Solid electrolyte layer comprising sulfur-based polymer, and all-solid-state battery comprising same

Abstract

The present invention relates to an all-solid-state battery. More specifically, the all-solid-state battery comprises: a positive electrode; a negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer includes a plurality of solid electrolyte particles and a polymer filler, the polymer filler comprises a polyolefin-based sulfur-containing polymer and a lithium salt, the content of the polymer filler may be 0.1 wt% to 8 wt% with respect to the total weight of the solid electrolyte layer, and the polyolefin-based sulfur-containing polymer may be 60 wt% to 90 wt% with respect to the total weight of the polymer filler.

Description

A solid electrolyte layer comprising a sulfur-based polymer, and an all-solid-state battery comprising the same

[0001] This is about all-solid-state batteries.

[0002] Recently, driven by industrial demands, the development of batteries with high energy density and stability is actively underway. For example, lithium-ion batteries are being commercialized not only in the fields of information and communication devices but also in the automotive sector. In the automotive sector, safety is considered particularly important because it is directly related to human life.

[0003] Recently, all-solid-state batteries in which liquid electrolytes are replaced with solid electrolytes have been proposed. By not using flammable organic dispersion media, all-solid-state batteries can significantly reduce the likelihood of fire or explosion in the event of a short circuit. Therefore, these all-solid-state batteries can offer significantly higher safety compared to lithium-ion batteries that use liquid electrolytes.

[0004] The problem that the present invention aims to solve is to improve the stability of an all-solid-state battery by maintaining the interfacial stability of the solid electrolyte layer and preventing interfacial delamination caused by volume changes during charging and discharging.

[0005] Another problem that the present invention aims to solve is to improve the charge / discharge performance of an all-solid-state battery by reducing pores within the solid electrolyte layer to suppress short circuits and improve ion conductivity.

[0006] A solid-state battery according to the concept of the present invention comprises a positive electrode; a negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer comprises a plurality of solid electrolyte particles and a polymer filler, and the polymer filler comprises a polyolefin-based sulfur-containing polymer and a lithium salt, wherein the content of the polymer filler is 0.1% to 8% by weight with respect to the total weight of the solid electrolyte layer, and the polyolefin-based sulfur-containing polymer may be 60% to 90% by weight with respect to the total weight of the polymer filler.

[0007] According to an embodiment of the present invention, the ion conductivity and mechanical stability can be improved by including a polymer in the solid electrolyte layer.

[0008] According to an embodiment of the present invention, the performance of an all-solid-state battery can be improved by providing stability to the solid interface of the all-solid-state battery.

[0009] FIG. 1 is a plan view of an all-solid-state battery according to an embodiment of the present invention.

[0010] Figure 2 is a cross-sectional view along the line A-A' of Figure 1.

[0011] Figure 3 is an enlarged view of the M region of Figure 2.

[0012] FIG. 4 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0013] FIG. 5 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0014] FIG. 6 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0015] FIG. 7 is a cross-sectional view of a solid electrolyte layer according to an embodiment of the present invention.

[0016] Figure 8 is an enlarged view of the N region of Figure 7, showing solid electrolyte particles.

[0017] FIGS. 9A and 9B are intended to illustrate an anode-solid electrolyte layer interface according to one embodiment of the present invention.

[0018] FIGS. 10a and FIGS. 10b are for illustrating a cathode-solid electrolyte layer interface according to one embodiment of the present invention.

[0019] FIG. 11a is a cross-sectional SEM image of an all-solid-state battery according to one embodiment of the present invention.

[0020] FIG. 11b is a cross-sectional SEM image of an all-solid-state battery according to a comparative example of the present invention.

[0021] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0022] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0023] The embodiments described herein will be described with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0024] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components to the mentioned components.

[0025] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) may be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0026] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0027] In this specification, “alloy” means a mixture of two or more metals.

[0028] In this specification, “electrode active material” refers to an electrode material capable of undergoing lithiation and delithiation.

[0029] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0030] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0031] In this specification, “lithiation” and “to lithiate” refer to the process of adding lithium to an electrode active material.

[0032] In this specification, “delithiation” and “to delithiate” refer to the process of removing lithium from an electrode active material.

[0033] In this specification, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery.

[0034] In this specification, “discharge” and “discharge” refer to the process of removing electrochemical energy from a battery.

[0035] In this specification, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0036] In this specification, “negative electrode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0037]

[0038] FIG. 1 is a plan view of an all-solid-state battery according to embodiments of the present invention. FIG. 2 is a cross-sectional view along line A-A' of FIG. 1. FIG. 3 is a cross-sectional view of region M of FIG. 2 enlarged to explain a positive electrode active material layer according to an embodiment of the present invention.

[0039] Referring to FIGS. 1 and 2, the all-solid-state battery (10) according to the present invention may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, not limited thereto, the all-solid-state battery (10) may further include an additional functional layer, such as an adhesion-enhancing layer, disposed between the positive electrode layer (100) and the solid electrolyte layer (300) or between the negative electrode layer (200) and the solid electrolyte layer (300).

[0040] An anode layer (100) according to one embodiment of the present invention may include an anode current collector (110) and an anode active material layer (120) disposed on the anode current collector (110). The anode active material layer (120) may include an anode active material, a solid electrolyte, a conductive material, and a binder.

[0041] The positive current collector (110) may provide a reference surface on which the positive active material layer (120) is disposed. The positive current collector (110) may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive current collector (110) may include a plate or a foil. In another embodiment of the present invention, the positive current collector (110) may be omitted. The thickness of the positive current collector (110) may be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0042] The positive current collector (110) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof.

[0043] The base film may be, for example, an insulator. Since the base film contains an insulating thermoplastic polymer, the base film may soften or liquefy upon the occurrence of a short circuit, thereby interrupting battery operation and suppressing a sudden increase in current.

[0044] The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or alloys thereof. The metal layer may act as an electrochemical fuse and cut off in the event of an overcurrent to perform a short-circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer may be plated or deposited on a base film. As the thickness of the metal layer decreases, the limit current and / or maximum current of the positive current collector (110) decreases, thereby improving the stability of the lithium battery in the event of a short circuit.

[0045] A lead tab may be added to the metal layer for external connection. The lead tab may be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or metal layer melt, allowing the metal layer to be electrically connected to the lead tab.

[0046] To make the weld between the metal layer and the lead tab more robust, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin sheet of the same material as the metal of the metal layer. The metal chip may be, for example, metal foil, metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to a metal chip / metal layer laminate or a metal chip / metal layer / base film laminate by placing the metal chip on the metal layer and then welding it to the lead tab. During welding, as the base film, metal layer, and / or metal chip melt, the metal layer or the metal layer / metal chip laminate may be electrically connected to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal layer.

[0047] The thickness of the base film may be, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. By having the base film within this thickness range, the weight of the electrode assembly can be reduced more effectively. The melting point of the base film may be, for example, 100 to 300 °C, 100 to 250 °C or lower, or 100 to 200 °C. By having the base film within this melting point range, the base film can melt during the welding process of the lead tab and be easily bonded to the lead tab. Surface treatments, such as corona treatment, may be performed on the base film to improve the adhesion between the base film and the metal layer.

[0048] The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. By having the metal layer within this range of thickness, the stability of the electrode assembly can be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. By having the metal piece within this range of thickness, the connection between the metal layer and the lead tab can be performed more easily. Since the positive current collector (110) has a laminated structure of the base film and the metal layer described above, the weight of the positive layer (100) can be reduced, and consequently, the energy density of the all-solid-state battery (10) can be improved.

[0049] In one embodiment of the present invention, the content of the positive active material in the positive active material layer (120) may be 10 wt% to 99 wt%, 30 wt% to 80 wt%, 40 wt% to 70 wt%, or 40 wt% to 50 wt% of the total weight of the positive active material layer (120). If the content of the positive active material is reduced excessively, the energy density of the all-solid-state battery (10) may decrease. If the content of the positive active material is increased excessively, the degradation of the all-solid-state battery (10) may be accelerated due to changes in the volume of the positive during charging and discharging.

[0050] The positive active material within the positive active material layer (120) can reversibly absorb and desorb lithium ions. The positive active material may include a plurality of particles. The positive active material according to the present invention may include an oxide-based positive active material, a sulfide-based positive active material, or a combination thereof.

[0051] The oxide-based cathode active material may include, for example, lithium transition metal oxides, metal oxides, or combinations thereof. Lithium transition metal oxides include, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt mangense oxide, lithium manganate, lithium iron phosphate, or combinations thereof. Lithium oxides may include, for example, iron oxide, vanadium oxide, or combinations thereof.

[0052] Sulfide-based cathode active materials may include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof. A more specific description of the sulfide-based cathode active material according to an embodiment of the present invention will be provided later.

[0053] For oxide-based cathode active materials, one or more types of composite oxides of lithium and a metal selected from, for example, cobalt, manganese, nickel, and combinations thereof may be used. For lithium-containing oxide-based cathode active materials, for example, Li a A 1-b B' b D2(wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O4-c D c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c Gd O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) It may include a compound represented by any one of the chemical formulas of Fe2(PO4)3(0 ≤ f ≤ 2); LiFePO4.

[0054] In the chemical formula representing the compound described above, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; and J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0055] The oxide-based cathode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen and metal atomic layers are alternately and regularly arranged in a specific direction, thereby forming a two-dimensional plane for each atomic layer. The "cubic rock salt type structure" represents a sodium chloride (NaCl) type structure, which is a type of crystal structure; specifically, it exhibits a structure in which face-centered cubic lattices (fcc) formed by cations and anions, respectively, are offset from each other by half the ridge of the unit lattice. Lithium transition metal oxides having such a layered rock salt type structure are, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0056] The oxide-based cathode active material may be covered by a coating layer (not shown). The oxide-based cathode active material may also be used as a mixture of the compound described above and the compound to which the coating layer is added. Meanwhile, the coating layer added to the surface of the cathode active material may include, for example, oxides, hydroxides, oxyhydroxides, oxycarbonates, or hydroxycarbonates of the following coating elements. The compounds forming this coating layer are amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer may be selected within a range that does not adversely affect the physical properties of the cathode active material. Examples of methods for forming the coating layer include spray coating and immersion methods.

[0057] When the oxide-based cathode active material contains nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, for example, the capacity density of the all-solid-state battery (10) is increased, and the metal leaching of the cathode active material in the charged state can be reduced. As a result, the cycle characteristics of the all-solid-state battery (10) in the charged state are improved. Meanwhile, "cycle characteristics" is a characteristic that indicates the degree of deterioration of the all-solid-state battery (10) due to charging and discharging of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics has a small degree of deterioration due to charging and discharging, while an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration due to charging and discharging.

[0058] The oxide-based cathode active material may have a particle shape such as a sphere or an ellipsoid. The particle size and content of the oxide-based cathode active material are not particularly limited. The size of the oxide-based cathode active material may be, for example, 0.1 to 30 μm, 0.5 to 20 μm, or 1 to 15 μm. The oxide-based cathode active material may be, for example, single-crystal particles or polycrystalline particles.

[0059] The positive active material layer (120) according to embodiments of the present invention may include a sulfide-based positive active material. Specifically, with reference to FIG. 3, the sulfide-based positive active material may include a Li2S-containing positive active material (CAC). The Li2S-containing positive active material (CAC) may include, for example, a composite of Li2S and carbon, a composite of Li2S, carbon and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S and a lithium salt, a composite of Li2S, a lithium salt and carbon, a composite of Li2S, a lithium salt, a metal halide and carbon, a composite of Li2S and a metal carbide, a composite of Li2S, carbon and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S, carbon and a metal nitride, or a combination thereof.

[0060] The cathode active material (CAC) may include a sulfide-based composite (CAM) and a conductive material (CMA). In one embodiment, the sulfide-based composite (CAM) may have a particle shape such as a perfect spherical or elliptical sphere. The particle size of the sulfide-based composite (CAM) is not particularly limited and may be within a range applicable to general cathode active materials. The size of the sulfide-based composite (CAM) may be, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm. The conductive material (CMA) may cover the surface of the sulfide-based composite (CAM).

[0061] The conductive material (CMA) may include carbon. The conductive material (CMA) may include, without limitation, materials containing carbon atoms that are used as conductive materials in the art. For example, the conductive material (CMA) may include crystalline carbon, amorphous carbon, or a combination thereof. The conductive material (CMA) may include, for example, a sintered product of a carbon precursor. The conductive material (CMA) may include, for example, carbon nanostructures.

[0062] The conductive material (CMA) may include, for example, porous carbon or non-porous carbon. The porous carbon may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black; graphite, activated carbon, or a combination thereof. The form of the carbon within the conductive material (CMA) may be, for example, in particle form, sheet form, fibrous form, etc., but is not limited thereto and may be any form of carbon used in the relevant art.

[0063] In one embodiment of the present invention, the conductive material (CMA) may include a fibrous carbon-based material. By including the fibrous carbon-based material in the conductive material (CMA), the electron conductivity of the positive electrode active material (CAC) can be further improved. By including the fibrous carbon-based material in the conductive material (CMA), electron conduction from the surface to the interior of the positive electrode active material (CAC) can be performed more easily. The internal resistance of the sulfide-based composite (CAM) is reduced by the conductive material (CMA), and the cycle characteristics of the secondary battery can be further improved.

[0064] The aspect ratio of the fibrous carbon-based material may be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. By having an aspect ratio within this range, the overall electron conductivity of the cathode active material (CAC) is improved, and the imbalance of local electron conductivity within the cathode active material (CAC) can be further alleviated.

[0065] Fibrous carbon-based materials may include, for example, carbon nanostructures. Carbon nanostructures may include, for example, carbon nanofibers (CNF), carbon nanotubes (CNT), carbon nanobelts, carbon nanorods, or combinations thereof. Carbon nanostructures may form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure formed by the aggregation of multiple carbon nanostructures.

[0066] The diameter of the primary carbon nanostructure may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure may be, for example, 10 nm to 2 µm, 10 nm to 1.5 µm, 10 nm to 1 µm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure may be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure may be measured by laser diffraction.

[0067] The secondary carbon nanostructure may be a structure formed by assembling primary carbon nanostructures, for example, to form a bundle or rope type, either wholly or partially. The secondary carbon nanostructure may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or a combination thereof. The diameter of the secondary carbon nanostructure may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length of the secondary carbon nanotube structure may be, for example, 20 nm to 2 µm, 30 nm to 1.5 µm, 50 nm to 1 µm, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured from scanning electron microscope (SEM) images or optical microscopes. Alternatively, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be converted into a primary carbon nanostructure by dispersing it in a solvent, for example, and then used to manufacture a cathode active material (CAC).

[0068] The method for manufacturing the cathode active material (CAC) according to the embodiments may be a dry method, a wet method, or a combination thereof, but is not limited thereto. In the art, the method for manufacturing the cathode active material (CAC) may be, for example, milling, heat treatment, deposition, etc., but is not necessarily limited thereto, and any method used in the art may be possible.

[0069] In one embodiment of the present invention, the sulfide-based composite (CAM) within the cathode active material (CAC) may comprise a composite of Li2S and a solid electrolyte. The solid electrolyte may be, for example, an amorphous solid electrolyte, any material used as an ion-conducting material in the art. 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, or a combination thereof. The solid electrolyte may be, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte may include, for example, Li, S, and P, and may optionally further include a halogen element. The sulfide-based solid electrolyte may be selected from among sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte may be, for example, 1 × 10⁻⁶ at room temperature. -5 It can have an ionic conductivity of S / cm or higher. Sulfide-based solid electrolytes are, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS6-x I x It may include one or more selected from , 0≤x≤2.

[0070] Oxide-based solid electrolytes contain, for example, Li, O, and transition metal elements, and may optionally contain other elements. Oxide-based solid electrolytes contain, for example, 1×10⁻⁶ at room temperature. -5 The solid electrolyte may have an ionic conductivity of S / cm or greater. The oxide-based solid electrolyte may be selected from among oxide-based solid electrolytes used in the solid electrolyte layer. The solid electrolyte may be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, it may be a mixture of Li3PO4-Li2SO4 and a binary lithium salt or a mixture of Li3PO4-Li2SO4 and a ternary lithium salt.

[0071] In one embodiment of the present invention, the sulfide-based complex (CAM) in the cathode active material (CAC) may include a complex of Li2S and a lithium salt. In other words, the complex (CAM) may include a compound of Li2S and a lithium salt. The lithium salt compound may not include, for example, sulfur (S) atoms.

[0072] The lithium salt compound may be a binary compound composed of, for example, lithium and one element selected from groups 13 to 17 of the periodic table. The binary compound may include, for example, one or more selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3. The lithium salt compound may be a ternary compound composed of, for example, lithium and two elements selected from groups 13 to 17 of the periodic table. The ternary compound may include, for example, one or more selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. For example, the lithium salt compound may be one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI.

[0073] In one embodiment of the present invention, the sulfide-based complex (CAM) may comprise a complex of Li2S and a metal carbide. The metal carbide may be, for example, a two-dimensional metal carbide. The two-dimensional metal carbide may be, for example, MXene. The two-dimensional metal carbide is, for example, M n+1 C n T x It can be expressed as (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups). Two-dimensional metal carbides are, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5)3C2T x , Ti3CNT x , Ta4C3T x , Nb4C3T x Or it may be a combination of these. The surface of the two-dimensional metal carbide may be terminated with O, OH and / or F.

[0074] In one embodiment of the present invention, the sulfide-based complex (CAM) may comprise a complex of Li2S and a metal nitride. The metal nitride may be, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x It can be expressed as (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups). The surface of a two-dimensional metal nitride can be terminated with O, OH and / or F.

[0075] A cathode active material (CAC) and a composite (CAM) containing Li2S according to one embodiment of the present invention will be described in more detail. The cathode active material (CAC) may comprise a composite of Li2S, a lithium salt, and carbon. More specifically, the cathode active material (CAC) may comprise a composite of Li2S, a lithium halide, and carbon.

[0076] The composite (CAM) according to the embodiments may have ductility. The composite (CAM) may function as a buffer material within the positive active material layer (120). The composite (CAM) may prevent the occurrence of defects due to volume changes in the positive active material layer (120).

[0077] A composite (CAM) according to one embodiment is Li2S-Li a X bIt may include a compound represented by (1≤a≤5, 1≤b≤5). X may 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, or a combination thereof. a may be, for example, 1, 2, 3, 4, or 5. b may be, for example, 1, 2, 3, 4, or 5.

[0078] In one embodiment, the composite (CAM) may include a solid solution of Li2S and a lithium salt. The ionic conductivity of the composite (CAM) may be improved by including the solid solution of Li2S and a lithium salt. For example, the ionic conductivity of the solid solution of Li2S and a lithium salt may be improved compared to the ionic conductivity of Li2S by including lithium ions disposed within the Li2S crystallites. Consequently, the composite (CAM) according to the present invention may have high ionic conductivity and low internal resistance. The cycle characteristics of an all-solid-state secondary battery including the composite (CAM) of the present invention may be improved.

[0079] The size of the Li2S crystallites of the composite (CAM) obtained from the XRD spectrum may be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of the Li2S crystallites of the composite (CAM) obtained from the XRD spectrum may be, for example, 1 to 20 nm, 1 to 15 nm, or 3 to 10 nm. As the size of the Li2S crystallites decreases, the contact area between Li2S and the lithium salt may increase. As the contact area between Li2S and the lithium salt increases, the ionic conductivity of the composite of Li2S and the lithium salt may be improved.

[0080] A composite (CAM) according to one embodiment may further include a metal halide. In other words, the composite (CAM) may include a composite of Li2S, a lithium salt, and a metal halide. The metal halide may contain a metal other than lithium.

[0081] The complex (CAM) is Li2S-Li a X1 b -MX2 c It may include a compound represented by . a may be an integer between 1 and 5, b may be an integer between 1 and 5, and c may be an integer between 1 and 5. M may be selected from the group consisting of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), bismuth (Bi), tin (Sn), and zinc (Zn). X1 and X2 may each be selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0082] The composite (CAM) may include a solid solution of Li2S, a lithium salt, and a metal halide. As an example, the composite (CAM) may include a compound (or solid solution) represented as Li2S-LiI-AlI3. As described above, the composite (CAM) and the conductive material (CMA, e.g., a carbon nanostructure) may constitute a cathode active material (CAC) according to the present invention.

[0083] The Mohs hardness of the composite (CAM) may be lower than that of the lithium salt. The composite (CAM) may have improved ductility compared to the lithium salt. By having improved ductility, internal defects caused by volume changes in the positive active material layer (120) can be effectively prevented.

[0084] The Mohs hardness of Li2S is, for example, 0.6. The Mohs hardness of the composite (CAM) may be, for example, less than 2, 1.5 or less, 1 or less, or 0.7 or less. If the Mohs hardness of the composite (CAM) increases excessively, it may be difficult to provide ductility.

[0085] The Mohs hardness of the lithium salt may be 0.7 or higher, 0.8 or higher, 0.9 or higher, 1.0 or higher, 1.5 or higher, or 2.0 or higher. For example, the Mohs hardness of LiI is 2.0. Since the lithium salt has a Mohs hardness in this range, the grinding of Li2S can be performed more easily during the milling process, and a solid solution of Li2S and the lithium salt can be formed more easily.

[0086] Since Li2S has relatively low ionic conductivity, a complex can be formed between Li2S and a lithium salt to improve ionic conductivity. A complex (CAM) formed between Li2S and a lithium salt can have improved ionic conductivity compared to Li2S alone. The content of Li2S in the complex (CAM) can be 50 wt% to 95 wt%, 50 wt% to 90 wt%, 50 wt% to 80 wt%, or 50 wt% to 70 wt% of the total weight of the complex (CAM). By having a Li2S content within this range, the complex (CAM) can simultaneously possess improved ionic conductivity and excellent ductility.

[0087] The content of the lithium salt in the composite (CAM) may be 5 wt% to 50 wt%, 10 wt% to 50 wt%, 20 wt% to 50 wt%, or 30 wt% to 50 wt% of the total weight of the composite (CAM). By having the lithium salt content within this range, the composite (CAM) can simultaneously have improved ionic conductivity and excellent ductility.

[0088] The content of metal halide in the composite (CAM) may be 5 wt% to 30 wt% or 5 wt% to 20 wt% of the total weight of the composite (CAM). By having a metal halide content within this range, the composite (CAM) can simultaneously have improved ionic conductivity and excellent ductility.

[0089] In one embodiment, the content of Li2S in the composite (CAM) may be greater than the content of the lithium salt. The content of Li2S in the composite (CAM) may be greater than the content of the metal halide. For example, the molar ratio of Li2S to the lithium salt in the composite (CAM) may be 51:49 to 95:5, 55:45 to 90:10, 60:40 to 90:10, or 70:30 to 90:10. By having such molar ratios, the composite (CAM) can simultaneously possess enhanced ionic conductivity and excellent ductility.

[0090] The ionic conductivity of the composite (CAM) according to the embodiments of the present invention is, for example, 1×10⁻⁶ at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4 It may be greater than S / cm. For example, ionic conductivity can be measured using electrochemical impedance spectrometry, DC polarization method, etc. As the composite (CAM) has ionic conductivity in this range, the internal resistance of the positive active material layer (120) containing the composite (CAM) can be further reduced.

[0091] The average particle size (D50) of the composite (CAM) may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The average particle size of the composite (CAM) may be, for example, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, or 0.1 μm to 1 μm.

[0092] The size of the Li2S particles in the composite (CAM) may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the Li2S particles may be, for example, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, or 0.1 μm to 1 μm.

[0093] Referring again to FIGS. 2 and FIG. 3, the positive active material layer (120) may further include a solid electrolyte (SEP) in addition to the Li2S-containing positive active material (CAC). The solid electrolyte (SEP) in the positive active material layer (120) may be the same as or different from the solid electrolyte in the solid electrolyte layer (300) to be described later.

[0094] The solid electrolyte (SEP) in the positive active material layer (120) may have an average particle size (D50) smaller than that of the solid electrolyte in the solid electrolyte layer (300). For example, the average particle size of the solid electrolyte (SEP) in the positive active material layer (120) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average particle size of the solid electrolyte in the solid electrolyte layer (300).

[0095] In one embodiment, the content of the positive active material (CAC) in the positive active material layer (120) may be 40 wt% to 90 wt%, 50 wt% to 90 wt%, or 60 wt% to 90 wt% of the total weight of the positive active material layer (120). Among the components in the positive active material layer (120), the positive active material (CAC) may have the largest content. The content of the solid electrolyte (SEP) in the positive active material layer (120) may be 10 wt% to 70 wt%, 10 wt% to 60 wt%, or 10 wt% to 40 wt% of the total weight of the positive active material layer (120).

[0096] The solid electrolyte (SEP) may be, for example, a sulfide-based solid electrolyte. Sulfide-based solid electrolytes are, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x, 0≤x≤2, and one or more selected from. Sulfide-based solid electrolytes are produced by processing starting materials, such as Li2S or P2S5, by methods such as melt quenching or mechanical milling. Additionally, heat treatment may be performed after such processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. Furthermore, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material comprising Li2S-P2S5 to form a solid electrolyte, the molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 20 : 80 to 90 : 10, 25 : 75 to 90 : 10, 30 : 70 to 70 : 30, and 40 : 60 to 60 : 40.

[0097] Sulfide-based solid electrolytes may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 1:

[0098] <Chemical Formula 1>

[0099] Li + 12-n-x A n+ X 2- 6-x Y - x

[0100] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; X is S, Se, or Te; Y is Cl, Br, I, F, CN, OCN, SCN, or N3; and 1≤n≤5, 0≤x≤2. Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x It may be an argyrodite-type compound containing one or more selected from 0≤x≤2. The sulfide-based solid electrolyte may be an argyrodite-type compound containing, for example, one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0101] Alternatively, sulfide-based solid electrolytes are Li 7-a-c M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)). Here, X may be F, Br, Cl, or a combination thereof. M may be candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof.

[0102] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0103] The positive active material layer (120) may further include a filler (FIL). In one embodiment, the content of the filler (FIL) in the positive active material layer (120) may be 0.1 to 20 wt%, 0.1 to 10 wt%, or 0.1 to 5 wt% of the total weight of the positive active material layer (120).

[0104] According to embodiments of the present invention, the filler (FIL) may be an inorganic filler, an organic filler, or a combination thereof. In one embodiment, the filler (FIL) may include an amorphous inorganic filler. The inorganic filler may be, for example, an amorphous lithium metal oxyhalide. In one embodiment, an amorphous lithium metal oxyhalide may be produced by manufacturing a crystalline lithium metal oxyhalide, then melting the crystalline lithium metal oxyhalide to produce a molten salt, and then cooling it. In another embodiment, an amorphous lithium metal oxyhalide may be directly produced by controlling the composition during the production of the lithium metal oxyhalide. The amorphous inorganic filler may have, for example, ductility. Since the amorphous inorganic filler has ductility, it can more effectively accommodate volume changes during charging and discharging of the all-solid-state battery (10). In contrast, the crystalline lithium metal oxyhalide may have relatively brittleness compared to the amorphous lithium metal oxyhalide. The amorphousness of inorganic fillers can be confirmed using XRD spectra.

[0105] The inorganic filler may be, for example, glassy. The inorganic filler may include, for example, a glassy lithium metal oxyhalide having a glass transition temperature (Tg). The glassy lithium metal oxyhalide may have ductility. Since the inorganic filler has ductility, it can effectively accommodate volume changes of the all-solid-state secondary battery (10) during charging and discharging, or be easily deformed according to volume changes of the all-solid-state secondary battery (10).

[0106] The glass transition temperature of the inorganic filler may be, for example, 20°C or lower, 10°C or lower, 0°C or lower, or -10°C or lower. Because the inorganic filler has such a low glass transition temperature, it can easily transition from a brittle crystalline metal salt state to a ductile glassy state. For example, the inorganic filler can be easily transitioned from a crystalline molten salt state to a glassy state by melting and then cooling it. Alternatively, a glassy state can be obtained during the manufacturing process of the inorganic filler. The glass transition temperature can be measured, for example, using a Differential Scanning Calorimeter (DSC). The glass transition temperature can be measured, for example, using a Dynamic Mechanical Analyzer (DMA).

[0107] The melting point of the inorganic filler may be, for example, 100°C or higher, 105°C or higher, 110°C or higher, 115°C or higher, 120°C or higher, 125°C or higher, 130°C or higher, 135°C or higher, 140°C or higher, or 145°C or higher. The melting point of the inorganic filler may be, for example, 200°C or lower, 190°C or lower, 180°C or lower, 170°C or lower, 160°C or lower, or 150°C or lower. Since the inorganic filler has a melting point within this range, the inorganic filler can be melted to a molten salt state and then cooled to easily produce an amorphous inorganic filler. The melting point of the inorganic filler can be measured, for example, using a differential scanning calorimeter (DSC).

[0108] The inorganic filler may be an ion-conductive inorganic filler. The inorganic filler may have an ion conductivity of, for example, 0.01 mS / cm or more, 0.05 mS / cm or more, 0.1 mS / cm or more, 0.3 mS / cm or more, 0.5 mS / cm or more, 0.7 mS / cm or more, or 1.0 mS / cm or more at 25 °C 1 atm. Ion conductivity may be measured by AC impedance analysis. The voltage amplitude used for AC impedance analysis may be 5 to 10 mV, and the frequency may be 1 MHz to 1 Hz. By having ion conductivity, the increase in interfacial resistance between positive active material (CAC) particles, between solid electrolyte (SEP) particles, and / or between the positive active material (CAC) and the solid electrolyte (SEP) within the positive active material layer (120) can be effectively suppressed (see FIG. 3).

[0109] The elastic modulus (or Young's modulus) of the inorganic filler at 30°C may be 10 GPa or less, 5 GPa or less, 3 GPa or less, or 2 GPa or less. Because the inorganic filler has an elastic modulus low in this range, the positive active material layer (120) can effectively accommodate volume changes of the all-solid-state battery (10). Thus, the cycle characteristics of the all-solid-state battery (10) according to the present invention can be improved. The elastic modulus of the inorganic filler can be measured, for example, using a Dynamic Mechanical Analyzer (DMA).

[0110] The elastic modulus of the inorganic filler may be smaller than, for example, the elastic modulus of the solid electrolyte (SEP). The elastic modulus of the solid electrolyte (SEP) at 30°C may be, for example, 22 GPa to 30 GPa. The elastic modulus of the inorganic filler may be, for example, 90% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the elastic modulus of the solid electrolyte (SEP).

[0111] Inorganic filler, i.e., filler (FIL), can be uniformly provided within the positive active material layer (120) (see FIG. 3). In the all-solid-state battery (10) of the present invention, since the inorganic filler has a lower elastic modulus than the solid electrolyte (SEP), the inorganic filler can easily fill the voids between the solid electrolytes (SEP) and / or the voids between the solid electrolyte (SEP) and the positive active material (CAC), thereby reducing the internal resistance of the positive active material layer (120) and easily accommodating volume changes of the positive active material layer (120) during charging and discharging. As a result, the cycle characteristics of the all-solid-state battery (10) can be further improved. The elastic modulus of the solid electrolyte (SEP) can be measured, for example, using a Dynamic Mechanical Analyzer (DMA).

[0112] The inorganic filler may, for example, have viscoelasticity. The inorganic filler may, for example, have viscoelastic creep. The viscoelastic creep rate of the inorganic filler may, for example, be 1×10⁻⁴ % / s or greater, 2×10⁻⁴ % / s or greater, or 4×10⁻⁴ % / s or greater. % / s is the ratio of the deformed size to the initial size per unit time (second). Because the inorganic filler has viscoelasticity, it can easily accommodate volume changes during charging and discharging of the all-solid-state battery (10) and can continuously deform its shape without defects. The creep rate is the rate of change over time, i.e., the deformation rate, of an inorganic filler subjected to stress at a constant temperature. The creep rate can be measured, for example, using a universal test machine.

[0113] The weapon filler is Li a Al b M c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e, M은 원소주기율표 3족 내지 15족에서 선택되는 금속) 표시되는 리튬금속옥시할라이드(lithium metal oxyhalide)를 포함할 수 있다. 리튬금속옥시할라이드의 금속 M은 예를 들어 Fe, Ga, In, As, Sb, Mo, Bi, B 또는 이들의 조합을 포함할 수 있다.

[0114] Lithium metal oxyhalides are, for example, Li a Al b O d Cl e (0 <a≤3; 0<b≤3; 0<d≤2; 1<e≤4; d<e), Li a Al b Fe c O d Cl e(0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Ga c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b In c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b As c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Sb c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Mo c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), ), Li a Al b Bi c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b B c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e) 또는 이들의 조합을 포함할 수 있다.

[0115] Lithium metal oxyhalides are, for example, LiAl x O z Cl w(0 <x≤2; 0<z≤1; 2<w<4; z<w), LiAlxFeyOzClw (0<x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Yes y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x In y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x I y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Sat y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Mo y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Bi y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x B y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w) 또는 이들의 조합을 포함할 수 있다.

[0116] The inorganic filler content in the positive active material layer (120) may be smaller than the solid electrolyte (SEP) content. The weight ratio of the solid electrolyte (SEP) to the inorganic filler in the positive active material layer (120) may be 99:1 to 50:50, 99:1 to 60:40, 99:1 to 70:30, 99:1 to 80:20, or 99:1 to 90:10. By having the solid electrolyte (SEP) and the inorganic filler in this range of weight ratios, the volume change during charging and discharging of the positive active material layer (120) can be more easily accommodated. As a result, the cycle characteristics of the all-solid-state battery (10) can be further improved.

[0117] In another embodiment, the filler (FIL) may include an organic filler. The organic filler may include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene (PP), cycloolefin polymer, and combinations thereof.

[0118] The positive active material layer (120) may further include a conductive material. The conductive material may be, for example, a carbon-based material, a metal-based material, or a combination thereof. In one embodiment of the present invention, as shown in FIG. 3, the conductive material (CMA) in the positive active material layer (120) may form a positive active material (CAC) together with a composite (CAM).

[0119] The conductive material content in the positive active material layer (120) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive active material layer (120).

[0120] Metallic materials may be metal powders, metal fibers, or combinations thereof, but are not limited to these; any metal-based material used as a conductive material in the relevant technical field is acceptable.

[0121] The carbon-based material may include, for example, amorphous carbon. By including amorphous carbon in the carbon-based material, side reactions between the carbon-based material and the solid electrolyte (SEP) can be suppressed. Accordingly, the cycle characteristics of the all-solid-state battery (10) containing the carbon-based material can be further improved. A specific description of the carbon-based material may be the same or similar as that described above regarding the conductive material (CMA).

[0122] The positive active material layer (120) may further include a binder (BID). The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene, etc., but is not limited to these and may be any binder used in the relevant technical field. The content of the binder (BID) in the positive active material layer (120) may be, for example, 0.1 wt% to 10 wt%, 0.5 to 5 wt%, or 0.5 to 2 wt% of the total weight of the positive active material layer (120). The binder (BID) may be omitted.

[0123] The positive active material layer (120) may further include additives such as a coating agent, a dispersant, and an ion conductivity aid in addition to the above-described positive active material (e.g., CAM), solid electrolyte (SEP), binder (BID), conductive material (CMA), and filler (FIL). Known materials generally used in electrodes of all-solid-state batteries may be used as coating agents, dispersants, and ion conductivity aids that may be included in the positive active material layer (120).

[0124] The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the negative electrode coating layer (220) is placed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, that is, does not form any alloys or compounds with lithium. For example, the negative electrode current collector (210) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (210) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0125] The negative current collector (210) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (210) may, for example, have a plate-like or foil-like shape. Meanwhile, in one embodiment, the negative current collector (210) may be omitted.

[0126] Although not illustrated, a negative current collector (210) according to one embodiment may include a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. By including an insulating thermoplastic polymer in the base film, the base film may soften or liquefy upon a short circuit, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative current collector (210) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode current collector (210), refer to the positive electrode current collector (110) described above. By having the negative electrode current collector (210) have this structure, the weight of the negative electrode layer (200) can be reduced, and consequently, the energy density of the all-solid-state battery (10) can be improved.

[0127] The negative electrode coating layer (220) can be configured to allow lithium metal to grow between the all-solid-state battery (10) and the negative electrode current collector (210) during charging. The negative electrode coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0128] The cathode coating layer (220) may include metal and carbon. For example, the cathode coating layer (220) may include at least one metal selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The cathode coating layer (220) may include at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene. In one embodiment, the cathode coating layer (220) may include a mixture of carbon black and silver (Ag).

[0129] The cathode coating layer (220) may further include other additives in addition to metal and carbon. The cathode coating layer (220) may further include at least one additive selected from the group consisting of, for example, binders, fillers, coating agents, dispersants, and ion-conducting aids.

[0130] The negative electrode coating layer (220) may have a smaller thickness compared to the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 1 µm to 20 µm, 2 µm to 10 µm, or 3 µm to 7 µm. If the thickness of the negative electrode coating layer (220) is excessively thin, lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210) may cause the negative electrode coating layer (220) to collapse, thereby degrading the cycle characteristics of the all-solid-state battery (10). If the thickness of the negative electrode coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) decreases, and the internal resistance of the all-solid-state battery (10) due to the negative electrode coating layer (220) increases, which may degrade the cycle characteristics of the cell.

[0131] Meanwhile, although not illustrated, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte layer (300).

[0132] A solid electrolyte layer (300) may be provided between the positive electrode layer (100) and the negative electrode layer (200). The solid electrolyte layer (300) may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. The solid electrolyte in the solid electrolyte layer (300) may be the same as or different from any one of the materials included in the solid electrolyte (SEP, see FIG. 3) in the aforementioned positive electrode active material layer (120).

[0133] The solid electrolyte layer (300) may include a first solid electrolyte layer (310) and a second solid electrolyte layer (320). The first solid electrolyte layer (310) may be adjacent to the anode layer (100), and the second solid electrolyte layer (320) may be adjacent to the cathode layer (200).

[0134] Referring to FIG. 2, the first solid electrolyte layer (310) may include a first solid electrolyte. The first solid electrolyte may have a particle shape such as a sphere or an ellipsoid. The first solid electrolyte may include a sulfide-based solid electrolyte. The first solid electrolyte may be amorphous, crystalline, or a mixture thereof. Additionally, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above, for example. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form the solid electrolyte, the molar ratio of Li2S and P2S5 may be, for example, in the range of Li2S : P2S5 = 50 : 50 to 90 : 10.

[0135] In one embodiment, the first solid electrolyte is Li 7-x PS6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include an argyrodite-type compound comprising one or more selected from (0≤x≤2). The first solid electrolyte may include an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0136] In another embodiment, the first solid electrolyte is Li 7-a-c M a PS 6-c X c It may include an argyrodite-type compound comprising. Here, X may be Cl, Br, or a combination thereof. M may be Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, or a combination thereof. a and c may each be a real number between 0 and 2.

[0137] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the azyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the first solid electrolyte is, for example, 15 GPa to 35 GPa.

[0138] The second solid electrolyte layer (320) may include a second solid electrolyte. The second solid electrolyte may have a particle shape such as a sphere or an ellipsoid. The second solid electrolyte may include a sulfide-based solid electrolyte. The description of the second solid electrolyte may be the same or similar as that described above for the first solid electrolyte. In one embodiment, the second solid electrolyte may have substantially the same composition as the first solid electrolyte. In another embodiment, the second solid electrolyte may have a composition similar to that of the first solid electrolyte.

[0139] The second solid electrolyte can come into direct contact with the negative electrode coating layer (220). By doing so, the second solid electrolyte can suppress lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210). The second solid electrolyte can effectively suppress negative side reactions. By doing so, the cell performance of the all-solid-state battery (10) according to the present invention can be improved.

[0140] Each of the first and second solid electrolyte layers (310, 320) may further include a binder. The binder in the solid electrolyte layer (300) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these. The binder in the solid electrolyte layer (300) may be the same as or different from the binder in the positive active material layer (120) or the binder in the negative coating layer (220).

[0141] The content of the binder in the solid electrolyte layer (300) may be 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the solid electrolyte layer (300).

[0142] In another embodiment of the present invention, the solid electrolyte layer (300) may be provided as a single layer structure rather than a double layer structure of the first solid electrolyte layer (310) and the second solid electrolyte layer (320).

[0143] Referring again to FIGS. 1 and FIGS. 2, the anode layer (100) and the first solid electrolyte layer (310) can form an anode composite layer (CSH). The cathode layer (200) and the second solid electrolyte layer (320) can form a cathode composite layer (ASH). An anode composite layer (CSH) can be laminated on the cathode composite layer (ASH).

[0144] The area of ​​the cathode composite layer (ASH) and the area of ​​the anode composite layer (CSH) may differ from each other. Specifically, the area of ​​the cathode composite layer (ASH) may be larger than the area of ​​the anode composite layer (CSH). The anode composite layer (CSH) may completely overlap within the cathode composite layer (ASH).

[0145] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the anode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the cathode layer (200).

[0146] Specifically, the positive electrode composite layer (CSH) may have a first width (WI1) in a first direction (D1). The negative electrode composite layer (ASH) may have a second width (WI2) in a first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The positive electrode composite layer (CSH) may have a third width (WI3) in a second direction (D2). The negative electrode composite layer (ASH) may have a fourth width (WI4) in a second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0147] The all-solid-state battery (10) according to the present embodiment can be manufactured by forming a negative electrode composite layer (ASH) on a first carrier film and forming a positive electrode composite layer (CSH) on a second carrier film, and then laminating the negative electrode composite layer (ASH) and the positive electrode composite layer (CSH).

[0148] In one embodiment, as shown in FIG. 2, the positive active material layer (120) in a discharged state may have a first thickness (TK1). The all-solid-state battery (10) may have a first height (HE1) in a third direction (D3). The first height (HE1) may be the sum of the thickness of the positive composite layer (CSH) and the thickness of the negative composite layer (ASH).

[0149] In the embodiments described below, detailed descriptions of technical features that overlap with those previously described with reference to FIGS. 1 to 3 are omitted, and differences are described in detail.

[0150] FIG. 4 is a cross-sectional view along line A-A' of FIG. 1, intended to illustrate an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 4, in one embodiment, an all-solid-state battery (10) in a charged state may further include a lithium metal layer (230) provided between a negative electrode current collector (210) and a negative electrode coating layer (220). The negative electrode layer (200) according to the present embodiment may include a negative electrode current collector (210), a negative electrode coating layer (220), and a lithium metal layer (230) between them.

[0151] The lithium metal layer (230) may include lithium or a lithium alloy. Since the lithium metal layer (230) is a metal layer containing lithium, it may function as, for example, a lithium reservoir. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, but is not limited to these; any alloy used as a lithium alloy in the relevant technical field may be possible. The lithium metal layer (230) may be composed of one of these alloys or lithium, or may be composed of various types of alloys. The lithium metal layer (230) may be, for example, a plated layer. The lithium metal layer (230) may be deposited between the negative electrode coating layer (220) and the negative electrode current collector (210) during the charging process of the all-solid-state battery (10), for example.

[0152] The lithium metal layer (230) may have a third thickness (TK3). The third thickness (TK3) is not particularly limited, but may be, for example, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the third thickness (TK3) of the lithium metal layer (230) is excessively thin, it may be difficult for the lithium metal layer (230) to perform the role of a lithium reservoir. If the third thickness (TK3) of the lithium metal layer (230) is excessively thick, the mass and volume of the all-solid-state battery (10) increase, and the cycle characteristics of the all-solid-state battery (10) may actually deteriorate.

[0153] In another embodiment of the present invention, a lithium metal layer (230) within the negative electrode layer (200) may be provided, for example, between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the all-solid-state battery (10). When the lithium metal layer (230) is placed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the all-solid-state battery (10), the lithium metal layer (230) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be placed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the all-solid-state battery (10).

[0154] When a lithium metal layer (230) is deposited by charging after assembly of the all-solid-state battery (10), the energy density of the all-solid-state battery (10) can be increased because the lithium metal layer (230) is not included during assembly of the all-solid-state battery (10). When charging the all-solid-state battery (10), it can be charged beyond the charging capacity of the negative electrode coating layer (220). That is, the negative electrode coating layer (220) is overcharged. At the beginning of charging, lithium can be absorbed in the negative electrode coating layer (220). When charging beyond the capacity of the negative electrode coating layer (220), lithium can be deposited, for example, between the negative electrode coating layer (220) and the negative electrode current collector (210). A lithium metal layer (230) can be formed by the deposited lithium.

[0155] The lithium metal layer (230) can be composed mainly of lithium (i.e., metallic lithium). During discharge, the lithium in the lithium metal layer (230) can be ionized and move to the positive electrode layer (100). In other words, lithium can be used as a negative electrode active material in the all-solid-state battery (10). In addition, since the negative electrode coating layer (220) covers the lithium metal layer (230), the negative electrode coating layer (220) can protect the lithium metal layer (230) and simultaneously suppress the precipitation growth of lithium dendrites. Therefore, the negative electrode coating layer (220) can suppress short circuits and capacity degradation of the all-solid-state battery (10) and improve the cycle characteristics of the all-solid-state battery (10).

[0156] When a lithium metal layer (230) is formed by charging after assembly of the all-solid-state battery (10), the negative electrode layer (200), that is, the negative electrode current collector (210) and the negative electrode coating layer (220) and the region between them may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the all-solid-state battery (10).

[0157] The positive active material layer (120) from which lithium ions are released by charging the all-solid-state battery (10) may have a second thickness (TK2). The second thickness (TK2) of the positive active material layer (120) may be smaller than the first thickness (TK1) of FIG. 2.

[0158] In one embodiment of the present invention, the difference between the first thickness (TK1) and the second thickness (TK2) may be substantially the same or similar to the third thickness (TK3) of the lithium metal layer (230). For example, the third thickness (TK3) may be 1.0 to 1.5 times, or 1.0 to 1.2 times, the difference between the first thickness (TK1) and the second thickness (TK2). According to the present invention, the thickness of the positive active material layer (120) may be reduced by the same amount as the thickness of the lithium metal layer (230) formed by charging the all-solid-state battery (10).

[0159] Although not illustrated, the all-solid-state battery (10) may operate (i.e., charge and / or discharge) while pressurized by a pressurizing jig. In one embodiment, the all-solid-state battery (10) may be pressurized to 0.8 MPa to 2 MPa. For example, the all-solid-state battery (10) may have an internal pressure of about 1 MPa when discharged, and the all-solid-state battery (10) may have an internal pressure of about 1.5 MPa when charged. The ratio of the internal pressure of the all-solid-state battery (10) in the charged state of FIG. 4 to the internal pressure of the all-solid-state battery (10) in the discharged state of FIG. 3 may be 1.0 to 2.0, or 1.2 to 1.8.

[0160] The height (or thickness or volume) of the all-solid-state battery (10) may change according to charging and discharging under the aforementioned pressurized state. In the all-solid-state battery (10) according to the present embodiment, the thickness of the positive active material layer (120) may decrease in correspondence with the lithium metal layer (230) formed by charging. Accordingly, the second height (HE2) of the charged all-solid-state battery (10) shown in FIG. 4 may be similar to the first height (HE1) of the discharged all-solid-state battery (10) shown in FIG. 2. For example, the second height (HE2) may be 1 to 1.5 times, or 1 to 1.2 times, the first height (HE1).

[0161] FIG. 5 is a cross-sectional view along line A-A' of FIG. 1, intended to illustrate an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 5, the all-solid-state battery (10) according to the present embodiment may further include a gasket (GSK). The gasket (GSK) may be provided to surround the positive electrode composite layer (CSH). The gasket (GSK) may fill the step difference on the side of the all-solid-state battery (10) caused by the difference in area between the negative electrode composite layer (ASH) and the positive electrode composite layer (CSH). The gasket (GSK) may surround the four sides of the positive electrode composite layer (CSH). For example, the thickness of the gasket (GSK) may be substantially the same as the thickness of the positive electrode composite layer (CSH).

[0162] The upper surface of the second solid electrolyte layer (320) may include a first region in contact with the first solid electrolyte layer (310) and a second region in contact with the gasket (GSK). The second region may be a peripheral region of the upper surface of the second solid electrolyte layer (320). The second region may surround the first region.

[0163] The gasket (GSK) can prevent cracking of the solid electrolyte layer (300) during the manufacturing of the all-solid-state battery (10) and / or during the charging and discharging of the all-solid-state battery (10). This can improve the cycle characteristics of the all-solid-state battery (10). If the all-solid-state battery (10) does not include the gasket (GSK), uneven pressure is applied to the negative electrode composite layer (ASH) in contact with the positive electrode composite layer (CSH), causing cracking in the solid electrolyte layer (300), and the likelihood of a short circuit occurring due to the growth of lithium metal through this may increase.

[0164] The thickness of the gasket (GSK) may be greater than the thickness of the positive composite layer (CSH) or substantially equal to the thickness of the positive composite layer (CSH). Since the thickness of the gasket (GSK) is equal to the thickness of the positive composite layer (CSH), a uniform pressure is applied between the positive composite layer (CSH) and the negative composite layer (ASH), and the positive composite layer (CSH) and the negative composite layer (ASH) are sufficiently in contact, thereby reducing the interfacial resistance between the first solid electrolyte layer (310) and the second solid electrolyte layer (320). Additionally, the internal resistance of the solid electrolyte layer (300) may be reduced as the solid electrolyte layer (300) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state battery (10).

[0165] The gasket (GSK) may have a single-layer structure, for example. Alternatively, although not shown in the drawings, the gasket (GSK) may have a multi-layer structure. In a gasket (GSK) having a multi-layer structure, each layer may have a different composition. A gasket (GSK) having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. A gasket (GSK) having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers.

[0166] The gasket (GSK) may include, for example, a flame-retardant inert member. By providing flame retardancy, the flame-retardant inert member can prevent thermal runaway and the possibility of ignition of the all-solid-state battery (10). Consequently, the gasket (GSK) can further enhance the safety of the all-solid-state battery (10). By absorbing residual moisture within the all-solid-state battery (10), the flame-retardant inert member prevents the deterioration of the all-solid-state battery (10), thereby improving the lifespan characteristics of the all-solid-state battery (10).

[0167]

[0168] FIG. 6 is a cross-sectional view along line A-A' of FIG. 1, illustrating an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 6, the positive electrode layer (100) may further include a coating layer (CTL) provided between the positive electrode current collector (110) and the positive electrode active material layer (120). The coating layer (CTL) may be placed directly on, for example, one or both sides of the positive electrode current collector (110). The coating layer (CTL) may be coated on one or both sides of the positive electrode current collector (110). No other layer may be placed between the positive electrode current collector (110) and the coating layer (CTL).

[0169] By placing the coating layer (CTL) directly on one or both sides of the positive current collector (110), the bonding strength between the positive current collector (110) and the positive active material layer (120) can be further improved. By placing the coating layer (CTL) between the positive current collector (110) and the positive active material layer (120), side reactions between the filler (FIL), solid electrolyte (SEP), or positive active material (CAC) and the positive current collector (110) can be more effectively suppressed. For example, the coating layer (CTL) can prevent corrosion of the sulfide-based positive active material (e.g., Li2S) by the positive current collector (110). Consequently, the coating layer (CTL) can suppress the degradation of the all-solid-state battery (10) during the charging and discharging process and improve the cycle characteristics of the all-solid-state battery (10).

[0170] The thickness of the coating layer (CTL) is, for example, 0.01 to 20%, 0.1 to 20%, 0.5 to 20%, 1 to 20%, 1 to 15%, 1 to 10%, 2 to 8%, or 3 to 7% of the thickness of the positive current collector (110). The thickness of the coating layer (CTL) may be, for example, 10 nm to 5 µm, 50 nm to 5 µm, 200 nm to 4 µm, 500 nm to 3 µm, 500 nm to 2 µm, 500 nm to 1.5 µm, or 700 nm to 1.3 µm. By having the coating layer (CTL) have a thickness within this range, the bonding strength between the positive current collector (110) and the positive active material layer (120) is further improved, and the increase in interfacial resistance can be suppressed. The thickness of the coating layer (CTL) can be measured, for example, from a scanning electron microscope (SEM) image of a cross- section of the coating layer (CTL).

[0171] The coating layer (CTL) may include, for example, a carbon-based conductive material. The carbon-based conductive material included in the coating layer (CTL) may be selected from among the carbon-based conductive materials used in the positive active material layer (120). The coating layer (CTL) may include the same carbon-based conductive material as the carbon-based conductive material used in the positive active material layer (120). By including the carbon-based conductive material, the coating layer (CTL) may be, for example, a conductive layer.

[0172] The coating layer (CTL) may additionally include, for example, a binder. By additionally including a binder in the coating layer (CTL), the bonding strength between the positive current collector (110) and the positive active material layer (120) can be further improved. The binder included in the coating layer (CTL) is, for example, a conductive binder or a non-conductive binder. The conductive binder is, for example, an ion-conducting binder and / or an electron-conducting binder. A binder having both ion conductivity and electron conductivity may belong to both an ion-conducting binder and an electron-conducting binder.

[0173] The binder included in the coating layer (CTL) may be selected from among the binders used in the positive active material layer (120). The coating layer (CTL) may include the same binder as the binder used in the positive active material layer (120). The binder included in the coating layer (CTL) is, for example, a fluorine-based binder. The fluorine-based binder included in the coating layer (CTL) is, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or a combination thereof. The coating layer (CTL) may be, for example, a binding layer containing a binder. The coating layer (CTL) may be, for example, a conductive layer containing a binder and a carbon-based conductive material.

[0174] The coating layer (CTL) can be disposed on the positive current collector (110) in a dry or wet manner, for example. The coating layer (CTL) can be disposed on the positive current collector (110) in a dry manner by deposition, for example, CVD, PVD, etc. The coating layer (CTL) can be disposed on the positive current collector (110) in a wet manner by, for example, spin coating, dip coating, etc. The coating layer (CTL) can be disposed on the positive current collector (110) by, for example, depositing a carbon-based conductive material onto a substrate by deposition. The dry-coated coating layer (CTL) may be made of a carbon-based conductive material and may not contain a binder. The coating layer (CTL) can be disposed on the positive current collector (110) by, for example, coating a composition comprising a carbon-based conductive material, a binder, and a solvent onto the surface of the electrode current collector and drying it. The coating layer (CTL) may have a single-layer structure or a multi-layer structure including multiple layers. The multi-story structure can be a 2-story structure, a 3-story structure, a 4-story structure, etc.

[0175] The negative electrode layer (200) may further include a thin film (TFL) provided between the negative electrode current collector (210) and the negative electrode coating layer (220). The thin film (TFL) may be provided on one side of the negative electrode current collector (210) to form an alloy with lithium.

[0176] The thin film (TFL) may include, for example, an element capable of forming an alloy with lithium. Elements capable of forming an alloy with lithium include, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but are not necessarily limited to these, and any element capable of forming an alloy with lithium in the relevant technical field is possible. The thin film (TFL) may be composed of one of these metals or may be composed of an alloy of various types of metals.

[0177] By placing the thin film (TFL) on one side of the negative current collector (210), the deposition pattern of the lithium metal layer (230, see FIG. 4) deposited between, for example, the thin film (TFL) and the negative coating layer (220) is further flattened, and the cycle characteristics of the all-solid-state battery (10) can be further improved.

[0178] The thickness of the thin film (TFL) may be, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (TFL) is less than 1 nm, it may be difficult to perform the function provided by the thin film (TFL). If the thickness of the thin film (TFL) is excessively thick, the thin film (TFL) itself absorbs lithium, which reduces the amount of lithium precipitated in the negative electrode layer (200), thereby lowering the energy density of the all-solid-state battery (10) and potentially degrading the cycle characteristics of the all-solid-state battery (10). The thin film (TFL) may be formed on the negative electrode current collector (210) by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods; any method capable of forming a thin film in the relevant technical field may be possible.

[0179]

[0180] Hereinafter, specific features of the present invention will be described with reference to the drawings. Referring to FIG. 7, a solid electrolyte layer (300) may be disposed between an anode (100) and a cathode (200). As described above, the solid electrolyte layer (300) may exist in a separated form as a first solid electrolyte layer (310) and a second solid electrolyte layer (320), but for convenience of explanation, it will be described based on a single layer.

[0181] As high-capacity batteries are required, attempts are being made to introduce lithium metal as the anode to improve the energy density of secondary batteries. Furthermore, research and development are underway to further improve energy density through anode-free structures, in which the anode active material is absent during manufacturing. However, lithium metal is highly reactive and is disadvantageous in terms of long-term lifespan due to dendrite formation caused by non-uniform lithium precipitation on the anode.

[0182] All-solid-state batteries replace conventional liquid electrolytes with solid electrolytes, and the solid electrolyte layer can simultaneously perform the roles of separator and electrolyte. They are being proposed as an alternative because the solid electrolyte layer can physically suppress dendrites on the lithium metal anode and resolve instability caused by reactions with the electrolyte.

[0183] However, since all components of an all-solid-state battery consist of solid particles, maintaining structural stability and improving contact performance between solid layers is an important task. In particular, as the charging and discharging process is repeated, the volume of the positive and negative electrodes changes, and the solid electrolyte layer between the positive and negative electrodes may be exposed to mechanical stress. Such mechanical stress can cause cracking or delamination of the interface of the all-solid-state battery, which can degrade the performance of the all-solid-state battery in the long term.

[0184] Accordingly, the solid electrolyte layer (300) according to an embodiment of the present invention aims to solve the above-mentioned problem by including a polymer filler (PFL). Referring to FIG. 7, according to an embodiment of the present invention, the solid electrolyte layer (300) may include solid electrolyte particles (SSP) and a polymer filler (PFL). For clearer explanation, the solid electrolyte particles (SSP) in the solid electrolyte layer in this specification may be distinguished from the solid electrolyte particles (SEP, see FIG. 3) in the positive electrode active material layer. The same content regarding the solid electrolyte described above may apply to the solid electrolyte particles (SSP) in the solid electrolyte layer. For example, the solid electrolyte particles (SSP) in the solid electrolyte layer may be an argyrodite-type sulfide-based solid electrolyte.

[0185] The polymer filler (PFL) may have viscosity and / or elasticity. The polymer filler (PFL) may fill the voids within the solid electrolyte layer (300). More specifically, the solid electrolyte layer (300) may comprise a plurality of solid electrolyte particles (SSP), and the polymer filler (PFL) may fill the voids between the plurality of solid electrolyte particles (SSP). For example, the solid electrolyte layer (300) may have a structure in which the polymer filler (PFL) is filled while surrounding the plurality of solid electrolyte particles (SSP).

[0186] By filling the aforementioned voids with a polymer filler (PFL), physical stability of the solid electrolyte layer (300) can be provided. The polymer filler (PFL) is dispersed within the solid electrolyte layer (300) to provide viscosity and / or elasticity, and can alleviate mechanical stress transmitted throughout the solid electrolyte layer (300). That is, by including the polymer filler (PFL) in the solid electrolyte layer (300), mechanical stress of the solid electrolyte layer (300) caused by volume changes of the positive and negative electrodes during charging and discharging can be reduced, and stability can be provided.

[0187] The polymer filler (PFL) can have ion conductivity. Since the polymer filler (PFL) has lithium ion conductivity, the ion conductivity of the solid electrolyte layer (300) can be improved. In addition, the polymer filler (PFL) exists in a fluid phase, which can further strengthen the electrical and chemical networks between solid particles within the all-solid-state battery.

[0188] FIG. 8 is an enlarged view of the N region of FIG. 7, intended to specifically describe a plurality of solid electrolyte particles (SSP) and a polymer filler (PFL) inside a solid electrolyte layer (300) according to an embodiment of the present invention.

[0189] In one embodiment, a void is defined between a plurality of solid electrolyte particles (SSP), and a polymer filler (PFL) can fill the void. For example, a solid electrolyte layer (300) includes a first solid electrolyte particle (SSP1), a second solid electrolyte particle (SSP2) adjacent to each other, and a void between said solid electrolyte particles, and a polymer filler (PFL) can fill said void. That is, the first and second solid electrolyte particles (SSP1, SSP2) can come into contact through the polymer filler (SSP).

[0190] In another embodiment, each of the plurality of solid electrolyte particles (SSP) may be coated with a polymer filler (PFL). Specifically, each of the plurality of solid electrolyte particles (SSP) may include a polymer layer covering at least a portion of the surface. The coated polymer layer may include a polymer filler (PFL). By having the solid electrolyte particles (SSP) coated with a polymer layer, ion conductivity can be improved and stability can be enhanced.

[0191] Referring again to FIG. 8, a plurality of solid electrolyte particles (SSP) can form an ion-conducting path (ICP) through a polymer filler (PFL). The polymer filler (PFL) can improve the lithium ion conductivity of the solid electrolyte layer (300) by possessing lithium ion conductivity itself. Additionally, the polymer filler (PFL) can improve ion conductivity by increasing the contact area of ​​the point-contact of the plurality of solid electrolyte particles (SSP) into a surface-contact.

[0192] In this way, by including a polymer filler (PFL) in the solid electrolyte layer (300), resistance within the solid electrolyte layer and structural instability caused by localized stress concentration resulting from only localized contact between solid electrolyte particles (SSP) can be mitigated.

[0193] In one embodiment, the interface stability with the anode (100) and the cathode (200) can be improved as the solid electrolyte layer (300) includes a polymer filler (PFL). For example, the contact force at the interface between the solid electrolyte layer (300) and the anode (100) or the cathode (200) can be improved.

[0194] Specifically, referring to FIGS. 9a and 9b, the interface between the anode (100) and the solid electrolyte layer (300) can be defined as a first interface (ESF1). The first interface (ESF1) can be defined as the region where the anode active material layer (120) and the solid electrolyte layer (300) come into contact. The first interface (ESF1) may include anode active material particles (CAC), solid electrolyte particles (SSP), and a first gap (GP1). The first gap (GP1) can be defined as the empty space between the solid particles of the first interface (ESF1). The first gap (GP1) can be defined as the empty space between the anode active material particles (CAC) and the solid electrolyte particles (SSP) of the first interface (ESF1).

[0195] As the charging / discharging process is repeated, a volume change occurs in the positive active material layer (120), and this volume change can reduce the stability of the interface between the positive active material layer (120) and the solid electrolyte layer (300). Due to the non-uniform volume change, the first gap (GP1) of the first interface (ESF1) may be further expanded. If the first gap (GP1) is expanded, the ion conductivity of the all-solid-state battery may be reduced. In addition, large pores may occur in some areas of the first interface (ESF1), or the interface may detach, preventing the battery from operating properly.

[0196] A polymer filler (PFL) within the solid electrolyte layer (300) can provide stability to the first interface (ESF1). For example, the interface bonding strength with the solid electrolyte layer (300) can be improved by the positive active material layer (120) further including the polymer filler (PFL). The positive active material layer (120) is in contact with the solid electrolyte layer (300) and may include a first region (AR1) that further includes the polymer filler (PFL). The polymer filler (PFL) in the first region (AR1) may originate from the solid electrolyte layer (300). Specifically, the polymer filler (PFL) may diffuse or penetrate into the first region (AR1) to fill the first gap (GP1). By improving the contact stability of the first interface (ESF1), the exchange of lithium ions can be carried out more smoothly. As a result, the performance of the all-solid-state battery can be improved.

[0197] Referring to FIGS. 10a and 10b, the interface between the cathode (200) and the solid electrolyte layer (300) can be defined as a second interface (ESF2). The same applies to the first interface (ESF1) described above. That is, by including a polymer filler (PFL) in the solid electrolyte layer (300), interface stability with the cathode (200) can also be provided. By stably forming a lithium ion path at the second interface (ESF2), the lithium metal layer (230) of the cathode (200) can be electrodeposited more uniformly. As a result, the long-term life characteristics of the all-solid-state battery can be improved.

[0198] In one embodiment, the content of the polymer filler (PFL) may be 10% by weight or less, 8% by weight or less, or 5% by weight or less with respect to the total weight of the solid electrolyte layer (300). For example, the content of the polymer filler (PFL) may be 0.1% by weight to 10% by weight, 0.1% by weight to 8% by weight, or 0.1% by weight to 5% by weight with respect to the total weight of the solid electrolyte layer (300). Within the above range, the performance of the solid electrolyte layer can be effectively improved.

[0199] The polymer filler (PFL) according to an embodiment of the present invention may contain a polyolefin-based sulfur-containing polymer and a lithium salt. As will be described specifically below, as the polymer filler (PFL) has such a composition, it can effectively perform the aforementioned function as an additive within the solid electrolyte layer (300).

[0200] In one embodiment, the polymer filler (PFL) may comprise a polyolefin-based sulfur-containing polymer. In this specification, the polyolefin-based sulfur-containing polymer may be referred to as the first polymer for convenience. In this specification, the polyolefin-based sulfur-containing polymer may refer to a polymer based on polyethylene, polypropylene, or copolymers thereof, wherein a sulfur atom is included in the chemical structure. The sulfur atom in the first polymer may be included in the chemical structure in the form of a sulfide (-S-) or a sulfoxide (-SO-). For example, the first polymer may comprise polyethylene sulfide, polypropylene sulfide, polyethylene sulfoxide, polypropylene sulfoxide, or copolymers thereof.

[0201] The first polymer is a sulfur-based polymer and can particularly reduce side reactions with sulfide-based solid electrolytes. The first polymer can maintain an electrically and chemically stable state within the operating voltage range of the all-solid-state battery.

[0202] Weight average molecular weight (M) of the first polymer w ) may be in the range of 1,000 to 30,000. In the above range, the physical properties of the first polymer are optimized so that the effect of the polymer filler (PFL) can be maximized.

[0203] In one embodiment, the polymer filler (PFL) may further include polyethylene oxide in addition to the first polymer. For convenience of explanation, polyethylene oxide may be referred to as the second polymer. The polymer filler (PFL) may include a polymer mixture in which the first polymer and the second polymer are blended. That is, the polymer filler (PFL) may include a mixture in which the first polymer and the second polymer are physically mixed without chemical bonding.

[0204] As the polymer filler (PFL) further includes a second polymer, the ion conductivity of the polymer filler (PFL) can be improved. Specifically, the second polymer may include repeating ether groups (-O-), and the ether groups may form a complex with lithium ions to provide multiple ion-conducting sites. Additionally, the second polymer may have a linear structure, thereby providing a more flexible polymer chain to improve ion conductivity.

[0205] In one embodiment, the weight average molecular weight (M) of the second polymer is w ) may be in the range of 500 to 1,000,000 or 100,000 to 300,000. In the above range, the physical properties of the second polymer are optimized so that the effect of the polymer filler (PFL) can be maximized.

[0206] In one embodiment, the terminal hydroxyl group (-OH) connected to the ethylene oxide main chain of the second polymer can be capped. For example, at least one of the terminal hydroxyl groups (-OH) of the second polymer can be converted to a methyl group (-CH3), an acetyl group (-COCH3), etc., to reduce reactivity. As a result, the polymer filler (PFL) can exist in a chemically stable state within the solid electrolyte layer (300).

[0207] However, the second polymer may have relatively low decomposition stability at high voltages. For example, the second polymer may exhibit a relatively high degree of side reactions in a high-voltage operating environment. The content of the second polymer within the polymer filler may be relatively lower compared to the first polymer. By including the second polymer in a relatively low amount in the polymer filler, it is possible to improve ion conductivity while also providing chemical stability.

[0208] When a second polymer is further included, a relatively low driving voltage may be advantageous for the all-solid-state battery. For example, the all-solid-state battery may include a sulfide-based cathode active material having a relatively low driving voltage range. Sulfide-based cathode active materials may have a lower driving voltage compared to oxide-based cathode active materials. In other words, a polymer filler containing a second polymer may be more suitable for an all-solid-state battery using a sulfide-based cathode active material as the cathode active material.

[0209] In one embodiment, the polymer filler (PFL) may include a lithium salt. By including a lithium salt in addition to the polymer described above, the polymer filler (PFL) may possess lithium ion conductivity. The lithium salt acts as a source of lithium ions and promotes the movement of lithium ions, and is not limited to those commonly used in the field of secondary batteries. For example, the lithium salt may be lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 It may include at least one of SO2)(x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), or lithium bis(oxalate)borate (LiBOB).

[0210] As the polymer filler (PFL) possesses lithium ion conductivity, the ion conductivity of the solid electrolyte layer can be improved. In one embodiment, the ion conductivity of the polymer filler (PFL) is 10 -6 S / cm to 10-9 It can be S / cm. The higher the weight of the second polymer in the polymer filler (PFL), the better the ion conductivity can be. The ion conductivity may be measured at a temperature of approximately 45°C.

[0211] In one embodiment, the first polymer may be included in an amount of 60 to 90 weight% or 60 to 80 weight% based on the total weight of the polymer filler (PFL). The second polymer may be included in an amount of 10 to 20 weight% based on the total weight of the polymer filler (PFL). The lithium salt may be included in an amount of 1 to 15 weight%, 5 to 15 weight%, or 5 to 10 weight% based on the total weight of the polymer filler (PFL). Within the above ranges, the polymer filler can effectively perform the functions described above.

[0212] The present invention will be explained in more detail below through embodiments. However, these embodiments are intended to illustrate the invention and the scope of the invention is not limited to these embodiments.

[0213] Preparation Example: Preparation of an all-solid-state battery

[0214] (Anode manufacturing)

[0215] Li2S, a sulfur compound, and LiI, an ion-conducting material, were mixed in a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C at 600 rpm for 10 hours.

[0216] The size of the Li2S-LiI composite was less than 1 μm. The size of the Li2S-LiI composite was calculated by software from scanning electron microscope images of the Li2S-LiI composite powder. The size of the Li2S-LiI composite is the D50 average particle size.

[0217] Li2S-LiI composites and carbon nanofibers (CNF) were mixed in a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to prepare Li2S-LiI-CNF. The milling conditions were 25°C at 510 rpm for 10 hours.

[0218] The lithium-sulfur carbon composite prepared as described above was used as the positive electrode active material.

[0219] A composition for forming a positive electrode active material layer was prepared by mixing the above positive electrode active material with an azirodite-type solid electrolyte (Li6PS5Cl) and a PTFE binder. The mixing weight ratio was positive electrode active material: solid electrolyte: binder = 80:19:1.

[0220] The above composition for forming the positive active material layer was dry-coated onto a positive current collector made of aluminum foil carbon-coated on one side, and the positive was manufactured by applying pressure for 10 minutes under conditions of 1 MPa and 130°C. The thickness of the positive active material layer was approximately 80 μm.

[0221] (Cathode manufacturing)

[0222] Carbon black (CB) was prepared as a carbon-based material and silver (Ag) particles were prepared as metal particles. After mixing the carbon black and silver particles in a weight ratio of 3:1, 4 g of the mixed powder was placed in a container, and a mixed solution was prepared by adding 4 g of a methylpyrrolidone (NMP) solution containing 7 wt% of a polyvinylidene fluoride (PVDF) binder (Kureha # 9300).

[0223] A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 10 hours to produce a laminate. The surface of the prepared laminate was flattened by cold roll pressing to produce a cathode having a cathode coating layer / cathode current collector structure. At this time, the thickness of the cathode coating layer was approximately 15 μm, and the area of ​​the cathode coating layer and the cathode current collector were the same.

[0224] (Preparation of solid electrolyte layer)

[0225] 95 wt% of Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal, 4 wt% of polymer filler, and 1 wt% of PVdF binder were mixed. A slurry was prepared by adding octyl acetate to the mixture while stirring. The prepared slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 2 hours to prepare a solid electrolyte layer.

[0226] Specifically, the polymer filler was prepared by adding the first polymer and a lithium salt to an octyl acetate solvent and stirring. The stirring temperature was approximately 60°C, and the polymer filler was finally prepared by leaving it for one day after stirring.

[0227] The composition of the manufactured polymer filler was first polymer:lithium salt = 88:12. Polypropylene sulfide was used as the first polymer, and the weight average molecular weight was approximately 14,000.

[0228]

[0229] Examples and Comparative Examples

[0230] Examples and comparative examples were distinguished by manufacturing according to the above manufacturing example, but with different compositions of the solid electrolyte layer.

[0231] Examples 1-1 to 4-1 (Examples containing only sulfide polymers)

[0232] In the case of Examples 1-1 to 4-1, the polymer filler comprises only the first polymer and the lithium salt. A mixture of the first polymer and the lithium salt in a weight ratio of approximately 88:12 was used. LiTFSI was used as the lithium salt.

[0233] In the case of Example 1-1, the first polymer is Polypropylene sulfide (M w =14,000), in the case of Example 2-1, polyethylene sulfoxide (M w =15,000), in the case of Example 3-1, polypropylene sulfoxide (M w =16,000), in the case of Example 4-1, polyethylene sulfide-propylene sulfide copolymer (M w =16,000, molar ratio = 1:1) was used.

[0234]

[0235] Examples 1-2 to 4-2 (+peo additional examples)

[0236] In the case of Examples 1-2 to 4-2, the polymer filler in Examples 1-1 to 4-1 further includes a second polymer in addition to the first polymer and lithium salt.

[0237] At this time, polyethylene oxide was used as the second polymer, and the weight average molecular weight (M w The amount was approximately 100,000. The polymer filler used was a mixture of the first polymer, the second polymer, and a lithium salt in a weight ratio of 75:15:10.

[0238] Examples 1-3 to 4-3 (based on Example n-1, filler 1 wt%)

[0239] In the case of Examples 1-3 to 4-3, the composition of the solid electrolyte layer was changed from Examples 1-1 to 4-1. The composition of the polymer filler in the solid electrolyte layer was reduced to 1 weight%.

[0240] Comparative Examples 1-1 to 4-1 (based on Example n-1, filler 14 wt%)

[0241] In the case of Comparative Examples 1-1 to 4-1, the composition of the solid electrolyte layer was changed from Examples 1-1 to 4-1. The composition of the polymer filler in the solid electrolyte layer was increased to 14 wt%.

[0242] Comparative Examples 1-2 to 4-2

[0243] In the case of Comparative Examples 1-2 to 4-2, the composition of the polymer filler was changed from Examples 1-2 to 4-2. Specifically, the polymer filler used was a mixture of the first polymer, the second polymer, and the lithium salt in a weight ratio of 55 wt%: 35 wt%: 10 wt%.

[0244] Comparative Examples 1-3

[0245] The polymer filler in the solid electrolyte layer is omitted, and it contains only solid electrolyte particles. Specifically, an azirodite-type sulfide-based solid electrolyte and a binder were mixed in a weight ratio of 95:5 and used.

[0246] This is specifically shown in Table 1 below.

[0247] Polymer Filler Composition Solid Electrolyte Layer Composition Polymer 1 Polymer 2 Polymer Lithium Salt Solid Electrolyte: Polymer Filler: Binder Example 1-1 Polypropylene sulfide (88wt%) LiTFSI (12wt%) 95wt% : 4wt% : 1wt% Example 2-1 Polyethylene sulfoxide (88wt%) LiTFSI (12wt%) 95wt% : 4wt% : 1wt% Example 3-1 Polypropylene sulfoxide (88wt%) LiTFSI (12wt%) 95wt% : 4wt% : 1wt% Example 4-1 Polyethylene sulfide / polypropylene sulfide (88wt%) LiTFSI (12wt%) 95wt% : 4wt% : 1wt% Example 1-2 Polypropylene sulfide (75wt%) Polyethylene oxide(15wt%)LiTFSI(10wt%)95wt%: 4wt%: 1wt%Example 2-2Polyethylene sulfoxide(75wt%)Polyethylene oxide(15wt%)LiTFSI(10wt%)95wt%: 4wt%: 1wt%Example 3-2Polypropylene sulfoxide(75wt%)Polyethylene oxide(15wt%)LiTFSI(10wt%)95wt%: 4wt%: 1wt%Example 4-2Polyethylene sulfide / polypropylene sulfide(75wt%)Polyethylene oxide(15wt%)LiTFSI(10wt%)95wt%: 4wt%: 1wt% Example 1-3Polypropylene sulfide (88wt%)LiTFSI (12wt%)98wt%: 1wt%: 1wt% Example 2-3 Polyethylene sulfoxide (88wt%) LiTFSI (12wt%) 98wt%: 1wt%: 1wt% Example 3-3 Polypropylene sulfoxide (88wt%) LiTFSI (12wt%) 98wt%: 1wt%: 1wt% Example 4-3 Polyethylene sulfide / polypropylene sulfide (88wt%) LiTFSI (12wt%) 98wt%: 1wt%:1wt% Comparative Example 1-1 Polypropylene sulfide (88wt%) LiTFSI (12wt%) 85wt% : 14wt% : 1wt% Comparative Example 2-1 Polyethylene sulfoxide (88wt%) LiTFSI (12wt%) 85wt% : 14wt% : 1wt% Comparative Example 3-1 Polypropylene sulfoxide (88wt%) LiTFSI (12wt%) 85wt% : 14wt% : 1wt% Comparative Example 4-1 Polyethylene sulfide / polypropylene sulfide (88wt%) LiTFSI (12wt%) 85wt% : 14wt% : 1wt% Comparative Example 1-2 Polypropylene sulfide (55wt%) Polyethylene oxide (35wt%) LiTFSI (10wt%) 95wt% : 4wt%: 1wt%Comparative Example 2-2Polyethylene sulfoxide(55wt%)Polyethylene oxide(35wt%)LiTFSI(10wt%)95wt%: 4wt%: 1wt%Comparative Example 3-2Polypropylene sulfoxide(55wt%)Polyethylene oxide(35wt%)LiTFSI(10wt%)95wt%: 4wt%: 1wt%Comparative example 4-2Polyethylene sulfide / polypropylene sulfide(55wt%)Polyethylene oxide(35wt%)LiTFSI(10wt%)95wt%: 4wt%: 1wt%Comparative example 1-3---95wt%: -: 5wt%

[0248]

[0249] Evaluation Example 1: All-solid-state battery performance evaluation

[0250] The performance of the all-solid-state battery according to the above-described examples and comparative examples was evaluated. Specifically, the first cycle was charged for 20 hours at a constant current of 0.05C until the battery voltage reached 2.8 V. Subsequently, discharge was performed for 20 hours at a current of 0.05C until the battery voltage reached 1.0 V.

[0251] The second cycle involved charging at a constant current of 0.1 C for 10 hours until the battery voltage reached 2.8 V. Subsequently, discharging was performed at a constant current of 0.1 C for 10 hours until the battery voltage reached 1.0 V.

[0252] After the second cycle, charging and discharging were performed for up to 100 cycles under the same conditions as the second cycle. The capacity retention rate was evaluated as shown in Equation 1 below.

[0253] [Mathematical Formula 1]

[0254] Capacity Retention Rate[%] = [n-th cycle discharge capacity / 1st cycle discharge capacity] × 100

[0255] Based on the initial charge / discharge capacity, the capacity after 100 cycles was evaluated. The results are shown in Table 2 below.

[0256] Dose Retention Rate (%, @100cyc) Example 1-191 Example 2-189 Example 3-192 Example 4-191 Example 1-288 Example 2-288 Example 3-289 Example 4-288 Example 1-381 Example 2-379 Example 3-381 Example 4-381 Comparative Example 1-155 Comparative Example 2-151 Comparative Example 3-153 Comparative Example 4-154 Comparative Example 1-262 Comparative Example 2-263 Comparative Example 3-261 Comparative Example 4-261 Comparative Example 1-366

[0257] Referring to the evaluation results above, it can be seen that the lifespan characteristics of the all-solid-state battery according to the embodiment of the present invention are superior to those of the comparative example.

[0258] Referring to the results of Comparative Examples 1-1 to 4-1, it can be seen that the effect is actually reduced when an excessive amount of polymer filler is added to the solid electrolyte layer. Additionally, referring to the results of Comparative Examples 1-2 to 4-2, the effect is negligible even when the content of the first polymer in the polymer filler is lowered below a certain level.

[0259]

[0260] Evaluation Example 2: All-solid-state battery interface analysis

[0261] The interface of the solid electrolyte layer of the all-solid-state battery according to Example 1-1 and Comparative Example 1-3 was analyzed after the charge / discharge process. The superiority of the embodiments of the present invention was confirmed by comparing the appearance at the initial stage with the appearance after 100 cycles. An SEM image of the interface of Example 1-1 is shown in FIG. 11a, and an SEM image of the interface of Comparative Example 1-3 is shown in FIG. 11b. Unlike the comparative example, it can be confirmed that in the case of the example, the solid interface maintains a relatively stable form even after multiple charge / discharge processes have been performed.

[0262] Specifically, in the case of FIG. 11a, it can be seen that the interface (ESF1) between the positive active material layer and the solid electrolyte layer is stably maintained. However, in the case of FIG. 11b, it can be seen that the interface (ESF1) between the positive active material layer and the solid electrolyte layer has detached.

Claims

Anode; cathode; and a solid electrolyte layer between the anode and the cathode, comprising: The above solid electrolyte layer comprises a plurality of solid electrolyte particles and a polymer filler, and The above polymer filler comprises a polyolefin-based sulfur-containing polymer and a lithium salt, and The content of the polymer filler is 0.1% to 8% by weight based on the total weight of the solid electrolyte layer, and The above polyolefin-based sulfur-containing polymer is 60% to 90% by weight based on the total weight of the polymer filler, All-solid-state battery. In paragraph 1, The above polymer filler further comprises polyethylene oxide, All-solid-state battery. In paragraph 2, With respect to 100 parts by weight of the above polymer filler, It comprises 60 to 80 parts by weight of the above-mentioned polyolefin-based sulfur-containing polymer, and It comprises 10 to 20 parts by weight of the above polyethylene oxide, and Comprising 1 to 15 parts by weight of the lithium salt, All-solid-state battery. In paragraph 2, The above polyethylene oxide is, A main chain comprising ethylene oxide units, and first and second end groups connected to both sides of the main chain, and At least one of the first and second terminal groups is a methyl group (-CH3), All-solid-state battery. In paragraph 2, The molecular weight of the above polyethylene oxide is 100,000 to 300,000, All-solid-state battery. In paragraph 1, The molecular weight of the above polyolefin-based sulfur-containing polymer is 1,000 to 30,000, All-solid-state battery. In paragraph 1, The above-mentioned polyolefin-based sulfur-containing polymer is, An all-solid-state battery comprising at least one of polyethylene sulfide, polypropylene sulfide, polyethylene sulfoxide, polypropylene sulfoxide, or a copolymer thereof. In paragraph 1, Each of the above plurality of solid electrolyte particles is Li 7-a-c M a PS 6-c X c It comprises an argyrodite-type sulfide-based solid electrolyte represented by (0≤a≤2, 0≤c≤2), and The above X is F, Br, Cl, or a combination thereof, and The above M is scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof, All-solid-state battery. In paragraph 1, The above solid electrolyte layer has defined voids between the plurality of solid electrolyte particles, and the polymer filler fills the voids, in an all-solid-state battery. In paragraph 1, An all-solid-state battery in which the content of the polymer filler is 0.1% to 5% by weight with respect to the total weight of the solid electrolyte layer. In paragraph 1, The above polymer filler covers at least a portion of the surface of each of the plurality of solid electrolyte particles, in an all-solid-state battery. In paragraph 1, The plurality of solid electrolyte particles include first particles and second particles adjacent to each other, and the first and second particles are in contact through the polymer filler, The polymer layer provides an ion conduction path between the first and second particles. All-solid-state battery. In paragraph 1, The above-mentioned anode is an all-solid-state battery comprising a first region containing the polymer filler and in contact with the solid electrolyte layer. In paragraph 1, The above-mentioned cathode comprises a second region containing the polymer filler and in contact with the solid electrolyte layer, in an all-solid-state battery. In paragraph 1, The above lithium salts are lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(x and y are integers from 1 to 20), comprising at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), or lithium bis(oxalate)borate (LiBOB), All-solid-state battery.

Images