All-solid-state battery

Abstract

The present invention relates to an all-solid-state battery, more specifically to an all-solid-state battery comprising first and second unit cells connected in series, each of the first and second unit cells comprising: a negative electrode current collector; a lithium metal layer on the negative electrode current collector; a negative electrode coating layer on the lithium metal layer; a solid electrolyte layer on the negative electrode coating layer; a positive electrode active material layer on the solid electrolyte layer; and a positive electrode current collector on the positive electrode active material layer, wherein the positive electrode active material layer contains sulfide-based positive electrode active material, the sulfide-based positive electrode active material content being 40-90 wt% with respect to 100 weight parts of the positive electrode active material layer, and the change in thicknesses of the positive electrode active material layer and lithium metal layer being complementary.

Description

All-solid-state batteries

[0001] The present invention relates to an all-solid-state battery comprising a sulfide-based positive electrode active material.

[0002]

[0003] Recent industrial demands have led to the active development of batteries with high energy density and stability. For example, lithium batteries are used in a variety of applications, including information technology, communications devices, and automobiles. Because automobiles are life-threatening, stability is also crucial.

[0004] Lithium batteries using liquid electrolytes may have an increased risk of fire and / or explosion in the event of a short circuit. All-solid-state batteries using solid electrolytes instead of liquid electrolytes are being proposed. Solid electrolytes are less likely to catch fire than liquid electrolytes.

[0005] All-solid-state batteries can reduce the risk of fire or explosion by using solid electrolytes instead of liquid ones. All-solid-state batteries can offer improved safety.

[0006]

[0007] The problem to be solved by the present invention is to provide an all-solid-state battery having high energy density and capable of high output.

[0008]

[0009] An all-solid-state battery according to the present invention comprises a first unit cell connected in series; and a second unit cell, wherein each of the first and second unit cells may include: a negative electrode current collector; a lithium metal layer on the negative electrode current collector; a negative electrode coating layer on the lithium metal layer; a solid electrolyte layer on the negative electrode coating layer; a positive electrode active material layer on the solid electrolyte layer; and a positive electrode current collector on the positive electrode active material layer.

[0010] The above positive electrode active material layer includes a sulfide-based positive electrode active material, and the content of the sulfide-based positive electrode active material is 40 wt% to 90 wt% based on 100 parts by weight of the positive electrode active material layer, and a change in the thickness of the positive electrode active material layer and a change in the thickness of the lithium metal layer may be mutually complementary.

[0011]

[0012] According to another concept of the present invention, an all-solid-state battery comprises a first unit cell connected in series; and a second unit cell, wherein each of the first and second unit cells may include: a negative electrode current collector; a negative electrode coating layer on the negative electrode current collector; a solid electrolyte layer on the negative electrode coating layer; a positive electrode active material layer on the solid electrolyte layer; and a positive electrode current collector on the positive electrode active material layer.

[0013] The above positive electrode active material layer includes a sulfide-based positive electrode active material, and the first unit cell in a charged state has a first thickness, the first unit cell in a discharged state has a second thickness, and the ratio of the first thickness to the second thickness may be 1 to 1.5.

[0014]

[0015] According to another concept of the present invention, an all-solid-state battery comprises a first unit cell connected in series; and a second unit cell, wherein each of the first and second unit cells may include: a negative electrode current collector; a negative electrode coating layer on the negative electrode current collector; a solid electrolyte layer on the negative electrode coating layer; a positive electrode active material layer on the solid electrolyte layer; and a positive electrode current collector on the positive electrode active material layer.

[0016] The above positive electrode active material layer includes a sulfide-based positive electrode active material, and the first unit cell in a charged state has a first internal pressure, the first unit cell in a discharged state has a second internal pressure, and the ratio of the first internal pressure to the second internal pressure may be 1.2 to 1.8.

[0017]

[0018] The all-solid-state battery according to the present invention can have a high energy density and exhibit high output.

[0019]

[0020] FIG. 1 is a plan view of a unit cell according to embodiments of the present invention.

[0021] Figure 2 is a cross-sectional view taken along line A-A' of Figure 1.

[0022] 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.

[0023] FIGS. 4 to 6 are cross-sectional views taken along line A-A' of FIG. 1 to explain a unit cell according to another embodiment of the present invention.

[0024] Figures 7 to 10 are cross-sectional views of all-solid-state batteries according to embodiments of the present invention.

[0025]

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In this specification, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic state.

[0032] As used herein, “alloy” means a mixture of two or more metals.

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

[0034] In this specification, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0035] In this specification, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0036] In this specification, “lithiation” and “lithiate” mean a process of adding lithium to an electrode active material.

[0037] In this specification, “delithiation” and “delithiate” refer to a process of removing lithium from an electrode active material.

[0038] In this specification, “charging” and “charging” mean the process of providing electrochemical energy to a battery.

[0039] In this specification, “discharge” and “discharge” mean the process of removing electrochemical energy from a battery.

[0040] In this specification, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during the discharge process.

[0041] In this specification, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0042]

[0043] Fig. 1 is a plan view of a unit cell 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.

[0044] Referring to FIGS. 1 and 2, a unit cell (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 unit cell (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).

[0045] The unit cell (10) according to embodiments of the present invention may be the smallest unit cell constituting an all-solid-state battery. For example, the unit cell (10) may be a monocell comprising one negative electrode and one positive electrode. As another example, the unit cell (10) may be a bicell.

[0046] 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.

[0047] 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 ㎛.

[0048] 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.

[0049] The base film may be, for example, an insulator. If the base film includes an insulating thermoplastic polymer, the base film may soften or liquefy when a short circuit occurs, thereby preventing battery operation and suppressing a rapid increase in current.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 can be improved.

[0055] 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%, 20 wt% to 80 wt%, 30 wt% to 70 wt%, or 30 wt% to 60 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 may be reduced. If the content of the positive electrode active material is excessively increased, deterioration of the all-solid-state battery may be accelerated due to a change in the volume of the positive electrode during charge and discharge.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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 전지의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0062] 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.

[0063] When the oxide-based cathode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), the capacity density of the all-solid-state battery can be increased, thereby reducing metal dissolution of the cathode active material in a charged state. As a result, the cycle characteristics of the all-solid-state battery in a charged state are improved. Meanwhile, the "cycle characteristics" are characteristics indicating the degree to which the all-solid-state battery is deteriorated due to charge / discharge of the all-solid-state battery. An all-solid-state battery with high cycle characteristics may be deteriorated less due to charge / discharge, and an all-solid-state battery with low cycle characteristics may be deteriorated more due to charge / discharge.

[0064] 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.

[0065] 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.

[0066] 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 spherical 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).

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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).

[0074] 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.

[0075] 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 Li 7-x PS6-x I x , may include one or more selected from 0≤x≤2.

[0076] 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.

[0077] 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.

[0078] The lithium salt compound may be, for example, a binary compound composed of lithium and one element selected from groups 13 to 17 of the periodic table of elements. The binary compound may include, for example, one or more selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3. The lithium salt compound may be, for example, a ternary compound composed of lithium and two elements selected from groups 13 to 17 of the periodic table of elements. The ternary compound may include, for example, one or more selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. For example, the lithium salt compound may be one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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).

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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).

[0088] 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.

[0089] 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).

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The content of the lithium salt in the composite (CAM) may be 5 wt% to 50 wt%, 10 wt% to 50 wt%, 20 wt% to 50 wt%, or 30 wt% to 50 wt% of the total weight of the composite (CAM). By having the lithium salt content in this range in the composite (CAM), the composite (CAM) can have both improved ionic conductivity and excellent ductility.

[0094] 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.

[0095] 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.

[0096] The ionic conductivity of the complex (CAM) according to embodiments of the present invention is, for example, 1ⅹ10 at 25°C. -5 S / cm or more, 2ⅹ10 -5 S / cm or more, 4x10 -5 S / cm or more, 6ⅹ10 -5 S / cm or more, 8ⅹ10 -5 S / cm or more, or 1ⅹ10 -4 It can be S / cm or more. For example, the ionic conductivity can be measured using electrochemical impedance spectroscopy, 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.

[0097] The size of the Li2S particles in the composite (CAM) may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the Li2S particles may be, for example, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, or 0.1 μm to 1 μm.

[0098] 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.

[0099] 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).

[0100] 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).

[0101] The solid electrolyte (SEP) may be, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x, may be at least one selected from 0≤x≤2. The sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one containing sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form a solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0102] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

[0103] <Chemical Formula 1>

[0104] Li + 12-n-x A n+ X 2- 6-x Y - x

[0105] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1≤n≤5, 0≤x≤2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0106] 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.

[0107] 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.

[0108] When the cathode active material according to embodiments of the present invention includes a sulfide-based cathode active material, the content of the sulfide-based cathode active material in the cathode active material layer (120) may be 30 wt% to 60%, or 30 wt% to 50 wt%, of the total weight of the cathode active material layer (120). In the present specification, the content of the sulfide-based cathode active material may mean the content of the Li2S-containing complex (CAC) in the cathode active material layer (120), that is, the sum of the content of the sulfide-based cathode active material (CAM) and the content of the conductive material (CMA).

[0109] When the content of the sulfide-based cathode active material satisfies the above range, the volume change of the all-solid-state battery can be effectively accommodated while maintaining an appropriate energy density.

[0110] 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).

[0111] 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 unit cell (10). In contrast, the crystalline lithium metal oxyhalide may be relatively brittle compared to the amorphous lithium metal oxyhalide. Whether or not the inorganic filler is amorphous can be confirmed using an XRD spectrum.

[0112] 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 unit cell (10) can be effectively accommodated during charge and discharge, or the unit cell (10) can be easily deformed according to the volume change.

[0113] 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).

[0114] 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).

[0115] 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).

[0116] 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 unit cell (10). Accordingly, the cycle characteristics of the unit cell (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).

[0117] 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).

[0118] 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 unit cell (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 can be further improved. The elastic modulus of the solid electrolyte (SEP) can be measured, for example, using a dynamic mechanical analyzer (DMA).

[0119] The inorganic filler may have viscoelasticity, for example. The inorganic filler may have viscoelastic creep, for example. 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 can be easily accommodated, and the shape can be continuously deformed without defects. The creep rate is the rate of change over time of the inorganic filler under stress at a constant temperature, i.e., the strain rate. The creep rate can be measured, for example, using a universal testing machine.

[0120] 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.

[0121] 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.

[0122] 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 Ga y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x In y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x As y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Sb y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Mo y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Bi y O z Cl w(0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x B y O z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w) 또는 이들의 조합을 포함할 수 있다.

[0123] 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 can be further improved.

[0124] 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.

[0125] 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).

[0126] 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).

[0127] The metal 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.

[0128] 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 cycling characteristics of an all-solid-state battery 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).

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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 can be improved.

[0134] The negative electrode coating layer (220) may be configured to allow lithium metal to grow between it and the negative electrode current collector (210) when the all-solid-state battery is charged. The negative electrode coating layer (220) may serve as a protective layer for the lithium metal and at the same time suppress the precipitation and growth of lithium dendrites.

[0135] 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).

[0136] 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.

[0137] 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. If the thickness of the cathode coating layer (220) increases excessively, the energy density of the all-solid-state battery may decrease and the internal resistance of the all-solid-state battery due to the cathode coating layer (220) may increase, thereby deteriorating the cycle characteristics of the cell.

[0138] 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).

[0139] 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.

[0140] 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).

[0141] 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.

[0142] In one embodiment, the first solid electrolyte is Li 7-x PS 6-xCl 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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 according to the present invention can be improved.

[0147] 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).

[0148] 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).

[0149] 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).

[0150] 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).

[0151] 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).

[0152] 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).

[0153] 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).

[0154] An all-solid-state battery 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).

[0155] 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 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).

[0156]

[0157] 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.

[0158] 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 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.

[0159] The lithium metal layer (230) may include lithium or a lithium alloy. Since the lithium metal layer (230) is a metal layer including 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 an all-solid-state battery.

[0160] 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 may increase, and the cycle characteristics of the all-solid-state battery may rather deteriorate.

[0161] 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. 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, 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.

[0162] When the lithium metal layer (230) is precipitated by charging after assembling the all-solid-state battery, the energy density of the all-solid-state battery can increase because the lithium metal layer (230) is not included during the assembly of the all-solid-state battery. When charging the all-solid-state battery, the charging capacity of the negative electrode coating layer (220) can be exceeded. 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).

[0163] 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 an all-solid-state battery. 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 and improve the cycle characteristics of the all-solid-state battery.

[0164] When a lithium metal layer (230) is formed by charging after assembling an all-solid-state battery, 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 or in the state after complete discharge.

[0165] The positive electrode active material layer (120) from which lithium ions are released by charging of the all-solid-state battery 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.

[0166] 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 to 1.5 times, or 1 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 reduced correspondingly to the thickness of the lithium metal layer (230) formed by charging the all-solid-state battery. In other words, the change in the thickness of the positive electrode active material layer (120) and the change in the thickness of the lithium metal layer (230) may be mutually complementary. In one embodiment, in the unit cell (10) in a discharged state, the positive electrode active material layer (120) may have a first thickness (TK1), and the thickness of the lithium metal layer (230) may converge to 0. In the unit cell (10) in a charged state, the positive electrode active material layer (120) may have a second thickness (TK2) smaller than the first thickness (TK1), and the lithium metal layer may have a third thickness (TK3). That is, as the state changes from a discharged state to a charged state, the thickness of the lithium metal layer (230) increases, while the thickness of the positive electrode active layer (120) decreases correspondingly, thereby exhibiting a seesaw structure.

[0167] Due to the complementary thickness changes as described above, even if a lithium metal layer (230) is formed by charging the all-solid-state battery, the second height (HE2) of the unit cell (10) may be similar to the first height (HE1) of FIG. 2. For example, the second height (HE2) may be 1 to 1.5 times, or 1 to 1.2 times, the first height (HE1).

[0168] Although not shown, the unit cell (10) can operate (i.e., charge and / or discharge) while pressurized by a pressurizing jig. In one embodiment, the unit cell (10) can be pressurized to 0.8 MPa to 2 MPa. For example, the unit cell (10) can have an internal pressure of about 1 MPa when discharged, and the unit cell (10) can have an internal pressure of about 1.5 MPa when charged. The ratio of the internal pressure of the unit cell (10) in a charged state of FIG. 4 to the internal pressure of the unit cell (10) in a discharged state of FIG. 2 can be 1.0 to 2.0, or 1.2 to 1.8. Since the height and pressure of the unit cell (10) before and after charging are substantially the same or similar, the all-solid-state battery according to the present invention does not require a separate structure or layer capable of accommodating a volume change.

[0169] FIG. 5 is a cross-sectional view taken along line A-A' of FIG. 1 to explain a unit cell according to another embodiment of the present invention. Referring to FIG. 5, the unit cell according to the present embodiment may further include a gasket (GSK) which is an inert member. 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 unit cell caused by the difference in area between the cathode 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).

[0170] 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.

[0171] The gasket (GSK) can prevent cracking of the solid electrolyte layer (300) during the manufacture of the all-solid-state battery and / or during charging and discharging of the all-solid-state battery. This can improve the cycle characteristics of the all-solid-state battery. If the all-solid-state battery 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.

[0172] 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, the internal resistance of the solid electrolyte layer (300) can be reduced.

[0173] 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.

[0174] 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. Consequently, the gasket (GSK) can further enhance the safety of the all-solid-state battery. The flame-retardant inert material absorbs residual moisture within the all-solid-state battery, thereby preventing deterioration of the all-solid-state battery and improving its lifespan.

[0175]

[0176] FIG. 6 is a cross-sectional view taken along line A-A' of FIG. 1 to explain a unit cell 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).

[0177] 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 during the charge / discharge process and improve the cycle characteristics of the all-solid-state battery.

[0178] 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).

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] By placing the thin film (TFL) on one side 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 can be further improved.

[0186] 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 exert its function. If the thickness of the thin film (TFL) is excessively thick, the thin film (TFL) itself may absorb lithium, reducing the amount of lithium precipitation in the negative electrode layer (200), thereby lowering the energy density of the all-solid-state battery and deteriorating the cycle characteristics of the all-solid-state battery. 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.

[0187]

[0188] Hereinafter, an all-solid-state battery including a first unit cell and a second unit cell connected in series will be described in more detail. Each of the first and second unit cells may be identical to or similar to the unit cells described above with reference to FIGS. 1 to 6.

[0189]

[0190] Figures 7 and 8 are cross-sectional views illustrating an all-solid-state battery according to one embodiment of the present invention. Referring to Figure 7, the all-solid-state battery according to the present invention may include a first unit cell (10') and a second unit cell (10") that are sequentially stacked. The first and second unit cells (10', 10") may be stacked along one direction.

[0191] In one embodiment, the negative current collector (210") of the second unit cell (10') may be disposed on the positive current collector (110') of the first unit cell (10'). The positive current collector (110') of the first unit cell (10') and the negative current collector (210") of the second unit cell (10'') may be in physical contact. Through the above-described physical contact, the positive electrode of the first unit cell (10') and the negative electrode of the second unit cell (10") may be directly connected in series. Since the first unit cell (10') and the second unit cell (10") are directly connected, additional connecting components (e.g., wires) for connection between the unit cells may be omitted. The present invention can reduce the volume of the all-solid-state battery and also reduce the resistance caused by the connecting components.

[0192] The all-solid-state battery according to the present invention may not include a separate structure (e.g., an elastic pad) for accommodating a volume change of the all-solid-state battery, since the thickness change of the positive electrode active material layer (120) and the thickness change of the lithium metal layer (230) are mutually complementary. Since the all-solid-state battery does not include the above-described separate structure and each unit cell is directly connected in series, the all-solid-state battery of the present invention may have a compact structure and high energy density.

[0193] The term "mutually complementary" used in the present invention may refer to the seesaw structure of the unit cell (10) described above with reference to FIGS. 2 and 4. The all-solid-state battery according to the present invention includes a sulfide-based positive electrode active material, and by controlling the composition and content of the sulfide-based positive electrode active material, the change in the thickness of the positive electrode active material layer (120) and the change in the thickness of the lithium metal layer (230) may be mutually complementary.

[0194] Referring to FIG. 8 as another embodiment of the present invention, the positive electrode current collector (400) of the first unit cell (10') and the negative electrode current collector (400) of the second unit cell (10'') may be substantially identical to each other. In other words, adjacent unit cells may share a single current collector. When the first unit cell (10') and the second unit cell (10") share a current collector, the volume of the all-solid-state battery is further reduced, thereby further improving the energy density.

[0195] Referring again to FIGS. 7 and 8, the all-solid-state battery according to the present invention may have unit cells sequentially stacked to form a stack. A first bipolar plate (50) may be provided at one end of the stack, and a second bipolar plate (60) may be provided at the other end of the stack. The first and second bipolar plates (50, 60) may sandwich the stacked first and second unit cells (10', 10").

[0196] In one embodiment, one surface of the first bipolar plate (50) may be in contact with the negative current collector (210') of the first unit cell (10'), and the other surface of the first bipolar plate (50) may be in contact with the positive terminal. In this case, one surface of the second bipolar plate (60) may be in contact with the positive current collector (110") of the second unit cell (10"), and the other surface of the second bipolar plate (60) may be in contact with the negative terminal.

[0197]

[0198] Fig. 9 is a cross-sectional view showing an all-solid-state battery according to another embodiment of the present invention. Referring to Fig. 9, the all-solid-state battery according to the present invention may include a first unit cell (10') and a second unit cell (10") arranged side-by-side. The first unit cell (10') and the second unit cell (10") arranged side-by-side may form a parallel body. The second unit cell (10") may be arranged inverted with respect to the first unit cell (10').

[0199] A first bipolar plate (50) may be provided on the lower surface of the parallel body, and a second bipolar plate (60) may be provided on the upper surface of the parallel body. The first and second bipolar plates (50, 60) may sandwich the first and second unit cells (10', 10").

[0200] The first and second unit cells (10', 10") arranged in reverse can be connected in series via the first and second bipolar plates (50, 60). Even when the unit cells form a battery, since the unit cells are connected in series via the bipolar plates, connecting components for connecting between the unit cells can be omitted. This can reduce the volume and resistance of the all-solid-state battery.

[0201] Since the thickness change of the positive electrode active material layer (120) and the thickness change of the lithium metal layer (230) in the all-solid-state battery according to the present invention are mutually complementary, a separate structure for accommodating the volume change of the all-solid-state battery may not be included. Since the all-solid-state battery not only does not include a separate structure for accommodating the volume change, but also each unit cell is connected in series, the all-solid-state battery of the present invention can have a compact structure and high energy density.

[0202] Referring to FIG. 10 as another embodiment of the present invention, the positive and negative current collectors of the first and second unit cells (10', 10") may be replaced with bipolar plates (50, 60). In this case, the volume of the all-solid-state battery is further reduced, thereby further improving the energy density.

[0203] Referring again to FIGS. 9 and 10, electrode terminals may be provided on one surface of the first and second bipolar plates. In one embodiment, one surface of the first bipolar plate (50) may be in contact with the unit cells, and a positive terminal may be provided on the other surface of the first bipolar plate (50). In this case, one surface of the second bipolar plate (60) may be in contact with the unit cells, and a negative terminal may be provided on the other surface of the second bipolar plate (60).

[0204]

[0205] 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.

[0206]

[0207] Manufacturing Example 1: Manufacturing of Li2S-LiI-AlI3 complex

[0208] Li2S, LiI, and AlI3 were mixed in a weight ratio of 40:4:16. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3 composite. The milling conditions were 25°C, 600 rpm, and 10 h.

[0209] The size of the Li2S-LiI-AlI3 complex was less than 1 μm. The size of the Li2S-LiI-AlI3 complex was calculated by software from scanning electron microscope images of the Li2S-LiI-AlI3 complex powder. The size of the Li2S-LiI-AlI3 complex is the average D50 particle diameter.

[0210] The Mohs hardness of Li2S was 0.6, and that of LiI was 2.0. The Mohs hardness of the Li2S-LiI-AlI3 composite was less than 2.

[0211]

[0212] Manufacturing Example 2: Manufacturing of Li2S-LiI-AlI3-CNF composite

[0213] Li2S and LiI were mixed in a weight ratio of 40:4:16. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3 composite. The milling conditions were 25°C, 510 rpm, and 10 h.

[0214] Li2S-LiI-AlI3 composite and carbon nanofiber (CNF) were mixed at a weight ratio of 60:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3-CNF composite. The milling conditions were 25°C, 510 rpm, and 10 h.

[0215] The manufactured Li2S-LiI-AlI3-CNF composite was used as a composite cathode active material.

[0216]

[0217] Manufacturing Example 3: LiAlCl 2.5 O 0.75 (LACO 75 ) Manufacturing of weapon fillers

[0218] First, LiCl and AlCl3 with a molar ratio of 1:1 were milled and uniformly mixed, then heated to 200°C in a sealed reactor and kept warm for 1 hour. Afterwards, LiAlCl4 was obtained by lowering the reaction system to room temperature. The manufactured LiAlCl4 and Sb2O3 were uniformly mixed with a molar ratio of 4:1, heated to 300°C in an argon protective atmosphere, and kept warm for 2 hours. During this reaction, SbCl3 was volatilized and removed after the reaction because the vaporization point of SbCl3 (223.5°C) was low, and LACO was obtained after cooling. 75 was obtained. The entire experimental process was performed under an inert atmosphere to prevent the reaction raw materials from reacting with air.

[0219]

[0220] (Manufacturing of positive and secondary batteries)

[0221] Example 1

[0222] (Polar electrode manufacturing)

[0223] As a cathode active material, the Li2S-LiI-AlI3-CNF composite manufactured in Manufacturing Example 2 was prepared. As a solid electrolyte, Li6PS5Cl (D50=3.0 um, crystalline), an argyrodite-type crystal, was prepared. LiAlCl was used as an inorganic filler. 2.5 O 0.75 (LACO75) was prepared. PVDF-HFP was prepared as a binder. These materials were mixed in a weight ratio of positive electrode active material: solid electrolyte (SE): binder: inorganic filler = 79:19:1:1 to prepare a composition for forming a positive electrode active material layer.

[0224] The composition for forming the above-mentioned positive electrode active material layer was milled, then dry-coated on one side of a positive electrode current collector made of aluminum foil coated with carbon on one side, and pressed at 1 MPa and 130°C for 10 minutes to manufacture a positive electrode.

[0225] The thickness of the positive electrode was approximately 120 μm, and the loading level of the positive electrode mixture was approximately 8 mg / cm2. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm. The areas of the positive electrode active material layer and the positive electrode current collector were the same.

[0226] (Cathode manufacturing)

[0227] A 10 ㎛ thick SUS foil was prepared as a negative electrode collector. Carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials.

[0228] A mixed powder of 4 g of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of an NMP solution containing 7 wt% of PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum-dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold roll pressed to flatten the surface, thereby preparing a negative electrode having a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0229] (gasket)

[0230] A flame-retardant gasket was manufactured by forming a slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0231] The weight ratio of cellulose fiber, glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder was 20:8:70:2. The thickness of the gasket was 120 ㎛.

[0232] Before placing the manufactured gasket on the solid electrolyte layer, moisture, etc. in the gasket was removed by vacuum heat treatment at 80°C for 5 hours.

[0233] (Manufacturing of all-solid-state secondary batteries)

[0234] A solid electrolyte layer was placed on the cathode, and an anode was placed on the solid electrolyte layer. A unit cell was prepared by placing a gasket surrounding the anode and in contact with the solid electrolyte layer. The gasket was placed so as to contact the side of the anode and the solid electrolyte layer. The anode was placed at the center of the solid electrolyte layer, and the gasket was placed so as to surround the anode and extend to the end of the solid electrolyte layer. The area of ​​the anode was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed over the entire remaining 10% of the area of ​​the solid electrolyte layer where the anode was not placed.

[0235] 85 prepared unit cells o The solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 μm. The density of the Li6PS5Cl solid electrolyte, which was an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc. The area of ​​the solid electrolyte layer was the same as that of the negative electrode.

[0236] A plurality of unit cells were connected in series and stacked. First and second bipolar plates were installed at each end of the stack to manufacture an all-solid-state battery.

[0237]

[0238] Example 2

[0239] An all-solid-state battery was manufactured in the same manner as Example 1, except that the positive electrode active material layer was mixed in a weight ratio of positive electrode active material: solid electrolyte (SE): binder: inorganic filler = 89:9:1:1.

[0240]

[0241] Comparative Example 1

[0242] An all-solid-state battery was manufactured using the same method as Example 1, except that the positive electrode active material layer was mixed in a weight ratio of positive electrode active material: solid electrolyte (SE): binder: inorganic filler = 35:49:1:15.

[0243]

[0244] Evaluation Example 1: Measurement of Unit Cell Thickness

[0245] The thickness of the unit cells manufactured according to Examples 1, 2, and Comparative Example 1 before and after charging was measured and is shown in Table 1 below. The thickness of the unit cells was measured using a jig from MTI (Model name: EQ-PTC-TEM).

[0246]

[0247] Thickness when discharged (㎛) Thickness when charged (㎛) Thickness when charged / Thickness when discharged Example 11201501.25 Example 21201301.17 Comparative example 11202001.67

[0248] Referring to Table 1, it can be confirmed that the unit cells manufactured according to Examples 1 and 2 have a very small ratio of the thickness during charging to the thickness during discharge of 1.3 or less. On the other hand, it can be confirmed that the unit cell manufactured according to Comparative Example 1 has a ratio of the thickness during charging to the thickness during discharge of 1.5 or more. This means that the all-solid-state batteries according to Examples 1 and 2 have a stable structure due to small volume changes during charging and discharging, while the all-solid-state battery according to Comparative Example 1 has a large volume change, making the all-solid-state battery structurally unstable and highly likely to cause a short circuit.

[0249]

[0250] Evaluation Example 2: Pressure measurement of a unit cell

[0251] The internal pressure of the unit cells manufactured according to Examples 1, 2, and Comparative Example 1 was measured and shown in Table 2 below. The internal pressure of the unit cells was measured by adding a pressure sensor to a jig (model name: EQ-PTC-TEM) from MTI.

[0252]

[0253] Pressure at discharge (MPa) Pressure at charge (MPa) Pressure at charge / Pressure at discharge Example 111.51.5 Example 211.21.2 Comparative example 112.52.5

[0254] Referring to Table 2, it can be confirmed that the unit cells manufactured according to Examples 1 and 2 have a very small ratio of the pressure during charging to the pressure during discharging of 1.5 or less. On the other hand, the unit cell manufactured according to Comparative Example 1 has a large pressure difference of 2.5, with a ratio of the pressure during charging to the pressure during discharging. This means that the all-solid-state batteries according to Examples 1 and 2 are structurally stable because the pressure change during charging and discharging is small, while the all-solid-state battery according to Comparative Example 1 has a large pressure change during charging and discharging, so there is a high possibility of a short circuit occurring.

[0255]

[0256] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. A first unit cell connected in series; and a second unit cell, Each of the first and second unit cells: negative current collector; A lithium metal layer on the negative electrode current collector; A cathode coating layer on the lithium metal layer; A solid electrolyte layer on the cathode coating layer; A positive electrode active material layer on the solid electrolyte layer; and Including a positive electrode current collector on the positive electrode active material layer, The above positive electrode active material layer includes a sulfide-based positive electrode active material, The content of the above sulfide-based positive electrode active material is 40 wt% to 90 wt% with respect to 100 parts by weight of the positive electrode active material layer, An all-solid-state battery in which the thickness change of the positive electrode active material layer and the thickness change of the lithium metal layer are mutually complementary.

2. In paragraph 1, Further comprising a coating layer between the positive electrode current collector and the positive electrode active material layer, The above coating layer is an all-solid-state battery including a carbon-based conductive material.

3. In paragraph 1, An all-solid-state battery, wherein the sulfide-based positive electrode active material comprises nickel sulfide, copper sulfide, Li2S, a Li2S-containing complex, or a combination thereof.

4. In paragraph 1, The above sulfide-based positive electrode active material is an all-solid-state battery including Li2S, a lithium salt, and a carbon-based conductive material.

5. In paragraph 1, The above sulfide-based cathode active material is an all-solid-state battery including a solid solution of Li2S, lithium halide, and metal halide.

6. In Article 5, An all-solid-state battery in which the content of the Li2S is 50 wt% to 80 wt% based on 100 parts by weight of the sulfide-based positive electrode active material.

7. In paragraph 1, The first unit cell in a discharged state has a first height, The first unit cell in a charged state has a second height, An all-solid-state battery wherein the ratio of the second height to the first height is 1 to 1.

5.

8. In paragraph 1, The first unit cell in a discharged state has a first internal pressure, The first unit cell in a charged state has a second internal pressure, An all-solid-state battery wherein the ratio of the second internal pressure to the first internal pressure is 1.2 to 1.

8.

9. In paragraph 1, The negative active material layer has a first area, and the positive active material layer has a second area. An all-solid-state battery wherein the first area is larger than the second area.

10. In paragraph 9, An all-solid-state battery further comprising an inert member arranged to surround a side surface of the positive electrode active material layer.

11. In paragraph 1, An all-solid-state battery wherein the positive electrode current collector and the negative electrode current collector are substantially the same.

12. In paragraph 1, An all-solid-state battery in which the first unit cell and the second unit cell are sequentially stacked to form a stack.

13. In paragraph 12, a first bipolar plate provided at one end of the laminate; and Further comprising a second bipolar plate provided at the other end of the laminate, The above first and second bipolar plates are an all-solid-state battery that sandwiches the stacked first and second unit cells.

14. In paragraph 1, The first unit cell and the second unit cell are arranged side-by-side to form a parallel body, An all-solid-state battery in which the second unit cell is arranged inverted with respect to the first unit cell.

15. In paragraph 14, a first bipolar plate on the above parallel body; and Further comprising a second bipolar plate below the above parallel body, An all-solid-state battery wherein the first and second bipolar plates sandwich the first and second unit cells.

16. In paragraph 1, An all-solid-state battery, wherein the cathode coating layer comprises at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene.

17. A first unit cell connected in series; and a second unit cell, Each of the first and second unit cells: negative current collector; A cathode coating layer on the above cathode current collector; A solid electrolyte layer on the cathode coating layer; A positive electrode active material layer on the solid electrolyte layer; and Including a positive electrode current collector on the positive electrode active material layer, The above positive electrode active material layer includes a sulfide-based positive electrode active material, The first unit cell in a discharged state has a first height, The first unit cell in a charged state has a second height, An all-solid-state battery wherein the ratio of the second height to the first height is 1 to 1.

5.

18. In paragraph 17, The above sulfide-based positive electrode active material is an all-solid-state battery including Li2S, a lithium salt, and a carbon-based conductive material.

19. A first unit cell connected in series; and a second unit cell, Each of the first and second unit cells: negative current collector; A cathode coating layer on the above cathode current collector; A solid electrolyte layer on the cathode coating layer; A positive electrode active material layer on the solid electrolyte layer; and Including a positive electrode current collector on the positive electrode active material layer, The above positive electrode active material layer includes a sulfide-based positive electrode active material, The first unit cell in a charged state has a first internal pressure, The first unit cell in a discharged state has a second internal pressure, An all-solid-state battery wherein the ratio of the first internal pressure to the second internal pressure is 1.2 to 1.

8.

20. In paragraph 19, An all-solid-state battery, wherein the above sulfide-based positive electrode active material comprises Li2S, a lithium salt, a metal halide, and a carbon-based conductive material.

Images