rpm.

[0173] This disclosure will be described in more detail through the following examples and comparative examples. However, it will be understood that the examples provided are for illustrative purposes only and are not to be construed as limiting the scope of this disclosure.

[0174] (Preparation of composite positive electrode active material) Preparation Example 1: Li₂S-LiI-CNF, 3 steps, secondary particle D₁₀ = 5.1 μm (Step 1) Li₂S and LiI were mixed at a weight ratio of 30:20. The resulting mixture was mechanically milled using a ball mill to produce a Li₂S-LiI composite. Milling was performed at 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G.

[0175] (Step 2) The Li₂S-LiI composite and carbon nanofibers (CNF) were mixed at a weight ratio of 50:10. The Li₂S-LiI-CNF composite was prepared by mechanically grinding the mixture using a ball mill. Grinding was carried out at 25°C and 600 rpm for 10 hours. The grinding energy applied to the sample during grinding was 28 G.

[0176] The Mohs hardness of Li2S is 0.6, that of LiI is 2.0, and that of carbon nanofibers (CNF) is 1.5.

[0177] (Step 3) The Li₂S-LiI-CNF composite was loaded into a NOBILTA MINI container from Hosokawa Micron. The loading was 40% by volume relative to the total volume of the container. The mixture was then run at 5000 rpm for 10 minutes to prepare secondary particles. The secondary particles of the Li₂S-LiI-CNF composite were used as the composite positive electrode active material.

[0178] The D10 (e.g., D10 size) of the Li2S-LiI-CNF composite secondary particles was measured using a laser scattering particle size distribution analyzer (HORIBA, LA-920) and refers to the median particle size (D10) at the point where 10% of the total volume of particles in the sample has been accumulated from the smallest particle size. The D10 (e.g., D10 size) of the Li2S-LiI-CNF composite secondary particles is 5.1 μm. The D50 (e.g., D50 size) of the Li2S-LiI-CNF composite secondary particles was measured using a laser scattering particle size distribution analyzer (HORIBA, LA-920) and refers to the median particle size (D50) at the point where 50% of the total volume of particles in the sample has been accumulated from the smallest particle size. The D90 (e.g., D90 size) of the Li2S-LiI-CNF composite secondary particles was measured using a laser scattering particle size distribution analyzer (HORIBA, LA-920) and refers to the value of the median particle size (D90) at the point where 90% of the total volume of particles in the sample has been accumulated from the smallest particle size.

[0179] Preparation Example 2: Li₂S-LiI-CNF, 3 steps, secondary particle D₁₀ = 7.2 μm Except for the preparation of secondary particles at 3,000 rpm and 10 minutes in step 3, and the resulting secondary particles having a D10 of 7.2 μm, the composite positive electrode active material was prepared following essentially the same process as in Example 1.

[0180] Preparation Example 3: Li₂S-LiI-CNF, 3 steps, secondary particle D₁₀ = 9.2 μm Except for the preparation of secondary particles at 5,000 rpm and 5 minutes in step 3, and the resulting secondary particles having a D10 of 9.2 μm, the composite positive electrode active material was prepared following essentially the same process as in Example 1.

[0181] Preparation Example 4: Li₂S-LiI-CNF, 3 steps, secondary particle D₁₀ = 7.4 μm In step 3, the Li2S-LiI-CNF powder was premixed with 5 wt% anhydrous xylene solvent using a Thinky mixer, and the resulting mixture was loaded into a NOBILT AMINI container for secondary granulation. The composite positive electrode active material was prepared following essentially the same process as in Example 1, except that xylene was used as an additive during secondary granulation to prepare secondary particles, and the resulting secondary particles had a D10 of 7.4 μm.

[0182] Comparative preparation example 1: Li₂S-LiI-CNF, 3 steps, secondary particle D₁₀ = 3.36 μm Except for the preparation of secondary particles at 9,000 rpm and 10 minutes in step 3, and the preparation of secondary particles with a D10 size (e.g., diameter or major axis) of 3.36 μm using modified granulation conditions for secondary particles, the composite positive electrode active material was prepared following essentially the same process as in Example 1.

[0183] Comparative preparation example 2: Li₂S-LiI-CNF, 2 steps, primary particle D₁₀ = 2.4 μm (Step 1) Li₂S and LiI were mixed at a weight ratio of 30:20. The resulting mixture was mechanically milled using a ball mill to produce a Li₂S-LiI composite. Milling was performed at 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 28 G.

[0184] (Step 2) The Li₂S-LiI composite and carbon nanofibers (CNF) were mixed at a weight ratio of 50:10. The Li₂S-LiI-CNF composite was prepared by mechanically grinding the mixture using a ball mill. Grinding was carried out at 25°C and 600 rpm for 10 hours. The grinding energy applied to the sample during grinding was 28 G.

[0185] The Mohs hardness of Li₂S is 0.6, that of LiI is 2.0, and that of carbon nanofibers (CNF) is 1.5. Primary particles of the Li₂S-LiI-CNF composite were used as the composite positive electrode active material. The D10 of the primary particles of the Li₂S-LiI-CNF composite was 2.4 μm.

[0186] (Evaluation Example 1) The D10, D50, and D90 of the composite positive electrode active materials prepared according to Preparation Examples 1 to 4, and Comparative Preparation Examples 1 and 2, were measured using a particle size analyzer. Particle size was measured using a laser scattering particle size distribution analyzer (LA-920 manufactured by HORIBA). For example, the median particle size at the point where 10% of the total volume of particles in the sample accumulated from the smallest particle size was taken as D10, the median particle size at the point where 50% of the total volume of particles in the sample accumulated from the smallest particle size was taken as D50, and the median particle size at the point where 90% of the total volume of particles in the sample accumulated from the smallest particle size was taken as D90. Anhydrous xylene was used as the solvent for the measurement. The measurement results are shown in Table 1.

[0187] [Table 1]

[0188] (Preparation of positive electrode and secondary battery) Example 1 (Preparation of the positive electrode) As the positive electrode active material, secondary particles of the Li2S-LiI-CNF composite prepared in Preparation Example 1 were prepared. As the solid electrolyte, Li6PS5Cl crystals (D50 = 3.0 μm, crystalline) of the argyrogermanium sulfide type (or similar) were prepared. As the binder, PTFE was prepared. The aforementioned materials were mixed at a weight ratio of composite positive electrode active material: solid electrolyte: binder = 60:40:1.2 to prepare a positive electrode mixture. The positive electrode mixture was obtained by dry mixing using a blender.

[0189] The positive electrode mixture was placed on one side of a positive electrode current collector made of aluminum foil coated with carbon on one side, and plated at a pressure of 200 MPa for 10 minutes to manufacture the positive electrode. 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 positive electrode active material layer and the positive electrode current collector had the same surface area.

[0190] (Preparation of the negative electrode) As the negative electrode current collector, a stainless steel (SUS) foil with a thickness of 10 μm is prepared. As the negative electrode active material, carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle size of about 60 nm are prepared.

[0191] A mixed solution was prepared by adding 4 grams of an n-methyl-2-pyrrolidone (NMP) solution containing 7 wt% polyvinylidene fluoride (PVDF) binder (#9300, KUREHA) to a container containing 4 grams of a mixed powder of CB and Ag particles in a weight ratio of 3:1. The mixed solution was stirred while NMP was gradually added to prepare a slurry. The prepared slurry was applied to a stainless steel (SUS) foil using a bar coater, then dried in the open air at 80°C for 10 minutes and under vacuum at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold-rolled to planarize its surface to prepare a negative electrode with 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 first negative electrode active material layer and the negative electrode current collector had the same surface area.

[0192] (Preparation of solid electrolyte layer) A mixture was prepared by adding 1.5 parts by weight of polyacrylic acid binder to 98.5 parts by weight of solid electrolyte in sulforaphane-germanium ore type (or similar) Li6PS5Cl solid electrolyte crystals (D50 = 3.0 μm, crystalline). The prepared mixture was stirred while octyl acetate was added to prepare a slurry. The prepared slurry was applied to a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate using a rod coater and dried in the open air at 80°C for 10 minutes to prepare a laminate. The prepared laminate was then vacuum dried at 80°C for 2 hours to prepare the solid electrolyte layer.

[0193] (Non-active component) A slurry obtained by mixing cellulose fibers, glass fibers, aluminum hydroxide (Al(OH)3), polyacrylic acid binder and solvent is molded into the form of a gasket, and then the solvent is removed from it to prepare a flame-retardant inactive component.

[0194] The weight ratio of pulp fiber (cellulose fiber): glass fiber: aluminum hydroxide (Al(OH)3): polyacrylic acid binder is 20:8:70:2. The thickness of the inactive component is 120μm.

[0195] Before placing the prepared flame-retardant inactive component on the solid electrolyte layer, the flame-retardant inactive component is heat-treated in a vacuum at 80°C for 5 hours to remove moisture and other substances.

[0196] (Preparation of all-solid-state secondary batteries) Reference Figure 1 A solid electrolyte layer is disposed on the negative electrode, such that a first negative electrode active material layer is in contact with the solid electrolyte layer, and a positive electrode is disposed on the solid electrolyte layer. A gasket is arranged to surround and be located around the positive electrode, thereby fabricating a laminate. The gasket thickness is approximately 120 μm. A flame-retardant inactive component is used as the gasket. The gasket is arranged to contact the side surface of the positive electrode and the top surface of the solid electrolyte. The positive electrode is disposed in the central portion of the solid electrolyte layer, and the gasket is positioned to extend to the end portion of the solid electrolyte layer while being located around (e.g., around) the positive electrode. The surface area of ​​the positive electrode is approximately 90% of the surface area of ​​the solid electrolyte layer, and the gasket is disposed over the remaining 10% of the entire surface area of ​​the solid electrolyte layer where the positive electrode is not disposed.

[0197] The prepared laminate was pressed at 85°C with a 500 MPa pressure plate for 30 minutes. This pressing process sintered the solid electrolyte layer, resulting in improved battery performance. The thickness of the sintered solid electrolyte layer was approximately 45 μm. The density of the Li6PS5Cl solid electrolyte, including the argyroclase-type (or quasi-argyroclase) crystals in the sintered solid electrolyte layer, was 1.6 g / cc. The surface area of ​​the solid electrolyte layer was the same as that of the negative electrode.

[0198] The pressed laminate is then placed in a bag and vacuum-sealed to manufacture an all-solid-state secondary battery. A portion of the positive current collector and a portion of the negative current collector are extended out of the sealed battery and used as the positive and negative terminals, respectively.

[0199] Examples 2 to 4 Except for using the composite positive electrode active materials prepared in Preparation Examples 2 to 4 respectively, the positive electrode and the all-solid-state secondary battery were prepared following essentially the same process as in Example 1.

[0200] Compare Example 1 and Compare Example 2 Except for using the composite positive electrode active material prepared in Comparative Preparation Example 1 and Comparative Preparation Example 2 respectively, the positive electrode and all-solid-state secondary battery were prepared following essentially the same process as in Example 1.

[0201] Evaluation Example 2: Charge and Discharge Test The charge-discharge characteristics of the all-solid-state secondary batteries prepared in Examples 1 to 4, as well as Comparative Examples 1 and 2, were evaluated by the following charge-discharge tests.

[0202] Charge-discharge tests were conducted with the all-solid-state secondary battery placed in a constant temperature bath at 45°C.

[0203] In the first cycle, each battery was charged at a constant current of 0.1C for 12.5 hours until the battery voltage reached 2.5V to 2.8V. Then, it was discharged at a constant current of 0.1C for 12.5 hours until the battery voltage reached 0.3V.

[0204] The discharge capacity from the first cycle was used as the standard capacity. The standard capacity is expressed as the specific capacity of Li₂S in Table 1.

[0205] After the first cycle, charge-discharge cycles were performed under the same conditions as the first cycle until 150 cycles were completed. The measurement results are shown in Table 2. The initial efficiency is represented by Equation 1.

[0206] Equation 1 Initial efficiency [%] = [Discharge capacity in the first cycle / Charge capacity in the first cycle] × 100 Cycle count refers to the number of cycles required for the discharge capacity to drop to 80% of the standard capacity after the first cycle. A higher cycle count is considered to indicate a better battery life.

[0207] [Table 2]

[0208] As shown in Table 2, compared with the all-solid-state secondary batteries of Comparative Example 1 and Comparative Example 2, the all-solid-state secondary batteries of Examples 1 to 4 exhibit improved discharge capacity (e.g., specific capacity), initial efficiency, and lifetime characteristics.

[0209] List of reference numerals for key components 1: Solid electrolyte; 10 positive electrode 11: Positive electrode current collector; 12: Positive electrode active material layer 20: Positive electrode; 21: Negative electrode current collector 22: First negative electrode active material layer; 23: Thin film 24: Second negative electrode active material layer; 30: Electrolyte layer 40: Inactive components.

Claims

1. A positive electrode active material, said positive electrode active material comprising: Secondary particles are aggregates of primary particles, including those containing Li2S complexes. The secondary particles have a D10 size of 5 μm or larger.

2. The positive electrode active material according to claim 1, wherein, The secondary particles have a D10 size of 5 μm to 10 μm, a D50 size of 9 μm to 20 μm, and a D90 size of 16 μm to 60 μm.

3. The positive electrode active material according to claim 1, wherein, The Li2S-containing complex includes a complex of Li2S and lithium salt.

4. The positive electrode active material according to claim 3, in, The lithium salt is a binary or ternary compound. The binary compounds include LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or combinations thereof, and The ternary compounds include Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or combinations thereof.

5. The positive electrode active material according to claim 3, wherein, The Li2S-lithium salt complex has the formula Li2S-Li a X b And where 1≤a≤5, 1≤b≤5, and X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or combinations thereof.

6. The positive electrode active material according to claim 3, wherein, In the Li2S-containing composite, the molar ratio of Li2S to lithium salt is from 50:50 to 95:

5.

7. The positive electrode active material according to claim 3, wherein, The Li2S-containing composite also includes carbon-based materials.

8. The positive electrode active material according to claim 7, in, The carbon-based materials include fibrous carbon materials. The fibrous carbon material includes carbon nanostructures. The carbon nanostructures include carbon nanofibers, carbon nanotubes, carbon nanoribbons, carbon nanorods, or combinations thereof.

9. The positive electrode active material according to claim 7, in, The amount of carbonaceous material is from 1 wt% to 20 wt% relative to the total weight of the Li2S-containing composite.

10. A positive electrode for a solid-state secondary battery, the positive electrode comprising: Positive current collector; as well as A positive electrode active material layer is disposed on the positive electrode current collector and includes the positive electrode active material according to any one of claims 1 to 8.

11. The positive electrode according to claim 10, in, The amount of the positive electrode active material is 40 wt% to 90 wt% relative to the total weight of the positive electrode active material layer.

12. The positive electrode according to claim 10, in, The positive electrode active material layer also includes a solid electrolyte.

13. The positive electrode according to claim 12, in, The solid electrolyte is a sulfide-based solid electrolyte, and The sulfide solid electrolyte is selected from at least one of the following: 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 Where m and n are both positive numbers, and Z is Ge, Zn, or Ga; Li2S-GeS2; Li2S-SiS2-Li3PO4; Li2S-SiS2-Li p MO q Where p and q are both positive numbers, and M is P, Si, Ge, B, Al, Ga, or In; Li 7-x PS 6-x Cl x Where 0 ≤ x ≤ 2; Li 7-x PS 6-x Br x Where 0 ≤ x ≤ 2; Li 7-x PS 6-x I x , where 0≤x≤2; and combinations thereof.

14. The positive electrode according to claim 13, The sulfide-based solid electrolytes include silver-germanium sulfide-type solid electrolytes. in, The sulfosilver-germanium ore type solid electrolyte includes one or more selected from Li6PS5Cl, Li6PS5Br and Li6PS5I, and the sulfosilver-germanium ore type solid electrolyte has a density of 1.5 g / cc to 2.0 g / cc.

15. The positive electrode according to claim 10, wherein, The positive electrode active material layer also includes one or more selected from binders and conductive materials.

16. The positive electrode according to claim 10, in, The positive current collector includes a substrate film and a metal layer on at least one side of the substrate film. The substrate film comprises a polymer, including polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or combinations thereof, and the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof.

17. A solid-state secondary battery, the solid-state secondary battery comprising: positive electrode; negative electrode; as well as A solid electrolyte layer is located between the positive electrode and the negative electrode. The positive electrode includes the positive electrode according to any one of claims 10 to 16.

18. The all-solid-state secondary battery according to claim 17, in, The solid electrolyte layer includes a solid electrolyte, a gel electrolyte, or a combination thereof. The solid electrolyte includes sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or combinations thereof, and The gel electrolyte includes a polymer gel electrolyte.

19. A method for preparing a composite positive electrode active material, the method comprising the following steps: Primary particles comprising a Li2S-containing complex were prepared by ball milling of a composition containing Li2S; and Secondary particles are prepared by granulation of the primary particles. The secondary particles have a D10 size of 5 μm or larger.

20. The method according to claim 19, wherein, The steps for preparing the primary particles comprising the Li2S-containing complex include: A first composition comprising first particles is prepared by first ball milling a composition containing Li2S and lithium salt; Injecting carbonaceous material into the first composition; and After the carbonaceous material is injected, the first composition is subjected to a second ball milling to produce the primary particles comprising the Li2S-containing composite.

Images