Cell structure for all-solid-state battery and all-solid-state battery comprising same

Abstract

The present invention relates to an all-solid-state battery. More specifically, the present invention relates to a lithium-sulfur all-solid-state battery comprising a unit cell comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the positive electrode active material layer contains a sulfide-based positive electrode active material, the positive electrode active material layer includes a body portion and an outer portion protruding outwards from the body portion, the outer portion has a bulging sidewall, the outer portion is spaced apart from the upper surface of the solid electrolyte layer, and the width in a first direction of the positive electrode active material layer is smaller than the width in the first direction of the solid electrolyte layer.

Description

Cell structure for an all-solid-state battery and an all-solid-state battery including the same

[0001] It relates to an all-solid-state battery including a solid electrolyte layer.

[0002] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries are being used not only in information and communication devices, but also in the automotive sector. Safety is particularly important in the automotive sector, as it is directly related to life.

[0003] Lithium-ion batteries currently on the market use electrolytes containing flammable organic solvents, which poses a risk of overheating and fire in the event of a short circuit. To address this issue, all-solid-state secondary batteries using solid electrolytes are being proposed.

[0004] All-solid-state secondary batteries do not use flammable organic solvents, significantly reducing the risk of fire or explosion even if a short circuit occurs. Therefore, these all-solid-state batteries significantly improve safety compared to lithium-ion batteries that use electrolytes.

[0005]

[0006] The problem to be solved by the present invention is to provide an all-solid-state battery with improved rate characteristics by suppressing electrical short-circuiting of the cell and improving interlayer interface bonding.

[0007] Another problem that the present invention seeks to solve is to provide an all-solid-state battery with improved mass productivity.

[0008]

[0009] A lithium-sulfur all-solid-state battery according to the concept of the present invention may include a unit cell including a positive electrode layer including a positive electrode active material layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The positive electrode active material layer includes a sulfide-based positive electrode active material, and the positive electrode active material layer includes a body portion and an outer portion protruding outward from the body portion, the outer portion having a convex side wall, the outer portion being spaced apart from an upper surface of the solid electrolyte layer, and a first width of the positive electrode active material layer in a first direction may be smaller than a second width of the solid electrolyte layer in the first direction.

[0010] According to another concept of the present invention, a lithium-sulfur all-solid-state battery may include a positive electrode active material layer including a sulfide-based positive electrode active material; a negative electrode layer; and a solid electrolyte layer between the positive electrode active material layer and the negative electrode layer. The solid electrolyte layer may include an inert member on a peripheral portion of an upper surface of the solid electrolyte layer. The inert member may be configured such that the positive electrode active material layer is spaced apart from the peripheral portion of the upper surface of the solid electrolyte layer. The positive electrode active material layer has a first width in a first direction, and the solid electrolyte layer including the inert member on the peripheral portion of the upper surface of the solid electrolyte layer has a third width in the first direction, and the first width may be smaller than the third width.

[0011] According to another concept of the present invention, a lithium-sulfur all-solid-state battery may include a unit cell including a cathode layer including a sulfide-based cathode active material layer; a cathode layer; and a solid electrolyte layer disposed between the cathode layer and the cathode layer. The sulfide-based cathode active material layer includes a complex of Li2S, a lithium salt, and a metal halide, wherein the metal halide may contain a metal other than lithium. The unit cell may include an inert member surrounding a side surface of the cathode layer and in contact with the solid electrolyte layer. With respect to a first direction, the cathode active material layer may have a first width, the solid electrolyte layer may have a second width, and the inert member may have a fourth width, and a width of the inert member with respect to the width of the solid electrolyte layer may be 0.05 to 0.20.

[0012]

[0013] According to one embodiment of the present invention, the interfacial bonding characteristics and bonding strength between the positive electrode layer and the solid electrolyte layer of an all-solid-state battery can be improved. Furthermore, an all-solid-state battery with improved stability can be provided by suppressing electrical short-circuiting of the cell.

[0014]

[0015] FIG. 1 is a plan view of an all-solid-state battery, which is intended to explain an all-solid-state battery according to one embodiment of the present invention.

[0016] FIG. 2 is a cross-sectional view of an all-solid-state battery taken along line A-A' of FIG. 1, which is intended to explain an all-solid-state battery according to one embodiment of the present invention.

[0017] FIG. 3 is a plan view of an all-solid-state battery, which is intended to explain an all-solid-state battery according to one embodiment of the present invention.

[0018] FIG. 4 is a cross-sectional view of an all-solid-state battery taken along line A-A' of FIG. 3, for explaining an all-solid-state battery according to one embodiment of the present invention.

[0019] FIG. 5 is a plan view of an all-solid-state battery, which is intended to explain an all-solid-state battery according to one embodiment of the present invention.

[0020] FIG. 6 is a cross-sectional view of an all-solid-state battery taken along line A-A' of FIG. 5, illustrating an all-solid-state battery according to one embodiment of the present invention.

[0021] FIG. 7 and FIG. 8 are cross-sectional views of an all-solid-state battery taken along line A-A' of FIG. 5, illustrating an all-solid-state battery according to one embodiment of the present invention.

[0022] FIG. 8 is a plan view of an all-solid-state battery, which is intended to explain an all-solid-state battery according to one embodiment of the present invention.

[0023] FIGS. 9 and 10 are cross-sectional views of an all-solid-state battery taken along line A-A' of FIG. 8, illustrating an all-solid-state battery according to one embodiment of the present invention.

[0024] FIG. 11 is an enlarged view of area M of FIG. 4, which is intended to explain a positive electrode active material layer according to one embodiment of the present invention.

[0025] Figure 12 is an enlarged view of a positive electrode active material layer according to one embodiment of the present invention.

[0026] Figure 13 is a cross-sectional view of an all-solid-state battery for explaining an all-solid-state battery according to a comparative example of the present invention.

[0027] Figure 14 is a cross-sectional view of an all-solid-state battery for explaining an all-solid-state battery according to a comparative example of the present invention.

[0028]

[0029] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications. However, the description of these embodiments is provided solely to ensure a complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention.

[0030] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. Furthermore, in the drawings, the thicknesses of the components are exaggerated for the sake of clarity. Parts designated by the same reference numerals throughout the specification represent the same components.

[0031] Embodiments described herein will be described with reference to cross-sectional and / or plan views, which are ideal illustrations of the present invention. In the drawings, the thicknesses of films and regions are exaggerated for the purpose of effectively explaining the technical contents. Accordingly, the regions illustrated in the drawings have a schematic nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific shapes of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, and third are used to describe various components in various embodiments of the present specification, these components should not be limited by such terms. These terms are used only to distinguish one component from another. The embodiments described and illustrated herein also include complementary embodiments thereof.

[0032] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the words "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0033] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well 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) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed 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 ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0034] In this specification, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic state.

[0035] As used herein, “alloy” means a mixture of two or more metals.

[0036] In this specification, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0037] In this specification, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0038] In this specification, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0039] In this specification, “lithiation” and “lithiate” mean a process of adding lithium to an electrode active material.

[0040] In this specification, “delithiation” and “delithiate” refer to a process of removing lithium from an electrode active material.

[0041] In this specification, “charging” and “charging” mean the process of providing electrochemical energy to a battery.

[0042] In this specification, “discharge” and “discharge” mean the process of removing electrochemical energy from a battery.

[0043] In this specification, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during the discharge process.

[0044] In this specification, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0045]

[0046] All-solid-state battery (10)

[0047] Fig. 1 is a plan view of an all-solid-state battery according to one embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line A-A' of Fig. 1. Fig. 12 is an enlarged cross-sectional view of a positive electrode active material layer for explaining a positive electrode active material layer according to one embodiment of the present invention.

[0048] 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, the present invention is not limited thereto, and 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).

[0049] Bipolar (100)

[0050] A positive electrode layer (100) according to one embodiment of the present invention may include a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on the positive electrode current collector (110). The positive electrode active material layer (120) may include a positive electrode active material, a solid electrolyte, a conductive material, and a binder.

[0051] The positive electrode current collector (110) can provide a reference surface on which the positive electrode active material layer (120) is arranged. The positive electrode current collector (110) can 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 electrode current collector (110) can include a plate or a foil. In another embodiment of the present invention, the positive electrode current collector (110) can be omitted. The thickness of the positive electrode current collector (110) can be, for example, 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, 5 ㎛ to 25 ㎛, or 10 ㎛ to 20 ㎛.

[0052] The cathode 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.

[0053] The base film may be, for example, an insulator. If the base film includes an insulating thermoplastic polymer, the base film may soften or liquefy when a short circuit occurs, thereby preventing battery operation and suppressing a rapid increase in current.

[0054] The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer may act as an electrochemical fuse to prevent short circuits by being cut off in the event of overcurrent. The limit current and maximum current can be controlled by controlling the thickness of the metal layer. The metal layer may be plated or deposited on the base film. When the thickness of the metal layer is reduced, the limit current and / or maximum current of the positive electrode current collector (110) decrease, thereby improving the stability of the lithium battery in the event of a short circuit.

[0055] 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 may melt, electrically connecting the metal layer to the lead tab.

[0056] In order to make the welding between the metal layer and the lead tab more solid, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin piece of the same material as the metal of the metal layer. The metal chip may be, for example, a metal foil, a metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. By placing the metal chip on the metal layer and then welding it with the lead tab, the lead tab may be welded to the metal chip / metal layer laminate or the metal chip / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal chip may melt, so that the metal layer or the metal layer / metal chip laminate may be electrically connected to the lead tab. The metal chip and / or the lead tab may be added to a portion of the metal layer.

[0057] 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. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300 °C, 100 to 250 °C or less, or 100 to 200 °C. When the base film has a melting point in this range, the base film can be melted during the process of welding the lead tab and easily bonded to the lead tab. In order to improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film.

[0058] The thickness of the metal layer may be, for example, 0.01 to 3 ㎛, 0.1 to 3 ㎛, 0.1 to 2 ㎛, or 0.1 to ㎛. By having a thickness in this range of the metal layer, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 ㎛, 2 to 7 ㎛, or 4 to 6 ㎛. By having a thickness in this range of the metal piece, the connection between the metal layer and the lead tab can be performed more easily. By having the laminated structure of the base film and the metal layer as described above, the positive electrode current collector (110) can reduce the weight of the positive electrode layer (100), and consequently, the energy density of the all-solid-state battery (10) can be improved.

[0059] Positive active material layer (120)

[0060] In one embodiment of the present invention, the content of the positive electrode active material in the positive electrode 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 electrode active material layer (120). If the content of the positive electrode active material is excessively reduced, the energy density of the all-solid-state battery (10) may be reduced. If the content of the positive electrode active material is excessively increased, the deterioration of the all-solid-state battery (10) may be accelerated due to a change in the volume of the positive electrode during charge and discharge.

[0061] The elastic modulus of the positive electrode active material layer (120) may be, for example, 1 GPa to 50 GPa, 10 GPa to 50 GPa, 15 GPa to 30 GPa, or 10 GPa to 20 GPa. The elastic modulus of the positive electrode active material layer (120) may be smaller than the elastic modulus of the solid electrolyte layer (300).

[0062] The positive electrode active material within the positive electrode active material layer (120) can reversibly absorb and desorb lithium ions. The positive electrode active material may include a plurality of particles. The positive electrode active material according to the present invention may include an oxide-based positive electrode active material, a sulfide-based positive electrode active material, or a combination thereof.

[0063] (oxide-based cathode active material)

[0064] The oxide-based cathode active material may include, for example, a lithium transition metal oxide, a metal oxide, or a combination thereof. The lithium transition metal oxide may 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 a combination thereof. The lithium oxide may include, for example, iron oxide, vanadium oxide, or a combination thereof.

[0065] The sulfide-based cathode active material may include, for example, nickel sulfide, copper sulfide, Li2S, a Li2S-containing complex, or a combination thereof. A more specific description of the sulfide-based cathode active material according to an embodiment of the present invention will be provided below.

[0066] The oxide-based cathode active material may be, for example, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. The lithium-containing oxide-based cathode active material may be, for example, Li. a A 1-bB' b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c 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 G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); may include a compound represented by any one of the chemical formulas of LiFePO4.

[0067] 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; J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0068] 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 atomic layers and metal atomic layers are alternately and regularly arranged in a direction, and thereby each atomic layer forms a two-dimensional plane. The "cubic rock salt structure" refers to the sodium chloride type (NaCl type) structure, which is a type of crystal structure, and specifically refers to a structure in which the face-centered cubic lattice (fcc) formed by each cation and anion is arranged with a displacement of half of the ridge of the unit lattice. Lithium transition metal oxides having this layered rock salt structure include, 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.

[0069] The oxide-based positive electrode active material may be covered by a coating layer (not shown). The oxide-based positive electrode active material may also be a mixture of the above-described compound and a compound to which a coating layer is added. Meanwhile, the coating layer added to the surface of the positive electrode active material may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of the coating elements below. The compound forming the coating layer may be 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 of forming the coating layer may be selected within a range that does not adversely affect the physical properties of the positive electrode active material. The method of forming the coating layer may include, for example, spray coating, dipping, etc.

[0070] When the oxide-based cathode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), it is possible to increase the capacity density of the all-solid-state battery (10) and reduce metal dissolution of the cathode active material in a charged state. As a result, the cycle characteristics of the all-solid-state battery (10) in a charged state are improved. Meanwhile, the "cycle characteristics" are characteristics indicating the degree to which the all-solid-state battery (10) is deteriorated due to charge / discharge of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics may have a small degree of deterioration of the all-solid-state battery (10) due to charge / discharge, and an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration of the all-solid-state battery (10) due to charge / discharge.

[0071] The oxide-based cathode active material may have a particle shape such as a sphere or an ellipsoid, for example. 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, a single-crystal particle or a polycrystalline particle.

[0072] (Sulphide-based positive electrode active material)

[0073] The cathode active material layer (120) according to embodiments of the present invention may include a sulfide-based cathode active material. Specifically, referring to FIG. 12, the sulfide-based cathode active material may include a Li2S-containing cathode active material (CAC). The Li2S-containing cathode active material (CAC) may include, for example, a complex of Li2S and carbon, a complex of Li2S, carbon, and a solid electrolyte, a complex of Li2S and a solid electrolyte, a complex of Li2S and a lithium salt, a complex of Li2S, a lithium salt, and carbon, a complex of Li2S, a lithium salt, a metal halide, and carbon, a complex of Li2S and a metal carbide, a complex of Li2S, carbon, and a metal carbide, a complex of Li2S and a metal nitride, a complex of Li2S, carbon, and a metal nitride, or a combination thereof.

[0074] 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 spherical shape or an elliptical shape. 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).

[0075] The conductive material (CMA) may include carbon. The conductive material (CMA) may include, without limitation, any material containing carbon atoms used as a conductive material 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.

[0076] 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, etc.; graphite, activated carbon, or a combination thereof. The form of the carbon in the conductive material (CMA) may be, but is not limited to, particle form, sheet form, fiber form, etc., and any form used as carbon in the art may be used.

[0077] In one embodiment of the present invention, the conductive material (CMA) may include a fibrous carbon-based material. Since the conductive material (CMA) includes a fibrous carbon-based material, the electronic conductivity of the cathode active material (CAC) may be further enhanced. Since the conductive material (CMA) includes a fibrous carbon-based material, electronic conduction may be facilitated from the surface to the interior of the cathode active material (CAC). The internal resistance of the sulfide-based composite (CAM) may be reduced by the conductive material (CMA), and the cycle characteristics of the secondary battery may be further improved.

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

[0079] The fibrous carbon-based material may include, for example, carbon nanostructures. The carbon nanostructures may include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanobelts, carbon nanorods, or combinations thereof. The carbon nanostructures may form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure composed of multiple carbon nanostructures aggregated together.

[0080] The diameter of the primary carbon nanostructure can be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure can be, for example, 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure can be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure can be measured by laser diffraction.

[0081] The secondary carbon nanostructure may be, for example, a structure formed by assembling primary carbon nanostructures in whole or in part to form a bundle or bunch shape. The secondary carbon nanostructure may include, for example, a bundle-type carbon nanostructure, a rope-type carbon nanostructure, 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 can be, for example, 20 nm to 2 ㎛, 30 nm to 1.5 ㎛, 50 nm to 1 ㎛, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured from a scanning electron microscope (SEM) image or an optical microscope. Alternatively, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be converted into the primary carbon nanostructure by, for example, dispersing it in a solvent or the like and then used in the manufacture of a cathode active material (CAC).

[0082] The method for manufacturing the cathode active material (CAC) according to the present embodiments may be, but is not limited to, a dry method, a wet method, or a combination thereof. In the art, methods for manufacturing the cathode active material (CAC) include, but are not necessarily limited to, milling, heat treatment, or deposition, and any method used in the art may be used.

[0083] In one embodiment of the present invention, the sulfide-based composite (CAM) in the cathode active material (CAC) may include a composite of Li2S and a solid electrolyte. The solid electrolyte may be, for example, an amorphous solid electrolyte, and any material used as an ion-conducting material in the art may be used. 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 includes, 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 have, for example, a molecular weight of 1×10 at room temperature. -5 It can have an ionic conductivity of S / cm or more. Sulfide-based solid electrolytes include, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0*?*x*?*2, Li 7-x PS 6-x Br x , 0*?*x*?*2, and Li7-x PS 6-x I x , may contain one or more selected from 0*?*x*?*2.

[0084] The oxide-based solid electrolyte contains, for example, Li, O, and transition metal elements, and may optionally contain other elements. The oxide-based solid electrolyte has, for example, a 1×10 -5 It may be a solid electrolyte having an ionic conductivity of S / cm or more. The oxide-based solid electrolyte may be selected from oxide-based solid electrolytes used in the solid electrolyte layer. The solid electrolyte may be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, it may be a mixture of Li3PO4-Li2SO4 and a binary lithium salt, or a mixture of Li3PO4-Li2SO4 and a ternary lithium salt.

[0085] In one embodiment of the present invention, the sulfide-based composite (CAM) within the cathode active material (CAC) may include a composite of Li2S and a lithium salt. In other words, the composite (CAM) may include Li2S and a lithium salt compound. The lithium salt compound may not include, for example, sulfur (S) atoms.

[0086] The lithium salt compound may be, for example, a binary compound composed of lithium and one element selected from groups 13 to 17 of the periodic table of elements. The 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, for example, a ternary compound composed of lithium and two elements selected from groups 13 to 17 of the periodic table of elements. The ternary compound 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.

[0087] In one embodiment of the present invention, the sulfide-based composite (CAM) may include a composite 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 may be, for example, M n+1 C n T x (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) can be expressed as 2D metal carbides, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5)3C2T x , Ti3CNT x , Ta4C3T x , Nb4C3T x or a combination thereof. The surface of the two-dimensional metal carbide may be terminated with O, OH and / or F.

[0088] In one embodiment of the present invention, the sulfide-based composite (CAM) may include a composite of Li2S and a metal nitride. The metal nitride may be, for example, a two-dimensional metal nitride. The two-dimensional metal nitride may be, for example, M n+1 N n T x (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) can be expressed as The surface of the two-dimensional metal nitride can be terminated with O, OH and / or F.

[0089] A composite (CAM) containing a cathode active material (CAC) and Li2S according to one embodiment of the present invention will be described in more detail. The cathode active material (CAC) may include a composite of Li2S, a lithium salt, and carbon. More specifically, the cathode active material (CAC) may include a composite of Li2S, a lithium halide, and carbon.

[0090] The composite (CAM) according to the present embodiments may have ductility. The composite (CAM) may function as a buffer material within the positive electrode active material layer (120). The composite (CAM) may prevent the occurrence of defects due to volume changes in the positive electrode active material layer (120).

[0091] In one embodiment, the composite (CAM) comprises Li2S-Li a X b(1≤a≤5, 1≤b≤5) may include a compound represented by X. The 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.

[0092] 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 the composite (CAM) including the solid solution of Li2S and a lithium salt. For example, since the solid solution of Li2S and a lithium salt includes lithium ions arranged within Li2S crystallites, the ionic conductivity of the solid solution of Li2S and a lithium salt may be improved compared to the ionic conductivity of Li2S. Consequently, the 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.

[0093] The size of the Li2S crystallites of the complex (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 complex (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 complex of Li2S and the lithium salt may be improved.

[0094] The complex (CAM) according to one embodiment may further comprise a metal halide. In other words, the complex (CAM) may comprise a complex of Li2S, a lithium salt, and a metal halide. The metal halide may contain a metal other than lithium.

[0095] The complex (CAM) is Li2S-Li a X1 b -MX2 c A compound represented by may include a compound represented by . a may be an integer from 1 to 5, b may be an integer from 1 to 5, and c may be an integer from 1 to 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). Each of X1 and X2 may be selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0096] The composite (CAM) may include a solid solution of Li2S, a lithium salt, and a metal halide. For example, the composite (CAM) may include a compound (or solid solution) represented by Li2S-LiI-AlI3. As described above, the composite (CAM) and a conductive material (CMA, e.g., carbon nanostructure) may constitute a cathode active material (CAC) according to the present invention.

[0097] 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. The improved ductility of the composite (CAM) effectively prevents internal defects due to volume changes in the positive electrode active material layer (120).

[0098] The Mohs hardness of Li2S is, for example, 0.6. The Mohs hardness of the composite (CAM) may be, for example, less than 2, less than 1.5, less than 1, or less than 0.7. If the Mohs hardness of the composite (CAM) increases excessively, it may be difficult to provide ductility.

[0099] The Mohs hardness of the lithium salt may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. For example, the Mohs hardness of LiI is 2.0. Since the lithium salt has a Mohs hardness within this range, the pulverization of Li2S can be performed more easily during the milling process, and a solid solution of Li2S and the lithium salt can be formed more easily.

[0100] Since Li2S has relatively low ionic conductivity, a complex of Li2S and a lithium salt can be formed to improve ionic conductivity. The complex (CAM), which is a complex of 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). When the complex (CAM) has a Li2S content in this range, the complex (CAM) can have both improved ionic conductivity and excellent ductility.

[0101] The content of the lithium salt in the composite (CAM) can 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 in this range, the composite (CAM) can have both improved ionic conductivity and excellent ductility.

[0102] The content of the 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 the metal halide content in this range, the composite (CAM) can have both improved ionic conductivity and excellent ductility.

[0103] 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 a molar ratio, the composite (CAM) may have both enhanced ionic conductivity and excellent ductility.

[0104] The ionic conductivity of the complex (CAM) according to embodiments of the present invention is, for example, 1×10 at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4 It can be S / cm or more. For example, the ionic conductivity can be measured using an electrochemical impedance spectroscopy, a direct current polarization method, etc. Since the composite (CAM) has an ionic conductivity in this range, the internal resistance of the positive electrode active material layer (120) including the composite (CAM) can be further reduced.

[0105] The average particle diameter (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 diameter 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.

[0106] The size of the Li2S particles in the composite (CAM) can be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the Li2S particles can be, for example, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, or 0.1 μm to 1 μm.

[0107] (Solid electrolyte within the positive electrode active material layer)

[0108] Referring back to FIGS. 2 and 12, the positive electrode active material layer (120) may further include a solid electrolyte (SEP) in addition to the Li2S-containing positive electrode active material (CAC). The solid electrolyte (SEP) in the positive electrode active material layer (120) may be the same as or different from the solid electrolyte in the solid electrolyte layer (300) described below.

[0109] The solid electrolyte (SEP) in the positive electrode active material layer (120) may have a smaller average particle diameter (D50) than the solid electrolyte in the solid electrolyte layer (300). For example, the average particle diameter of the solid electrolyte (SEP) in the positive electrode 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 diameter of the solid electrolyte in the solid electrolyte layer (300).

[0110] In one embodiment, the content of the cathode active material (CAC) in the cathode 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 cathode active material layer (120). Among the components in the cathode active material layer (120), the cathode active material (CAC) may have the largest content. The content of the solid electrolyte (SEP) in the cathode 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 cathode active material layer (120).

[0111] The solid electrolyte (SEP) may be, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0*?*x*?*2, Li 7-x PS 6-x Br x , 0*?*x*2, and Li 7-x PS 6-x I x, may be one or more selected from 0*x*2. The sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one containing sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form a solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0112] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

[0113] <Chemical Formula 1>

[0114] Li + 12-n-x A n+ X 2- 6-x Y - x

[0115] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1*n*5, 0*x*2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0116] Alternatively, the sulfide-based solid electrolyte is Li 7-a M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)), where X may be F, Br, Cl, or a combination thereof. M is 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. Can be.

[0117] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0118] (filler)

[0119] The positive electrode active material layer (120) may further include a filler (FIL). In one embodiment, the content of the filler (FIL) in the positive electrode 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 electrode active material layer (120).

[0120] 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, after preparing a crystalline lithium metal oxyhalide, the crystalline lithium metal oxyhalide may be melted to prepare a molten salt, which may then be cooled to prepare an amorphous lithium metal oxyhalide. In another embodiment, the composition of the lithium metal oxyhalide may be controlled to directly prepare the amorphous 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 charge and discharge of the all-solid-state battery (10). In contrast, the crystalline lithium metal oxyhalide may be relatively brittle compared to the amorphous lithium metal halide. Whether or not the inorganic filler is amorphous can be confirmed using an XRD spectrum.

[0121] 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, the volume change of the all-solid-state secondary battery (10) can be effectively accommodated during charge and discharge or can be easily deformed according to the volume change of the all-solid-state secondary battery (10).

[0122] 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, the glassy state can be obtained during the manufacturing process of the inorganic filler. The glass transition temperature can be measured, for example, using a differential scanning calorimeter (DSC). The glass transition temperature can be measured, for example, using a dynamic mechanical analyzer (DMA).

[0123] 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 form 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 differential scanning calorimetry (DSC).

[0124] The inorganic filler may be an ionic conductive inorganic filler. The inorganic filler may have, for example, an ionic conductivity of 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°C1 atm. The ionic conductivity may be measured by AC impedance analysis. The voltage amplitude used in the AC impedance analysis may be 5 to 10 mV, and the frequency may be 1 MHz to 1 Hz. Since the inorganic filler has ionic conductivity, it can effectively suppress an increase in the interfacial resistance between the positive active material (CAC) particles, between the solid electrolyte (SEP) particles, and / or between the positive active material (CAC) and the solid electrolyte (SEP) within the positive active material layer (120) (see FIG. 12).

[0125] The elastic modulus (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. Since the inorganic filler has an elastic modulus in this low range, the positive electrode active material layer (120) can effectively accommodate the volume change of the all-solid-state battery (10). Accordingly, 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).

[0126] The elastic modulus of the inorganic filler may be, for example, lower than 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).

[0127] An inorganic filler, i.e., a filler (FIL), can be uniformly provided within the positive electrode active material layer (120) (see FIG. 12). 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 pores between the solid electrolytes (SEP) and / or the pores between the solid electrolyte (SEP) and the positive electrode active material (CAC), thereby reducing the internal resistance of the positive electrode active material layer (120) and easily accommodating a volume change of the positive electrode active material layer (120) during charge and discharge. 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).

[0128] The inorganic filler may have, for example, viscoelasticity. The inorganic filler may have, for example, viscoelastic creep. The viscoelastic creep rate of the inorganic filler may be, for example, 1×10-4 % / s or more, 2×10-4 % / s or more, or 4×10-4 % / s or more. % / s is the ratio of the deformed size to the initial size per unit time (second). Since the inorganic filler has viscoelasticity, the volume change during charge and discharge of the all-solid-state battery (10) can be easily accommodated, and the shape can be continuously deformed without defects. The creep rate is the change rate over time of the inorganic filler under stress at a constant temperature, i.e., the strain rate. The creep rate can be measured using, for example, a universal testing machine.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] The content of the inorganic filler in the positive electrode active material layer (120) may be smaller than the content of the solid electrolyte (SEP). The weight ratio of the solid electrolyte (SEP) and the inorganic filler in the positive electrode 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. Since the solid electrolyte (SEP) and the inorganic filler have a weight ratio in this range, the volume change during charge and discharge of the positive electrode 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.

[0133] 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 polymers, and combinations thereof.

[0134] (Challenge)

[0135] The positive electrode 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. 12, the conductive material (CMA) within the positive electrode active material layer (120) may form a positive electrode active material (CAC) together with a composite material (CAM).

[0136] The conductive material content in the positive electrode 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 electrode active material layer (120).

[0137] The metal-based material may be, but is not limited to, metal powder, metal fiber, or a combination thereof, and any metal-based material used as a conductive material in the relevant technical field may be used.

[0138] 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. Therefore, the cycle characteristics of the all-solid-state battery (10) including the carbon-based material can be further improved. The specific description of the carbon-based material may be the same as or similar to that described above regarding the conductive agent (CMA).

[0139] (bookbinder)

[0140] The positive electrode 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 thereto, and any binder used in the relevant technical field may be used. The content of the binder (BID) in the positive electrode 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 electrode active material layer (120). The binder (BID) may be omitted.

[0141] The positive electrode active material layer (120) may further include additives such as a coating agent, a dispersant, an ion-conducting aid, etc., in addition to the above-described positive electrode active material (e.g., CAM), solid electrolyte (SEP), binder (BID), conductive agent (CMA), and filler (FIL). The coating agent, dispersant, ion-conducting aid, etc. that may be included in the positive electrode active material layer (120) may be a known material generally used in the electrode of an all-solid-state battery.

[0142] (coating layer)

[0143] Although not shown, 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 directly disposed on, for example, one side or both sides of the positive electrode current collector (110). The coating layer (CTL) may be coated on one side or both sides of the positive electrode current collector (110). No other layer may be disposed between the positive electrode current collector (110) and the coating layer (CTL).

[0144] By directly disposing the coating layer (CTL) on one or both sides of the positive electrode current collector (110), the bonding force between the positive electrode current collector (110) and the positive electrode active material layer (120) can be further improved. By disposing the coating layer (CTL) between the positive electrode current collector (110) and the positive electrode active material layer (120), side reactions between the filler (FIL), the solid electrolyte (SEP), or the positive electrode active material (CAC) and the positive electrode current collector (110) can be more effectively suppressed. For example, the coating layer (CTL) can prevent corrosion of the sulfide-based positive electrode active material (e.g., Li2S) by the positive electrode current collector (110). As a result, the coating layer (CTL) can suppress deterioration of the all-solid-state battery (10) during the charge / discharge process and improve the cycle characteristics of the all-solid-state battery (10).

[0145] 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 electrode current collector (110). The thickness of the coating layer (CTL) may be, for example, 10 nm to 5 ㎛, 50 nm to 5 ㎛, 200 nm to 4 ㎛, 500 nm to 3 ㎛, 500 nm to 2 ㎛, 500 nm to 1.5 ㎛, or 700 nm to 1.3 ㎛. When the coating layer (CTL) has a thickness in this range, the bonding force between the positive electrode current collector (110) and the positive electrode active material layer (120) is further improved, and an 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).

[0146] 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 electrode 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 electrode active material layer (120). Since the coating layer (CTL) includes a carbon-based conductive material, the coating layer (CTL) may be, for example, a conductive layer.

[0147] The coating layer (CTL) may additionally include, for example, a binder. By the coating layer (CTL) additionally including a binder, the bonding strength between the positive electrode current collector (110) and the positive electrode active material layer (120) may be further improved. The binder included in the coating layer (CTL) may be, for example, a conductive binder or a non-conductive binder. The conductive binder may be, for example, an ion-conductive binder and / or an electron-conductive binder. A binder having both ion-conductivity and electron-conductivity may belong to both an ion-conductive binder and an electron-conductive binder.

[0148] The binder included in the coating layer (CTL) may be selected from among the binders used in the positive electrode active material layer (120). The coating layer (CTL) may include the same binder as the binder used in the positive electrode active material layer (120). The binder included in the coating layer (CTL) is, for example, a fluorinated binder. The fluorinated 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 including a binder. The coating layer (CTL) may be, for example, a conductive layer including a binder and a carbon-based conductive material.

[0149] The coating layer (CTL) can be disposed on the positive electrode current collector (110) in a dry or wet manner, for example. The coating layer (CTL) can be disposed on the positive electrode current collector (110) in a dry manner, for example, by deposition such as CVD or PVD. The coating layer (CTL) can be disposed on the positive electrode current collector (110) in a wet manner, for example, by spin coating, dip coating, or the like. The coating layer (CTL) can be disposed on the positive electrode current collector (110) in a dry manner, for example, by deposition of a carbon-based conductive material on a substrate by deposition. A dry-coated coating layer (CTL) is made of a carbon-based conductive material and may not include a binder. The coating layer (CTL) can be disposed on the positive electrode current collector (110) in a dry manner, for example, by coating a composition including a carbon-based conductive material, a binder, and a solvent on the surface of the electrode current collector and drying it. The coating layer (CTL) can have a single-layer structure or a multi-layer structure including a plurality of layers. Multi-layer structures can be two-layer, three-layer, four-layer, etc.

[0150] Cathode (200)

[0151] 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 disposed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound 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.

[0152] (negative current collector)

[0153] The negative electrode current collector (210) may be composed of one of the above-described metals, or may include an alloy or coating material of two or more metals. The negative electrode current collector (210) may have, for example, a plate shape or a foil shape. Meanwhile, in one embodiment, the negative electrode current collector (210) may be omitted.

[0154] Although not shown, an anode 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. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The anode 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. Since the negative electrode current collector (210) has this structure, the weight of the negative electrode layer (200) can be reduced, and as a result, the energy density of the all-solid-state battery (10) can be improved.

[0155] (Cathode coating layer)

[0156] The negative electrode coating layer (220) can be configured to allow lithium metal to grow between it and the negative electrode current collector (210) when the all-solid-state battery (10) is charged. 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.

[0157] The cathode coating layer (220) may include a 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).

[0158] The cathode coating layer (220) may further include additives other than metal and carbon. The cathode coating layer (220) may further include, for example, at least one additive selected from the group consisting of a binder, a filler, a coating agent, a dispersant, and an ion conductive additive.

[0159] The negative electrode coating layer (220) may have a smaller thickness than 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 um to 20 um, 2 um to 10 um, or 3 um to 7 um. If the thickness of the negative electrode coating layer (220) is too 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 deteriorating the cycle characteristics of the all-solid-state battery (10). If the thickness of the cathode coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) may decrease and the internal resistance of the all-solid-state battery (10) due to the cathode coating layer (220) may increase, thereby deteriorating the cycle characteristics of the cell.

[0160] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte layer (300).

[0161] (lithium metal layer)

[0162] Although not shown, in one embodiment, the all-solid-state battery (10) in a charged state may further include a lithium metal layer provided between the negative electrode current collector (210) and the negative electrode coating layer (220). The negative electrode layer (200) according to the present embodiment may include the negative electrode current collector (210), the negative electrode coating layer (220), and the lithium metal layer therebetween.

[0163] The lithium metal layer may include lithium or a lithium alloy. Since the lithium metal layer is a metal layer containing lithium, it can act as a lithium reservoir, for example. The lithium alloy includes, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., and any lithium alloy used in the art may be used. The lithium metal layer may be formed of one of these alloys or lithium, or may be formed of several types of alloys. The lithium metal layer may be, for example, a plated layer. The lithium metal layer may be deposited between the negative electrode coating layer (220) and the negative electrode current collector (210), for example, during the charging process of the all-solid-state battery (10).

[0164] The lithium metal layer 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 is too thin, it may be difficult for the lithium metal layer to perform the role of a lithium reservoir. If the third thickness (TK3) of the lithium metal layer is too thick, the mass and volume of the all-solid-state battery (10) may increase, and the cycle characteristics of the all-solid-state battery (10) may rather deteriorate.

[0165] In another embodiment of the present invention, the lithium metal layer in the negative electrode layer (200) may be provided between the negative electrode current collector (210) and the negative electrode coating layer (220), for example, before assembling the all-solid-state battery (10). When the lithium metal layer is disposed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembling the all-solid-state battery (10), the lithium metal layer acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be disposed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembling the all-solid-state battery (10).

[0166] When a lithium metal layer is precipitated by charging after assembling the all-solid-state battery (10), the energy density of the all-solid-state battery (10) can increase because the lithium metal layer is not included when assembling the all-solid-state battery (10). When charging the all-solid-state battery (10), the charging can exceed the charging capacity of the negative electrode coating layer (220). That is, the negative electrode coating layer (220) is overcharged. At the initial stage of charging, lithium can be absorbed into the negative electrode coating layer (220). When charging exceeds the capacity of the negative electrode coating layer (220), lithium can be precipitated, for example, between the negative electrode coating layer (220) and the negative electrode current collector (210). A lithium metal layer can be formed by the precipitated lithium.

[0167] The lithium metal layer may be mainly composed of lithium (i.e., metallic lithium). During discharge, lithium in the lithium metal layer may be ionized and move to the positive electrode layer (100). In other words, lithium may be used as an anode active material in the all-solid-state battery (10). In addition, since the anode coating layer (220) covers the lithium metal layer, the anode coating layer (220) may protect the lithium metal layer and simultaneously suppress the precipitation and growth of lithium dendrites. Therefore, the anode coating layer (220) may suppress short-circuiting and capacity degradation of the all-solid-state battery (10) and improve the cycle characteristics of the all-solid-state battery (10).

[0168] When a lithium metal layer is formed by charging after assembling the all-solid-state battery (10), the negative electrode layer (200), i.e., 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 of the all-solid-state battery (10) or in the state after complete discharge.

[0169] Referring to FIG. 2, the positive electrode active material layer (120) of the all-solid-state battery (10) may have a positive electrode thickness (CTK). The positive electrode thickness (ctk) of the positive electrode active material layer (120) may vary depending on the charge and discharge process. The positive electrode active material layer (120) into which lithium ions are inserted by discharging the all-solid-state battery (10) may have a first thickness (TK1). The positive electrode active material layer (120) into 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 electrode active material layer (120) may be smaller than the first thickness (TK1) which is the thickness of the positive electrode active material layer (120) before lithium ions are released.

[0170] In one embodiment of the present invention, the difference between the first thickness (TK1) and the second thickness (TK2) may be substantially the same as or similar to the third thickness (TK3) of the lithium metal layer. 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 electrode active material layer (120) may be correspondingly reduced by the thickness of the lithium metal layer formed by charging the all-solid-state battery (10).

[0171] Although not shown, the all-solid-state battery (10) can operate (i.e., charge and / or discharge) while pressurized by a pressurizing jig. In one embodiment, the all-solid-state battery (10) can be pressurized to 0.8 MPa to 2 MPa. For example, the all-solid-state battery (10) can have an internal pressure of about 1 MPa when discharging, and the all-solid-state battery (10) can have an internal pressure of about 1.5 MPa when charging. The ratio of the internal pressure of the all-solid-state battery (10) in a charged state to the internal pressure of the all-solid-state battery (10) in a discharged state can be 1.0 to 2.0, or 1.2 to 1.8.

[0172] The all-solid-state battery (10) may have a height (he) in the third direction (d3). The height (he) of the all-solid-state battery may be the sum of the thickness of the positive electrode composite layer (csh) and the thickness of the negative electrode composite layer (ash).

[0173] The all-solid-state battery (10) can change its height (or thickness or volume) according to charging and discharging in the pressurized state described above. In the all-solid-state battery (10) according to the present embodiment, the thickness of the positive electrode active material layer (120) can decrease corresponding to the lithium metal layer formed by charging. Therefore, the height (HE) of the all-solid-state battery shown in FIG. 2 can change according to the charging and discharging process. The height of the all-solid-state battery in a discharged state can be referred to as a first height (he1), and the height of the all-solid-state battery in a charged state can be referred to as a second height (he2). The second height (HE2) of the charged all-solid-state battery (10) can be similar to the first height (HE1) of the discharged all-solid-state battery (10). For example, the second height (HE2) can be 1 to 1.5 times, or 1 to 1.2 times, the first height (HE1).

[0174] (pellicle)

[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) is provided on one surface of the negative electrode current collector (210) and may 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, but are not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium within the scope of the art may be used. The thin film (TFL) may be composed of one of these metals, or may be composed of an alloy of multiple metals.

[0177] By placing the thin film (TFL) on one surface of the negative electrode current collector (210), for example, the deposition shape of the lithium metal layer deposited between the thin film (TFL) and the negative electrode coating layer (220) becomes flatter, 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 for the thin film (TFL) to exhibit its function. If the thickness of the thin film (TFL) is excessively thick, the thin film (TFL) itself may absorb lithium, which may reduce the amount of lithium precipitation in the negative electrode layer (200), thereby lowering the energy density of the all-solid-state battery (10) and deteriorating the cycle characteristics of the all-solid-state battery (10). The thin film (TFL) may be formed on the negative electrode current collector (21) by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to these methods, and any method capable of forming a thin film in the relevant technical field may be used.

[0179] Solid electrolyte layer (300)

[0180] 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 having 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. 12) in the positive electrode active material layer (120) described above.

[0181] 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 positive electrode layer (100), and the second solid electrolyte layer (320) may be adjacent to the negative electrode layer (200).

[0182] 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. In addition, the solid electrolyte may include, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material including Li2S-P2S5. When using a sulfide-based solid electrolyte material including Li2S-P2S5 to form the solid electrolyte, the mixing molar ratio of Li2S and P2S5 may be, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0183] In one embodiment, the first solid electrolyte is 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 The first solid electrolyte may include an argyrodite-type compound including at least one selected from (0≤x≤2). The first solid electrolyte may include an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0184] In another embodiment, the first solid electrolyte is Li 7-a M a PS 6-c X cArgyrodite-type compounds may include, wherein 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. Each of a and c may be a real number between 0 and 2.

[0185] The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. When the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state battery is reduced, and the defect of the solid electrolyte membrane being penetrated and short-circuited due to the formation of lithium dendrites can be prevented. The elastic modulus of the first solid electrolyte is, for example, 15 GPa to 35 GPa.

[0186] 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 as or similar to 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 similar composition as the first solid electrolyte.

[0187] The second solid electrolyte can be in direct contact with the negative electrode coating layer (220). As a result, 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 electrode side reactions. As a result, the cell performance of the all-solid-state battery (10) according to the present invention can be improved.

[0188] Each of the first and second solid electrolyte layers (310, 320) may further include a binder. The binder in the solid electrolyte layer (300) may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or the like, but is not limited thereto. The binder in the solid electrolyte layer (300) may be the same as or different from the binder in the positive electrode active material layer (120) or the binder in the negative electrode coating layer (220).

[0189] 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).

[0190] 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).

[0191] Referring back to FIGS. 1 and 2, the positive electrode layer (100) and the first solid electrolyte layer (310) may form a positive electrode composite layer (CSH). The negative electrode layer (200) and the second solid electrolyte layer (320) may form a negative electrode composite layer (ASH). The positive electrode composite layer (CSH) may be laminated on the negative electrode composite layer (ASH).

[0192] The area of ​​the cathode composite layer (ASH) and the area of ​​the cathode composite layer (CSH) may be different. Specifically, the area of ​​the cathode composite layer (ASH) may be larger than that of the cathode composite layer (CSH). The cathode composite layer (CSH) may be completely overlapped within the cathode composite layer (ASH).

[0193] In one embodiment, the second solid electrolyte layer (320) may have substantially the same area as the cathode layer (200). The first solid electrolyte layer (310) may have substantially the same area as the anode layer (100).

[0194] In one embodiment, the area of ​​the positive electrode active material layer (120) may be smaller than the area of ​​the solid electrolyte layer (300). In one embodiment, the area of ​​the positive electrode active material layer (120) may be smaller than the area of ​​the first solid electrolyte layer (310).

[0195] The width of the positive electrode active material layer (120) in the first direction (d1) may be referred to as the first width (WI1). The width of the solid electrolyte layer (300) in the first direction (d1) may be referred to as the second width (wi2). In one embodiment, when the solid electrolyte layer (300) has a double-layer structure including a first solid electrolyte layer (310) and a second solid electrolyte layer (320), the second width (wi2) may refer to the width of the first solid electrolyte layer (310) in the first direction (d1).

[0196] The length of the positive electrode active material layer (120) in the second direction (d2) may be referred to as the first length (LN1). The length of the solid electrolyte layer (300) in the second direction (d2) may be referred to as the second length (LN2). In one embodiment, when the solid electrolyte layer (300) has a double-layer structure including a first solid electrolyte layer (310) and a second solid electrolyte layer (320), the second length (LN2) may refer to the length of the first solid electrolyte layer in the second direction (d2).

[0197] 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, 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).

[0198]

[0199] Hereinafter, descriptions of technical features overlapping with those described above will be omitted, and embodiments of the present invention will be described in detail.

[0200] All-solid-state battery cell structure

[0201] In this specification, the third direction (d3) refers to the direction in which the all-solid-state battery stacks are stacked. That is, it refers to the normal direction of each stack plane that constitutes the battery.

[0202] The first direction (d1) and the second direction (d2) are each perpendicular to the third direction (d3), and also have a perpendicular relationship with each other. For example, Fig. 2 is a cross-sectional view taken along the line A-A' of Fig. 1, and the first direction (d1) can be said to be the direction of the line A-A' in Fig. 1. The second direction (d2) can be said to be a direction perpendicular to both the first direction (d1) and the third direction (d3).

[0203] In this specification, the measure for measuring the dimension in the first direction (d1) may be referred to as width. The measure for measuring the dimension in the second direction (d2) may be referred to as length. The measure for measuring the dimension in the third direction (d3) may be referred to as thickness.

[0204] Figures 1 to 4 illustrate an all-solid-state battery according to one embodiment of the present invention. Figure 11 is an enlarged view of area M of Figure 4. Referring to Figure 11, the positive electrode active material layer (120) may include a body portion (MBD) and an outer portion (OTR) protruding outward from the body portion.

[0205] Referring to FIGS. 2, 4, and 11, the body portion (MBD) may refer to a flat portion of the positive electrode active material layer (120) in a unit cell formed by pressurizing the all-solid-state battery (10). The surface where the positive electrode active material layer (120) contacts the positive electrode current collector (110) in the third direction (D3) may be referred to as the upper surface of the positive electrode active material layer, and the surface where the positive electrode active material layer (120) contacts the solid electrolyte layer (300) may be referred to as the lower surface of the positive electrode active material layer. The body portion (MBD) may include an upper surface contacting the positive electrode current collector (110) and a lower surface contacting the solid electrolyte layer (300). The body portion may have a constant thickness. Referring to the above description, the thickness of the body portion (MBD) may be equal to the positive electrode thickness (CTK).

[0206] Although not specifically illustrated, referring to FIG. 1, in the plan view of the all-solid-state battery, the body portion (MBD) may be expressed as a portion having a constant area in the shape of a rectangle within the entire area of ​​the positive electrode active material layer (120). More specifically, in the three-dimensional structure, the body portion (MBD) may be expressed as a portion having a constant volume in the shape of a rectangular parallelepiped within the positive electrode active material layer (120). The outer portion (OTR) may refer to an area within the positive electrode active material layer (120) excluding the body portion (MBD).

[0207] The positive electrode active material layer (120) may further include an outer portion (OTR) protruding outward from the body portion (MBD). The outer portion (OTR) of the positive electrode active material layer (120) may have a constant curvature (CV) with respect to the first direction (D1) and / or the second direction (D2). The outer portion (OTR) may have a convex side wall (CVX). The convex side wall (CVX) may have a constant range of curvature (CV). The curvature (CV) of the convex side wall (CVX) may be used in the same sense as the curvature (CV) of the outer portion (OTR).

[0208] The outer portion (otr) may be formed in the first direction (D1) and / or the second direction (D2). The distance by which the outer portion (otr) protrudes in the first direction (D1) or the distance by which the outer portion (otr) protrudes in the second direction (D2) may be defined as the protrusion distance (r). The protrusion distance (r) may be the distance from the reference plane where the body portion (mbd) and the outer portion (otr) are distinguished to the outermost edge of the positive electrode active material layer.

[0209] The convex side wall of the outer portion can have a curvature (CV) within a certain range. The curvature (CV) of the convex side wall (cvx) can be defined by the following mathematical expression 1.

[0210] [Mathematical Formula 1]

[0211] CV = R / CTK

[0212] Since the outer portion (otr) of the positive electrode active material layer (120) has a curvature, the outer portion may not come into contact with the positive electrode current collector (110) or the solid electrolyte layer (300). In one embodiment, the curvature (cv) of the outer portion may be 0.5 to 1.5, 0.5 to 1.0, 1.0 to 1.5, or 0.5 to 2.0. Since the outer portion (OTR) has the above-described curvature (CV), stability problems due to short circuits or excessive size of the positive electrode layer in a unit cell can be solved.

[0213] Referring to FIGS. 1 to 4, the first width (wi1) of the positive electrode active material layer (120) may be smaller than the second width (WI2) of the solid electrolyte layer (300). The first width (WI1) of the positive electrode active material layer (120) in the first direction (D1) may be equal to the distance between the two ends of the outer portion in the first direction (D1).

[0214] In one embodiment, when the solid electrolyte layer (300) is a single layer, the first width (WI1) of the positive electrode active material layer (120) may be smaller than the second width (WI1) of the solid electrolyte layer (300). In one embodiment, when the solid electrolyte layer (300) is a double layer, the first width (WI1) of the positive electrode active material layer (120) may be smaller than the second width (WI1) of the first solid electrolyte layer (310). That is, the first width (WI1) of the positive electrode active material layer (120) may be smaller than the width of the closest solid electrolyte layer in the first direction (D1).

[0215] In one embodiment, the first width (WI1) of the positive electrode active material layer (120) may be larger than the second width (WI2) of the solid electrolyte layer (300), but the width of the body portion (MBD) may be smaller than the second width (WI2).

[0216] In one embodiment, the width of the body portion (MBD) may be in a range of 70% to 90%, 60% to 80%, or 70% to 80% of the first width (WI1) of the positive electrode active material layer (120). That is, the ratio of the width of the body portion (MBD) to the first width (WI1) may be 0.70 to 0.90, 0.60 to 0.80, or 0.70 to 0.80.

[0217] In one embodiment, the width of the body portion (MBD) may be 60% to 80%, 70% to 90%, 65% to 85%, or 70% to 80% of the second width (WI2) of the solid electrolyte layer (300). That is, the ratio of the width of the body portion (MBD) to the second width (WI2) may be 0.60 to 0.80, 0.70 to 0.90, 0.65 to 0.85, or 0.70 to 0.80.

[0218] The same is true from the perspective of the second direction (d2). For example, the first length (LN1) of the positive electrode active material layer (120) may be smaller than the second length (LN2) of the solid electrolyte layer (300). For example, the first length (LN1) of the positive electrode active material layer (120) may be smaller than the second length (LN2) of the first solid electrolyte layer (310).

[0219] The structural stability of an all-solid-state battery can be improved by ensuring that the outer portion of the positive electrode active material layer satisfies the above-described curvature range and / or dimensional range. More specifically, even after pressurization, excessive formation of the positive electrode active material layer due to the ductility of the positive electrode active material layer can be restricted. Furthermore, even if the positive electrode active material layer is excessively formed due to the ductility of the positive electrode active material layer, the stability of the laminated structure and short-circuiting can be prevented by ensuring that the outer portion satisfies a certain range of curvature. The structural stability of a lithium-sulfur all-solid-state battery including a relatively ductile sulfide-based positive electrode active material layer can be improved.

[0220] Consequently, the structural stability of the all-solid-state battery is enhanced after pressurization, thereby improving mass production. The all-solid-state battery according to the present invention can be manufactured by pressing using a plate press or roll press method. This provides an all-solid-state battery with improved mass production compared to the hydrostatic press (WIP) method.

[0221] Referring to FIGS. 5 to 10, the all-solid-state battery (10) according to the present embodiment may further include an inert member (GSK). The inert member (GSK) may prevent cracking of the solid electrolyte layer (300) during the manufacturing of the all-solid-state battery (10) and / or during charging and discharging. As a result, the cycle characteristics of the all-solid-state battery (10) may be improved. By including the inert member (GSK), a uniform pressure may be applied to the interface between the positive electrode active material layer (120) and the solid electrolyte layer (300). As a result, the interfacial resistance between the positive electrode active material layer (120) and the solid electrolyte layer (300) may be reduced. In addition, as the solid electrolyte layer (300) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state battery (10), the internal resistance of the solid electrolyte layer (300) may be reduced and ionic conductivity may be improved.

[0222] The inert member (GSK) may have, for example, a single-layer structure. Alternatively, although not shown, it may have a multi-layer structure. In the inert member (GSK) having a multi-layer structure, each layer may have a different composition. The inert member (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. The inert member (GSK) having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers.

[0223] The inert member (GSK) may include, for example, a flame-retardant inert member. The flame-retardant inert member can prevent thermal runaway and ignition of the all-solid-state battery (10) by providing flame retardancy. Consequently, the inert member (GSK) can further improve the stability of the all-solid-state battery (10). The flame-retardant inert member can prevent deterioration of the all-solid-state battery (10) by absorbing residual moisture within the all-solid-state battery (10), thereby improving the lifespan characteristics of the all-solid-state battery (10).

[0224] The inert member (gsk) may be a lithium ion insulator or an electronic insulator. That is, the inert member (gsk) may not be an electronic conductor. The inert member (gsk) may be an ionic insulator. The inert member (gsk) may include, for example, an organic material, an inorganic material, or an organic-inorganic composite material. The organic material may be, for example, a polymer. The inorganic material may be, for example, a metal oxide and a ceramic. The organic-inorganic composite material may be a composite of a polymer and a metal oxide. The adhesive layer may include, for example, an organic material, and the support layer may include, for example, one or more selected from an organic material and an inorganic material. The adhesive layer may include, for example, a curable polymer. The support layer may include, for example, one or more selected from paper, an insulating polymer, an ion-conducting polymer, an insulating inorganic material, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE). Additionally, the inert (gsk) member may be made of a material used in the art.

[0225] FIGS. 5 to 7 are for explaining an all-solid-state battery according to another embodiment of the present invention. FIG. 5 is a plan view of the all-solid-state battery, and FIGS. 6 and 7 are cross-sectional views taken along line A-A' of FIG. 5.

[0226] Referring to FIG. 6, the inert member (GSK) may be arranged on the upper surface of the solid electrolyte layer (300). Referring to FIG. 5, on the upper surface of the solid electrolyte layer, a region having a certain range of the edge portion may be defined as a perimeter, and the other region may be defined as a central region. For example, the perimeter may be a region having a range of 0.01 to 0.40 with respect to the second width (wi2) of the solid electrolyte layer (300) based on the first direction (d1). For example, the perimeter may be a region having a range of 0.01 to 0.40 with respect to the second length (LN2) of the solid electrolyte layer (300) based on the second direction (d2). The perimeter may have substantially the same meaning as a portion where the upper surface of the solid electrolyte layer (300) and the inert member (gsk) come into contact.

[0227] An inert member (GSK) may be positioned on a portion of the upper surface of the solid electrolyte layer (300). In one embodiment, the inert member (GSK) may be in the form of a gasket that is positioned on the periphery of the solid electrolyte layer (300) and has a constant thickness in the third direction (D3). The thickness of the inert member may be smaller than the anode thickness (CTK). For example, the thickness of the inert member may be 10% to 30%, 20% to 50%, 30% to 100%, or 50% to 90% of the anode thickness (CTK).

[0228] In one embodiment, referring to FIG. 5, the inert member (GSK) may be in contact with the periphery of the solid electrolyte layer (300) and may have a frame-shaped structure. In one embodiment, when the solid electrolyte layer is a double layer as in FIG. 7, the inert member (GSK) may be in contact with the upper surface of the first solid electrolyte layer (310) that is closest to the positive electrode active material layer (120).

[0229] Referring to FIGS. 5 and 6, the inert member (GSK) may include a region in contact with the periphery of the solid electrolyte layer (300) and a region that extends in the first direction (D1) and / or the second direction (D2) and does not contact the solid electrolyte layer (300). Referring to FIGS. 6 and 7, with respect to the width of the solid electrolyte layer (300) in the first direction (D1), the width of the solid electrolyte layer (300) in the first direction (D1) including the inert member (GSK) extended in the first direction (D1) may be referred to as a third width (WI3). That is, the third width (WI3) may be referred to as the width of the solid electrolyte layer (300) including the inert member (GSK) on the periphery of the upper surface in the first direction (D1). Alternatively, the third width (WI3) may be referred to as the width in the first direction (D1) of the first solid electrolyte layer (310) including the inert member (GSK) on the periphery of the upper surface. In one embodiment, the first width (WI1) may be smaller than the third width (WI3).

[0230] By providing an inert member, the structural stability of an all-solid-state battery can be improved. Even after pressurizing the all-solid-state battery, excessive formation of a positive electrode active material layer due to the ductility of the positive electrode active material layer can be restricted. Referring to FIGS. 6 and 7, the inert member can be configured to separate the periphery of the upper surface of the solid electrolyte layer from the positive electrode active material layer. Consequently, excessive formation of the positive electrode active material layer after pressurization and a decrease in battery performance can be prevented. In addition, contact between adjacent layers of the battery stack can be prevented, thereby preventing a short circuit inside the battery. In a lithium-sulfur all-solid-state battery including a relatively ductile sulfide-based positive electrode active material layer, the structural stability of the battery can be improved.

[0231] FIGS. 8 to 10 are for explaining an all-solid-state battery according to another embodiment of the present invention. FIG. 8 is a plan view of the all-solid-state battery, and FIGS. 9 and 10 are cross-sectional views taken along line A-A' of FIG. 8.

[0232] Referring to FIG. 9, the inert member (gsk) may be arranged on the upper surface of the solid electrolyte layer (300). Referring to FIG. 8, on the upper surface of the solid electrolyte layer (300), a region having a certain range of the edge portion may be defined as a perimeter, and the other region may be defined as a central region. For example, the perimeter may be a region having a range of 0.01 to 0.40 with respect to the second width (wi2) of the solid electrolyte layer (300) in the first direction (d1). For example, the perimeter may be a region having a range of 0.01 to 0.40 with respect to the second length (LN2) of the solid electrolyte layer (300) in the second direction (d2). The perimeter may have substantially the same meaning as a portion where the upper surface of the solid electrolyte layer (300) and the inert member (gsk) come into contact.

[0233] In one embodiment, the inert member on the periphery of the solid electrolyte layer may be in a form that contacts the positive electrode current collector. In one embodiment, referring to FIG. 9, the inert member may be in a form that surrounds the side of the positive electrode active material layer and contacts the solid electrolyte layer. The side of the positive electrode active material layer may have the same meaning as the first direction and / or the second direction. That is, the inert member may be in the form of a frame that is located on the upper surface of the solid electrolyte layer and surrounds the side of the positive electrode active material layer.

[0234] Referring to FIGS. 8 to 10, the width of the inert member (gsk) in contact with the periphery of the solid electrolyte layer (300) in the first direction may be referred to as a fourth width (wi4). The width of the solid electrolyte layer (300) in the first direction may be referred to as a second width (wi2). The ratio of the fourth width (WI4) to the second width (WI2) may be 0.10 to 0.15, 0.10 to 0.20, 0.05 to 0.10, 0.10 to 0.15, or 0.05 to 0.20. In the first direction, the sum of the widths of the positive electrode active material layer (120) and the inert member (gsk) may be substantially equal to or smaller than the width of the solid electrolyte layer (300) in the first direction. For example, in FIGS. 9 and 10, {(WI4 + WI1 + WI4) ≤ WI2} can be satisfied.

[0235] By providing an inert member, the structural stability of an all-solid-state battery can be improved. Even after pressurizing the all-solid-state battery, excessive formation of the positive electrode active material layer due to the ductility of the positive electrode active material layer can be restricted. Referring to FIGS. 9 and 10, the positive electrode active material layer is separated from the negative electrode layer through a structure in which the inert member surrounds the side surface of the positive electrode active material layer. Therefore, the possibility of a short circuit occurring due to physical contact or overcharging, etc. is suppressed. In addition, in a lithium-sulfur all-solid-state battery including a relatively ductile sulfide-based positive electrode active material layer, the structural stability of the battery can be further improved.

[0236] When the all-solid-state battery (10) is plate pressed, a uniaxial pressing process can be performed on the all-solid-state battery (10) in a third direction (D3). By plate pressing, the outer portion (OTR) of the positive electrode active material layer (120) can be formed in the first direction (D1) and / or the second direction (D2). Each of the first direction (D1) and the second direction (D2) can be a horizontal direction perpendicular to the third direction (D3).

[0237] When the all-solid-state battery (10) is roll pressed, a pressing process can be performed on the all-solid-state battery (10) on which electrodes are laminated in a third direction (D3). As the roll pressing process progresses, the direction in which the all-solid-state battery (10) moves through the pressing roll can be referred to as the second direction (D2). In the case of roll pressing, the outer portion (OTR) of the positive electrode active material layer can be formed in the first direction (D1).

[0238] All-solid-state batteries according to embodiments of the present invention can improve mass production by enhancing the stability of the battery stack structure. They can effectively address issues such as cracks and short circuits that occur when manufactured using flat-plate pressing or roll pressing methods.

[0239] The all-solid-state battery according to embodiments of the present invention can maintain the structure of the positive electrode active material layer even after pressurization despite the high ductility of the sulfide-based positive electrode active material layer, thereby suppressing electrical short-circuiting and improving rate characteristics through enhanced interfacial bonding.

[0240]

[0241] Manufacturing method of all-solid-state secondary battery

[0242] The method comprises the steps of providing Li2S or a complex thereof; providing a sulfide-based solid electrolyte; preparing a mixture by mixing the Li2S complex, the gamma sulfur-carbon nanofiber composite, and the sulfide-based solid electrolyte; and preparing a positive electrode by coating and drying the mixture on a positive electrode current collector.

[0243] The Li2S complex provides a complex of Li2S and a lithium salt or a complex of Li2S, a lithium salt, and a carbon-based material. The complex of Li2S and a lithium salt can be prepared, for example, by mechanically milling Li2S and a lithium salt. The milling conditions are not particularly limited, and any conditions that can form a complex of Li2S and a lithium salt can be used. The complex of Li2S and a lithium salt can be prepared by placing Li2S particles and a lithium salt in a ball mill and stirring at a speed of 100 to 1000 rpm for 1 to 20 hours. The stirring can be performed more than once.

[0244] As lithium salts, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or combinations thereof can be used.

[0245] A composite of Li2S, a lithium salt, and a carbon-based material can be manufactured, for example, through a step of mechanically milling Li2S and a lithium salt; a step of adding a carbon-based material to the milled product, and milling the same.

[0246] A sulfide-based solid electrolyte is provided. A mixture is prepared by mixing a Li2S-lithium salt complex and the sulfide-based solid electrolyte.

[0247] The mixing ratio of the Li2S complex and the sulfide-based solid electrolyte may be, for example, a weight ratio of 50:50 to 95:5, 50:50 to 90:10, 50:50 to 80:20, or 50:50 to 70:30.

[0248] The mixture may additionally include a process solvent. By additionally including a process solvent, the mixture may take the form of a slurry. The solvent may be, for example, octyl acetate, but is not limited thereto, and any solvent used in the art may be used. Alternatively, the mixture may be prepared dry without including a process solvent.

[0249] Mechanical milling can be used in the above milling. A ball mill, etc. can be used in the mechanical milling.

[0250] After the step of placing a solid electrolyte layer between the positive and negative electrodes, a step of obtaining a battery assembly and pressurizing it may be performed.

[0251] Pressurization is not limited to a roll press, a flat press, etc., but any pressurization method used in the relevant technical field may be used. The pressurization step may be omitted.

[0252] Pressurization is performed at a temperature of, for example, room temperature (20°C to 25°C to 90°C). Alternatively, pressurization is performed at a high temperature of 100°C or higher. The time for which pressurization is applied is, for example, 30 minutes or less, 20 minutes or less, 15 minutes or less, or 10 minutes or less. The time for which pressurization is applied is 1 ms to 30 minutes, 1 ms to 20 minutes, 1 ms to 15 minutes, or 1 ms to 10 minutes. The pressurization method is, for example, isotactic press, roll press, flat press, etc., but is not necessarily limited to these methods and any pressurization used in the art is possible. The pressure applied during pressurization is, for example, 500 MPa or less, for example, 400 MPa or less, 300 MPa or less, 200 MPa or less, or 100 MPa or less. The pressure applied during pressurization is, for example, 50 MPa to 500 MPa, 50 MPa to 400 MPa, 50 MPa to 300 MPa, 50 MPa to 200 MPa, 50 MPa to or 100 MPa. By this pressurization, for example, the solid electrolyte powder is sintered to form a single solid electrolyte.

[0253] The pressurizing step is for example 40 to 100°C, for example 85 o A plate press treatment is performed at a pressure of 500 MPa for 30 min at C. This press treatment sinteres the solid electrolyte layer, thereby improving battery characteristics. According to another embodiment, the press treatment process described above may be omitted.

[0254] While exemplary implementation examples have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

Claims

1. A unit cell comprising a positive electrode layer including a positive electrode active material layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, The above positive electrode active material layer includes a sulfide-based positive electrode active material, The above positive electrode active material layer includes a body portion and an outer portion protruding outward from the body portion, The above outer portion has a convex side wall, The outer portion is spaced apart from the upper surface of the solid electrolyte layer, The first width of the positive electrode active material layer in the first direction is smaller than the second width of the solid electrolyte layer in the first direction. Lithium-sulfur solid-state battery.

2. In paragraph 1, The curvature of the convex side wall of the outer portion is 0.5 to 2.0, Lithium-sulfur solid-state battery.

3. In paragraph 1, The ratio of the width of the body portion to the first width of the positive electrode active material layer is 0.7 to 0.90, Lithium-sulfur solid-state battery.

4. In paragraph 1, The ratio of the width of the body to the second width of the solid electrolyte layer is 0.70 to 0.90, Lithium-sulfur solid-state battery.

5. In paragraph 1, The ratio of the internal pressure in the charged state to the internal pressure in the discharged state is 1.0 to 2.0, Lithium-sulfur solid-state battery.

6. In paragraph 1, The above sulfide-based positive electrode active material comprises a complex containing Li2S and LiX, The above LiX is one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI, Lithium-sulfur solid-state battery.

7. In paragraph 1, The above positive electrode active material layer 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 원소 주기율표 3족 내지 15족에서 선택되는 금속)으로 표시되는 리튬금속옥시할라이드(lithium metal oxyhalide)를 포함하는, Lithium-sulfur solid-state battery.

8. In paragraph 1, The elastic modulus of the positive electrode active material layer is smaller than the elastic modulus of the solid electrolyte layer. Lithium-sulfur solid-state battery.

9. A cathode active material layer including a sulfide-based cathode active material; cathode layer; and Including a solid electrolyte layer between the positive electrode active material layer and the negative electrode layer, The solid electrolyte layer includes an inert member on the upper surface periphery of the solid electrolyte layer, The above inert member is configured such that the positive electrode active material layer is spaced apart from the upper surface periphery of the solid electrolyte layer, The width of the positive electrode active material layer in the first direction is smaller than the width of the solid electrolyte layer including the inert member on the upper surface periphery in the first direction. Lithium-sulfur solid-state battery.

10. In paragraph 9, The above sulfide-based positive electrode active material comprises a complex containing Li2S and LiX, The above LiX is one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI, Lithium-sulfur solid-state battery.

11. In paragraph 9, The above positive electrode active material layer 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 원소 주기율표 3족 내지 15족에서 선택되는 금속)으로 표시되는 리튬금속옥시할라이드(lithium metal oxyhalide)를 포함하는, Lithium-sulfur solid-state battery.

12. In paragraph 9, The above inert member has a multilayer structure, Lithium-sulfur solid-state battery.

13. In paragraph 9, The elastic modulus of the above positive electrode active material layer is 10 GPa. In the range of 20 GPa, Lithium-sulfur solid-state battery.

14. In paragraph 9, The above solid electrolyte layer comprises at least one argyrodite-type sulfide-based solid electrolyte selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. Lithium-sulfur solid-state battery.

15. In paragraph 9, The ratio of the internal pressure in the charged state to the internal pressure in the discharged state is 1.0 to 2.0, Lithium-sulfur solid-state battery.

16. A unit cell comprising a positive electrode layer including a sulfide-based positive electrode active material layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, The above sulfide-based positive electrode active material layer comprises a complex of Li2S, lithium salt, and metal halide, wherein the metal halide contains a metal other than lithium, The above unit cell includes an inert member surrounding the side of the positive electrode layer and in contact with the solid electrolyte layer, With respect to the first direction, the positive electrode active material layer has a first width, the solid electrolyte layer has a second width, and the inert member has a fourth width. The ratio of the fourth width of the inert member to the second width of the solid electrolyte layer is 0.05 to 0.20, Lithium-sulfur solid-state battery.

17. In paragraph 16, The above inert member has a multilayer structure, Lithium-sulfur solid-state battery.

18. In paragraph 16, The ratio of the internal pressure in the charged state to the internal pressure in the discharged state is 1.0 to 2.0, Lithium-sulfur solid-state battery.

19. In paragraph 16, The above solid electrolyte layer comprises at least one argyrodite-type sulfide-based solid electrolyte selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. Lithium-sulfur solid-state battery.

20. In paragraph 16, The above positive electrode active material layer 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 원소 주기율표 3족 내지 15족에서 선택되는 금속)으로 표시되는 리튬금속옥시할라이드(lithium metal oxyhalide)를 포함하는, Lithium-sulfur solid-state battery.

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