Elastic layer for all-solid-state battery, and all-solid-state battery comprising same

Abstract

The present invention relates to an electrode assembly for an all-solid-state battery. More specifically, the electrode assembly comprises: a unit cell comprising a positive electrode comprising a sulfide-based positive electrode active material, a solid electrolyte layer comprising a sulfide-based solid electrolyte, and a negative electrode; and an elastic layer disposed on at least one side of the unit cell.

Description

Elastic layer for all-solid-state battery and all-solid-state battery including the same

[0001] The present invention relates to an elastic layer for an all-solid-state battery and an all-solid-state battery including the same.

[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] One embodiment provides an electrode assembly including an elastic layer for an all-solid-state battery that can apply uniform pressure to the electrode assembly while improving stability in the event of an internal short circuit.

[0006] One embodiment provides an electrode assembly including an elastic layer for an all-solid-state battery that reduces hydrogen sulfide generation in a sulfide-based solid electrolyte by adsorbing hydrogen sulfide.

[0007] According to the present invention, an electrode assembly may include a unit cell including a positive electrode including a sulfide-based positive electrode active material, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte; and an elastic layer disposed on at least one side of the unit cell. The elastic layer may include an elastic material and a functional additive. The thermal conductivity of the functional additive may be 50 W / mK to 1500 W / mK. The electrical resistance of the functional additive may be 10 6 Ωcm to 10 15 It can be Ωcm.

[0008] According to another concept of the present invention, an electrode assembly may include a unit cell including a positive electrode including a sulfide-based positive electrode active material, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte; and an elastic layer disposed on at least one side of the unit cell. The elastic layer may include an elastic material and a functional additive, and may be configured to adsorb hydrogen sulfide (H2S).

[0009] According to another concept of the present invention, an electrode assembly may include a plurality of stacked unit cells. Each of the plurality of unit cells may include a positive electrode including a sulfide-based positive electrode active material, a solid electrolyte layer including a sulfide-based solid electrolyte, and a negative electrode. The plurality of stacked unit cells may include an elastic layer between the plurality of unit cells.

[0010] The elastic layer may include an elastic material and a functional additive, and the porosity of the elastic layer may be 70% to 90%.

[0011] An electrode assembly according to one embodiment can distribute stress applied to a solid electrolyte when pressurizing an all-solid-state secondary battery including the same to ensure uniform pressurization, and can provide stability when subjected to external impact, thereby providing an all-solid-state battery exhibiting excellent charge / discharge characteristics and safety.

[0012] An electrode assembly according to one embodiment can effectively lower the temperature by releasing the generated heat to the outside when internal heat generation occurs in an all-solid-state secondary battery including the electrode assembly, and can solve the problem of exposure to the atmosphere by absorbing hydrogen sulfide.

[0013] Figure 1 is a plan view of a unit cell for explaining a unit cell of an all-solid-state battery.

[0014] Fig. 2 is a cross-sectional view taken along line AA` of Fig. 1.

[0015] FIG. 3 is a cross-sectional view illustrating a positive electrode active material layer according to embodiments of the present invention, which is an enlarged view of area M of FIG. 2.

[0016] Figures 4 to 6 are cross-sectional views taken along line AA` of Figure 1 to explain a unit cell of an all-solid-state battery.

[0017] FIG. 7 is a cross-sectional view schematically representing a unit cell including an elastic sheet according to one embodiment of the present invention.

[0018] Figure 8 is a cross-sectional view schematically representing a unit cell including an elastic sheet according to one embodiment of the present invention.

[0019] Figure 9 is a cross-sectional view of an electrode assembly according to one embodiment of the present invention.

[0020] Figure 10 is a cross-sectional view of an electrode assembly according to one embodiment of the present invention.

[0021] Figure 11 is an enlarged cross-sectional view of an electrode assembly according to one embodiment of the present invention.

[0022] FIG. 12 is a cross-sectional view of a pouch-type battery including an electrode assembly according to one embodiment of the present invention.

[0023] FIG. 13 is an enlarged cross-sectional view of a pouch-type battery including an electrode assembly according to one embodiment of the present invention.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In this specification, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic state.

[0030] As used herein, “alloy” means a mixture of two or more metals.

[0031] In this specification, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0032] In this specification, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0033] In this specification, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0034] In this specification, “lithiation” and “lithiate” mean a process of adding lithium to an electrode active material.

[0035] In this specification, “delithiation” and “delithiate” refer to a process of removing lithium from an electrode active material.

[0036] In this specification, “charging” and “charging” mean the process of providing electrochemical energy to a battery.

[0037] In this specification, “discharge” and “discharge” mean the process of removing electrochemical energy from a battery.

[0038] In this specification, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during the discharge process.

[0039] In this specification, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0040] Fig. 1 is a plan view of an all-solid-state battery according to embodiments of the present invention. Fig. 2 is a cross-sectional view taken along line A-A' of Fig. 1. Fig. 3 is an enlarged cross-sectional view of area M of Fig. 2, which is intended to explain a positive electrode active material layer according to one embodiment of the present invention.

[0041] 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).

[0042] 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.

[0043] 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 ㎛.

[0044] 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.

[0045] 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 blocking battery operation and suppressing a rapid increase in current.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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-b B' b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O4-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 Gd 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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. 3, 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.

[0062] 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).

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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).

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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. 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. 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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).

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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).

[0084] 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.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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 simultaneously have improved ionic conductivity and excellent ductility.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] Referring back to FIGS. 2 and 3, 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.

[0096] 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).

[0097] 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).

[0098] 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, 0*?*x*?*2 may be one or more selected from among. 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, a 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.

[0099] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

[0100] <Chemical Formula 1>

[0101] Li + 12-n-x A n+ X 2- 6-x Y - x

[0102] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1*?*n*?*5, 0*?*x*?*2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x, 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , 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.

[0103] 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.

[0104] 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.

[0105] 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).

[0106] 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.

[0107] 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).

[0108] 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).

[0109] 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).

[0110] 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 electrode active material (CAC) particles, between the solid electrolyte (SEP) particles, and / or between the positive electrode active material (CAC) and the solid electrolyte (SEP) within the positive electrode active material layer (120) (see FIG. 3).

[0111] 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 GP a 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).

[0112] 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).

[0113] An inorganic filler, i.e., a filler (FIL) can be uniformly provided within the positive electrode active material layer (120) (see FIG. 3). In the all-solid-state battery (10) of the present invention, since the inorganic filler has a lower elastic modulus than the solid electrolyte (SEP), the inorganic filler can easily fill the 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).

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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. 3, 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).

[0121] 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).

[0122] 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.

[0123] 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).

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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).

[0131] 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.

[0132] 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.

[0133] 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).

[0134] 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. 3) in the positive electrode active material layer (120) described above.

[0135] 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).

[0136] 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.

[0137] In one embodiment, the first solid electrolyte is Li 7-x PS6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x 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.

[0138] In another embodiment, the first solid electrolyte is Li 7-a M a PS 6-c X c Argyrodite-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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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).

[0143] 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).

[0144] 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).

[0145] 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).

[0146] 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).

[0147] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the positive electrode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the negative electrode layer (200).

[0148] Specifically, the positive electrode composite layer (CSH) may have a first width (WI1) in a first direction (D1). The negative electrode composite layer (ASH) may have a second width (WI2) in the first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The positive electrode composite layer (CSH) may have a third width (WI3) in the second direction (D2). The negative electrode composite layer (ASH) may have a fourth width (WI4) in the second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0149] 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).

[0150] In one embodiment, as shown in FIG. 2, the discharged positive electrode active material layer (120) may have a first thickness (TK1). The all-solid-state battery (10) may have a first height (HE1) in the third direction (D3). The first height (HE1) may be the sum of the thickness of the positive electrode composite layer (CSH) and the thickness of the negative electrode composite layer (ASH).

[0151]

[0152] In the embodiments described below, detailed descriptions of technical features that overlap with those described above with reference to FIGS. 1 to 3 will be omitted, and differences will be described in detail.

[0153] FIG. 4 is a cross-sectional view taken along line A-A' of FIG. 1 to explain an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 4, in one embodiment, the all-solid-state battery (10) in a charged state may further include a lithium metal layer (230) 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 (230) therebetween.

[0154] The lithium metal layer (230) may include lithium or a lithium alloy. Since the lithium metal layer (230) is a metal layer containing lithium, it may function as a lithium reservoir, for example. The lithium alloy may be, 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 (230) may be formed of one of these alloys or lithium, or may be formed of several types of alloys. The lithium metal layer (230) may be, for example, a plated layer. The lithium metal layer (230) may be deposited between the negative electrode coating layer (220) and the negative electrode current collector (210), for example, during the charging process of the all-solid-state battery (10).

[0155] The lithium metal layer (230) may have a third thickness (TK3). The third thickness (TK3) is not particularly limited, but may be, for example, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the third thickness (TK3) of the lithium metal layer (230) is too thin, it may be difficult for the lithium metal layer (230) to perform the role of a lithium reservoir. If the third thickness (TK3) of the lithium metal layer (230) is 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.

[0156] In another embodiment of the present invention, the lithium metal layer (230) 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 (230) 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 (230) 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).

[0157] When the lithium metal layer (230) 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 (230) 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). The precipitated lithium can form a lithium metal layer (230).

[0158] The lithium metal layer (230) may be mainly composed of lithium (i.e., metallic lithium). When discharging, lithium in the lithium metal layer (230) 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 (230), the anode coating layer (220) may protect the lithium metal layer (230) and simultaneously suppress the precipitation and growth of lithium dendrites. Therefore, the anode coating layer (220) may suppress short-circuiting and capacity reduction of the all-solid-state battery (10) and improve the cycle characteristics of the all-solid-state battery (10).

[0159] When a lithium metal layer (230) 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 therebetween 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.

[0160] The positive electrode active material layer (120) from which lithium ions are released by charging the all-solid-state battery (10) may have a second thickness (TK2). The second thickness (TK2) of the positive electrode active material layer (120) may be smaller than the first thickness (TK1) of FIG. 2.

[0161] 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 (230). For example, the third thickness (TK3) may be 1.0 to 1.5 times, or 1.0 to 1.2 times, the difference between the first thickness (TK1) and the second thickness (TK2). According to the present invention, the thickness of the positive electrode active material layer (120) may be correspondingly reduced by the thickness of the lithium metal layer (230) formed by charging the all-solid-state battery (10).

[0162] 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 of FIG. 4 to the internal pressure of the all-solid-state battery (10) in a discharged state of FIG. 3 can be 1.0 to 2.0, or 1.2 to 1.8.

[0163] The all-solid-state battery (10) can change its height (or thickness or volume) depending on charging and discharging under 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 (230) formed by charging. Therefore, the second height (HE2) of the charged all-solid-state battery (10) shown in FIG. 4 can be similar to the first height (HE1) of the discharged all-solid-state battery (10) shown in FIG. 2. For example, the second height (HE2) can be 1 to 1.5 times, or 1 to 1.2 times, the first height (HE1).

[0164] FIG. 5 is a cross-sectional view taken along line A-A' of FIG. 1 to explain an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 5, the all-solid-state battery (10) according to the present embodiment may further include a gasket (GSK). The gasket (GSK) may be provided to surround the cathode composite layer (CSH). The gasket (GSK) may fill a step in the side surface of the all-solid-state battery (10) caused by the difference in area between the anode composite layer (ASH) and the cathode composite layer (CSH). The gasket (GSK) may surround four side surfaces of the cathode composite layer (CSH). For example, the thickness of the gasket (GSK) may be substantially the same as the thickness of the cathode composite layer (CSH).

[0165] The upper surface of the second solid electrolyte layer (320) may include a first region in contact with the first solid electrolyte layer (310) and a second region in contact with the gasket (GSK). The second region may be a peripheral region of the upper surface of the second solid electrolyte layer (320). The second region may surround the first region.

[0166] The gasket (GSK) can prevent cracking of the solid electrolyte layer (300) during the manufacture of the all-solid-state battery (10) and / or during charging and discharging of the all-solid-state battery (10). This can improve the cycle characteristics of the all-solid-state battery (10). If the all-solid-state battery (10) does not include the gasket (GSK), cracks may occur in the solid electrolyte layer (300) due to uneven pressure applied to the negative electrode composite layer (ASH) in contact with the positive electrode composite layer (CSH), and the possibility of a short circuit occurring due to the growth of lithium metal through the cracks may increase.

[0167] The thickness of the gasket (GSK) may be greater than the thickness of the cathode composite layer (CSH) or substantially the same as the thickness of the cathode composite layer (CSH). Since the thickness of the gasket (GSK) is the same as the thickness of the cathode composite layer (CSH), a uniform pressure is applied between the cathode composite layer (CSH) and the anode composite layer (ASH), and the cathode composite layer (CSH) and the anode composite layer (ASH) are sufficiently adhered to each other, so that the interfacial resistance between the first solid electrolyte layer (310) and the second solid electrolyte layer (320) can be reduced. In addition, since 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) can be reduced.

[0168] The gasket (GSK) may have, for example, a single-layer structure. Alternatively, although not illustrated in the drawing, the gasket (GSK) may have a multi-layer structure. In a multi-layer gasket (GSK), each layer may have a different composition. A multi-layer gasket (GSK) may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. A multi-layer gasket (GSK) may include, for example, one or more adhesive layers and one or more support layers.

[0169] The gasket (GSK) may include, for example, a flame-retardant inert material. The flame-retardant inert material provides flame retardancy, thereby preventing thermal runaway and ignition of the all-solid-state battery (10). Consequently, the gasket (GSK) may further enhance the safety of the all-solid-state battery (10). The flame-retardant inert material may absorb residual moisture within the all-solid-state battery (10), thereby preventing deterioration of the all-solid-state battery (10), thereby improving the lifespan characteristics of the all-solid-state battery (10).

[0170] FIG. 6 is a cross-sectional view taken along line A-A' of FIG. 1 to explain an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 6, the positive electrode layer (100) may further include a coating layer (CTL) provided between the positive electrode current collector (110) and the positive electrode active material layer (120). The coating layer (CTL) may be 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).

[0171] 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).

[0172] 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).

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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.

[0179] 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 (230, see FIG. 4) 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.

[0180] 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.

[0181] Electrode assembly including an elastic layer and an all-solid-state secondary battery

[0182] Hereinafter, an electrode assembly according to the present invention will be described with reference to FIGS. 7 to 13. A secondary battery including a sulfide-based positive electrode active material may be referred to as a lithium-sulfur battery or a lithium-sulfur battery.

[0183] unit cell (UNC)

[0184] Fig. 7 schematically illustrates the structure of an electrode assembly according to one embodiment. Referring to Fig. 7, the electrode assembly may include a unit cell in which a positive electrode layer (100), a solid electrolyte layer (300), and a negative electrode layer (200) are sequentially arranged. In addition, the electrode assembly may include an elastic layer (ELS) arranged on one side of the unit cell. The positive electrode layer (100) may include a positive electrode current collector (110) and a positive electrode active material layer (120) laminated on one or both sides thereof. The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) on one or both sides thereof.

[0185] A unit cell can be formed by sequentially stacking a cathode layer, a solid electrolyte layer, an anode layer, a solid electrolyte layer, and a cathode layer in that order. Conversely, a unit cell can be formed by sequentially stacking a cathode layer, a solid electrolyte layer, a cathode layer, a solid electrolyte layer, and anode layer in that order.

[0186] When the negative electrode is a precipitation-type negative electrode, it may include a negative electrode coating layer (220) positioned on the negative electrode current collector (210). Initial charging begins in the absence of a negative electrode active material, and during charging, high-density lithium metal or the like is precipitated between the negative electrode current collector (210) and the negative electrode coating layer (220) to form a lithium metal layer (not shown), which may function as a negative electrode active material layer.

[0187] Accordingly, in an all-solid-state battery that has been charged more than once, the precipitation-type negative electrode may include a negative electrode current collector (210), a lithium metal layer (not shown) positioned on the negative electrode current collector (210), and a negative electrode coating layer (220) positioned on the lithium metal layer (not shown). The lithium metal layer (not shown) refers to a layer in which lithium metal or the like is precipitated during the charging process of the battery, and may be referred to as a metal layer or a negative electrode active material layer.

[0188] Elastic layer (ELS)

[0189] The unit cell may further include an elastic layer (ELS) attached to the negative electrode current collector (210) or the positive electrode current collector (110). The elastic layer may be laminated on the outermost surface of the unit cell to buffer changes in the volume of the unit cell during charging and discharging. The elastic layer may have a compressive strength within a set range. The elastic layer may be provided in the form of an elastic sheet.

[0190] The elastic layer may be located on the outermost surface of the unit cell, or in a structure in which multiple unit cells are stacked, it may be located on the outermost layer and / or between multiple unit cells. Considering that the thickness of the negative electrode in particular changes significantly during charge and discharge due to reasons such as dendrite formation, the elastic layer may be located on the outer side of the negative electrode, i.e., on the opposite side of the surface of the negative electrode where the solid electrolyte layer is in contact, so as to buffer problems caused by thickness changes. In addition, by being located on the outer side of the positive electrode and / or the negative electrode, the elastic layer can prevent deterioration by reacting with lithium, thereby increasing the Coulombic efficiency of the battery.

[0191] In one embodiment, the unit cells may be stacked in multiples. An elastic layer (ELS) may be included between the first cathode and the second cathode of adjacent unit cells in the stacked structure. In another embodiment, the electrode assembly may be stacked in multiples of the unit cells and may include an elastic layer (ELS) between the first cathode and the second cathode of adjacent unit cells.

[0192] The elastic layer (ELS) may include an elastic material. The elastic material may include, but is not limited to, at least one of polyurethane, natural rubber, spandex, isobutylene isoprene rubber (IIR), fluoroelastomer, elastomer, ethylene-propylene rubber (EPR), styrene-butadiene rubber (SBR), chloroprene, elastomer, rubber epichlorohydrin, nylon, terpene, isoprene rubber, polybutadiene, nitrile rubber, thermoplastic elastomer, silicone rubber, ethylene-propylene-diene rubber (EPDM), ethylene vinyl acetate (EVA), halogenated butyl rubber, neoprene, and copolymers thereof, and any material having elasticity may be used without limitation. In one embodiment, the elastic layer (ELS) may be made of a urethane-based material, for example, polyurethane.

[0193] The elastic layer (ELS) may be pressurized so that the thickness upon installation is 40 to 90% of the initial thickness prior to applying pressure. For example, the elastic layer (ELS) may be pressurized so that the thickness upon installation is 50 to 85% of the initial thickness prior to applying pressure, specifically 60 to 80%, or 65 to 75%. Within the above range, the volume change of the negative electrode can be effectively absorbed, thereby enabling smooth charging and discharging of the secondary battery.

[0194] The elastic layer (ELS) can effectively suppress changes in the volume of the negative electrode of an all-solid-state battery including the above-described negative electrode coating layer (220).

[0195] The thickness of the elastic layer (ELS) can be determined in the range of 200 to 500% of the thickness of the negative electrode coating layer (220) formed when charging the all-solid-state battery including the negative electrode coating layer (220). In the all-solid-state battery including the negative electrode coating layer (220), the thickness of the negative electrode coating layer (220) is determined in proportion to the current density of the positive electrode. That is, the thickness of the negative electrode coating layer (220) is determined according to the amount of lithium moving from the positive electrode to the negative electrode, and thereby a change in the volume of the negative electrode occurs. Therefore, the thickness of the elastic layer (ELS) can be determined so as to be able to absorb this change in the volume of the negative electrode. Therefore, by setting the thickness of the elastic layer (ELS) in the range of 200 to 500% of the thickness of the negative electrode coating layer (220) formed when charging the all-solid-state battery including the negative electrode coating layer, the change in the volume of the negative electrode can be effectively absorbed. For example, the thickness of the elastic layer (ELS) may be in the range of 250 to 450%, specifically, in the range of 300 to 400%, of the thickness of the negative electrode coating layer (220) formed when charging an all-solid-state battery including the negative electrode coating layer (220).

[0196] The thickness of the elastic layer (ELS) can be set in the range of, for example, 50 μm to 300 μm, and can be selectively set in some cases, for example, 30 μm to 100 μm, 100 μm to 150 μm, 200 μm to 300 μm, or 50 μm to 100 μm.

[0197] By including an elastic layer (ELS) between the negative electrode current collectors, the volume change of the negative electrode due to the lithium deposition reaction used in the negative electrode can be absorbed, thereby suppressing the volume change of the entire cell and obtaining a stable lifespan.

[0198] Functional additives

[0199] In addition to the elastic material, the elastic layer (ELS) may include a functional additive. The functional additive may be a material having heat dissipation and insulation properties. When heat is generated in the unit cell, the elastic layer (ELS) can quickly dissipate the heat to the outside, thereby helping to dissipate heat inside the cell. Therefore, the temperature inside the cell can be effectively lowered. In addition, the functional additive can provide electrical insulation, thereby preventing short circuits and thermal runaway. The functional additive can adsorb hydrogen sulfide (H2S). When a sulfide-based positive electrode active material or a sulfide-based solid electrolyte is used, the problem of hydrogen sulfide generated when exposed to the air can be effectively resolved. The elastic layer containing the functional additive can be formed in contact with the unit cell and configured to adsorb hydrogen sulfide. For example, when hydrogen sulfide is generated inside the cell due to exposure to the air or moisture, an elastic layer containing the functional additive can be provided in each unit cell to adsorb hydrogen sulfide, thereby reducing the amount of hydrogen sulfide exposure to the air and reducing the cascading damage.

[0200] As previously explained, functional additives can reduce the chain reactions of short-circuiting, overheating, thermal runaway, and combustion. This can be even more effective when applied to all-solid-state batteries containing sulfide-based cathode active materials.

[0201] By incorporating an elastic layer containing functional additives, the all-solid-state battery cell can exhibit a multifaceted effect, including suppressing volume changes, heat dissipation, and insulation, thereby improving battery life and performance. Furthermore, in lithium-sulfur batteries using sulfide-based active materials or solid electrolytes, the solution can effectively address the issue of hydrogen sulfide generation resulting from exposure to the atmosphere due to external impacts.

[0202] In one embodiment, the functional additive may include at least one of hexagonal boron nitride (h-BN), cubic boron nitride (c-BN), silicon nitiride (Si3N4), aluminum nitiride (AlN), and zeolite.

[0203] In one embodiment, the functional additive may have a particle form having an average particle diameter of 0.01 μm to 2.0 μm, 0.10 μm to 2.0 μm, or 0.10 μm to 1.0 μm. The functional additive may be uniformly dispersed within the polymer matrix of the elastic layer (ELS).

[0204] In one embodiment, the functional additive can have a thermal conductivity of 50 W / mK to 1500 W / mK, 50 W / mK to 100 W / mK, 70 W / mK to 250 W / mK, 140 W / mK to 250 W / mK, or 140 W / mK to 320 W / mK.

[0205] In one embodiment, the functional additive is 10 6 Ωcm to 10 15 Ωcm, 10 13 Ωcm to 10 15 Ωcm, 10 10 Ωcm to 10 14 Ωcm, or 10 2 Ωcm to 10 10 It can have an electrical resistance of Ωcm.

[0206] In one embodiment, the content of the functional additive in the elastic layer may be 1 wt% to 20 wt%, 5 wt% to 20 wt%, 1 wt% to 10 wt%, or 5 wt% to 10 wt% with respect to 100 wt% of the elastic layer. The higher the filling density of the functional additive in the elastic layer, the better the heat dissipation effect.

[0207] In one embodiment, the porosity of the elastic layer may be from 50% to 95%, from 60% to 90%, or from 70% to 90%.

[0208] In this way, by arranging an elastic layer including a functional additive, the efficiency and stability of an all-solid-state secondary battery can be improved. A unit cell having the elastic layer can effectively improve the tracking properties of the negative electrode current collector even when the thickness of the lithium metal layer precipitated by charge and discharge changes, thereby preventing the deterioration of the contact state between the solid electrolyte layer and the negative electrode current collector, thereby providing an all-solid-state secondary battery with high Coulombic efficiency. In addition, since the elastic layer is arranged on the opposite side of the solid electrolyte layer with respect to the negative electrode current collector, there is an advantage in that the elastic layer can be prevented from reacting with the lithium in the negative electrode layer and deteriorating. In this respect as well, the Coulombic efficiency can be increased. In the event of an internal short circuit or deformation / destruction due to an external force, the elastic layer with heat dissipation and insulation properties can prevent a chain reaction such as explosion / thermal runaway from occurring. In addition, the problem of hydrogen sulfide generation when the pouch is destroyed / deformed due to a high-temperature reaction of the sulfide-based positive electrode and the sulfide-based solid electrolyte during heating or when exposed to the atmosphere due to an external impact can be effectively solved.

[0209] In one embodiment, the structure of the unit cell electrode assembly may have a structure in which a plurality of symmetrical unit cells are stacked on both sides centered on the positive electrode collector. More specifically, an electrode assembly may be formed in the order of (negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative electrode). In the case of such an electrode assembly, an elastic layer may be disposed between adjacent unit cells to absorb volume changes in the negative electrode layer within the electrode assembly. By including the elastic layer, the electrode assembly can suppress volume changes of the entire cell, thereby obtaining a stable lifespan, and can have a stack and bipolar structure, thereby allowing for free design of capacity and voltage. In addition, a functional additive may be included in the elastic layer to suppress volume changes as well as obtain a heat dissipation or insulation effect, and this may be more effective when a sulfide-based solid electrolyte is used.

[0210] The above electrode assembly can be applied to various battery types and is not limited to a specific structure. In one embodiment, the electrode assembly can be packaged in a pouch to manufacture a pouch-type all-solid-state secondary battery.

[0211] Manufacturing method of all-solid-state secondary battery

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] A sulfide-based solid electrolyte is provided. A mixture is prepared by mixing a Li2S-lithium salt complex and the sulfide-based solid electrolyte.

[0217] 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.

[0218] 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.

[0219] In the above milling, mechanical milling can be used. A ball mill, etc. can be used in the mechanical milling.

[0220] 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.

[0221] 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.

[0222] 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.

[0223] The pressurizing step is for example 40 to 100℃, for example 85 o Plate press treatment is performed at a pressure of 500 MPa for 30 min at C. This pressurization treatment sinteres the solid electrolyte layer, thereby improving battery characteristics.

[0224] In another implementation example, the pressurization process described above may be omitted.

[0225] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0226]

[0227] (Manufacturing of all-solid-state secondary batteries)

[0228] A lithium-sulfur battery was manufactured using an all-solid-state secondary battery, comprising a positive electrode including a sulfide-based positive electrode active material, a sulfide-based solid electrolyte, and a negative electrode, and further comprising an elastic layer. According to the following examples, a lithium-sulfur battery was manufactured using only a different elastic layer.

[0229] Example 1: Preparation of an elastic layer comprising h-BN

[0230] A resin mixture was prepared by mixing 70 parts by weight of n-butyl acrylate (hereinafter also referred to as 'BA') as a resin component, 10 parts by weight of 2-hydroxyethyl acrylate (2-HEA), and 20 parts by weight of isobornyl acrylate in a reactor. To this resin mixture, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator and 150 parts by weight of ethyl acetate as a solvent were mixed, and the temperature was raised to 75°C while stirring to carry out a polymerization reaction. Additionally, a polymerization catalyst solution prepared by dissolving 0.1 parts by weight of azobisisobutyronitrile in 10 parts by weight of ethyl acetate was sequentially added, and the polymerization was completed over 8 hours at the same temperature. After completion of the polymerization, a solution having a solid content of 35 wt% and including a carboxyl group-free acrylic copolymer having a weight average molecular weight of 1 million was prepared by adding a diluting solvent (ethyl acetate).

[0231] Based on 100 parts by weight of the solution of the acrylate copolymer having a weight average molecular weight of 1 million manufactured above, 7 parts by weight of Expancel 551 DU 40 (Akzo Nobel Chemicals) as a pore-forming agent and 0.2 parts by weight of an isocyanate crosslinking agent (XDI (Xylylene Diisocyanate), trade name "Takenate D110N", product of Mitsui Chemicals Polyurethane Co., Ltd., molecular weight 698, trifunctionality, solid content 75 wt%)) were mixed into the solution of the acrylate copolymer, and h-BN was mixed as a functional additive, and the mixed resultant was coated on a PET release film and dried at 150°C for 5 minutes to manufacture a sheet-shaped elastic layer having a thickness of 300 μm.

[0232] Example 2: Preparation of an elastic layer containing c-BN

[0233] An elastic layer was manufactured under the same conditions as Example 1, except that c-BN was used as a functional additive.

[0234] Example 3: Preparation of an elastic layer comprising silicon nitride

[0235] An elastic layer was manufactured under the same conditions as Example 1, except that silicon nitride (Si3N4) was used as a functional additive.

[0236] Example 4: Preparation of an elastic layer containing AlN

[0237] An elastic layer was manufactured under the same conditions as Example 1, except that aluminum nitride (AlN) was used as a functional additive.

[0238] Example 5: Preparation of an elastic layer containing zeolite

[0239] An elastic layer was manufactured under the same conditions as Example 1, except that zeolite was used as a functional additive.

[0240] Depending on the type of functional additive, it is summarized in Table 1 below.

[0241] Functional additive typeFunctional additive contentElastic layer thicknessExample 1h-BN5wt%50μmExample 2c-BN5wt%50μmExample 3Si3N45wt%50μmExample 4AlN5wt%50μmExample 5zeolite5wt%50μm

[0242] Comparative Example 1: All-solid-state secondary battery without elastic layer

[0243] A lithium-sulfur battery was manufactured using an all-solid-state secondary battery, a positive electrode including a sulfide-based positive electrode active material, a sulfide-based solid electrolyte, and a negative electrode. Compared to the embodiment, the only difference is the presence or absence of an elastic layer.

[0244]

[0245] Evaluation Example 1: Charge / Discharge Test

[0246] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 5 and Comparative Example 1 were evaluated by the following charge / discharge test. The charge / discharge test was performed by placing the all-solid-state secondary batteries in a 45°C constant temperature chamber.

[0247] First, for the all-solid-state secondary batteries according to the examples and comparative examples, constant current charging was performed until the voltage reached 4.25 V at a current of 0.1 C, and then constant voltage charging was performed until the voltage reached 0.05 C. After the charging was completed, the cells were allowed to rest for approximately 10 minutes, and then constant current discharge was performed at a current of 0.1 C until the voltage reached 2.5 V.

[0248] The above charge-discharge cycle was repeated a total of 300 times to evaluate the charge-discharge efficiency and the occurrence of short circuits. The charge-discharge efficiency was evaluated by the capacity retention rate expressed by Equation 1 below after 300 cycles.

[0249] <Formula 1>

[0250] Capacity retention rate (%) = (discharge capacity after each cycle / discharge capacity of the first cycle) X 100

[0251] Examples 1 to 5 achieved a charge / discharge efficiency of 80% or more during 300 cycles.

[0252] In comparison, in Comparative Example 1, a short occurred in less than 50 cycles.

[0253] Through the above charge-discharge test, it can be confirmed that the lithium-sulfur batteries according to Examples 1 to 5 have an elastic layer with excellent compressive strength and stress relaxation characteristics, and thus the coulombic efficiency is improved without occurrence of a short circuit even when the volume of the cell changes due to charge-discharge.

Claims

1. A unit cell comprising a positive electrode including a sulfide-based positive electrode active material, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte; and Including an elastic layer disposed on at least one side of the above unit cell, The elastic layer comprises an elastic material and a functional additive, The thermal conductivity of the above functional additive is 50 W / mK to 1500 W / mK, The electrical resistance of the above functional additive is 10 6 Ωcm to 10 15 Ωcm, Electrode assembly.

2. In paragraph 1, The functional additive is at least one of hexagonal boron nitride (h-BN), cubic boron nitride (c-BN), silicon nitride (Si3N4), aluminum nitride (AlN), and zeolite. Electrode assembly.

3. In paragraph 1, An electrode assembly in which the content of the functional additive is 1% to 10% by weight based on the total weight of the elastic layer.

4. In paragraph 1, The thickness of the elastic layer is set to be in the range of 200% to 500% of the thickness of the lithium deposition layer formed when charging a battery including a negative electrode coating layer. Electrode assembly.

5. In paragraph 1, The above sulfide-based solid electrolyte is, An argyrodite-type sulfide solid electrolyte comprising at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. Electrode assembly.

6. In paragraph 1, The above positive electrode active material comprises a Li2S-LiI-AlI3 complex. Electrode assembly.

7. In paragraph 1, The elastic material comprises at least one of polyurethane, natural rubber, spandex, isobutylene isoprene rubber (IIR), fluoroelastomer, elastomer, ethylene-propylene rubber (EPR), styrene-butadiene rubber (SBR), chloroprene, elastomer, rubber epichlorohydrin, nylon, terpene, isoprene rubber, polybutadiene, nitrile rubber, thermoplastic elastomer, silicone rubber, ethylene-propylene-diene rubber (EPDM), ethylene vinyl acetate (EVA), halogenated butyl rubber, neoprene, and copolymers thereof. Electrode assembly.

8. In paragraph 7, The thickness of the elastic layer is 30 μm to 100 μm. Electrode assembly.

9. A unit cell comprising a positive electrode including a sulfide-based positive electrode active material, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte; and Including an elastic layer disposed on at least one side of the above unit cell, The elastic layer comprises an elastic material and a functional additive, configured to adsorb hydrogen sulfide (H2S), Electrode assembly.

10. In paragraph 9, The functional additive is at least one of hexagonal boron nitride (h-BN), cubic boron nitride (c-BN), silicon nitride (Si3N4), aluminum nitride (AlN), and zeolite. Electrode assembly.

11. In paragraph 9, An electrode assembly in which the content of the functional additive is 5 to 10 wt% based on the total weight of the elastic layer.

12. In paragraph 9, The above positive electrode active material comprises a Li2S-LiI-AlI3 complex. Electrode assembly.

13. In paragraph 9, An electrode assembly wherein the thickness of the elastic layer is 30 μm to 100 μm.

14. In paragraph 9, The above elastic material is an electrode assembly made of polyethylene, polyacrylic polymer, polyurethane, or a combination thereof.

15. In paragraph 9, The above unit cell is sequentially stacked in the order of a cathode, a sulfide-based solid electrolyte layer, a cathode including a sulfide-based positive electrode active material layer, a sulfide-based solid electrolyte layer, and a cathode. Electrode assembly.

16. In paragraph 9, The above unit cells are configured by stacking multiple units, Electrode assembly.

17. In paragraph 9, The thermal conductivity of the above functional additive is 50 W / mK to 1500 W / mK. Electrode assembly.

18. In paragraph 9, The electrical resistance of the above functional additive is 10 6 Ωcm to 10 15 Ωcm, Electrode assembly.

19. A plurality of stacked unit cells, each of the plurality of unit cells including a positive electrode including a sulfide-based positive electrode active material, a solid electrolyte layer including a sulfide-based solid electrolyte, and a negative electrode; and Including an elastic layer between the above plurality of unit cells, The above elastic layer comprises an elastic material and a functional additive, The porosity of the elastic layer is 70% to 90%, Electrode assembly.

20. In paragraph 19, The thickness of the elastic layer is 30 μm to 100 μm, Electrode assembly.

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