Positive electrode active material, and positive electrode and all-solid-state battery comprising same

Abstract

The present invention relates to a positive electrode and an all-solid-state battery comprising same, wherein: the positive electrode comprises a positive electrode current collector and a positive electrode active material layer thereon; the positive electrode active material layer comprises a first positive electrode active material, a second positive electrode active material, and a solid electrolyte; the first positive electrode active material comprises a first composite containing a first lithium sulfide, a first metal halide salt, and a carbon-based conductive material; and the second positive electrode active material may comprise a second composite containing a second lithium sulfide, a second metal halide salt, and a transition metal sulfide.

Description

Cathode active material, anode including the same, and all-solid-state battery

[0001] The present invention relates to a positive electrode active material, a positive electrode comprising the same, and an all-solid-state battery.

[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 provide an anode with high ionic conductivity and electronic conductivity.

[0005] Another problem that the present invention aims to solve is to provide an all-solid-state battery comprising the anode.

[0006] A positive electrode according to the concept of the present invention comprises a positive electrode current collector; and a positive electrode active material layer on the positive electrode current collector; wherein the positive electrode active material layer comprises a first positive electrode active material, a second positive electrode active material, and a solid electrolyte, the first positive electrode active material comprises a first composite containing a first lithium sulfide, a first metal halide salt, and a carbon-based conductive material, and the second positive electrode active material may comprise a second composite containing a second lithium sulfide, a second metal halide salt, and a transition metal sulfide.

[0007] A solid-state battery according to another concept of the present invention may include: the positive electrode; a negative electrode comprising a negative electrode current collector and a coating layer disposed on the negative electrode current collector; and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0008] The anode according to the present invention may have excellent electronic conductivity and ionic conductivity. In addition, an all-solid-state battery including the anode may have improved lifespan characteristics.

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

[0010] FIG. 2 is a cross-sectional view of an all-solid-state battery according to another exemplary embodiment of the present invention.

[0011] Figure 3 is an enlarged view of region A of Figure 1 and is a schematic diagram exemplarily showing a cross-section of the positive active material layer of an all-solid-state battery.

[0012] FIG. 4 is an enlarged view of the M region of FIG. 3 and is a schematic diagram of a first positive active material according to an exemplary embodiment of the present invention.

[0013] FIG. 5 is an enlarged view of the N region of FIG. 3 and is a schematic diagram of a second positive active material according to an exemplary embodiment of the present invention.

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

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0022] In this specification, “alloy” means a mixture of two or more metals.

[0023] In this specification, “electrode active material” refers to an electrode material capable of undergoing lithiation and delithiation.

[0024] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0025] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0026] In this specification, “lithiation” and “to lithiate” refer to the process of adding lithium to an electrode active material.

[0027] In this specification, “delithiation” and “to delithiate” refer to the process of removing lithium from an electrode active material.

[0028] In this specification, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery.

[0029] In this specification, “discharge” and “discharge” refer to the process of removing electrochemical energy from a battery.

[0030] In this specification, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0031] In this specification, “negative electrode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0032]

[0033] All-solid-state battery (1000)

[0034] FIGS. 1 and FIGS. 2 are cross-sectional views of an all-solid-state battery according to an exemplary embodiment of the present invention.

[0035] Referring to FIG. 1, an all-solid-state battery (1000) according to one embodiment includes 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 all-solid-state battery (1000) 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).

[0036] anode layer (100)

[0037] The positive layer (100) of one embodiment includes a positive current collector (110) and a positive active material layer (120) disposed on the positive current collector (110).

[0038] Figure 3 is an enlarged view of region A of Figure 1, which is a cross-sectional view of the positive active material layer (120).

[0039] Referring to FIG. 3, the positive active material layer (120) may include a first positive active material (11), a second positive active material (12), and a solid electrolyte (20). The positive active material layer (120) may further include a binder (not shown).

[0040] 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.

[0041] The thickness of the positive current collector (110) may be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0042] 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).

[0043] The positive current collector (110) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof.

[0044] The base film may be, for example, an insulator. Since the base film contains an insulating thermoplastic polymer, the base film may soften or liquefy upon the occurrence of a short circuit, thereby interrupting battery operation and suppressing a sudden increase in current.

[0045] The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or alloys thereof. The metal layer may act as an electrochemical fuse and cut off in the event of an overcurrent to perform a short-circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer may be plated or deposited on a base film. As the thickness of the metal layer decreases, the limit current and / or maximum current of the positive current collector (110) decreases, thereby improving the stability of the lithium battery in the event of a short circuit.

[0046] A lead tab may be added to the metal layer for external connection. The lead tab may be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or metal layer melt, allowing the metal layer to be electrically connected to the lead tab.

[0047] To make the weld between the metal layer and the lead tab more robust, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin sheet of the same material as the metal of the metal layer. The metal chip may be, for example, metal foil, metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to a metal chip / metal layer laminate or a metal chip / metal layer / base film laminate by placing the metal chip on the metal layer and then welding it to the lead tab. During welding, as the base film, metal layer, and / or metal chip melt, the metal layer or the metal layer / metal chip laminate may be electrically connected to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal layer.

[0048] The thickness of the base film may be, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. By having the base film within this thickness range, the weight of the electrode assembly can be reduced more effectively. The melting point of the base film may be, for example, 100 to 300 °C, 100 to 250 °C or lower, or 100 to 200 °C. By having the base film within this melting point range, the base film can melt during the welding process of the lead tab and be easily bonded to the lead tab. Surface treatments, such as corona treatment, may be performed on the base film to improve the adhesion between the base film and the metal layer.

[0049] The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. By having the metal layer within this range of thickness, the stability of the electrode assembly can be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. By having the metal piece within this range of thickness, the connection between the metal layer and the lead tab can be performed more easily. Since the positive current collector (110) has a laminated structure of the base film and the metal layer described above, the weight of the positive layer (100) can be reduced, and consequently, the energy density of the all-solid-state battery (1000) can be improved.

[0050]

[0051] In this specification, “anode active material” may be used to mean including the first anode active material (11) and the second anode active material (12). For example, “total content of anode active material” may mean the sum of the content of the first anode active material (11) and the content of the second anode active material (12). An anode active material may mean a material capable of reversibly absorbing and desorbing lithium ions.

[0052] In this specification, “lithium sulfide” may be used to mean including the first lithium sulfide (LS1) and the second lithium sulfide (LS2).

[0053] In this specification, “metal halide salt” may be used to mean including a first metal halide salt (MH1) and a second metal halide salt (MH2).

[0054]

[0055] First positive active material (11) and second positive active material (12)

[0056] Again, referring to FIG. 3, the positive active material layer (120) may include a first positive active material (11), a second positive active material (12), and a solid electrolyte (20). The positive active material layer (120) may further include a binder (not shown).

[0057] The first positive active material (11) may include a first lithium sulfide, a first metal halide salt, and a carbon-based conductive material. The first positive active material (11) may include a first composite containing the first lithium sulfide, the first metal halide salt, and a carbon-based conductive material.

[0058] FIG. 4 is an enlarged view of the M region of FIG. 3, showing a cross-section of the first positive active material (11). Referring to FIG. 4, the first positive active material (11) may include a first composite containing a first lithium sulfide (LS1), a first metal halide salt (MH1), and a carbon-based conductive material (CA).

[0059] The first composite may refer to particles comprising a first lithium sulfide (LS1), a first metal halide salt (MH1), and a carbon-based conductive material (CA). The first composite may be particles in which the first lithium sulfide (LS1), the first metal halide salt (MH1), and the carbon-based conductive material (CA) are mixed. The first composite may be particles of various shapes, such as spherical, elliptical, plate-shaped, or rod-shaped, but is not limited to the shapes of the particles described above. In the first composite, the first lithium sulfide (LS1), the first metal halide salt (MH1), and the carbon-based conductive material (CA) may each maintain their unique properties. The first lithium sulfide (LS1) may have the effect of increasing the energy density of the first positive active material (11). The first metal halide salt (MH1) may have the effect of increasing the ion conductivity of the first positive active material (11). The carbon-based conductive material (CA) can have the effect of increasing the electron conductivity of the first positive active material (11).

[0060] The first composite can be manufactured by mixing the first lithium sulfide (LS1), the first metal halide salt (MH1), and the carbon-based conductive material (CA), followed by mechanical milling using a ball mill or the like. However, the method is not limited to the above method, as long as there is a method capable of forming the composite by mixing the first lithium sulfide (LS1), the first metal halide salt (MH1), and the carbon-based conductive material (CA).

[0061]

[0062] The second positive active material (12) may include a second lithium sulfide, a second metal halide salt, and a transition metal sulfide. The second positive active material (12) may include a second complex containing the second lithium sulfide, the second metal halide salt, and the transition metal sulfide.

[0063] FIG. 5 is an enlarged view of the N region of FIG. 3, showing a cross-section of the second positive active material (12). Referring to FIG. 5, the second positive active material (12) may include a second composite containing a second lithium sulfide (LS2), a second metal halide salt (MH2), and a transition metal sulfide (MS).

[0064] The second complex may refer to particles comprising a second lithium sulfide (LS2), a second metal halide salt (MH2), and a transition metal sulfide (MS). The second complex may be particles in which the second lithium sulfide (LS2), the second metal halide salt (MH2), and the transition metal sulfide (MS) are mixed. The second complex may be particles of various shapes, such as spherical, elliptical, plate-like, or rod-like, but is not limited to the shapes of the particles described above. In the second complex, the second lithium sulfide (LS2), the second metal halide salt (MH2), and the transition metal sulfide (MS) may each maintain their unique properties. The second lithium sulfide (LS2) may have the effect of increasing the energy density of the second positive electrode active material (12). The second metal halide salt (MH2) may have the effect of increasing the ion conductivity of the second positive electrode active material (12). Transition metal sulfide (MS) can have the effect of increasing the electron conductivity of the second positive active material (12).

[0065] The second composite can be manufactured by mixing the second lithium sulfide (LS2), the second metal halide salt (MH2), and the transition metal sulfide (MS), followed by mechanical milling using a ball mill or the like. However, the above method is not limited to any method that can form a composite by mixing the second lithium sulfide (LS2), the second metal halide salt (MH2), and the transition metal sulfide (MS).

[0066] By using the first positive active material (11) and the second positive active material (12) in the positive active material layer (120), a battery with excellent capacity and excellent ion conductivity and electron conductivity can be realized.

[0067] The first positive active material (11) can be used to increase energy density within the battery by including the first lithium sulfide (LS1) to enable high capacity. Additionally, the first positive active material (11) can be used to improve electronic conductivity by including a carbon-based conductive material (CA). However, if the content of the first positive active material (11) in the positive active material layer (120) is increased, a decrease in the content of other components is inevitable, so the content of the solid electrolyte (20), etc. may decrease. Therefore, when the first positive active material (11) is used in excess in the positive active material layer (120) to enable high capacity, a battery with excellent capacity can be secured, but the ion conductivity decreases, and consequently, the lifespan and efficiency of the battery may decrease somewhat.

[0068] The second positive active material (12) can contribute to an increase in capacity by including a second lithium sulfide (LS2), and can also perform the role of a solid electrolyte and a conductive material to some extent by including a second metal halide salt (MS2) with excellent ion conductivity and a transition metal sulfide (MS) with excellent electron conductivity. That is, when the second positive active material (12) is used in the positive active material layer (120), a battery with excellent conductivity can be realized even if the solid electrolyte and conductive material are not used or their content is reduced. However, if only the second positive active material (12) is used in the positive active material layer (120), the second positive active material may not have sufficient lithium sources, and thus a battery with low capacity may be realized.

[0069] Accordingly, one embodiment of the present invention can realize a battery with excellent capacity by using both a first positive active material (11) with excellent capacity characteristics and a second positive active material (12) with excellent conductivity, and can compensate for the conductivity problem caused by the reduction in the content of the conductive material and solid electrolyte.

[0070] The weight ratio of the first positive active material (11) and the second positive active material (12) within the positive active material layer (11) may be, for example, 1:1 to 20:1, 1:1 to 15:1, 1:1 to 12:1, 1:1 to 10:1, 2:1 to 10:1, or 5:1 to 10:1. If the weight ratio of the first positive active material (11) and the second positive active material (12) falls outside the above range, sufficient capacity or conductivity may not be secured.

[0071] The average particle size (D50) of the first positive active material (11) may be, for example, 1 μm to 15 μm, or 5 μm to 10 μm. If the average particle size (D50) of the first positive active material (11) exceeds the above range, the surface area of ​​the first positive active material (11) decreases, thereby reducing charge / discharge efficiency and structural stability.

[0072] The average particle size (D50) of the second positive active material (12) may be, for example, 1 μm to 15 μm, 1 μm to 10 μm, or 3 μm to 7 μm. If the average particle size (D50) of the second positive active material (12) exceeds the above range, the surface area of ​​the second positive active material (12) decreases, thereby reducing charge / discharge efficiency and reducing structural stability.

[0073] The above average particle size (D50) may refer to the diameter of a particle whose cumulative volume in the particle size distribution is 50 volume%. The average particle size (D50) can be measured using scanning electron microscope images, but is not limited to any method that can be selected by a person skilled in the art.

[0074] The weight ratio of the first lithium sulfide (LS1) and the first metal halide salt (MS1) in the first positive electrode active material (11) may be, for example, 1:1 to 5:1, 1:1 to 4:1, or 1:1 to 3:1. If the weight ratio of the first lithium sulfide (LS1) and the first metal halide salt (MS1) falls outside the above range, the energy density may decrease or the ion conductivity may decrease.

[0075] The content of the carbon-based conductive material (CA) in the first positive active material (11) may be, for example, 1% to 30% by weight, 5% to 30% by weight, 5% to 25% by weight, 10% to 25% by weight, or 10% to 20% by weight of the total weight of the first positive active material (11). If the content of the carbon-based conductive material (CA) is less than the above range, the electronic conductivity may decrease. If the content of the carbon-based conductive material (CA) exceeds the above range, the content of the first lithium sulfide (LS1) or the first metal halide salt (MS1) decreases relatively, and the energy density or ion conductivity may decrease.

[0076] The weight ratio of the second lithium sulfide (LS2) and the second metal halide salt (MS2) in the second positive active material (12) may be, for example, 1:1 to 5:1, 1:1 to 4:1, or 1:1 to 3:1. If the weight ratio of the second lithium sulfide (LS2) and the second metal halide salt (MS2) falls outside the above range, the energy density may decrease or the ion conductivity may decrease.

[0077] The weight ratio of the transition metal sulfide (MS) in the second positive active material (12) may be, for example, 20% to 80% by weight, 30% to 70% by weight, or 40% to 60% by weight, or 45% to 55% by weight of the total weight of the second positive active material (12). If the content of the transition metal sulfide (MS) is less than the above range, the electronic conductivity may decrease. If the content of the transition metal sulfide (MS) exceeds the above range, the energy density and ion conductivity may decrease.

[0078] Lithium sulfide is Li2S n It may include at least one of (1≤n≤8, where n is an integer). The first lithium sulfide (LS1) is Li2S n It may include at least one of (1≤n≤8, where n is an integer). The second lithium sulfide (LS2) is Li2S n It may include at least one of (1 ≤ n ≤ 8, where n is an integer). The first lithium sulfide (LS1) and the second lithium sulfide (LS2) may be the same or different.

[0079] The positive active material layer (100) can improve capacity by including a first lithium sulfide (LS1) and a second lithium sulfide (LS2). The first lithium sulfide (LS1) and the second lithium sulfide (LS2) may be lithium sources for the all-solid-state battery (1000). Through a continuous oxidation / reduction reaction of the first lithium sulfide (LS1) and the second lithium sulfide (LS2), lithium ions can move between the positive and negative electrodes, and at the same time, electrons can move through an external circuit to generate current. When a sulfide-based material is used as the positive electrode, the lithium sulfide can act as a lithium source, so the provision of a lithium source at the negative electrode can be omitted. That is, by including a lithium-containing sulfide in the positive electrode, a negative electrode structure with lithium omitted at the negative electrode can be introduced, and the energy density of the battery can be improved.

[0080] Metal halide salts can enhance ionic conductivity. Metal halide salts can refer to compounds composed of metal elements and halogen elements. The term "metal halide salt" can be used interchangeably with "metal halide."

[0081] The metals of the metal halide salts may include, for example, lithium (Li), aluminum (Al), iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), copper (Cu), titanium (Ti), vanadium (V), chromium (Cr), molybdenum (Mo), silver (Ag), tin (Sn), zinc (Zn), gallium (Ga), indium (In), and thallium (Tl), but are not limited thereto as long as they are metals capable of forming metal halides. The metal halide salts may include, for example, alkali metal halide salts, alkaline earth metal halide salts, transition metal halide salts, boron group metal halide salts, carbon group metal halide salts, etc. The halogen elements of the metal halide salts may include, for example, fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and combinations thereof.

[0082] Alkali metal halide salts may refer to metal halide salts containing alkali metals. The alkali metals of alkali metal halide salts may include, for example, lithium (Li), sodium (Na), potassium (K), etc. Alkali metal halide salts may include, for example, lithium halide salts.

[0083] Lithium halide salts may refer to compounds formed by the combination of lithium and a halogen element. Lithium halide salts may include, for example, at least one of LiF, LiCl, LiBr, LiI, LiAlF4, LiMgCl3, Li2CaBr4, LiKCl2, or a combination thereof.

[0084] Boron group metal halide salts may refer to compounds containing boron group elements (Group 13 elements) and halogen elements. The boron group metal elements of boron group metal halide salts may include aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). Examples of boron group metal halide salts include AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TlF3, TlCl3, TlBr3, and TlI 3, Or it may include at least one combination of these. Boron group metal halide salts may include, for example, aluminum halide salts.

[0085] Aluminum halide salts can refer to compounds containing aluminum and halogen elements. Examples of aluminum halide salts include AlCl3, AlF3, AlBr3, and AlI 3, Or it may include at least one combination of these.

[0086] Each of the first metal halide salt (MH1) and the second metal halide salt (MH2) may include an alkali metal halide salt, a boron group metal halide salt, or a combination thereof. The first metal halide salt (MH1) may include, for example, an alkali metal halide salt, a boron group metal halide salt, or a combination thereof. The second metal halide salt (MH2) may include an alkali metal halide salt. The first metal halide salt (MH1) and the second metal halide salt (MH2) may each increase the ion conductivity in the first positive active material (11) and the second positive active material (12).

[0087] In one embodiment, the first positive active material (11) uses LiI and AlI3 as the first metal halide salt (MH1), and the second positive active material (12) uses V2S3, FeS2, and MoS2 as the first metal halide salt (MH2).

[0088] A carbon-based conductive material (CA) may refer to a conductive material containing carbon atoms. The carbon-based conductive material (CA) may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon-based conductive material (CA) may include, for example, carbon nanostructures. The carbon nanostructures may include one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, or a combination thereof. The carbon nanostructures may include, for example, at least one of carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, graphene, or a combination thereof. By including the carbon-based conductive material (CA) in the first positive electrode active material (11), the electronic conductivity can be increased and the cycle characteristics of the battery can be improved.

[0089] Transition metal sulfide (MS) may refer to a compound containing a transition metal element and sulfur. Transition metal sulfide (MS) may include, for example, at least one element among Ti, V, Cr, Mn, Fe, Co, Zr, Nb, Mo, Tc, Ru, or a combination thereof. Transition metal sulfide (MS) may include at least one of MoS2, Mo3S4, Mo5S6, Mo6S8, FeS, FeS2, Fe3S4, Fe7S8, VS2, V5S8, V2S3, or a combination thereof. The second positive active material (12) can enhance conductivity by including a transition metal sulfide.

[0090]

[0091] solid electrolyte (20)

[0092] The positive active material layer (120) may include a solid electrolyte (20). The solid electrolyte (20) may be any material used as an ion-conducting material in the art, for example. The solid electrolyte (20) may be, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

[0093] The solid electrolyte (20) in the positive active material layer (120) may have an average particle size (D50) smaller than that of the solid electrolyte in the solid electrolyte layer (300). For example, the average particle size of the solid electrolyte (20) in the positive active material layer (120) may be 100% or less, 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).

[0094] The solid electrolyte (20) may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. The sulfide-based solid electrolyte is, 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 Brx (0≤x≤2), and Li 7-x PS 6-x I x It may include at least one selected from (0≤x≤2).

[0095] Sulfide-based solid electrolytes may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 1:

[0096] <Chemical Formula 1>

[0097] Li + 12-n-x A n+ X 2- 6-x Y - x

[0098] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; X is S, Se, or Te; Y is Cl, Br, I, F, CN, OCN, SCN, or N3; and 1≤n≤5, 0≤x≤2. Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x It may be an argyrodite-type compound containing one or more selected from 0≤x≤2. The sulfide-based solid electrolyte may be an argyrodite-type compound containing one or more selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0099] Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Brx (0≤x≤2), and Li 7-x PS 6-x I x It may be an argyrodite-type compound comprising one or more selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0100] 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, or a combination thereof. M can be 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. there is.

[0101] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. By having a density of 1.5 g / cc or higher for the azyrodite-type solid electrolyte, 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.

[0102] The solid electrolyte (20) in the positive electrode active material (11, 12) may be the same as or different from the solid electrolyte in the solid electrolyte layer (300).

[0103] The solid electrolyte (20) included in the positive electrode active material layer (120) may have the same average particle size (D50) as the solid electrolyte included in the solid electrolyte layer (300). The solid electrolyte (20) included in the positive electrode active material layer (120) may have a smaller average particle size (D50) compared to the solid electrolyte included in the solid electrolyte layer (300). For example, the average particle size (D50) of the solid electrolyte (20) included 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 size (D50) of the solid electrolyte included in the solid electrolyte layer (300). Meanwhile, the median average particle size (D50) may be the median diameter measured using a laser particle size distribution meter.

[0104] The content of the solid electrolyte (20) in the positive active material layer (11) may be, for example, 1% to 40% by weight, 1% to 35% by weight, 1% to 30% by weight, 1% to 25% by weight, or 1% to 20% by weight of the total weight of the positive active material layer. When the positive active material is increased to increase energy density in an all-solid-state battery, the content of the solid electrolyte (20) in the positive active material layer (120) is inevitably reduced. In one embodiment of the present invention, even if the content of the solid electrolyte (20) in the positive active material layer (120) of the all-solid-state battery is reduced, it can be confirmed that the ion conductivity is supplemented by the positive active material (11, 12).

[0105]

[0106] The positive active material layer (120) may further include a binder (not shown). The binder may include a material for bonding the first positive active material (11), the second positive active material (12), the solid electrolyte (20), etc. included in the positive active material layer (120), and for improving the bonding strength with the positive current collector (110). The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene, etc., but is not limited to these, and any material used as a binder in the relevant technical field may be possible. 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). The binder may be omitted. This can be used interchangeably with the binder content within the anode, and may refer to a ratio calculated based on the weight excluding the anode current collector within the anode.

[0107]

[0108] The positive active material layer (120) may further include additives such as a filler, a coating agent, a dispersant, an ion conductivity aid, and a conductive material, in addition to the first positive active material (11), the second positive active material (12), the solid electrolyte (20), and a binder (not shown) described above.

[0109]

[0110] The positive active material layer (120) may further include a conductive material. The conductive material may have conductivity without causing chemical changes in the all-solid-state battery (1000), thereby increasing the conductivity of the positive active material and the solid electrolyte. The conductive material may include any material used as a conductive material in the relevant technical field without limitation. The conductive material may be, for example, a carbon-based material, a metal-based material, or a combination thereof. The metal-based material may be a metal powder, a metal fiber, or a combination thereof, but is not limited to these, and any metal-based material used as a conductive material in the relevant technical field is possible. The carbon-based material may include crystalline carbon, amorphous carbon, or a combination thereof. The carbon-based material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, and graphene.

[0111]

[0112] FIG. 6 is a cross-sectional view of an all-solid-state battery according to an exemplary embodiment of the present invention. Referring to FIG. 6, the positive electrode layer (100) may further include a coating layer (CTL) provided between the positive electrode current collector (110) and the positive electrode active material layer (120). The coating layer (CTL) may be placed directly, for example, on one or both sides of the positive electrode current collector (110). The coating layer (CTL) may be coated on one or both sides of the positive electrode current collector (110). No other layer may be placed between the positive electrode current collector (110) and the coating layer (CTL).

[0113] By placing the coating layer (CTL) directly on one or both sides of the positive current collector (110), the bonding strength between the positive current collector (110) and the positive active material layer (120) can be further improved. By placing the coating layer (CTL) between the positive current collector (110) and the positive active material layer (120), side reactions between the solid electrolyte (20) or the positive active material (11, 12) and the positive current collector (110) can be more effectively suppressed. For example, the coating layer (CTL) can prevent corrosion of the sulfide-based positive active material (e.g., Li2S) by the positive current collector (110). Consequently, the coating layer (CTL) can suppress the deterioration of the all-solid-state battery (1000) during the charging and discharging process and improve cycle characteristics.

[0114] The thickness of the coating layer (CTL) is, for example, 0.01 to 20%, 0.1 to 20%, 0.5 to 20%, 1 to 20%, 1 to 15%, 1 to 10%, 2 to 8%, or 3 to 7% of the thickness of the positive current collector (110). The thickness of the coating layer (CTL) may be, for example, 10 nm to 5 µm, 50 nm to 5 µm, 200 nm to 4 µm, 500 nm to 3 µm, 500 nm to 2 µm, 500 nm to 1.5 µm, or 700 nm to 1.3 µm. By having the coating layer (CTL) have a thickness within this range, the bonding strength between the positive current collector (110) and the positive active material layer (120) is further improved, and the increase in interfacial resistance can be suppressed. The thickness of the coating layer (CTL) can be measured, for example, from a scanning electron microscope (SEM) image of a cross- section of the coating layer (CTL).

[0115] 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 the same as or different from the carbon-based conductive material (CA) of the first positive active material (11). The carbon-based conductive material included in the coating layer (CTL) may include a carbon-based conductive material identical to the carbon-based conductive material (CA) of the first positive active material (11). By including a carbon-based conductive material, the coating layer (CTL) may be, for example, a conductive layer.

[0116] The coating layer (CTL) may additionally include, for example, a binder. By additionally including a binder in the coating layer (CTL), the bonding strength between the positive current collector (110) and the positive active material layer (120) can be further improved. The binder included in the coating layer (CTL) is, for example, a conductive binder or a non-conductive binder. The conductive binder is, for example, an ion-conducting binder and / or an electron-conducting binder. A binder having both ion conductivity and electron conductivity may belong to both an ion-conducting binder and an electron-conducting binder.

[0117] The binder included in the coating layer (CTL) may be selected from among the binders used in the positive active material layer (120). The coating layer (CTL) may include the same binder as the binder used in the positive active material layer (120). The binder included in the coating layer (CTL) is, for example, a fluorine-based binder. The fluorine-based binder included in the coating layer (CTL) is, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or a combination thereof. The coating layer (CTL) may be, for example, a binding layer containing a binder. The coating layer (CTL) may be, for example, a conductive layer containing a binder and a carbon-based conductive material.

[0118] The coating layer (CTL) can be disposed on the positive current collector (110) in a dry or wet manner, for example. The coating layer (CTL) can be disposed on the positive current collector (110) in a dry manner by deposition, for example, CVD, PVD, etc. The coating layer (CTL) can be disposed on the positive current collector (110) in a wet manner by, for example, spin coating, dip coating, etc. The coating layer (CTL) can be disposed on the positive current collector (110) by, for example, depositing a carbon-based conductive material onto a substrate by deposition. The dry-coated coating layer (CTL) may be made of a carbon-based conductive material and may not contain a binder. The coating layer (CTL) can be disposed on the positive current collector (110) by, for example, coating a composition comprising a carbon-based conductive material, a binder, and a solvent onto the surface of the electrode current collector and drying it. The coating layer (CTL) may have a single-layer structure or a multi-layer structure including multiple layers. The multi-story structure can be a 2-story structure, a 3-story structure, a 4-story structure, etc.

[0119]

[0120] solid electrolyte layer (300)

[0121] The solid electrolyte layer (300) is disposed between the positive electrode layer (100) and the negative electrode layer (200) and may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. The solid electrolyte included in the solid electrolyte layer (300) may be the same as or different from any one of the materials that may be included in the solid electrolyte (20) included in the aforementioned positive electrode active material layer (120).

[0122] In one embodiment, the solid electrolyte layer (300) may include a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be manufactured by processing starting materials, such as Li2S or P2S5, by a melt quenching method or a mechanical milling method. Additionally, heat treatment may be performed after such processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. Furthermore, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material 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.

[0123] 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), and Li 7-x PS 6-x I x It may be an argyrodite-type compound comprising one or more selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0124] Alternatively, sulfide-based solid electrolytes are Li 7-a M a PS 6-c X cIt may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)). Here, X may be F, Br, Cl, or a combination thereof. M may be candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof.

[0125] 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 is, for example, 15 GPa to 35 GPa.

[0126] The solid electrolyte layer (300) 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 solid electrolyte layer (300) may be the same as or different from the binder included in the positive electrode active material layer (120) or the binder included in the coating layer (220).

[0127] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the coating layer (220) and the solid electrolyte layer (300).

[0128]

[0129] cathode layer (200)

[0130] Referring to FIG. 1, in one embodiment, an all-solid-state battery (1000) may include a negative electrode layer (200) comprising a negative electrode current collector (210) and a coating layer (220) disposed on the negative electrode current collector (210).

[0131] The negative electrode layer (200) may include a negative electrode current collector (210) and a coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the 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.

[0132] 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.

[0133] 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 (1000) can be improved.

[0134] The coating layer (220) can be configured to allow lithium metal to grow between the all-solid-state battery (1000) and the negative current collector (210) during charging. The coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0135] The coating layer (220) may include metal and carbon. For example, the 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 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 coating layer (220) may include a mixture of carbon black and silver (Ag).

[0136] The coating layer (220) may further include other additives in addition to metal and carbon. The coating layer (220) may further include at least one additive selected from the group consisting of, for example, binders, fillers, coating agents, dispersants, and ion-conducting aids.

[0137] The coating layer (220) may have a smaller thickness compared to the positive active material layer (120). The thickness of the 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 active material layer (120). The thickness of the 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 coating layer (220) is excessively thin, lithium dendrites formed between the coating layer (220) and the negative current collector (210) may cause the coating layer (220) to collapse, thereby degrading the cycle characteristics of the all-solid-state battery (1000). If the thickness of the coating layer (220) increases excessively, the energy density of the all-solid-state battery (1000) decreases, and the internal resistance of the all-solid-state battery (1000) due to the coating layer (220) increases, which may degrade the cycle characteristics of the cell.

[0138] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the coating layer (220) and the solid electrolyte layer (300).

[0139] Referring to FIG. 2, an all-solid-state battery (1000) according to one embodiment may further include a lithium metal layer (230) disposed between a negative electrode current collector (210) and a coating layer (220) by charging.

[0140] The lithium metal layer (230) may include lithium or a lithium alloy. Since the lithium metal layer (230) is a metal layer containing lithium, it may function as, for example, a lithium reservoir. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, but is not limited to these; any alloy used as a lithium alloy in the relevant technical field may be possible. The lithium metal layer (230) may be composed of one of these alloys or lithium, or may be composed of various types of alloys. The lithium metal layer (230) may be, for example, a plated layer. The lithium metal layer (230) may be deposited between the coating layer (220) and the negative electrode current collector (210) during the charging process of the all-solid-state battery (1000), for example.

[0141] The thickness of the lithium metal layer (230) is not particularly limited, but, for example, it may be 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 thickness of the lithium metal layer (230) is excessively thin, it may be difficult for the lithium metal layer (230) to perform the role of a lithium reservoir. If the thickness of the lithium metal layer (230) is excessively thick, the mass and volume of the all-solid-state battery (1000) increase, and the cycle characteristics of the all-solid-state battery (1000) may actually deteriorate.

[0142] In another embodiment, the lithium metal layer (230) within the negative electrode layer (200) may be provided, for example, between the negative electrode current collector (210) and the coating layer (220) before assembly of the all-solid-state battery (1000). When the lithium metal layer (230) is placed between the negative electrode current collector (210) and the coating layer (220) before assembly of the all-solid-state battery (1000), the lithium metal layer (230) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be placed between the negative electrode current collector (210) and the coating layer (220) before assembly of the all-solid-state battery (1000).

[0143] When a lithium metal layer (230) is deposited by charging after assembly of the all-solid-state battery (1000), the energy density of the all-solid-state battery (1000) can be increased because the lithium metal layer (230) is not included during assembly of the all-solid-state battery (1000). When charging the all-solid-state battery (1000), it can be charged beyond the charging capacity of the coating layer (220). That is, the coating layer (220) is overcharged. At the beginning of charging, lithium can be absorbed in the coating layer (220). When charging beyond the capacity of the coating layer (220), lithium can be deposited, for example, between the coating layer (220) and the negative electrode current collector (210). A lithium metal layer (230) can be formed by the deposited lithium.

[0144] The lithium metal layer (230) can be composed mainly of lithium (i.e., metallic lithium). During discharge, the lithium in the lithium metal layer (230) can be ionized and move to the positive electrode layer (100). In other words, lithium can be used as a negative electrode active material in the all-solid-state battery (1000). In addition, since the coating layer (220) covers the lithium metal layer (230), the coating layer (220) can protect the lithium metal layer (230) and simultaneously suppress the precipitation growth of lithium dendrites. Therefore, the coating layer (220) can suppress short circuits and capacity degradation of the all-solid-state battery (1000) and improve the cycle characteristics of the all-solid-state battery (1000).

[0145] When a lithium metal layer (230) is formed by charging after assembly of the all-solid-state battery (1000), the negative electrode layer (200), that is, the negative electrode current collector (210) and the coating layer (220) and the region between them may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the all-solid-state battery (1000).

[0146] FIG. 6 is a cross-sectional view of an all-solid-state battery according to an exemplary embodiment of the present invention. Referring to FIG. 6, the negative electrode layer (200) may further include a thin film (TFL) provided between the negative electrode current collector (210) and the coating layer (220). The thin film (TFL) may be provided on one surface of the negative electrode current collector (210) to form an alloy with lithium.

[0147] The thin film (TFL) may include, for example, an element capable of forming an alloy with lithium. Elements capable of forming an alloy with lithium include, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but are not necessarily limited to these, and any element capable of forming an alloy with lithium in the relevant technical field is possible. The thin film (TFL) may be composed of one of these metals or may be composed of an alloy of various types of metals.

[0148] By placing the thin film (TFL) on one side of the negative electrode current collector (210), the deposition pattern of the lithium metal layer (230) deposited between, for example, the thin film (TFL) and the coating layer (220) is further flattened, and the cycle characteristics of the all-solid-state battery (1000) can be further improved.

[0149] The thickness of the thin film (TFL) may be, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (TFL) is less than 1 nm, it may be difficult to perform the function provided by the thin film (TFL). If the thickness of the thin film (TFL) is excessively thick, the thin film (TFL) itself absorbs lithium, and the amount of lithium precipitated in the negative electrode layer (200) decreases, which lowers the energy density of the all-solid-state battery (1000) and may degrade the cycle characteristics of the all-solid-state battery (1000). The thin film (TFL) may be formed on the negative electrode current collector (210) by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods, and any method capable of forming the thin film (TFL) in the relevant technical field may be possible.

[0150]

[0151] The present invention will be explained in more detail below through examples. However, these examples are intended to illustrate the invention and the scope of the invention is not limited to these examples.

[0152]

[0153] Preparation Example 1 - Preparation of First Anode Active Material (Li2S-LiI-AlI3-CNF)

[0154] Li2S, LiI, and AlI3 were mixed in a weight ratio of 40:5:15. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3 composite. The milling conditions were 25 ℃ and 450 rpm for 10 hours. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-AlI3 composite thus prepared was mixed with carbon nanofiber (CNF) in 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 ℃ and 450 rpm for 10 hours. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-AlI3-CNF composite thus prepared was used as the first cathode active material.

[0155]

[0156] Preparation Example 2 - Preparation of second cathode active material (Li2S-LiI-V2S3)

[0157] Li2S, LiI, and V2S3 were mixed in a weight ratio of 3.49:1.5:5.01. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI-V2S3 composite. Milling was performed at 450 rpm for 40 hours. The Li2S-LiI-V2S3 composite produced in this way was used as one of the second positive active materials (12).

[0158]

[0159] Preparation Example 3 - Preparation of Second Anode Active Material (Li2S-LiI-FeS2)

[0160] The product was prepared in the same manner as in Example 2, but FeS2 was used instead of V2S3. The Li2S-LiI-FeS2 composite prepared in this way was used as one of the second positive active materials (12).

[0161]

[0162] Preparation Example 4 - Preparation of second cathode active material (Li2S-LiI-MoS2)

[0163] The product was prepared in the same manner as in Example 2, but MoS2 was used instead of V2S3. The Li2S-LiI-MoS2 composite prepared in this way was used as one of the second positive active materials (12).

[0164]

[0165] Example 1 - Preparation Example 1:Preparation Example 2:Solid Electrolyte = 7:1:2

[0166] (Cathode manufacturing)

[0167] A lower mold made of SUS material was placed inside a POM insulator having an inner diameter of 13 pi, and after placing a SUS foil (SUS foil, thickness 10 µm, size 13 pi), a Li metal foil (thickness 20 µm, size 13 pi) and an Indium metal foil (thickness 50 µm, size 13 pi) were laminated.

[0168] (Preparation of solid electrolyte layer)

[0169] Then, 150 mg of solid electrolyte Li6PS5Cl (D50 = 3.0 μm, crystalline), which is an argyrodite-type crystal, was added, and uniaxial pressurization was performed at 38 MPa for 2 seconds.

[0170] (Manufacturing of positive and all-solid-state batteries)

[0171] An anode was prepared having a content of 7:1:2 of the first anode active material of Preparation Example 1, the second anode active material of Preparation Example 2, and a solid electrolyte. The solid electrolyte used was Li6PS5Cl (D50 = 1.0 μm, crystalline), an argyrodite-type crystal. The three types of powders were placed in a mortar and pestle and mixed evenly for 20 minutes to obtain a mixed anode powder.

[0172] 15 mg of the above powder was placed on the solid electrolyte layer inside the torque cell to form an anode layer, then an upper mold made of SUS material was inserted and uniaxial pressure was applied at 300 MPa for 2 minutes. After that, an all-solid-state battery was manufactured by tightening with a torque value of 4 Nm.

[0173] Example 2 - Preparation Example 1:Preparation Example 3:Solid Electrolyte = 7:1:2

[0174] An all-solid-state battery was manufactured in the same manner as in Example 1, except that the second positive active material of Preparation Example 3 was used instead of the second positive active material of Preparation Example 2.

[0175]

[0176] Example 3 - Preparation Example 1:Preparation Example 4:Solid Electrolyte = 7:1:2

[0177] An all-solid-state battery was manufactured in the same manner as in Example 1, except that the second positive active material of Preparation Example 4 was used instead of the second positive active material of Preparation Example 2.

[0178]

[0179] Comparative Example 1 - Preparation Example 1:Solid Electrolyte = 8:2

[0180] An all-solid-state battery was manufactured in the same manner as in Example 1, except that the content of the first positive active material and solid electrolyte of Manufacturing Example 1 was 8:2.

[0181]

[0182] Evaluation Example 1. Dosage Evaluation

[0183] An all-solid-state battery was prepared by mixing the first positive active material and the second positive active material as in Examples 1 to 3, and the capacity of the battery was evaluated. As a control, Comparative Example 1, which did not use the second positive active material, was used.

[0184] The compositions of Examples 1 to 3 and Comparative Example 1 used at this time are summarized in Table 1 below. In addition, the results of evaluating the capacity characteristics of Examples 1 to 3 and Comparative Example 1 are shown in Tables 2 and 3.

[0185] At this time, the charge-discharge test was performed by placing the all-solid-state battery in a constant temperature bath at 45°C. The first cycle was charged for 20 hours with a constant current of 0.05C until the battery voltage reached 2.8 V. Subsequently, discharge was performed for 20 hours with a current of 0.05C until the battery voltage reached 0.3 V.

[0186] The second cycle involved charging at a constant current of 0.1 C for 10 hours until the battery voltage reached 2.8 V. Subsequently, discharging was performed at a constant current of 0.1 C for 10 hours until the battery voltage reached 0.3 V.

[0187] The charge / discharge efficiency of each cycle was calculated using the following mathematical formula 1.

[0188] <Mathematical Formula 1>

[0189] Charge / Discharge Efficiency (%) = [Nth Cycle Discharge Capacity / Nth Cycle Charge Capacity] × 100 (N is an integer)

[0190] The capacity reduction rate was calculated using the following mathematical formula 2.

[0191] <Mathematical Formula 2>

[0192] Capacity Reduction Rate (%) = [(1st Charge Capacity - 2nd Charge Capacity) / 1st Charge Capacity] × 100

[0193] The charging start voltage was measured as the voltage value at the first point where charging begins after the OCV.

[0194] The real capacity per unit area was calculated using the following mathematical formula 3.

[0195] <Mathematical Formula 3>

[0196] Capacity per unit area (mAh / cm²) 2 ) = Electrode capacity (mAh) / Electrode area (cm²) 2 )

[0197] Content (Weight%) (Based on total weight of the anode active material layer) Li2S content in electrode 1st anode active material 2nd anode active material Solid electrolyte Li2SLiI-AlI3CNFLi2SLiI Transition metal sulfide Example 1 40 20 10 3.49 1.5 5.01 (V2S3) 20 43.49 Example 2 5.01 (FeS2) Example 3 5.01 (MoS2) Comparative Example 1 4 5.7 22.9 11.4 - 45.7

[0198] Charging start voltage (V)1 st cycle (0.05C)(Li2S standard)2 nd cycle (0.05C) (Li2S basis) Capacity reduction rate (%) Charge capacity Discharge capacity Charge-discharge efficiency (%) Charge capacity Discharge capacity Charge-discharge efficiency (%) Example 1 1.80 869 868 99.9 79 67 68 96.5 8.40 Example 2 1.81 85 78 44 98.5 77 47 49 96.8 9.68 Example 3 1.80 85 28 23 96.6 75 47 29 96.6 11.50 Comparative Example 11.84 84 67 8 192.4 72 47 0 29 71 4.42

[0199] The units of charging capacity and discharging capacity are mAh / g.

[0200] Capacity per unit area (mAh / cm²) 2 Example 14.27 Example 24.21 Example 34.19 Comparative Example 14.03

[0201] Looking at Tables 1 to 3 above, it can be confirmed that Examples 1 to 3 exhibit superior capacity per unit area despite having a lower Li2S content in the positive electrode active material layer compared to Comparative Example 1. In particular, it can be confirmed that the charge-discharge capacity and charge-discharge efficiency of the Examples are significantly superior to those of the Comparative Example. Furthermore, it can be confirmed that the capacity reduction rate of Comparative Example 1 is greater than that of Examples 1 to 3. Accordingly, it can be seen that cell performance is improved by adding a small amount of a second positive electrode active material having high ionic and electrical conductivity into the electrode. Additionally, through Examples 1 to 3, it was confirmed that similar effects can be exhibited in various transition metal sulfides.

[0202]

[0203] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

1. Positive current collector; and The anode active material layer on the anode current collector above; The above positive active material layer comprises a first positive active material, a second positive active material, and a solid electrolyte, and The first positive active material comprises a first composite containing a first lithium sulfide, a first metal halide salt, and a carbon-based conductive material, and The second positive electrode active material comprises a second complex containing a second lithium sulfide, a second metal halide salt, and a transition metal sulfide. anode.

2. In Paragraph 1, Each of the above first lithium sulfide and the above second lithium sulfide is Li2S n including at least one of (1 ≤ n ≤ 8, n is an integer), anode.

3. In Paragraph 1, Each of the first metal halide salt and the second metal halide salt comprises an alkali metal halide salt, a boron group metal halide salt, or a combination thereof. anode.

4. In Paragraph 1, The first metal halide salt comprises an alkali metal halide salt, a boron group metal halide salt, or a combination thereof, and The above second metal halide salt comprises an alkali metal halide salt, anode.

5. In Paragraph 4, The above alkali metal halide salt comprises at least one of LiF, LiCl, LiBr, LiI, or a combination thereof, and The above boron group metal halide salts are AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TlF3, TlCl3, TlBr3, and TlI 3, or including at least one combination thereof, anode.

6. In Paragraph 1, The above transition metal sulfide comprises at least one element selected from Ti, V, Cr, Mn, Fe, Co, Zr, Nb, Mo, Tc, Ru, or a combination thereof. anode.

7. In Paragraph 1, The above transition metal sulfide comprises at least one element among V, Fe, Mo, or a combination thereof, anode.

8. In Paragraph 1, The above transition metal sulfide comprises at least one of MoS2, Mo3S4, Mo5S6, Mo6S8, FeS, FeS2, Fe3S4, Fe7S8, VS2, V5S8, V2S3, or a combination thereof. anode.

9. In Paragraph 1, The above carbon-based conductive material comprises at least one of carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, graphene, or a combination thereof. anode.

10. In Paragraph 1, The above 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), Li 7-x PS 6-x I x (0≤x≤2), or including at least one of a combination thereof, anode.

11. In Paragraph 1, The content of the above solid electrolyte is 1% to 40% by weight of the total weight of the positive electrode active material layer, anode.

12. In Paragraph 1, The weight ratio of the first positive active material and the second positive active material is 1:1 to 20:1, anode.

13. In Paragraph 1, The weight ratio of the first lithium sulfide and the first metal halide salt in the first positive electrode active material is 1:1 to 5:1, anode.

14. In Paragraph 1, The content of the carbon-based conductive material is 1 to 30 weight percent of the total weight of the first positive active material, anode.

15. In Paragraph 1, The weight ratio of the second lithium sulfide and the second metal halide salt in the second positive electrode active material is 1:1 to 5:1, anode.

16. In Paragraph 1, The content of the transition metal sulfide is 20% to 80% by weight of the total weight of the second positive electrode active material, anode.

17. Anode according to paragraph 1; A cathode comprising a cathode current collector and a coating layer disposed on the cathode current collector; and A solid electrolyte layer disposed between the anode and the cathode, All-solid-state battery.

18. In Paragraph 17, The region between the negative current collector and the coating layer of the above-mentioned negative electrode is a Li-free region that does not contain lithium (Li) before the initial charge / discharge, All-solid-state battery.

19. In Paragraph 17, The above cathode further includes a lithium metal layer disposed between the cathode current collector and the coating layer, and The above lithium metal layer comprises lithium or a lithium alloy, All-solid-state battery.

20. In Paragraph 19, The above lithium alloy comprises at least one of 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, or a combination thereof. All-solid-state battery.

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