Negative electrode for all-solid-state battery and all-solid-state battery comprising same

Abstract

The present invention relates to an all-solid-state battery. More specifically, the all-solid-state battery comprises: a positive electrode; a negative electrode comprising a negative electrode current collector and a coating layer on the negative electrode current collector; and a solid electrolyte layer that is between the positive electrode and the negative electrode, wherein the coating layer may comprise carbon-based particles and metal-based particles. The metal-based particles may comprise: a lithiophilic metal; an alloy of the lithiophilic metal and lithium; and a sulfide of the lithiophilic metal.

Description

Negative electrode for an all-solid-state battery, and an all-solid-state battery including the same

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

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

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

[0004] The problem that the present invention aims to solve is to improve the initial efficiency and capacity of all-solid-state batteries.

[0005] Another problem that the present invention aims to solve is to improve the rate characteristics and life characteristics of all-solid-state batteries.

[0006] A solid-state battery according to the concept of the present invention comprises: a positive electrode; a negative electrode current collector; and a negative electrode including a coating layer on the negative electrode current collector; and a solid electrolyte layer between the positive electrode and the negative electrode, wherein the coating layer may include carbon-based particles and metal-based particles. The metal-based particles may include a lithium-affinity metal, an alloy of the lithium-affinity metal and lithium, and a sulfide of the lithium-affinity metal.

[0007] A method for manufacturing an all-solid-state battery according to another concept of the present invention may include preparing a negative electrode, wherein the negative electrode comprises a negative electrode current collector and a coating layer on the negative electrode current collector; and pre-lithiating the coating layer through a lithium source. The coating layer comprises carbon-based particles and metal-based particles, and the metal-based particles may comprise a lithium-affinity metal. Pre-lithiating the coating layer may include forming an alloy between the lithium-affinity metal and lithium within the metal-based particles; and forming a sulfide of the lithium-affinity metal within the metal-based particles.

[0008] According to an embodiment of the present invention, the initial efficiency and capacity of an all-solid-state battery can be improved. In addition, the rate characteristics and life characteristics of an all-solid-state battery can be improved.

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

[0010] FIG. 2 shows an all-solid-state battery according to one embodiment of the present invention, and is a cross-sectional view along line A-A' of FIG. 1.

[0011] FIG. 3 shows an all-solid-state battery according to one embodiment of the present invention, and is a cross-sectional view along line A-A' of FIG. 1.

[0012] FIG. 4 shows a coating layer according to one embodiment of the present invention, which is an enlarged view of the M region of FIG. 2.

[0013] FIG. 5 shows a coating layer according to one embodiment of the present invention, which is an enlarged view of the M region of FIG. 2.

[0014] FIGS. 6 to 8 illustrate a method for manufacturing an all-solid-state battery according to an embodiment of the present invention.

[0015]

[0016] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0017] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0018] The embodiments described herein will be described with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0019] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components to the mentioned components.

[0020] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0021] In this specification, each of the phrases such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0022] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) may be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0023] In one embodiment, the average particle size in this specification may refer to the diameter measured by randomly selecting about 100 particles from an electron microscope image. Alternatively, the average particle size in this specification may refer to the diameter of a particle that has a cumulative volume of 50% in the particle size distribution, which can be measured by a particle size analyzer.

[0024]

[0025] FIG. 1 is a plan view of an all-solid-state battery according to embodiments of the present invention. FIG. 2 is a cross-sectional view along line A-A' of FIG. 1. Referring to FIG. 1 and FIG. 2, an all-solid-state battery according to the present invention may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, not limited thereto, the all-solid-state battery 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).

[0026] An anode layer (100) according to one embodiment of the present invention may include an anode current collector (110) and an anode active material layer (120) disposed on the anode current collector (110). The anode active material layer (120) may include an anode active material, a solid electrolyte, a conductive material, and a binder.

[0027] The positive current collector (110) can provide a reference surface on which the positive active material layer (120) is placed. The positive current collector (110) may include, for example, a plate or foil comprising 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.

[0028] Meanwhile, unlike as illustrated in FIG. 1, the positive current collector (110) may be omitted in one embodiment of the present invention. Although not illustrated, a carbon layer with a thickness of 0.1 μm to 4 μm may be further disposed between the positive current collector (110) and the positive active material layer (120) to increase the bonding strength between the positive current collector (110) and the positive active material layer (120).

[0029] The positive active material of the positive active material layer (120) may include a material capable of reversibly absorbing and desorbing lithium ions. The positive active material may include a plurality of particles. The positive active material may include, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide (Lithi㎛ nickel oxide), lithium nickel cobalt oxide (Lithi㎛ nickel cobalt oxide), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide (Lithi㎛ manganate), and lithium iron phosphate (Lithi㎛ iron phosphate), nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide (Vanad㎛ oxide), but is not necessarily limited to these. Each positive active material may be a single material or a mixture of two or more materials.

[0030] Lithium transition metal oxides are, for example, Li a A 1-b B b D2(0.90≤a≤1, 0≤b≤0.5), Li a E 1-b B b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05), LiE 2-b B b O 4-c D c (0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (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 (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Mnb B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Nor 1-b-c Mn b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Nor b E c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Nor b Co c Mn d GeO2(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(0.9≤a≤1, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a MnG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-fIt is a compound represented by any one of Fe2(PO4)3 (0≤f≤2) or LiFePO4. In such compounds, the uppercase “A” is Ni, Co, Mn, or a combination thereof; the uppercase “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; the uppercase “D” is O, F, S, P, or a combination thereof; the uppercase “E” is Co, Mn, or a combination thereof; the uppercase “F” is F, S, P, or a combination thereof; the uppercase “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; the uppercase “Q” is Ti, Mo, Mn, or a combination thereof; the uppercase “I” is Cr, V, Fe, Sc, Y, or a combination thereof; and the uppercase “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0031] The positive electrode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen and metal atomic layers are alternately and regularly arranged in a specific direction, thereby forming a two-dimensional plane for each atomic layer. The "cubic rock salt type structure" represents a sodium chloride (NaCl) type structure, which is a type of crystal structure; specifically, it exhibits a structure in which face-centered cubic lattices (fcc) formed by cations and anions, respectively, are offset from each other by half the ridge of the unit lattice. Lithium transition metal oxides having such a layered rock salt type structure are, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0032] The aforementioned compound contained in the positive electrode active material may be covered by a coating layer (not shown). The positive electrode active material may also be a mixture of the aforementioned compound and the compound to which the coating layer is added. Meanwhile, the coating layer added to the surface of the positive electrode active material may include, for example, oxides, hydroxides, oxyhydroxides, oxycarbonates, or hydroxycarbonates of the following coating elements. The compounds forming this coating layer are amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The method for forming the coating layer is, for example, spray coating or immersion.

[0033] When the cathode active material is a ternary lithium transition metal oxide, such as NCA or NCM, containing nickel (Ni), it is possible to increase the capacity density of the all-solid-state battery and reduce metal leaching from the cathode active material during charging. Consequently, the cycle characteristics of the all-solid-state battery during charging are improved. Meanwhile, "cycle characteristics" refers to the degree of degradation of an all-solid-state battery due to charging and discharging; all-solid-state batteries with high cycle characteristics degrade less due to charging and discharging, while those with low cycle characteristics degrade more significantly.

[0034] The positive active material may have particle shapes such as, for example, spheres or ellipsoids. The particle size and content of the positive active material are not particularly limited.

[0035] The cathode active material layer according to embodiments of the present invention may include a sulfide-based cathode active material. Specifically, the sulfide-based cathode active material may include a Li2S-containing cathode active material. The Li2S-containing cathode active material may include, for example, a composite of Li2S and carbon, a composite of Li2S, carbon, and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S and a lithium salt, a composite of Li2S, a lithium salt, and carbon, a composite of Li2S, a lithium salt, a metal halide, and carbon, a composite of Li2S and a metal carbide, a composite of Li2S, carbon, and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S, carbon, and a metal nitride, or a combination thereof.

[0036] The positive electrode active material may include a sulfide-based composite and a conductive material. In one embodiment, the sulfide-based composite may have a particle shape such as a perfect spherical or elliptical sphere. The particle size of the sulfide-based composite is not particularly limited and may be within a range applicable to general positive electrode active materials. The size of the sulfide-based composite 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 may cover the surface of the sulfide-based composite.

[0037] The conductive material may include carbon. The conductive material may include, without limitation, materials containing carbon atoms that are used as conductive materials in the relevant art. For example, the conductive material may include crystalline carbon, amorphous carbon, or a combination thereof. The conductive material may include, for example, a sintered product of a carbon precursor. The conductive material may include, for example, carbon nanostructures.

[0038] The conductive material may include, for example, porous carbon or non-porous carbon. Porous carbon may include, for example, periodic and regular two-dimensional or three-dimensional pores. Porous carbon may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black; graphite, activated carbon, or a combination thereof. The form of carbon within the conductive material may be, for example, particle form, sheet form, fibrous form, etc., but is not limited thereto and may be any form of carbon used in the relevant technical field.

[0039] In one embodiment of the present invention, the conductive material may include a fibrous carbon-based material. By including a fibrous carbon-based material in the conductive material, the electron conductivity of the positive electrode active material can be further improved. By including a fibrous carbon-based material in the conductive material, electron conduction from the surface to the interior of the positive electrode active material can be performed more easily. The internal resistance of the sulfide-based composite is reduced by the conductive material, and the cycle characteristics of the secondary battery can be further improved.

[0040] The aspect ratio of the fibrous carbon-based material may be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. By having an aspect ratio within this range, the overall electron conductivity of the positive active material is improved, and the imbalance of local electron conductivity within the positive active material can be further alleviated.

[0041] Fibrous carbon-based materials may include, for example, carbon nanostructures. Carbon nanostructures may include, for example, carbon nanofibers (CNF), carbon nanotubes (CNT), carbon nanobelts, carbon nanorods, or combinations thereof. Carbon nanostructures may form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure formed by the aggregation of multiple carbon nanostructures.

[0042] The diameter of the primary carbon nanostructure may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure may be, for example, 10 nm to 2 µm, 10 nm to 1.5 µm, 10 nm to 1 µm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure may be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure may be measured by laser diffraction.

[0043] The secondary carbon nanostructure may be a structure formed by assembling primary carbon nanostructures, for example, to form a bundle or rope type, either wholly or partially. The secondary carbon nanostructure may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or a combination thereof. The diameter of the secondary carbon nanostructure may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length of the secondary carbon nanotube structure may be, for example, 20 nm to 2 µm, 30 nm to 1.5 µm, 50 nm to 1 µm, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured from scanning electron microscope (SEM) images or optical microscopes. Alternatively, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be converted into a primary carbon nanostructure by dispersing it in a solvent, for example, and then used to manufacture a positive electrode active material.

[0044] The method for manufacturing the positive electrode active material according to the embodiments may be a dry method, a wet method, or a combination thereof, but is not limited thereto. In the art, the method for manufacturing the positive electrode active material may be, for example, milling, heat treatment, deposition, etc., but is not necessarily limited thereto, and any method used in the art may be possible.

[0045] In one embodiment of the present invention, the sulfide-based composite within the cathode active material may comprise a composite of Li2S and a solid electrolyte. The solid electrolyte may be, for example, an amorphous solid electrolyte, any material used as an ion-conducting material in the art. The solid electrolyte may be, for example, an inorganic solid electrolyte. The solid electrolyte may be, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte may be, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte may include, for example, Li, S, and P, and may optionally further include a halogen element. The sulfide-based solid electrolyte may be selected from among sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte may be, for example, 1×10⁻⁶ at room temperature. -5 It can have an ionic conductivity of S / cm or higher. Sulfide-based solid electrolytes are, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS6-x I x It may include one or more selected from , 0≤x≤2.

[0046] Oxide-based solid electrolytes contain, for example, Li, O, and transition metal elements, and may optionally contain other elements. Oxide-based solid electrolytes contain, for example, 1×10⁻⁶ at room temperature. -5 The solid electrolyte may have an ionic conductivity of S / cm or higher. The oxide-based solid electrolyte may be selected from among oxide-based solid electrolytes used in the solid electrolyte layer. The solid electrolyte may be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, it may be a mixture of Li3PO4-Li2SO4 and a binary lithium salt or a mixture of Li3PO4-Li2SO4 and a ternary lithium salt.

[0047] In one embodiment of the present invention, the sulfide-based complex in the cathode active material may include a complex of Li2S and a lithium salt. In other words, the complex may include a Li2S and a lithium salt compound. The lithium salt compound may not include, for example, sulfur (S) atoms.

[0048] The lithium salt compound may be a binary compound composed of, for example, lithium and one element selected from groups 13 to 17 of the periodic table. The binary compound may include, for example, one or more selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3. The lithium salt compound may be a ternary compound composed of, for example, lithium and two elements selected from groups 13 to 17 of the periodic table. The ternary compound may include, for example, one or more selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. For example, the lithium salt compound may be one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI.

[0049] In one embodiment of the present invention, the sulfide-based composite may comprise 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 is, for example, M n+1 C n T x It can be expressed as (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups). Two-dimensional metal carbides are, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5 )3C2Tx , Ti3CNT x , Ta4C3T x , Nb4C3T x Or it may be a combination of these. The surface of the two-dimensional metal carbide may be terminated with O, OH and / or F.

[0050] In one embodiment of the present invention, the sulfide-based complex may include a complex of Li2S and a metal nitride. The metal nitride may be, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x It can be expressed as (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups). The surface of a two-dimensional metal nitride can be terminated with O, OH and / or F.

[0051] A cathode active material and a composite containing Li2S according to one embodiment of the present invention will be described in more detail. The cathode active material may comprise a composite of Li2S, a lithium salt, and carbon. More specifically, the cathode active material may comprise a composite of Li2S, a lithium halide, and carbon.

[0052] The composite according to the embodiments may have ductility. The composite may function as a buffer material within the positive active material layer (120). The composite may prevent the occurrence of defects due to volume changes in the positive active material layer (120).

[0053] A composite according to one embodiment is Li2S-Li a X bIt may include a compound represented by (1≤a≤5, 1≤b≤5). X may be I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof. a may be, for example, 1, 2, 3, 4, or 5. b may be, for example, 1, 2, 3, 4, or 5.

[0054] In one embodiment, the composite may include a solid solution of Li2S and a lithium salt. By including the solid solution of Li2S and a lithium salt, the ionic conductivity of the composite may be improved. For example, by including lithium ions disposed within the Li2S crystallites in the solid solution of Li2S and a lithium salt, 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 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 of the present invention may be improved.

[0055] The size of the Li2S crystallites of the composite obtained from the XRD spectrum may be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of the Li2S crystallites of the composite 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 Li2S and lithium salt composite may be improved.

[0056] A composite according to one embodiment may further include a metal halide. In other words, the composite may include a composite of Li2S, a lithium salt, and a metal halide. The metal halide may contain a metal other than lithium.

[0057] The complex is Li2S-Li a X1 b -MX2 c It may include a compound represented by . a may be an integer between 1 and 5, b may be an integer between 1 and 5, and c may be an integer between 1 and 5. M may be selected from the group consisting of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), bismuth (Bi), tin (Sn), and zinc (Zn). X1 and X2 may each be selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0058] The composite may include a solid solution of Li2S, a lithium salt, and a metal halide. As an example, the composite may include a compound (or solid solution) represented as Li2S-LiI-AlI3. As described above, the composite and a conductive material (e.g., a carbon nanostructure) may constitute a positive electrode active material according to the present invention.

[0059] The Mohs hardness of the composite may be lower than that of the lithium salt. The composite may have improved ductility compared to the lithium salt. By having improved ductility, internal defects caused by volume changes in the positive active material layer (120) can be effectively prevented.

[0060] The Mohs hardness of Li2S is, for example, 0.6. The Mohs hardness of the composite may be, for example, less than 2, 1.5 or less, 1 or less, or 0.7 or less. If the Mohs hardness of the composite increases excessively, it may be difficult to provide ductility.

[0061] The Mohs hardness of the lithium salt may be 0.7 or higher, 0.8 or higher, 0.9 or higher, 1.0 or higher, 1.5 or higher, or 2.0 or higher. For example, the Mohs hardness of LiI is 2.0. Since the lithium salt has a Mohs hardness in this range, the grinding of Li2S can be performed more easily during the milling process, and a solid solution of Li2S and the lithium salt can be formed more easily.

[0062] Since Li2S has relatively low ionic conductivity, a composite of Li2S and a lithium salt can be formed to improve ionic conductivity. The composite, which is a combination of Li2S and a lithium salt, can have improved ionic conductivity compared to Li2S alone. The content of Li2S in the composite 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 composite. By having a Li2S content within this range, the composite can simultaneously possess improved ionic conductivity and excellent ductility.

[0063] The content of the lithium salt in the composite 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. By having a lithium salt content within this range, the composite can simultaneously have improved ionic conductivity and excellent ductility.

[0064] The content of metal halides in the composite may be 5 wt% to 30 wt% or 5 wt% to 20 wt% of the total weight of the composite (CAM). By having a metal halide content within this range, the composite can simultaneously have enhanced ionic conductivity and excellent ductility.

[0065] In one embodiment, the content of Li2S in the composite may be greater than the content of the lithium salt. The content of Li2S in the composite may be greater than the content of the metal halide. For example, the molar ratio of Li2S to the lithium salt in the composite may be 51:49 to 95:5, 55:45 to 90:10, 60:40 to 90:10, or 70:30 to 90:10. By having such molar ratios, the composite can simultaneously possess enhanced ionic conductivity and excellent ductility.

[0066] The ionic conductivity of the composite according to the embodiments of the present invention is, for example, 1×10⁻⁶ at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4 It may be greater than S / cm. For example, ionic conductivity can be measured using electrochemical impedance spectrometry, DC polarization method, etc. As the composite has ionic conductivity in this range, the internal resistance of the positive active material layer (120) containing the composite can be further reduced.

[0067] The average particle size (D50) of the composite may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The average particle size of the composite may be, for example, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, or 0.1 μm to 1 μm.

[0068] The size of the Li2S particles in the composite 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.

[0069]

[0070] The solid electrolyte of the positive active material layer (120) may have a particle shape. The solid electrolyte may be dispersed among the positive active materials. The solid electrolyte may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. Sulfide-based solid electrolytes are, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers, uppercase “Z” is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, uppercase “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), or Li 7-x PS 6-x I x It may include at least one of (0≤x≤2).

[0071] Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), or Li 7-x PS 6-x I xIt may be an argyrodite-type compound comprising at least one of (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising at least one of Li6PS5Cl, Li6PS5Br, or Li6PS5I.

[0072] Alternatively, sulfide-based solid electrolytes are Li 7-a M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, 0≤c≤2). Here, X may be F, Br, Cl, I, or a combination thereof. M may be candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof.

[0073] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the azyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0074] The solid electrolyte in the positive active material layer (120) may have a smaller average particle size compared to the first and second solid electrolytes in the solid electrolyte layer (300) described later. For example, the average particle size of the solid electrolyte in the positive active material layer (120) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average particle size of the solid electrolyte in the solid electrolyte layer (300). Meanwhile, the average particle size may be the median diameter measured using a laser particle size distribution meter.

[0075] The positive active material layer (120) may include a conductive material. The conductive material may have conductivity without causing chemical changes in the all-solid-state battery, thereby increasing the conductivity of the positive active material and the solid electrolyte. The conductive material may include a carbon-based material. The conductive material may include, for example, at least one of graphite, carbon black, acetylene black, carbon nanofiber, or carbon nanotube.

[0076] The positive active material layer (120) may further include a binder. The binder may bind the positive active material, solid electrolyte, and conductive material within the positive active material layer (120) together. The binder may include a material to improve the bonding strength between the positive active material layer (120) and the positive current collector (110). The binder may include, for example, at least one of polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, or polymethyl methacrylate.

[0077] In one embodiment, the content of the positive active material in the positive active material layer (120) may be 40% to 90% by weight, 50% to 90% by weight, or 60% to 90% by weight of the total weight of the positive active material layer (120). Among the components in the positive active material layer (120), the positive active material may have the largest content.

[0078] The content of the solid electrolyte in the positive active material layer (120) may be 10% to 70% by weight, 10% to 60% by weight, or 10% to 40% by weight of the total weight of the positive active material layer (120).

[0079] The content of the binder in the positive active material layer (120) may be, for example, 0.1% to 10% by weight, 0.5% to 5% by weight, or 0.5% to 2% by weight of the total weight of the positive active material layer (120).

[0080] The content of the conductive material in the positive active material layer (120) may be, for example, 1% to 30% by weight, 1% to 20% by weight, or 1% to 10% by weight of the total weight of the positive active material layer (120).

[0081] The positive active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductivity aids in addition to the positive active material, solid electrolyte, conductive material, and binder described above.

[0082] The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the negative electrode coating layer (220) is placed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, that is, does not form any alloys or compounds with lithium. For example, the negative electrode current collector (210) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (210) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0083] The negative current collector (210) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (210) may, for example, have a plate-like or foil-like shape. Meanwhile, in one embodiment, the negative current collector (210) may be omitted.

[0084] Although not illustrated, a negative current collector (210) according to one embodiment may include a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. By including an insulating thermoplastic polymer in the base film, the base film may soften or liquefy upon a short circuit, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative current collector (210) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode current collector (210), refer to the positive electrode current collector (110) described above. By having the negative electrode current collector (210) have this structure, the weight of the negative electrode layer (200) can be reduced, and consequently, the energy density of the all-solid-state battery (10) can be improved.

[0085] The negative electrode coating layer (220) can be configured to allow lithium metal to grow between the all-solid-state battery (10) and the negative electrode current collector (210) during charging. The negative electrode coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0086] The negative electrode coating layer (220) may have a smaller thickness compared to the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 1 µm to 20 µm, 2 µm to 10 µm, or 3 µm to 7 µm. If the thickness of the negative electrode coating layer (220) is excessively thin, lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210) may cause the negative electrode coating layer (220) to collapse, thereby degrading the cycle characteristics of the all-solid-state battery (10). If the thickness of the negative electrode coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) decreases, and the internal resistance of the all-solid-state battery (10) due to the negative electrode coating layer (220) increases, which may degrade the cycle characteristics of the cell.

[0087]

[0088] A solid electrolyte layer (300) may be provided between the anode layer (100) and the cathode layer (200). The solid electrolyte layer (300) may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. The solid electrolyte in the solid electrolyte layer (300) may be the same as or different from any one of the materials included in the solid electrolyte in the aforementioned anode active material layer (120).

[0089] The solid electrolyte layer (300) may include a first solid electrolyte layer (310) and a second solid electrolyte layer (320). The first solid electrolyte layer (310) may be adjacent to the anode layer (100), and the second solid electrolyte layer (320) may be adjacent to the cathode layer (200).

[0090] Referring to FIG. 2, the first solid electrolyte layer (310) may include a first solid electrolyte. The first solid electrolyte may have a particle shape such as a sphere or an ellipsoid. The first solid electrolyte may include a sulfide-based solid electrolyte. The first solid electrolyte may be amorphous, crystalline, or a mixture thereof. Additionally, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above, for example. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form the solid electrolyte, the molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 50 : 50 to 90 : 10.

[0091] In one embodiment, the first solid electrolyte is Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), or Li 7-x PS 6-x I x It may include an argyrodite-type compound comprising at least one of (0≤x≤2). The first solid electrolyte may include an argyrodite-type compound comprising at least one of Li6PS5Cl, Li6PS5Br, or Li6PS5I.

[0092] In another embodiment, the first solid electrolyte is Li 7-a-c M a PS 6-c X cIt may include an argyrodite-type compound comprising. Here, X may be Cl, Br, or a combination thereof. M may be Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, or a combination thereof. a and c may each be real numbers between 0 and 2.

[0093] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the azyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the first solid electrolyte is, for example, 15 GPa to 35 GPa.

[0094] The first solid electrolyte layer (310) may further include a binder. The binder included in the solid electrolyte layer (300) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these. The binder of the first solid electrolyte layer (310) may be the same as or different from the binder included in the positive active material layer (120) or the binder included in the coating layer (220).

[0095] 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.

[0096] The second solid electrolyte may include a sulfide-based solid electrolyte. The description of the second solid electrolyte may be the same or similar as that described above for the first solid electrolyte. In one embodiment, the second solid electrolyte may have substantially the same composition as the first solid electrolyte. In another embodiment, the second solid electrolyte may have a composition similar to that of the first solid electrolyte.

[0097] The second solid electrolyte can come into direct contact with the coating layer (220). By doing so, the second solid electrolyte can suppress lithium dendrites formed between the coating layer (220) and the negative electrode current collector (210). The second solid electrolyte can effectively suppress negative electrode side reactions. This can improve the cell performance of the all-solid-state battery according to the present invention.

[0098] Referring again to FIGS. 1 and FIGS. 2, the anode layer (100) and the first solid electrolyte layer (310) can form an anode composite layer (CSH). The cathode layer (200) and the second solid electrolyte layer (320) can form a cathode composite layer (ASH). An anode composite layer (CSH) can be laminated on the cathode composite layer (ASH).

[0099] The area of ​​the cathode composite layer (ASH) and the area of ​​the anode composite layer (CSH) may differ from each other. Specifically, the area of ​​the cathode composite layer (ASH) may be larger than the area of ​​the anode composite layer (CSH). The anode composite layer (CSH) may completely overlap within the cathode composite layer (ASH).

[0100] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the anode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the cathode layer (200).

[0101] Specifically, the positive electrode composite layer (CSH) may have a first width (WI1) in a first direction (D1). The negative electrode composite layer (ASH) may have a second width (WI2) in a first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The positive electrode composite layer (CSH) may have a third width (WI3) in a second direction (D2). The negative electrode composite layer (ASH) may have a fourth width (WI4) in a second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0102] The 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 and forming an 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).

[0103] The all-solid-state battery according to the present embodiment may further include a gasket (GSK). The gasket (GSK) may be provided to surround the positive composite layer (CSH). The gasket (GSK) may fill the step on the side of the all-solid-state battery caused by the difference in area between the negative composite layer (ASH) and the positive composite layer (CSH). The gasket (GSK) may surround the four sides of the positive composite layer (CSH). For example, the thickness of the gasket (GSK) may be substantially the same as or smaller than the thickness of the positive composite layer (CSH). In one embodiment, the positive current collector (110) may be provided at a position higher than the gasket (GSK).

[0104] FIG. 3 is a cross-sectional view along line A-A' of FIG. 1, illustrating an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 3, the negative electrode layer (200) of the all-solid-state battery may further include a lithium metal layer (230) between the negative electrode current collector (210) and the coating layer (220). The thickness of the lithium metal layer (230) may increase further during charging of the all-solid-state battery. The coating layer (220) serves as a protective layer for the lithium metal layer (230) and, at the same time, can suppress the growth of lithium dendrites from the lithium metal layer (230).

[0105] The lithium metal layer (230) may be a thin metal film containing lithium or a lithium alloy. The lithium alloy is not limited to, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., and any alloy used as a lithium alloy is possible. The lithium metal layer (230) may contain one of these alloys or lithium. Alternatively, the lithium metal layer (230) may contain various types of alloys.

[0106] The lithium metal layer (230) can serve as a negative electrode active material layer. That is, the negative electrode according to an embodiment of the present invention may use lithium or a lithium alloy as the negative electrode active material. The negative electrode active material may form the lithium metal layer (230) or exist in a dispersed form within the coating layer (220). The negative electrode active material may exist within the lithium metal layer or the coating layer.

[0107]

[0108] Hereinafter, detailed descriptions of technical features that overlap with those previously described with reference to FIGS. 1 to 3 will be omitted, and embodiments of the present invention will be described in more detail.

[0109] FIG. 4 is an enlarged view of the M region of FIG. 2, showing a coating layer (220) according to one embodiment of the present invention. Referring to FIG. 4, the coating layer (220) is located on the negative current collector (210) and can come into contact with the second solid electrolyte layer (320).

[0110] The coating layer (220) may include a carbon-based material (CCM) and a first metal particle (MTP). The coating layer (220) may include pores (POR) between the carbon-based material (CCM) and the first metal particle (MTP). In one embodiment, the carbon-based material (CCM) may have a particle shape. The average particle size (D50) of the carbon-based material (CCM) may be 100 nm to 10 µm. For example, the average particle size (D50) of the carbon-based material (CCM) may be 100 nm or more, 300 nm or more, 500 nm or more, or 1 µm. For example, the average particle size (D50) of the carbon-based material (CCM) may be 10 µm or less, 7 µm or less, 5 µm or less, 3 µm or less, or 2 µm or less.

[0111] If the average particle size (D50) of the carbon-based material (CCM) satisfies the range described above, the volume change of the all-solid-state battery during charging and discharging can be minimized, and an all-solid-state battery with a long lifespan can be provided.

[0112] In one embodiment, the carbonaceous material (CCM) may have a porous structure. For example, the BET specific surface area of ​​the carbonaceous material (CCM) is 5 m² 2 / g to 1000m 2 It can be / g. For example, the BET specific surface area of ​​a carbonaceous material (CCM) is 5m² 2 / g or more, 10m 2 / g or more, 20m 2 / g or more, 30m 2 / g or more, 40m 2 / g or more, 50m 2 / g or more, 60m 2 / g or more, 100m 2 / g or more, 200m 2 / g or more, 300m 2 / g or more, or 400m 2 It can be greater than / g. For example, the BET specific surface area of ​​a carbonaceous material (CCM) is 1000 m² 2 / g or less, 900m 2 / g or less, 800m 2 / g or less, 700m 2 / g or less, 600m 2 / g or less, 500m 2 / g or less, 400m 2 / g or less, 300m 2 / g or less, 200m 2 / g or less, 100m 2 / g or less, 90m 2 / g or less, 80m 2 / g or less, or 70m 2 It may be less than / g.

[0113] If the BET specific surface area of ​​the carbon-based material (CCM) satisfies the range described above, the volume change of the all-solid-state battery during charging and discharging can be minimized, and an all-solid-state battery with a long lifespan can be provided.

[0114] For example, a carbon-based material (CCM) may include at least one of non-graphitizable carbons (hard carbon) or graphitizable carbons (soft carbons). For example, the carbon-based material (CCM) may include non-graphitizable carbons (hard carbon).

[0115] For example, a carbon-based material (CCM) may include at least one selected from the group consisting of carbon black, carbon nanotubes, acetylene black, furnace black, Kettjen black, and graphene. However, the carbon-based material (CCM) is not limited to the examples described above.

[0116] The shape of the carbonaceous material (CCM) may be at least one of spherical, elliptical, plate-like, or a combination thereof. However, the shape of the carbonaceous material (CCM) is not limited to the examples described above.

[0117] The coating layer (220) may include a plurality of first metal particles (MTP1). The first metal particles (MTP1) can help lithium ions move toward the negative electrode current collector (210) during charging and discharging of the all-solid-state battery.

[0118] The first metal particle (MTP1) may include at least one selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), magnesium (Mg), titanium (Ti), gallium (Ga), zinc oxide (ZnO), germanium (Ge), lead (Pb), antimony (Sb), and indium (In). For example, the metal particle (MTP) may include at least one of silver (Ag), magnesium (Mg), bismuth (Bi), gold (Au), platinum (Pt), zinc (Zn), or a combination thereof.

[0119] The first metal-based particle (MTP1) according to the embodiments of the present invention may include a lithium-affinity metal. The characteristics of the lithium-affinity metal can be represented by Equation 1 below.

[0120] [Equation 1]

[0121] △G=△H 523.15K -T△S 523.15K ≤ 0

[0122] In other words, the Gibbs free energy (△G) of the chemical reaction of a lithium-affinity metal with molten lithium at 250°C may be 0 kJ / mol or less. For example, the Gibbs free energy (△G) of the chemical reaction of a lithium-affinity metal with molten lithium at 250°C may be -1500 kJ / mol to 0 kJ / mol. Under the above conditions, the lithium-affinity metal may spontaneously form an alloy with lithium.

[0123] The first metal-based particle (MTP1) according to an embodiment of the present invention may be a nanoparticle. The first metal-based particle (MTP1) may include at least one of a single particle or an aggregate. For example, single particles may aggregate to form a single particle shape, which can be defined as an aggregate. The aggregate may have a shape in which 10 or fewer single particles are aggregated. In other words, the size of the aggregate may have a nano size similar to that of the single particle.

[0124] The average particle size of the first metal-based particle (MTP1) may be 5 nm to 300 nm. For example, the average particle size of the first metal-based particle (MTP1) may be 5 nm or more, or 10 nm or more. For example, the average particle size of the first metal-based particle (MTP1) may be 300 nm or less, 200 nm or less, or 100 nm or less. If the average particle size of the first metal-based particle (MTP1) satisfies the range described above, lithium ions can easily move toward the negative electrode current collector (210) during charging and discharging of the all-solid-state battery.

[0125] According to embodiments of the present invention, the average particle size of the first metal particles (MTP1) may be relatively small. The average particle size of the first metal particles (MTP1) may refer to the average size of the first metal particles (MTP1), i.e., single particles and aggregates, present in the coating layer (220). The average particle size may be defined as the average length of the major and minor axes measured by randomly selecting 100 first metal particles (MTP1) in the coating layer (220) in an electron microscope image. This average particle size may be calculated as a geometric average or an arithmetic average.

[0126] The content of the first metal-based particles (MTP1) in the coating layer (220) may be 1% to 50% by weight relative to the total weight of the coating layer (220). For example, the content of the first metal-based particles (MTP1) may be 3% or more by weight, 5% or more by weight, or 10% or more by weight relative to the total weight of the coating layer (220). For example, the content of the first metal-based particles (MTP1) may be 50% or less by weight, 40% or less by weight, 30% or less by weight, 25% or less by weight, 20% or less by weight, or 15% or less by weight relative to the total weight of the coating layer (220). If the content of the first metal-based particles (MTP1) satisfies the range described above, lithium ions can easily move toward the negative electrode current collector (210) during charging and discharging of the all-solid-state battery.

[0127] As described above, the all-solid-state battery according to the embodiment of the present invention may not include a separate lithium-containing negative electrode active material on the negative electrode current collector (210) during manufacturing. An all-solid-state battery of the initial form may include a lithium-free negative electrode in which lithium is not present, as shown in FIG. 4. The negative electrode layer (200) may include a coating layer (220) and may include an additional lithium metal layer formed after the formation process.

[0128] By not including the initial negative electrode active material in the negative electrode layer (200), the energy density per unit volume of the all-solid-state battery can be improved. However, since the negative electrode does not contain lithium separately, the lithium released from the positive electrode is irreversibly consumed, which may reduce the initial efficiency and capacity.

[0129] Accordingly, the cathode (200) according to an embodiment of the present invention aims to solve the above problem by pre-lithiating the coating layer (220). Pre-lithiation can be performed by chemical, electrochemical, or physical methods using a lithium source (Li-source). The lithium source may include lithium metal, lithium salt, lithium-containing organic compound, or lithium-containing inorganic compound, but is not limited to any other source that contains lithium and can lithiate the cathode.

[0130] For example, prelithiation can be performed in a manner such as applying lithium powder to the cathode surface, reacting the cathode with a lithium-containing compound, electrically connecting lithium metal after contact, pressing a lithium metal thin film onto the cathode, or depositing it on the cathode surface via lithium vapor.

[0131] In one embodiment, referring to FIG. 6, the coating layer (220) can be lithiated by physically contacting a lithium metal film (LP) to the surface of the coating layer (220). Lithium within the lithium metal film (LP) can be absorbed into the coating layer (220). In one embodiment, the coating layer (220) can be lithiated by flowing an electric current between the lithium metal film (LP) and the negative current collector (210). The lithium metal film (LP) may be a lithium metal in the form of a thin film or a lithium metal in the form of a plate.

[0132] In one embodiment, referring to FIG. 7, the cathode can be immersed in a solution (LSL) containing a lithium compound to lithiate the coating layer (220). The solution may contain a lithium salt. For example, the solution may contain a lithium salt such as Li3N, LiNO3, or LiCl, but is not limited thereto.

[0133] In one embodiment, referring to FIG. 8, pre-lithiation can be performed through an ion-conducting polymer layer (PL) interposed between a negative electrode current collector (210) and a coating layer (220). The ion-conducting polymer layer (PL) may include a lithium salt. The lithium salt of the ion-conducting polymer layer (PL) may include those commonly used. In one embodiment, pre-lithiation can be performed by discharging an all-solid-state battery containing the ion-conducting polymer layer (PL). Specifically, the coating layer can be lithiated by lithium ions of the ion-conducting polymer layer (PL) disposed on the negative electrode current collector (210) passing through the coating layer (220) during the discharge process.

[0134] Specifically, the coating layer (220) according to an embodiment of the present invention may undergo a pre-lithiation process through a sulfide-based lithium source (Li-source). The sulfide-based lithium source may include lithium sulfate (Li2SO4), lithium sulfide (Li2S), etc. For example, pre-lithiation may be performed by immersing the cathode in a solution containing a sulfide-based lithium source.

[0135] FIG. 5 illustrates a coating layer (220) after pre-lithiation treatment as an embodiment of the present invention.

[0136] Referring to FIG. 5, the coating layer after pre-lithiation may include a second metal-based particle (MTP2). The second metal-based particle (MTP2) may be derived from the first metal-based particle (MTP1) described above. Specifically, the first metal-based particle (MTP1) may be converted into a second metal-based particle (MTP2) after pre-lithiation.

[0137] The second metal-based particle (MTP2) may include the aforementioned lithium-affinity metal, an alloy of the lithium-affinity metal and lithium, and / or a sulfide of the lithium-affinity metal. For example, the second metal-based particle (MTP2) may include an alloy of silver (Ag) and lithium (Li). As the lithium-affinity metal forms an alloy with lithium, it can facilitate lithium diffusion within the cathode.

[0138] When a lithium-affinity metal forms an alloy, the molar ratio of the lithium-affinity metal to the alloy may be in the range of 1:1 to 1:8, 1:1 to 1:3, or 1:1 to 1:2.6. Within the above range, the initial efficiency of the cathode can be effectively compensated.

[0139] The second metal-based particle (MTP2) may include a sulfide of a lithium-affinity metal. The sulfide of the lithium-affinity metal may originate from the aforementioned sulfide-based lithium source. Lithium ions originating from the sulfide-based lithium source may form an alloy with a portion of the lithium-affinity metal, and sulfur-based materials from the sulfide-based lithium source may form compounds with a portion of the lithium-affinity metal. For example, the sulfide of the lithium-affinity metal may include silver sulfide. More specifically, the sulfide of the lithium-affinity metal is Ag x It may include S (1≤x≤3, where x is an integer). Since the second metal-based particle (MTP2) contains a sulfide, it can prevent abrupt compositional changes with the sulfide-based solid electrolyte layer, thereby improving the chemical stability of the battery.

[0140] The lithium source absorbed into the coating layer (220) by prelithiation can react with the first metal particle (MTP1), which is mostly a lithium-affinity metal. Some of the lithium source can be adsorbed onto the surface of the carbon-based material (CCM). Some of the lithium source may also form the lithium particle (LTP) described later.

[0141] Referring again to FIG. 5, in one embodiment of the present invention, the coating layer (220) after prelithiation may further contain lithium. In the coating layer (220), lithium may exist in the form of lithium particles (LTP). The lithium particles (LTP) may be formed from lithium remaining without reacting with the first metal particles (MTP1) among the lithium sources absorbed into the coating layer (220) by prelithiation. Specifically, the lithium particles (LTP) may be formed on the surface of carbon-based particles (CCM) or in the pores (POR) of the coating layer.

[0142] As described above, the pre-lithiated coating layer (220) may include at least one of lithium particles, an alloy of a lithium-affinity metal and lithium, or a sulfide of a lithium-affinity metal, which can facilitate the diffusion of lithium within the negative electrode and compensate for initial efficiency. In particular, the chemical stability of the all-solid-state battery can be improved by the second metal-based particle (MTP2) including a sulfide derived from a sulfide-based lithium source.

[0143] In one embodiment, the second metal-based particles (MTP2) within the coating layer (220) may have a content gradient. Specifically, the coating layer (220) may include a first region (AR1) adjacent to the second solid electrolyte layer (320) and a second region (AR2) adjacent to the negative electrode current collector (210), wherein the content of the second metal-based particles (MTP2) may be greater in the first region (AR1). That is, the coating layer (220) may contain a greater content of the second metal-based particles (MTP2) in the region adjacent to the second solid electrolyte layer (320). The second metal-based particles (MTP2) contain a lithium-affinity metal and a sulfide, and by being present in a relatively large amount in the region adjacent to the solid electrolyte layer (300), the stability of the interface between the negative electrode (200) and the solid electrolyte layer (300) can be improved.

[0144] The first region (AR1) may refer to an area occupying about 20 to 60% of the total volume of the coating layer (220) from the interface between the coating layer (220) and the second solid electrolyte layer (320). The second region (AR2) may refer to an area occupying about 40 to 80% of the total volume of the coating layer (220) from the interface between the coating layer (220) and the negative current collector (210). Each of the first region (AR1) and the second region (AR2) may be defined as an independent region that does not overlap with each other. By including a higher content of the second metal-based particles (MTP2) in the region adjacent to the solid electrolyte layer (300), lithium ion conductivity can be improved and the electrochemical stability of the interface can be improved. As a result, a rapid increase in resistance caused by changes in the composition of the coating layer (220) and the solid electrolyte layer (300) can be suppressed.

[0145] The present invention will be explained in more detail below through embodiments. However, these embodiments are intended to illustrate the invention and the scope of the invention is not limited to these embodiments.

[0146] Example 1

[0147] (Cathode manufacturing)

[0148] (1) Preparation of the coating layer

[0149] Carbon black (CB) was prepared as a carbon-based material and silver (Ag) particles were prepared as metal particles. After mixing the carbon black and silver particles in a weight ratio of approximately 3:1, 4g of the mixed powder was placed in a container, and 4g of an N-methylpyrrolidone (NMP) solution containing 7% by weight of a polyvinylidene fluoride (PVdF) binder (Kureha # 9300) was added to prepare a mixed solution.

[0150] A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 10 hours to produce a laminate. The surface of the prepared laminate was flattened by cold roll pressing to produce a cathode having a cathode coating layer / cathode current collector structure. At this time, the thickness of the cathode coating layer was approximately 15 μm, and the area of ​​the cathode coating layer and the cathode current collector were the same.

[0151] (2) Pre-lithiation

[0152] The cathode prepared as described above was pre-lithiated. Specifically, the pre-lithiation step was performed by immersing the coating layer in an aqueous solution of lithium sulfate (Li2SO4). The concentration of the aqueous lithium sulfate solution was approximately 1.0 M. To allow sufficient lithiation reaction to occur, the electrode was immersed at room temperature for approximately 1 hour. After removing the immersed electrode, it was dried at approximately 80°C to produce a pre-lithiated cathode.

[0153] (Anode manufacturing)

[0154] Li2S, a sulfur compound, and LiI, an ion-conducting material, were mixed in a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C at 600 rpm for 10 hours.

[0155] The size of the Li2S-LiI composite was less than 1 μm. The size of the Li2S-LiI composite was calculated by software from scanning electron microscope images of the Li2S-LiI composite powder. The size of the Li2S-LiI composite is the D50 average particle size.

[0156] Li2S-LiI composites and carbon nanofibers (CNF) were mixed in a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to prepare Li2S-LiI-CNF. The milling conditions were 25°C at 510 rpm for 10 hours.

[0157] The lithium-sulfur carbon composite prepared as described above was used as the positive electrode active material.

[0158] A composition for forming a positive electrode active material layer was prepared by mixing the above positive electrode active material with an azirodite-type solid electrolyte and a PTFE binder. The mixing weight ratio was positive electrode active material: solid electrolyte: binder = 80:19:1.

[0159] The above composition for forming the positive active material layer was dry-coated onto a positive current collector made of aluminum foil carbon-coated on one side, and the positive was manufactured by applying pressure for 10 minutes under conditions of 1 MPa and 130°C. The thickness of the positive active material layer was approximately 80 μm.

[0160] (Preparation of solid electrolyte layer)

[0161] 98.5 wt% of Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal, and 1.5 wt% of an acrylic binder were mixed. Octyl acetate was added to the mixture while stirring to prepare a slurry. The prepared slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 2 hours to prepare a solid electrolyte layer.

[0162] (Battery Assembly)

[0163] Subsequently, a solid electrolyte layer was placed on the cathode, and an anode was placed on the solid electrolyte layer. The prepared laminate was 85 oPlate press treatment was performed at a pressure of 500 MPa for 30 min at C. This pressurization treatment sintered the solid electrolyte layer, improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 μm.

[0164] An all-solid-state battery was manufactured by placing a pressurized laminate into a pouch and vacuum sealing it. Parts of the positive and negative current collectors were extended outside the sealed battery to serve as the positive and negative terminals.

[0165] Comparative example

[0166] An all-solid-state battery with the same composition as the example was manufactured, but the pre-lithiation process was omitted. The example and comparative example are distinguished and shown in Table 1 below.

[0167] Pre-lithiation Status Remarks Example 1 Pre-lithiated Li2SO4 solution immersion Comparative Example 1--

[0168] Evaluation Example 1: Coating Layer Analysis

[0169] After pre-lithiating the coating layer using an aqueous lithium sulfate solution, changes in the crystal phase of the coating layer were analyzed through X-ray diffraction (XRD).

[0170] In the case of Comparative Example 1 before pre-lithiation treatment, the main peak (2θ) was identified at around 38.1°, 44.1°, and 64.4°, which is determined to correspond to the crystalline phase of Ag.

[0171] On the other hand, in the case of Example 1 after pre-lithiation treatment, the main peak (2θ) was identified around 32.3°, 55.1°, 28.0°, 32.6°, and 34.1°. Of these, the values ​​of 32.3° and 55.1° appear to correspond to the Ag-Li alloy phase, while 28.0°, 32.6°, and 34.1° can be interpreted as being attributed to Ag2S.

[0172] XRD analysis results showed that a diffraction pattern corresponding to an Ag-Li alloy phase was observed in the coating layer of Example 1, which was pre-lithiated, suggesting the possibility that a phase such as AgLi and / or AgLi3 was formed. The silver and lithium alloy phase was formed through a chemical reaction between Ag particles and lithium ions during the pre-lithiation process.

[0173] In addition, diffraction peaks corresponding to the Ag2S phase were also identified. This is formed by the reaction of silver with sulfate ions or byproducts derived therefrom in an aqueous lithium sulfate solution.

[0174] Based on these results, it can be seen that the silver particles in the coating layer of Example 1 may have both an alloy phase of silver and lithium and a silver sulfide phase. The silver and lithium alloy phase and the silver sulfide phase formed on the silver particles provide lithium ion conductivity to the coating layer, contribute to increasing the diffusion rate of lithium during the charging / discharging process, and can improve the interfacial stability of the negative electrode.

[0175]

[0176] Evaluation Example 2: Charge / Discharge Test and Life Characteristics

[0177] The performance of all-solid-state batteries manufactured according to the examples and comparative examples was evaluated.

[0178] Specifically, the first cycle involved charging at a constant current of 0.05C for 20 hours until the battery voltage reached 2.7V. Subsequently, discharging was performed at a constant current of 0.1C for 10 hours until the battery voltage reached 1.0V. The initial efficiency was evaluated based on the charge / discharge capacity of the first cycle. The initial efficiency was evaluated using the following Equation 1.

[0179] [Mathematical Formula 1]

[0180] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0181] The second cycle involved charging at a constant current of 0.1C for 10 hours until the battery voltage reached 2.7V. Subsequently, discharging was performed at a constant current of 0.1C for 10 hours until the battery voltage reached 1.0V.

[0182] After the second cycle, charging and discharging were performed under the same conditions as the second cycle. Subsequently, the number of cycles until the discharge capacity reached 80% based on the measured initial capacity was measured, and the results are shown in Table 2 below.

[0183] Initial Efficiency (%) Life Cycle Characteristics (CYC) Example 194253 Comparative Example 186150

[0184] Referring to the above results, it was found that the initial efficiency of Example 1, which applied pre-lithiation treatment, was significantly improved compared to Comparative Example 1. This is believed to be because the lithium formed during the pre-lithiation process acts as a lithium storage medium within the cathode and compensates for the initial irreversible capacity.

[0185] This is presumed to be because lithium forms an alloy with silver particles and is dispersed within the coating layer, thereby activating the lithium diffusion pathway within the coating layer. Additionally, it is presumed that the coating layer contains sulfides, which reduces the interfacial resistance with the sulfide-based solid electrolyte layer and improves initial reactivity.

[0186] These results indicate that the prelithiation process can have a positive impact on the overall cell cycle characteristics and lifespan by improving initial efficiency in anode-free all-solid-state batteries.

Claims

1. Anode; A cathode comprising a cathode current collector and a coating layer on the cathode current collector; and It includes a solid electrolyte layer between the anode and the cathode, The above coating layer comprises carbon-based particles and metal-based particles, and The above metal particles are: Lithium-affinity metal; The above-mentioned lithium-affinity metal and lithium alloy; and Serving with the sulfide of the above lithium-affinity metal, All-solid-state battery.

2. In Paragraph 1, The above coating layer further comprises lithium particles formed on the surface of the carbon-based particles, in an all-solid-state battery.

3. In Paragraph 1, An all-solid-state battery in which the molar ratio of the lithium-affinity metal to the lithium in the alloy is 1:1 to 1:

8.

4. In Paragraph 1, The above carbon-based material comprises at least one of amorphous carbon, crystalline carbon, or porous carbon, in an all-solid-state battery.

5. In Paragraph 1, An all-solid-state battery comprising at least one of the lithium-affinity metals selected from gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), or zinc (Zn).

6. In Paragraph 1, An all-solid-state battery in which the sulfide of the above-mentioned lithium-affinity metal includes silver sulfide.

7. In Paragraph 1, It further includes a lithium metal layer between the above-mentioned negative current collector and the above-mentioned coating layer, and The above lithium metal layer comprises lithium metal or an alloy of lithium metal, All-solid-state battery.

8. In Paragraph 1, An all-solid-state battery having a coating layer thickness of 10 μm to 50 μm.

9. In Paragraph 1, The above-mentioned positive electrode is an all-solid-state battery comprising a sulfide-based positive electrode active material.

10. In Paragraph 9, The above-mentioned sulfide-based positive electrode active material comprises a composite of lithium sulfide and a conductive material, in an all-solid-state battery.

11. In Paragraph 1, The above solid electrolyte layer is Li 7-c-a M a PS 6-c X c It comprises an argyrodite-type sulfide-based solid electrolyte represented by (0≤a≤2, 0≤c≤2), and The above X is F, Br, Cl, or a combination thereof, and The above M is scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof, All-solid-state battery.

12. Preparing a cathode, wherein the cathode comprises a cathode current collector and a coating layer on the cathode current collector; and The method includes pre-lithiating the coating layer using a lithium source, wherein The above coating layer comprises carbon-based particles and metal-based particles, and the metal-based particles comprise a lithium-affinity metal, and Pre-lithiating the above coating layer is: Forming an alloy between the lithium-affinity metal and lithium within the metal-based particles; and Comprising forming a sulfide of the lithium-affinity metal within the metal-based particles, Method for manufacturing an all-solid-state battery.

13. In Paragraph 12, The above lithium source includes a sulfide-based lithium source, Method for manufacturing an all-solid-state battery.

14. In Paragraph 13, The above prelithiation is performed by immersing the coating layer in a solution containing the above sulfide-based lithium source, Method for manufacturing an all-solid-state battery.

15. In Paragraph 13, The above sulfide-based lithium source includes Li2SO4 or Li2S, Method for manufacturing an all-solid-state battery.

16. In Paragraph 12, Forming an ion-conductive polymer layer interposed between the above-mentioned cathode current collector and the above-mentioned coating layer; Further comprising providing the lithium source to the ion-conducting polymer layer, Method for manufacturing an all-solid-state battery.

17. In Paragraph 12, A method for manufacturing an all-solid-state battery, wherein the molar ratio of the lithium-affinity metal to the lithium in the alloy is 1:1 to 1:8.

Images