Positive electrode for all-solid-state battery, and all-solid-state battery comprising same

Abstract

The present invention relates to a composite positive electrode material. More specifically, the present invention may comprise: a core that can reversibly absorb and desorb lithium ions; and a functional layer present on at least a portion of the surface of the core, wherein the functional layer may comprise a lithium-ion-conductive sulfide containing borohydride (-BH4).

Description

Anode for all-solid-state batteries and all-solid-state batteries including the same

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

[0002]

[0003] Recently, driven by industrial demands, the development of batteries with high energy density and stability 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.

[0004] 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.

[0005]

[0006] The problem that the present invention aims to solve is to provide a composite cathode material with improved ion conductivity and lifespan characteristics.

[0007] Another problem that the present invention aims to solve is to provide a positive electrode for an all-solid-state battery and an all-solid-state battery with improved interfacial resistance and lifespan characteristics.

[0008]

[0009] A composite cathode material according to the concept of the present invention comprises a core capable of reversibly absorbing and releasing lithium ions; and a coating layer on at least a portion of the surface of the core, wherein the coating layer may comprise a lithium ion-conducting sulfide containing borohydride (-BH4).

[0010] A positive electrode for an all-solid-state battery according to another concept of the present invention may include the composite positive electrode material; and a sulfide-based solid electrolyte.

[0011] A solid-state battery according to another concept of the present invention may include the anode; a solid electrolyte layer comprising a sulfide-based solid electrolyte; and a cathode.

[0012]

[0013] According to an embodiment of the present invention, a cathode with reduced side reactions and improved bonding characteristics with a solid electrolyte can be provided. In addition, an all-solid-state battery capable of low-pressure operation and with improved capacity and lifespan characteristics can be provided.

[0014]

[0015] FIG. 1 is a plan view of an all-solid-state battery according to embodiments of the present invention.

[0016] Figure 2 is a cross-sectional view along the line AA' of Figure 1.

[0017] FIG. 3 is a cross-sectional view of the enlarged region M of FIG. 2, intended to explain a positive electrode active material layer according to one embodiment of the present invention.

[0018] FIG. 4 is a cross-sectional view of a composite cathode material according to one embodiment of the present invention.

[0019] FIG. 5 is an enlarged cross-sectional view of a positive electrode active material layer according to one embodiment of the present invention.

[0020] FIG. 6 is an enlarged cross-sectional view of the interface between the positive active material layer and the solid electrolyte layer according to one embodiment of the present invention.

[0021] FIG. 7 is a cross-sectional view of a positive electrode active material according to one embodiment of the present invention.

[0022] FIG. 8 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0023] FIG. 9 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0024] FIG. 10 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0025]

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

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

[0032] In this specification, “alloy” means a mixture of two or more metals.

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

[0034] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0035] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

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

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

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

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

[0040] In this specification, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0041] In this specification, “negative electrode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0042]

[0043] 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. FIG. 3 is a cross-sectional view of region M of FIG. 2 enlarged to explain a positive electrode active material layer according to an embodiment of the present invention.

[0044] Referring to FIGS. 1 and 2, the all-solid-state battery (10) according to the present invention may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, not limited thereto, the all-solid-state battery (10) may further include an additional functional layer, such as an adhesion-enhancing layer, disposed between the positive electrode layer (100) and the solid electrolyte layer (300) or between the negative electrode layer (200) and the solid electrolyte layer (300).

[0045] 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).

[0046] The positive current collector (110) may provide a reference surface on which the positive active material layer (120) is disposed. The positive current collector (110) 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), lithium (Li), or an alloy thereof. The positive current collector (110) may include a plate or a foil. In another embodiment of the present invention, the positive current collector (110) may be omitted. 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 (10) can be improved.

[0054] Referring to FIG. 3, the positive active material layer (120) may include a composite positive material (CMS) and a solid electrolyte (SEP). Although not illustrated, the positive active material layer (120) may further include a conductive material and a binder.

[0055] FIG. 4 is a cross-sectional view of a composite cathode material (CMS) according to an embodiment of the present invention. Referring to FIG. 4, the composite cathode material (CMS) may include a core (COR) and a functional layer (FCL) on the surface of the core (COR). For example, the composite cathode material (CMS) may form a core-shell structure including a core (COR) and a functional layer (FCL). Specifically, the composite cathode material (CMS) may include a core (COR) located in the center and occupying most of the volume, and a functional layer (FCL) located on the surface of the core (COR).

[0056] The core (COR) can reversibly absorb and desorb lithium ions. That is, the core (COR) can serve as a lithium ion source for a lithium secondary battery. In this way, the composite cathode material (CMS) including the core (COR) can be utilized as an energy source for a lithium secondary battery. The core (COR) may have a particle shape such as a perfect spherical or elliptical spherical shape. In one embodiment, the core (COR) may include a cathode active material. The core (COR) may include a plurality of cathode active material particles. The core (COR) according to the present invention may include an oxide-based cathode active material, a sulfide-based cathode active material, or a combination thereof.

[0057] A composite cathode material (CMS) according to embodiments of the present invention may include a functional layer (FCL) on at least a portion of the surface of a core (COR). That is, the functional layer (FCL) may cover the entire surface of the core (COR) or cover only a portion thereof.

[0058] The functional layer (FCL) can act as a buffer layer. For example, the functional layer (FCL) can absorb volume changes of the composite cathode material (CMS). Specifically, the functional layer (FCL) can maintain a constant volume of the composite cathode material (CMS) by compensating for volume changes of the increasing or decreasing core (COR). For example, the functional layer (FCL) can absorb volume changes of the cathode active material through the charge-discharge process.

[0059] In addition, by coating the core (COR) with a functional layer (FCL), direct contact with the electrolyte can be prevented and chemical reactions can be suppressed. For example, chemical stability can be improved by reducing surface side reactions of the cathode active material and the generation of decomposition gases. In particular, it can prevent decomposition reactions caused by contact between the sulfide-based solid electrolyte and the cathode active material. As a result, the structural stability, chemical stability, and electrochemical stability of the composite cathode material (CMS) can be improved.

[0060] The functional layer (FCL) may have ion conductivity and / or electron conductivity. Therefore, the ion conductivity and electron conductivity of the composite cathode material (CMS) can be improved. The speed of electron transfer between the cathode active material layer (120) and the cathode current collector (110) can be improved. Ion transfer between the cathode active material layer (120) and the solid electrolyte layer (300) can be facilitated. Additionally, ion transfer between the solid electrolyte (SEP) within the cathode active material layer and the composite cathode material (CMS) can be facilitated.

[0061] Hereinafter, the positive active material layer (120) according to embodiments of the present invention will be described in more detail with reference to FIG. 5. The positive active material layer (120) may include a composite positive material (CMS) and a solid electrolyte (SEP). The solid electrolyte (SEP) in the positive active material layer (120) may be the same as or different from the solid electrolyte in the solid electrolyte layer (300) to be described later. The solid electrolyte (SEP) in the positive active material layer (120) may have a smaller average particle size (D50) compared to the solid electrolyte in the solid electrolyte layer (300). For example, the average particle size of the solid electrolyte (SEP) 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).

[0062] In particular, the composite cathode material (CMS) may comprise a core (COR) and a functional layer (FCL) on at least a portion of the surface of the core. The functional layer (FCL) may comprise an ion-conducting sulfide (ICP). The ion-conducting sulfide (ICP) may be an inorganic material that possesses lithium ion conductivity and contains a sulfur (S) element. Since the functional layer (FCL) comprises a sulfide-based inorganic material, it may improve chemical stability with a sulfide-based solid electrolyte. The ion-conducting sulfide (ICP) may include sulfide-based inorganic particles to possess mechanical strength and thermal stability. For example, the ion-conducting sulfide (ICP) may comprise a sulfide-based solid electrolyte.

[0063] Ionic conductive sulfides (ICPs) may include borohydride (-BH4). As a result, the lithium ion conductivity of the ionic conductive sulfide (ICP) may be improved. The lithium ion conductivity of the ionic conductive sulfide (ICP) may be 5.0 to 7.0 mS / cm or 5.8 to 6.3 mS / cm at 25°C.

[0064] The density of ion-conducting sulfides (ICPs) can be relatively low. For example, the density of ion-conducting sulfides (ICPs) is 1.2 to 1.6 g / cm³. 3 , or about 1.5 g / cm³ 3 It is possible. Since the ion-conducting sulfide (ICP) has a low density, it can have a high volume relative to the same weight. As the volume covering the core increases relative to the same weight, the contact range between solid particles within the anode active material layer can be increased.

[0065] The ion-conducting sulfide (ICP) may contain primary particles. The average particle size of the primary particles of the ion-conducting sulfide (ICP) may be 300 to 500 nm, 400 to 600 nm, 300 to 400 nm, or 400 to 500 nm. By including small nano-structured particles in the ion-conducting sulfide (ICP), it can densely fill the voids between solid particles within the positive electrode active material layer (120). Consequently, the lithium transport pathway between the positive electrode active material and the electrolyte can be supplemented through the ion-conducting sulfide (ICP) containing low-density nano-particles.

[0066] In one embodiment, the ion-conducting sulfide (ICP) may comprise a sulfide-based complex containing lithium borohydride (LiBH4). For example, the ion-conducting sulfide (ICP) may comprise a glass-ceramic solid electrolyte of Li3PS4-LiBH4. The ion-conducting sulfide (ICP) is Li 7-X PS 6-x (BH4) x It may be an argyrodite-type glass-ceramic solid electrolyte expressed as (0≤x≤2).

[0067] Because all components of all-solid-state batteries are solid, they present a challenge in forming networks between components compared to lithium-ion batteries that use liquid electrolytes. For example, solid electrolyte particles cannot naturally fill every space as they do in liquid electrolytes. Since lithium ions can only move at the points where individual solid particles come into contact, interfacial resistance is high. Furthermore, solid electrolytes are susceptible to mechanical stress, which can shorten the lifespan of the electrodes due to volume changes occurring during charging and discharging. Therefore, to improve the performance of all-solid-state batteries, it is crucial to enhance the contact forces between each component.

[0068] According to embodiments of the present invention, the performance of an all-solid-state battery can be improved by including an ion-conducting sulfide (ICP) in the functional layer (FCL) of the composite cathode material (CMS). By including low-density nanoparticles in the ion-conducting sulfide (ICP), the contact area between the cathode active material and the solid electrolyte particles can be improved. Since the low-density ion-conducting sulfide (ICP) has a relatively large volume per unit mass, it can effectively coat the surface of the core. In this case, the solid-phase materials can come into contact in the form of surface contact rather than point contact. Furthermore, by including a sulfide-based inorganic material having lithium ion conductivity in the functional layer (FCL), chemical stability with the sulfide-based solid electrolyte can be improved. This allows for the improvement of contact between the cathode active material and the solid electrolyte while simultaneously enhancing chemical stability with the sulfide-based solid electrolyte. A stable structure can be established by the solid particles of the all-solid-state battery mutually bonding to form a network. As a result, both ion conductivity and stability are improved, enabling the provision of a high-performance all-solid-state battery.

[0069] More specifically, as shown in FIG. 6, by including an ion-conducting sulfide (ICP) coated on the surface of the core (COR) in the composite cathode material (CMS), the contact area between the core (COR) and the solid electrolyte (SEP) particles within the cathode active material layer (120) can be increased. Additionally, the contact area of ​​the interface between the cathode active material layer (120) and the solid electrolyte layer (300) can be increased. As a result, the interfacial resistance of the all-solid-state battery can be reduced and the ion conductivity can be improved.

[0070] Ionic conductive sulfides (ICPs) can partially replace the solid electrolyte (SEP) within the cathode active material layer by including sulfide-based inorganic materials that possess lithium ion conductivity. As described above, since the contact force between solid particles is improved, the content of the solid electrolyte (SEP) within the cathode active material layer can be reduced. Consequently, the content of the cathode active material within the cathode active material layer increases, thereby improving the energy density of the all-solid-state battery.

[0071]

[0072] In one embodiment, the content of the composite cathode material (CMS) in the cathode active material layer (120) may be 10 to 99 weight%, 30 to 80 weight%, 40 to 70 weight%, 40 to 90 weight%, 50 to 90 weight%, 60 to 90 weight%, or 70 to 90 weight% of the total weight of the cathode active material layer (120). If the content of the composite cathode material (CMS) is reduced excessively, the energy density of the all-solid-state battery may decrease.

[0073] In one embodiment, the content of the positive active material in the positive active material layer (120) may be 50 to 90 weight%, 60 to 90 weight%, 70 to 90 weight%, or 80 to 90 weight% of the total weight of the positive active material layer (120).

[0074] In one embodiment, the content of the ion-conducting sulfide (ICP) may be 1 to 20 weight%, 1 to 15 weight%, or 5 to 15 weight% with respect to the total weight of the composite cathode material (CMS).

[0075] The content of the solid electrolyte (SEP) in the positive active material layer (120) may be 10 to 40 wt%, 1 to 20 wt%, 10 to 20 wt%, or 5 to 20 wt% of the total weight of the positive active material layer (120).

[0076] Among the components within the positive active material layer (120), the composite cathode material (CMS) may have the largest content. In particular, among the components within the positive active material layer, the positive active material may have the largest content. By having the above content ratio, it is possible to provide an all-solid-state battery with improved energy density while simultaneously solving problems such as interfacial resistance and lifespan characteristics. Furthermore, the above-described effect can be maximized by forming a functional layer on the surface of the positive active material, rather than simply mixing the components in the above composition ratio within the positive active material layer.

[0077] Hereinafter, each of the components described above will be explained through specific examples. The core (COR) may include a positive electrode active material. The positive electrode active material may include an oxide-based or sulfide-based positive electrode active material. The oxide-based positive electrode active material may include, for example, a lithium transition metal oxide, a metal oxide, or a combination thereof. The lithium transition metal oxide includes, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganate, lithium iron phosphate, or a combination thereof. The lithium oxide may include, for example, iron oxide, vanadium oxide, or a combination thereof.

[0078] Sulfide-based cathode active materials may include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof. A more specific description of the sulfide-based cathode active material according to an embodiment of the present invention will be provided later.

[0079] For oxide-based cathode active materials, one or more types of composite oxides of lithium and a metal selected from, for example, cobalt, manganese, nickel, and combinations thereof may be used. For lithium-containing oxide-based cathode active materials, for example, Li a A 1-b B' b D2(wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B' c O 2-α F' α(In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG bO2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) It may include a compound represented by any one of the chemical formulas of Fe2(PO4)3(0 ≤ f ≤ 2); LiFePO4.

[0080] In the chemical formula representing the compound described above, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; and J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0081] The oxide-based cathode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen 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 z O2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0082] When the oxide-based cathode active material contains nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, for example, the capacity density of the all-solid-state battery (10) is increased, and the metal leaching of the cathode active material in the charged state can be reduced. As a result, the cycle characteristics of the all-solid-state battery (10) in the charged state are improved. Meanwhile, "cycle characteristics" is a characteristic that indicates the degree of deterioration of the all-solid-state battery (10) due to charging and discharging of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics has a small degree of deterioration due to charging and discharging, while an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration due to charging and discharging.

[0083] The oxide-based cathode active material may have a particle shape such as a sphere or an ellipsoid. The particle size and content of the oxide-based cathode active material are not particularly limited. The size of the oxide-based cathode active material may be, for example, 0.1 to 30 μm, 0.5 to 20 μm, or 1 to 15 μm. The oxide-based cathode active material may be, for example, single-crystal particles or polycrystalline particles.

[0084] The core (COR) may include a sulfide-based cathode active material (CAC). Specifically, the sulfide-based cathode active material may include a complex of a sulfur compound, a lithium salt, and a metal halide. The sulfur compounds are S8 and Li2S nIt may include at least one of (1 ≤ n ≤ 8, where n is an integer). The sulfide-based cathode active material (CAC) may include a Li2S-containing cathode active material. The Li2S-containing cathode active material may include, for example, a complex of Li2S and carbon, a complex of Li2S and carbon and a solid electrolyte, a complex of Li2S and a solid electrolyte, a complex of Li2S and a lithium salt, a complex of Li2S and a lithium salt and carbon, a complex of Li2S, a lithium salt, a metal halide and carbon, a complex of Li2S and a metal carbide, a complex of Li2S and carbon and a metal carbide, a complex of Li2S and a metal nitride, a complex of Li2S and a metal nitride, or a combination thereof.

[0085] Referring to FIG. 7, the sulfide-based cathode active material (CAC) may include a sulfide-based composite (CAM) and a conductive material (CMA). In one embodiment, the sulfide-based composite (CAM) may have a particle shape such as a perfect spherical or elliptical sphere. The particle size of the sulfide-based composite (CAM) is not particularly limited and may be within a range applicable to general cathode active materials. The size of the sulfide-based composite (CAM) may be, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm. The conductive material (CMA) may cover the surface of the sulfide-based composite (CAM).

[0086] The conductive material (CMA) may include carbon. The conductive material (CMA) may include, without limitation, materials containing carbon atoms that are used as conductive materials in the art. For example, the conductive material (CMA) may include crystalline carbon, amorphous carbon, or a combination thereof. The conductive material (CMA) may include, for example, a sintered product of a carbon precursor. The conductive material (CMA) may include, for example, carbon nanostructures.

[0087] The conductive material (CMA) may include, for example, porous carbon or non-porous carbon. The porous carbon may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black; graphite, activated carbon, or a combination thereof. The form of the carbon within the conductive material (CMA) may be, for example, in particle form, sheet form, fibrous form, etc., but is not limited thereto and may be any form of carbon used in the relevant art.

[0088] In one embodiment of the present invention, the conductive material (CMA) may include a fibrous carbon-based material. By including the fibrous carbon-based material in the conductive material (CMA), the electron conductivity of the positive electrode active material (CAC) can be further improved. By including the fibrous carbon-based material in the conductive material (CMA), electron conduction from the surface to the interior of the positive electrode active material (CAC) can be performed more easily. The internal resistance of the sulfide-based composite (CAM) is reduced by the conductive material (CMA), and the cycle characteristics of the secondary battery can be further improved.

[0089] 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 cathode active material (CAC) is improved, and the imbalance of local electron conductivity within the cathode active material (CAC) can be further alleviated.

[0090] 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.

[0091] 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.

[0092] 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 cathode active material (CAC).

[0093] The method for manufacturing the sulfide-based cathode active material (CAC) 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 sulfide-based cathode active material (CAC) 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.

[0094] In one embodiment of the present invention, the sulfide-based composite (CAM) within the sulfide-based cathode active material (CAC) 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 Li7-x PS 6-x I x It may include one or more selected from , 0≤x≤2.

[0095] 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.

[0096] In one embodiment of the present invention, the sulfide-based complex (CAM) within the sulfide-based cathode active material (CAC) may comprise a complex of Li2S and a lithium salt. In other words, the complex (CAM) may comprise a compound of Li2S and a lithium salt. The lithium salt compound may not contain, for example, sulfur (S) atoms.

[0097] 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.

[0098] In one embodiment of the present invention, the sulfide-based complex (CAM) may comprise a complex 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)3C2T x , 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.

[0099] In one embodiment of the present invention, the sulfide-based complex (CAM) may comprise 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.

[0100] A sulfide-based cathode active material (CAC) and a composite (CAM) containing Li2S according to one embodiment of the present invention will be described in more detail. The sulfide-based cathode active material (CAC) may comprise a composite of Li2S, a lithium salt, and carbon. More specifically, the sulfide-based cathode active material (CAC) may comprise a composite of Li2S, a lithium halide, and carbon.

[0101] The composite (CAM) according to the embodiments may have ductility. The composite (CAM) may function as a buffer material within the positive active material layer (120). The composite (CAM) may prevent the occurrence of defects due to volume changes in the positive active material layer (120).

[0102] A composite (CAM) 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.

[0103] In one embodiment, the composite (CAM) may include a solid solution of Li2S and a lithium salt. The ionic conductivity of the composite (CAM) may be improved by including the solid solution of Li2S and a lithium salt. For example, the ionic conductivity of the solid solution of Li2S and a lithium salt may be improved compared to the ionic conductivity of Li2S by including lithium ions disposed within the Li2S crystallites. Consequently, the composite (CAM) according to the present invention may have high ionic conductivity and low internal resistance. The cycle characteristics of an all-solid-state secondary battery including the composite (CAM) of the present invention may be improved.

[0104] The size of the Li2S crystallites of the composite (CAM) obtained from the XRD spectrum may be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of the Li2S crystallites of the composite (CAM) obtained from the XRD spectrum may be, for example, 1 to 20 nm, 1 to 15 nm, or 3 to 10 nm. As the size of the Li2S crystallites decreases, the contact area between Li2S and the lithium salt may increase. As the contact area between Li2S and the lithium salt increases, the ionic conductivity of the composite of Li2S and the lithium salt may be improved.

[0105] A composite (CAM) according to one embodiment may further include a metal halide. In other words, the composite (CAM) may include a composite of Li2S, a lithium salt, and a metal halide. The metal halide may contain a metal other than lithium. For example, the metal of the metal halide may include at least one selected from the group consisting of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), bismuth (Bi), tin (Sn), and zinc (Zn).

[0106] The complex (CAM) 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).

[0107] The composite (CAM) may include a solid solution of Li2S, a lithium salt, and a metal halide. As an example, the composite (CAM) may include a compound (or solid solution) represented as Li2S-LiI-AlI3. As described above, the composite (CAM) and the conductive material (CMA, e.g., a carbon nanostructure) may constitute a cathode active material (CAC) according to the present invention.

[0108] The Mohs hardness of the composite (CAM) may be lower than that of the lithium salt. The composite (CAM) may have improved ductility compared to the lithium salt. By having improved ductility, internal defects caused by volume changes in the positive active material layer (120) can be effectively prevented.

[0109] The Mohs hardness of Li2S is, for example, 0.6. The Mohs hardness of the composite (CAM) 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 (CAM) increases excessively, it may be difficult to provide ductility.

[0110] 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.

[0111] Since Li2S has relatively low ionic conductivity, a complex can be formed between Li2S and a lithium salt to improve ionic conductivity. A complex (CAM) formed between Li2S and a lithium salt can have improved ionic conductivity compared to Li2S alone. The content of Li2S in the complex (CAM) can be 50 wt% to 95 wt%, 50 wt% to 90 wt%, 50 wt% to 80 wt%, or 50 wt% to 70 wt% of the total weight of the complex (CAM). By having a Li2S content within this range, the complex (CAM) can simultaneously possess improved ionic conductivity and excellent ductility.

[0112] The content of the lithium salt in the composite (CAM) may be 5 wt% to 50 wt%, 10 wt% to 50 wt%, 20 wt% to 50 wt%, or 30 wt% to 50 wt% of the total weight of the composite (CAM). By having the lithium salt content within this range, the composite (CAM) can simultaneously have improved ionic conductivity and excellent ductility.

[0113] The content of metal halide in the composite (CAM) may be 5 wt% to 30 wt% or 5 wt% to 20 wt% of the total weight of the composite (CAM). By having a metal halide content within this range, the composite (CAM) can simultaneously have improved ionic conductivity and excellent ductility.

[0114] In one embodiment, the content of Li2S in the composite (CAM) may be greater than the content of the lithium salt. The content of Li2S in the composite (CAM) may be greater than the content of the metal halide. For example, the molar ratio of Li2S to the lithium salt in the composite (CAM) may be 51:49 to 95:5, 55:45 to 90:10, 60:40 to 90:10, or 70:30 to 90:10. By having such molar ratios, the composite (CAM) can simultaneously possess enhanced ionic conductivity and excellent ductility.

[0115] The ionic conductivity of the composite (CAM) 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 (CAM) has ionic conductivity in this range, the internal resistance of the positive active material layer (120) containing the composite (CAM) can be further reduced.

[0116] The average particle size (D50) of the composite (CAM) may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The average particle size of the composite (CAM) may be, for example, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, or 0.1 μm to 1 μm.

[0117] The size of the Li2S particles in the composite (CAM) may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the Li2S particles may be, for example, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, or 0.1 μm to 1 μm.

[0118] The solid electrolyte (SEP) in the positive active material layer (120) may be, for example, a sulfide-based solid electrolyte. 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, Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x, 0≤x≤2, and one or more selected from. Sulfide-based solid electrolytes are produced by processing starting materials, such as Li2S or P2S5, by methods such as melt quenching or mechanical milling. 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 comprising Li2S-P2S5 to form a solid electrolyte, the molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 20 : 80 to 90 : 10, 25 : 75 to 90 : 10, 30 : 70 to 70 : 30, and 40 : 60 to 60 : 40.

[0119] Sulfide-based solid electrolytes may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 1:

[0120] <Chemical Formula 1>

[0121] Li + 12-n-x A n+ X 2- 6-x Y - x

[0122] 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, Li7-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.

[0123] Alternatively, sulfide-based solid electrolytes are Li 7-a-c 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 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.

[0124] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0125] The positive active material layer (120) may further include a filler (FIL). In one embodiment, the content of the filler (FIL) in the positive active material layer (120) may be 0.1 to 20 wt%, 0.1 to 10 wt%, or 0.1 to 5 wt% of the total weight of the positive active material layer (120).

[0126] According to embodiments of the present invention, the filler (FIL) may be an inorganic filler, an organic filler, or a combination thereof. In one embodiment, the filler (FIL) may include an amorphous inorganic filler. The inorganic filler may be, for example, an amorphous lithium metal oxyhalide. In one embodiment, an amorphous lithium metal oxyhalide may be produced by manufacturing a crystalline lithium metal oxyhalide, then melting the crystalline lithium metal oxyhalide to produce a molten salt, and then cooling it. In another embodiment, an amorphous lithium metal oxyhalide may be directly produced by controlling the composition during the production of the lithium metal oxyhalide. The amorphous inorganic filler may have, for example, ductility. Since the amorphous inorganic filler has ductility, it can more effectively accommodate volume changes during charging and discharging of the all-solid-state battery (10). In contrast, the crystalline lithium metal oxyhalide may have relatively brittleness compared to the amorphous lithium metal oxyhalide. The amorphousness of inorganic fillers can be confirmed using XRD spectra.

[0127] The inorganic filler may be, for example, glassy. The inorganic filler may include, for example, a glassy lithium metal oxyhalide having a glass transition temperature (Tg). The glassy lithium metal oxyhalide may have ductility. Since the inorganic filler has ductility, it can effectively accommodate volume changes of the all-solid-state secondary battery (10) during charging and discharging, or be easily deformed according to volume changes of the all-solid-state secondary battery (10).

[0128] The glass transition temperature of the inorganic filler may be, for example, 20°C or lower, 10°C or lower, 0°C or lower, or -10°C or lower. Because the inorganic filler has such a low glass transition temperature, it can easily transition from a brittle crystalline metal salt state to a ductile glassy state. For example, the inorganic filler can be easily transitioned from a crystalline molten salt state to a glassy state by melting and then cooling it. Alternatively, a glassy state can be obtained during the manufacturing process of the inorganic filler. The glass transition temperature can be measured, for example, using a Differential Scanning Calorimeter (DSC). The glass transition temperature can be measured, for example, using a Dynamic Mechanical Analyzer (DMA).

[0129] The melting point of the inorganic filler may be, for example, 100°C or higher, 105°C or higher, 110°C or higher, 115°C or higher, 120°C or higher, 125°C or higher, 130°C or higher, 135°C or higher, 140°C or higher, or 145°C or higher. The melting point of the inorganic filler may be, for example, 200°C or lower, 190°C or lower, 180°C or lower, 170°C or lower, 160°C or lower, or 150°C or lower. Since the inorganic filler has a melting point within this range, the inorganic filler can be melted to a molten salt state and then cooled to easily produce an amorphous inorganic filler. The melting point of the inorganic filler can be measured, for example, using a differential scanning calorimeter (DSC).

[0130] The inorganic filler may be an ion-conductive inorganic filler. The inorganic filler may have an ion conductivity of, for example, 0.01 mS / cm or more, 0.05 mS / cm or more, 0.1 mS / cm or more, 0.3 mS / cm or more, 0.5 mS / cm or more, 0.7 mS / cm or more, or 1.0 mS / cm or more at 25°C and 1 atm. Ion conductivity may be measured by AC impedance analysis. The voltage amplitude used for AC impedance analysis may be 5 to 10 mV, and the frequency may be 1 MHz to 1 Hz. By having ion conductivity, the increase in interfacial resistance between composite cathode material (CMS) particles, between solid electrolyte (SEP) particles, and / or between the composite cathode material (CMS) and the solid electrolyte (SEP) within the cathode active material layer (120) can be effectively suppressed.

[0131] The elastic modulus (or Young's modulus) of the inorganic filler at 30°C may be 10 GPa or less, 5 GPa or less, 3 GPa or less, or 2 GPa or less. Because the inorganic filler has an elastic modulus low in this range, the positive active material layer (120) can effectively accommodate volume changes of the all-solid-state battery (10). Thus, the cycle characteristics of the all-solid-state battery (10) according to the present invention can be improved. The elastic modulus of the inorganic filler can be measured, for example, using a Dynamic Mechanical Analyzer (DMA).

[0132] The elastic modulus of the inorganic filler may be smaller than, for example, the elastic modulus of the solid electrolyte (SEP). The elastic modulus of the solid electrolyte (SEP) at 30°C may be, for example, 22 GPa to 30 GPa. The elastic modulus of the inorganic filler may be, for example, 90% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the elastic modulus of the solid electrolyte (SEP).

[0133] Inorganic filler, i.e., filler (FIL), can be uniformly provided within the positive active material layer (120). In the all-solid-state battery (10) of the present invention, the inorganic filler has a lower elastic modulus compared to the solid electrolyte (SEP), so that the inorganic filler can easily fill the voids between the solid electrolytes (SEP) and / or the voids between the solid electrolyte (SEP) and the composite positive material (CMS), thereby reducing the internal resistance of the positive active material layer (120) and easily accommodating volume changes of the positive active material layer (120) during charging and discharging. As a result, the cycle characteristics of the all-solid-state battery (10) can be further improved. The elastic modulus of the solid electrolyte (SEP) can be measured, for example, using a Dynamic Mechanical Analyzer (DMA).

[0134] The inorganic filler may, for example, have viscoelasticity. The inorganic filler may, for example, have viscoelastic creep. The viscoelastic creep rate of the inorganic filler may, for example, be 1×10⁻⁴ % / s or greater, 2×10⁻⁴ % / s or greater, or 4×10⁻⁴ % / s or greater. % / s is the ratio of the deformed size to the initial size per unit time (second). Because the inorganic filler has viscoelasticity, it can easily accommodate volume changes during charging and discharging of the all-solid-state battery (10) and can continuously deform its shape without defects. The creep rate is the rate of change over time, i.e., the deformation rate, of an inorganic filler subjected to stress at a constant temperature. The creep rate can be measured, for example, using a universal test machine.

[0135] The weapon filler is Li a Al b M c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e, M은 원소주기율표 3족 내지 15족에서 선택되는 금속) 표시되는 리튬금속옥시할라이드(lithium metal oxyhalide)를 포함할 수 있다. 리튬금속옥시할라이드의 금속 M은 예를 들어 Fe, Ga, In, As, Sb, Mo, Bi, B 또는 이들의 조합을 포함할 수 있다.

[0136] Lithium metal oxyhalides are, for example, Li a Al b O d Cl e (0 <a≤3; 0<b≤3; 0<d≤2; 1<e≤4; d<e), Li a Al b Fe c O d Cl e(0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Ga c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b In c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b As c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Sb c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b Mo c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), ), Li a Al b Bi c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e), Li a Al b B c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤2; 1<e≤4; d<e) 또는 이들의 조합을 포함할 수 있다.

[0137] Lithium metal oxyhalides are, for example, LiAl x O z Cl w(0 <x≤2; 0<z≤1; 2<w<4; z<w), LiAlxFeyOzClw (0<x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Yes y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x In y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x I y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Sat y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Mo y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x Bi y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w), LiAl x B y Oh z Cl w (0 <x≤2; 0≤y<1; 0<z≤1; 2<w<4; z<w) 또는 이들의 조합을 포함할 수 있다.

[0138] The inorganic filler content in the positive active material layer (120) may be smaller than the solid electrolyte (SEP) content. The weight ratio of the solid electrolyte (SEP) to the inorganic filler in the positive active material layer (120) may be 99:1 to 50:50, 99:1 to 60:40, 99:1 to 70:30, 99:1 to 80:20, or 99:1 to 90:10. By having the solid electrolyte (SEP) and the inorganic filler in this range of weight ratios, the volume change during charging and discharging of the positive active material layer (120) can be more easily accommodated. As a result, the cycle characteristics of the all-solid-state battery (10) can be further improved.

[0139] In another embodiment, the filler (FIL) may include an organic filler. The organic filler may include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene (PP), cycloolefin polymer, and combinations thereof.

[0140] The positive active material layer (120) may further include a conductive material. The conductive material may be, for example, a carbon-based material, a metal-based material, or a combination thereof.

[0141] The conductive material content in the positive active material layer (120) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive active material layer (120).

[0142] Metallic materials may be metal powders, metal fibers, or combinations thereof, but are not limited to these; any metallic material used as a conductive material in the relevant technical field is acceptable.

[0143] The carbon-based material may include, for example, amorphous carbon. By including amorphous carbon in the carbon-based material, side reactions between the carbon-based material and the solid electrolyte (SEP) can be suppressed. Accordingly, the cycle characteristics of the all-solid-state battery (10) containing the carbon-based material can be further improved. A specific description of the carbon-based material may be the same or similar as that described above regarding the conductive material (CMA).

[0144] The positive active material layer (120) may further include a binder (BID). The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene, etc., but is not limited to these and may be any binder used in the relevant technical field. The content of the binder (BID) in the positive active material layer (120) may be, for example, 0.1 wt% to 10 wt%, 0.5 to 5 wt%, or 0.5 to 2 wt% of the total weight of the positive active material layer (120). The binder (BID) may be omitted.

[0145] The positive active material layer (120) may further include additives such as a coating agent, a dispersant, and an ion conductivity aid in addition to the aforementioned composite positive material (CMS), solid electrolyte (SEP), binder (BID), conductive material (CMA), and filler (FIL). Known materials generally used in electrodes of all-solid-state batteries may be used as the coating agent, dispersant, and ion conductivity aid that may be included in the positive active material layer (120).

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] The cathode coating layer (220) may include metal and carbon. For example, the cathode coating layer (220) may include at least one metal selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The cathode coating layer (220) may include at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene. In one embodiment, the cathode coating layer (220) may include a mixture of carbon black and silver (Ag).

[0151] The cathode coating layer (220) may further include other additives in addition to metal and carbon. The cathode 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.

[0152] 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.

[0153] Meanwhile, although not illustrated, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte layer (300).

[0154] 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 (SEP) in the aforementioned anode active material layer (120).

[0155] 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).

[0156] 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 mixed molar ratio of Li2S and P2S5 may be, for example, in the range of Li2S : P2S5 = 50 : 50 to 90 : 10.

[0157] In one embodiment, the first solid electrolyte is Li 7-x PS6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include an argyrodite-type compound comprising one or more selected from (0≤x≤2). The first solid electrolyte may include an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0158] In another embodiment, the first solid electrolyte is Li 7-a-c M a PS 6-c X c It 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 a real number between 0 and 2.

[0159] 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.

[0160] The second solid electrolyte layer (320) may include a second solid electrolyte. The second solid electrolyte may have a particle shape such as a sphere or an ellipsoid. The second solid electrolyte may include a sulfide-based solid electrolyte. The description of the second solid electrolyte may be the same 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.

[0161] The second solid electrolyte can come into direct contact with the negative electrode coating layer (220). By doing so, the second solid electrolyte can suppress lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210). The second solid electrolyte can effectively suppress negative side reactions. By doing so, the cell performance of the all-solid-state battery (10) according to the present invention can be improved.

[0162] Each of the first and second solid electrolyte layers (310, 320) may further include a binder. The binder 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 in the solid electrolyte layer (300) may be the same as or different from the binder in the positive active material layer (120) or the binder in the negative coating layer (220).

[0163] The content of the binder in the solid electrolyte layer (300) may be 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the solid electrolyte layer (300).

[0164] In another embodiment of the present invention, the solid electrolyte layer (300) may be provided as a single layer structure rather than a double layer structure of the first solid electrolyte layer (310) and the second solid electrolyte layer (320).

[0165] 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).

[0166] 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).

[0167] 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).

[0168] 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).

[0169] The all-solid-state battery (10) according to the present embodiment can be manufactured by forming a negative electrode composite layer (ASH) on a first carrier film and forming a positive electrode composite layer (CSH) on a second carrier film, and then laminating the negative electrode composite layer (ASH) and the positive electrode composite layer (CSH).

[0170] In one embodiment, as shown in FIG. 2, the positive active material layer (120) in a discharged state may have a first thickness (TK1). The all-solid-state battery (10) may have a first height (HE1) in a third direction (D3). The first height (HE1) may be the sum of the thickness of the positive composite layer (CSH) and the thickness of the negative composite layer (ASH).

[0171]

[0172] In the embodiments described below, detailed descriptions of technical features that overlap with those previously described are omitted, and differences are described in detail.

[0173] FIG. 8 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. 8, in one embodiment, an all-solid-state battery (10) in a charged state may further include a lithium metal layer (230) provided between a negative electrode current collector (210) and a negative electrode coating layer (220). The negative electrode layer (200) according to the present embodiment may include a negative electrode current collector (210), a negative electrode coating layer (220), and a lithium metal layer (230) between them.

[0174] 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 negative electrode coating layer (220) and the negative electrode current collector (210) during the charging process of the all-solid-state battery (10), for example.

[0175] The lithium metal layer (230) may have a third thickness (TK3). The third thickness (TK3) is not particularly limited, but may be, for example, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the third thickness (TK3) of the lithium metal layer (230) is excessively thin, it may be difficult for the lithium metal layer (230) to perform the role of a lithium reservoir. If the third thickness (TK3) of the lithium metal layer (230) is excessively thick, the mass and volume of the all-solid-state battery (10) increase, and the cycle characteristics of the all-solid-state battery (10) may actually deteriorate.

[0176] In another embodiment of the present invention, a lithium metal layer (230) within the negative electrode layer (200) may be provided, for example, between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the all-solid-state battery (10). When the lithium metal layer (230) is placed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the all-solid-state battery (10), the lithium metal layer (230) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be placed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the all-solid-state battery (10).

[0177] When a lithium metal layer (230) is deposited by charging after assembly of the all-solid-state battery (10), the energy density of the all-solid-state battery (10) can be increased because the lithium metal layer (230) is not included during assembly of the all-solid-state battery (10). When charging the all-solid-state battery (10), it can be charged beyond the charging capacity of the negative electrode coating layer (220). That is, the negative electrode coating layer (220) is overcharged. At the beginning of charging, lithium can be absorbed in the negative electrode coating layer (220). When charging beyond the capacity of the negative electrode coating layer (220), lithium can be deposited, for example, between the negative electrode coating layer (220) and the negative electrode current collector (210). A lithium metal layer (230) can be formed by the deposited lithium.

[0178] 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 (10). In addition, since the negative electrode coating layer (220) covers the lithium metal layer (230), the negative electrode coating layer (220) can protect the lithium metal layer (230) and simultaneously suppress the precipitation growth of lithium dendrites. Therefore, the negative electrode coating layer (220) can suppress short circuits and capacity degradation of the all-solid-state battery (10) and improve the cycle characteristics of the all-solid-state battery (10).

[0179] When a lithium metal layer (230) is formed by charging after assembly of the all-solid-state battery (10), the negative electrode layer (200), that is, the negative electrode current collector (210) and the negative electrode coating layer (220) and the region between them may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the all-solid-state battery (10).

[0180] The positive active material layer (120) from which lithium ions are released by charging the all-solid-state battery (10) may have a second thickness (TK2). The second thickness (TK2) of the positive active material layer (120) may be smaller than the first thickness (TK1) of FIG. 2.

[0181] In one embodiment of the present invention, the difference between the first thickness (TK1) and the second thickness (TK2) may be substantially the same or similar to the third thickness (TK3) of the lithium metal layer (230). For example, the third thickness (TK3) may be 1.0 to 1.5 times, or 1.0 to 1.2 times, the difference between the first thickness (TK1) and the second thickness (TK2). According to the present invention, the thickness of the positive active material layer (120) may be reduced by the same amount as the thickness of the lithium metal layer (230) formed by charging the all-solid-state battery (10).

[0182] Although not illustrated, the all-solid-state battery (10) may operate (i.e., charge and / or discharge) while pressurized by a pressurizing jig. In one embodiment, the all-solid-state battery (10) may be pressurized to 0.8 MPa to 2 MPa. For example, the all-solid-state battery (10) may have an internal pressure of about 1 MPa when discharged, and the all-solid-state battery (10) may have an internal pressure of about 1.5 MPa when charged. The ratio of the internal pressure of the all-solid-state battery (10) in the charged state to the internal pressure of the all-solid-state battery (10) in the discharged state may be 1.0 to 2.0, or 1.2 to 1.8.

[0183] The height (or thickness or volume) of the all-solid-state battery (10) may change according to charging and discharging under the aforementioned pressurized state. In the all-solid-state battery (10) according to the present embodiment, the thickness of the positive active material layer (120) may decrease in correspondence with the lithium metal layer (230) formed by charging. Accordingly, the second height (HE2) of the charged all-solid-state battery (10) shown in FIG. 8 may be similar to the first height (HE1) of the discharged all-solid-state battery (10) shown in FIG. 2. For example, the second height (HE2) may be 1 to 1.5 times, or 1 to 1.2 times, the first height (HE1).

[0184]

[0185] FIG. 9 is a cross-sectional view along line A-A' of FIG. 1, intended to illustrate an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 5, the all-solid-state battery (10) according to the present embodiment may further include a gasket (GSK). The gasket (GSK) may be provided to surround the positive electrode composite layer (CSH). The gasket (GSK) may fill the step difference on the side of the all-solid-state battery (10) caused by the difference in area between the negative electrode composite layer (ASH) and the positive electrode composite layer (CSH). The gasket (GSK) may surround the four sides of the positive electrode composite layer (CSH). For example, the thickness of the gasket (GSK) may be substantially the same as the thickness of the positive electrode composite layer (CSH).

[0186] The upper surface of the second solid electrolyte layer (320) may include a first region in contact with the first solid electrolyte layer (310) and a second region in contact with the gasket (GSK). The second region may be a peripheral region of the upper surface of the second solid electrolyte layer (320). The second region may surround the first region.

[0187] The gasket (GSK) can prevent cracking of the solid electrolyte layer (300) during the manufacturing of the all-solid-state battery (10) and / or during the charging and discharging of the all-solid-state battery (10). This can improve the cycle characteristics of the all-solid-state battery (10). If the all-solid-state battery (10) does not include the gasket (GSK), uneven pressure is applied to the negative electrode composite layer (ASH) in contact with the positive electrode composite layer (CSH), causing cracking in the solid electrolyte layer (300), and the likelihood of a short circuit occurring due to the growth of lithium metal through this may increase.

[0188] The thickness of the gasket (GSK) may be greater than the thickness of the positive composite layer (CSH) or substantially equal to the thickness of the positive composite layer (CSH). Since the thickness of the gasket (GSK) is equal to the thickness of the positive composite layer (CSH), a uniform pressure is applied between the positive composite layer (CSH) and the negative composite layer (ASH), and the positive composite layer (CSH) and the negative composite layer (ASH) are sufficiently in contact, thereby reducing the interfacial resistance between the first solid electrolyte layer (310) and the second solid electrolyte layer (320). Additionally, the internal resistance of the solid electrolyte layer (300) may be reduced as the solid electrolyte layer (300) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state battery (10).

[0189] The gasket (GSK) may have a single-layer structure, for example. Alternatively, although not shown in the drawings, the gasket (GSK) may have a multi-layer structure. In a gasket (GSK) having a multi-layer structure, each layer may have a different composition. A gasket (GSK) having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. A gasket (GSK) having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers.

[0190] The gasket (GSK) may include, for example, a flame-retardant inert member. By providing flame retardancy, the flame-retardant inert member can prevent thermal runaway and the possibility of ignition of the all-solid-state battery (10). Consequently, the gasket (GSK) can further enhance the safety of the all-solid-state battery (10). By absorbing residual moisture within the all-solid-state battery (10), the flame-retardant inert member prevents the deterioration of the all-solid-state battery (10), thereby improving the lifespan characteristics of the all-solid-state battery (10).

[0191]

[0192] FIG. 10 is a cross-sectional view along line A-A' of FIG. 1 for illustrating an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 6, the positive electrode layer (100) may further include a coating layer (CTL) provided between the positive electrode current collector (110) and the positive electrode active material layer (120). The coating layer (CTL) may be placed directly on, for example, 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).

[0193] 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 filler (FIL), solid electrolyte (SEP), or positive active material (CAC) 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 degradation of the all-solid-state battery (10) during the charging and discharging process and improve the cycle characteristics of the all-solid-state battery (10).

[0194] 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).

[0195] The coating layer (CTL) may include, for example, a carbon-based conductive material. The carbon-based conductive material included in the coating layer (CTL) may be selected from among the carbon-based conductive materials used in the positive active material layer (120). The coating layer (CTL) may include the same carbon-based conductive material as the carbon-based conductive material used in the positive active material layer (120). By including the carbon-based conductive material, the coating layer (CTL) may be, for example, a conductive layer.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] The negative electrode layer (200) may further include a thin film (TFL) provided between the negative electrode current collector (210) and the negative electrode coating layer (220). The thin film (TFL) may be provided on one side of the negative electrode current collector (210) to form an alloy with lithium.

[0200] 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.

[0201] By placing the thin film (TFL) on one side of the negative current collector (210), the deposition pattern of the lithium metal layer (230, see FIG. 4) deposited between, for example, the thin film (TFL) and the negative coating layer (220) is further flattened, and the cycle characteristics of the all-solid-state battery (10) can be further improved.

[0202] 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 of 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 (10) and may lower the cycle characteristics of the all-solid-state battery (10). The thin film (TFL) may be formed on the negative electrode current collector (21) by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods, and any method capable of forming a thin film in the relevant technical field may be possible.

[0203]

[0204] The creative idea described below will be explained in more detail through examples and comparative examples. However, the examples are merely illustrative and the scope of the creative idea described below is not limited solely to these examples.

[0205]

[0206] Preparation Example 1: Preparation of Sulfide-based Anode Active Material

[0207] (Stage 1)

[0208] The sulfur compound Li2S, the lithium salt LiI, and the metal halide AlI3 were mixed. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3 composite. The milling conditions were 25 °C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was approximately 28 G.

[0209] (Stage 2)

[0210] A Li2S-LiI-AlI3 composite and carbon nanofiber (CNF) were mixed. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-AlI3-CNF cathode active material. The milling conditions were 25 ℃ and 600 rpm for 10 hours. The milling energy applied to the sample during milling was approximately 28 G.

[0211] Based on the total manufactured cathode active material, Li2S 57.1 wt%, (LiI-AlI3) It was mixed with 28.6 wt% and 14.3 wt% CNF. For the lithium salt and metal halide, LiI and AlI3 were mixed in a 1:1 molar ratio and used.

[0212] Example 1: All-solid-state battery fabrication / Partial coating

[0213] [anode]

[0214] A composite cathode material was prepared by milling the cathode active material and the ion-conducting sulfide prepared according to Preparation Example 1 using a thin mixer and then drying. Li3PS4-LiBH4 was used as the ion-conducting sulfide, and a composite cathode material was prepared in which a functional layer containing the ion-conducting sulfide was formed on the surface of the cathode active material.

[0215] An example was prepared in which a portion of the surface of the positive electrode active material is covered with an ion-conductive sulfide by controlling the mixing speed and mixing time.

[0216] The composite cathode material and the solid electrolyte were placed in a mixer and mixed for about 2 minutes. An azirodite-based solid electrolyte (Li6PS5Cl, D50 = 3.0 μm) was used as the solid electrolyte. The above mixed composition was applied onto an aluminum cathode current collector to form a cathode active material layer.

[0217] The composition of the positive active material layer was positive active material: ion-conducting sulfide: sulfide-based solid electrolyte = 85 wt%: 1 wt%: 14 wt%.

[0218] [cathode]

[0219] A SUS foil with a thickness of about 10 μm was prepared as a cathode current collector. As cathode coating materials, carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle size of about 60 nm were prepared.

[0220] 4 g of a mixed powder, prepared by mixing carbon black (CB) and silver particles in a weight ratio of 3:1, was placed in a container, and 4 g of an NMP solution containing 7 wt% of a PVdF binder (Kureha # 9300) was added to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while gradually adding NMP to it. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold-roll-pressed to flatten the surface to manufacture a cathode having a cathode coating layer / cathode current collector structure. The thickness of the cathode coating layer was approximately 15 μm. The surface areas of the cathode coating layer and the cathode current collector were the same.

[0221] [Solid Electrolyte Layer]

[0222] A mixture was prepared by adding an acrylic binder to a solid electrolyte, Li6PS5Cl, which is an argyrodite-type crystal. The solid electrolyte and the acrylic binder were mixed in an amount of 98.5 parts by weight and 1.5 parts by weight, respectively. A slurry was prepared by stirring while adding octyl acetate to the prepared mixture. The prepared slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, and a laminate was prepared by drying in air at a temperature of 80 °C for 10 minutes. After vacuum drying the prepared laminate at 80 °C for 2 hours, the solid electrolyte layer was separated from the PET substrate to produce a solid electrolyte layer.

[0223] [All-solid-state battery manufacturing]

[0224] Each of the anode, solid electrolyte layer, and cathode prepared as described above was sequentially stacked, and the prepared stack was plate-pressed at a pressure of 500 MPa at approximately 85 ℃ for 30 minutes. Through this pressure treatment, the solid electrolyte layer is sintered, thereby improving battery characteristics.

[0225]

[0226] Example 2: All-solid-state battery manufacturing / Perfect coating

[0227] A composite cathode material was prepared by milling the cathode active material and the ion-conducting sulfide prepared according to Preparation Example 1 using a thin mixer and then drying. Li3PS4-2LiBH4 was used as the ion-conducting sulfide, and a composite cathode material was prepared in which a functional layer containing the ion-conducting sulfide was formed on the surface of the cathode active material. By controlling the mixing speed and mixing time, an example was prepared in which the ion-conducting sulfide covered most of the surface of the cathode active material.

[0228] The composite cathode material and the solid electrolyte were placed in a mixer and mixed for about 2 minutes. An azirodite-based solid electrolyte (Li6PS5Cl, D50 = 3.0 μm) was used as the solid electrolyte. The above mixed composition was applied onto an aluminum cathode current collector to form a cathode active material layer.

[0229] The composition of the positive active material layer was positive active material: ion-conducting sulfide: sulfide-based solid electrolyte = 85 wt%: 1 wt%: 14 wt%. In addition, the composition of the negative electrode and solid electrolyte layer was the same as in Example 1 to manufacture an all-solid-state battery.

[0230]

[0231] Example 3: All-solid-state battery manufacturing / Perfect coating

[0232] A composite cathode material was prepared by milling the cathode active material and the ion-conducting sulfide prepared according to Preparation Example 1 using a thin mixer and then drying. Li3PS4-2LiBH4 was used as the ion-conducting sulfide, and a composite cathode material was prepared in which a functional layer containing the ion-conducting sulfide was formed on the surface of the cathode active material. By controlling the mixing speed and mixing time, an example was prepared in which the ion-conducting sulfide covered most of the surface of the cathode active material.

[0233] The composite cathode material and the solid electrolyte were placed in a mixer and mixed for about 2 minutes. An azirodite-based solid electrolyte (Li6PS5Cl, D50 = 3.0 μm) was used as the solid electrolyte. The above mixed composition was applied onto an aluminum cathode current collector to form a cathode active material layer.

[0234] The composition of the positive active material layer was positive active material: ion-conducting sulfide: sulfide-based solid electrolyte = 85 wt%: 7 wt%: 8 wt%. In addition, the negative electrode and solid electrolyte layer were the same as those in Example 1, and an all-solid-state battery was manufactured.

[0235]

[0236] Example 4: All-solid-state battery manufacturing / Perfect coating

[0237] A composite cathode material was prepared by milling the cathode active material and the ion-conducting sulfide prepared according to Preparation Example 1 using a thin mixer and then drying. Li3PS4-2LiBH4 was used as the ion-conducting sulfide, and a composite cathode material was prepared in which a functional layer containing the ion-conducting sulfide was formed on the surface of the cathode active material. By controlling the mixing speed and mixing time, an example was prepared in which the ion-conducting sulfide covered most of the surface of the cathode active material.

[0238] The composite cathode material and the solid electrolyte were placed in a mixer and mixed for about 2 minutes. An azirodite-based solid electrolyte (Li6PS5Cl, D50 = 3.0 μm) was used as the solid electrolyte. The above mixed composition was applied onto an aluminum cathode current collector to form a cathode active material layer.

[0239] The composition of the positive active material layer was positive active material: ion-conducting sulfide: sulfide-based solid electrolyte = 85 wt%: 14 wt%: 1 wt%. In addition, the negative electrode and solid electrolyte layer were the same as those in Example 1, and an all-solid-state battery was manufactured.

[0240] Comparative Example 1

[0241] A cathode comprising a cathode active material and a solid electrolyte prepared according to Preparation Example 1 was prepared. An azirodite-based solid electrolyte (Li6PS5Cl, D50 = 3.0 μm) was used as the solid electrolyte. The composition of the cathode active material layer was cathode active material: solid electrolyte = 85 wt%: 15 wt%. In addition, the anode and solid electrolyte layer were identical to those in Example 1, and an all-solid-state battery was prepared.

[0242]

[0243] Comparative Example 2

[0244] A positive active material layer was prepared by simply mixing the positive active material, ion-conducting sulfide, and solid electrolyte prepared according to Preparation Example 1. Li3PS4-2LiBH4 was used as the ion-conducting sulfide, and an azirodite-based solid electrolyte (Li6PS5Cl, D50 = 3.0 μm) was used as the solid electrolyte.

[0245] The composition of the positive active material layer was positive active material: ion-conducting sulfide: sulfide-based solid electrolyte = 85 wt%: 1 wt%: 14 wt%.

[0246]

[0247] Hereinafter, all-solid-state batteries according to the embodiments and comparative examples of the present invention are shown in Table 1 below.

[0248] Anode Solid Electrolyte Layer Cathode Ratio High Anode Active Material Ion-conductive Sulfide Solid Electrolyte Example 185 wt% 1 wt% 14 wt% Li6PS5ClAg / C Surface Partial Example 285 wt% 1 wt% 14 wt% Li6PS5ClAg / C Surface All Example 385 wt% 7 wt% 8 wt% Li6PS5ClAg / C Surface All Example 485 wt% 14 wt% 1 wt% Li6PS5ClAg / C Surface All Comparative Example 185 wt% -15 wt% Li6PS5ClAg / COrigin-Active Material Comparative Example 285 wt% 1 wt% 14 wt% Li6PS5ClAg / C Simple Mixture

[0249] Evaluation Example 1: Battery Performance Evaluation

[0250] The performance of all-solid-state batteries according to the embodiments and comparative examples of the present invention was evaluated. Specifically, efficiency, capacity, lifespan characteristics, and rate capability characteristics were evaluated and are shown in Table 2 below.

[0251] The obtained test cell was charged to an upper limit voltage of 4.3 V with a constant current of 0.1 C at 45 ℃ and a pressure of 0.5 MPa, and then discharged to a lower limit voltage of 2.5 V with a constant current of 0.1 C to measure the initial discharge capacity. Afterward, a 1 C discharge was performed to measure the rate capability. The ratio of the 1 C discharge capacity to the initial discharge capacity was used as an indicator of the load characteristics. The higher the above value, the lower the internal resistance of the battery and the better the load characteristics.

[0252] Lifespan was measured by the number of cycles until the cell's SOH (state-of-health) decreased to 80%. SOH (state-of-health) represents the current performance relative to the cell's initial performance. A higher measured value indicates a longer-lifespan battery.

[0253] Efficiency (%) Anode Capacity @0.1C Lifespan (Cycle @ SOH 80) Load Characteristics 1C / 0.1C (%) Example 190 195 280 89 Example 29 2210 510 92 Example 389 194 250 86 Example 49 1200 320 92 Comparative Example 185 182 82 82 Comparative Example 287 192 210 86

[0254] Referring to the evaluation results above, it can be seen that the lifespan characteristics of the all-solid-state battery according to the embodiments of the present invention are improved compared to the comparative examples. In addition, looking at the results of the load characteristics calculated based on the rate capability characteristics, it can be seen that the load characteristics of the all-solid-state battery according to the embodiments of the present invention are low. That is, it can be seen that the internal resistance of the battery is low and the network between solid particles is well formed.

[0255] This means that by further including ion-conductive sulfides on the surface of the positive electrode active material, the solid compositions constituting the positive electrode active material layer are densely bonded to form a network, thereby establishing a stable structure.

Claims

1. A core capable of reversible absorption and release of lithium ions; and The above core includes a functional layer on at least a portion of its surface, The above functional layer comprises a lithium ion-conducting sulfide containing borohydride (-BH4), Composite cathode material.

2. In Paragraph 1, The above lithium ion-conducting sulfide comprises Li3PS4-2LiBH4, Composite cathode material.

3. In Paragraph 1, The above lithium ion-conducting sulfide is Li 7-x PS 6-x (BH4) x Comprising an azirodite-type compound of (0≤x≤2), Composite cathode material.

4. In Paragraph 1, The above functional layer comprises primary particles of the lithium ion-conducting sulfide, and The average particle size of the primary particles is 300 to 500 nm, Composite cathode material.

5. In Paragraph 1, The density of the above lithium ion-conducting sulfide is 1.2 g / cm³ 3 Up to 1.6 g / cm³ 3 person, Composite cathode material.

6. In Paragraph 1, The content of the lithium ion-conducting sulfide is 1 to 20 weight% with respect to the total weight of the composite cathode material, Composite cathode material.

7. In Paragraph 1, The above functional layer covers the entire surface of the core, Composite cathode material.

8. In Paragraph 1, The lithium ion conductivity of the lithium ion-conducting sulfide measured at 25℃ is 5.0 to 7.0 mS / cm, Composite cathode material.

9. In Paragraph 1, The above core comprises an oxide-based cathode active material, Composite cathode material.

10. In Paragraph 1, The above core includes a sulfide-based cathode active material, and The above sulfide-based cathode active material comprises a complex of a sulfur compound, a lithium salt, and a metal halide, and The above sulfur compounds are S8 and Li2S n Includes at least one of (1 ≤ n ≤ 8, n is an integer), and The above lithium salt includes LiF, LiCl, LiBr, LiI, or a combination thereof, and The metal of the above metal halide comprises at least one selected from the group consisting of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), bismuth (Bi), tin (Sn), and zinc (Zn). Composite cathode material.

11. In Paragraph 10, The above lithium salt is LiI, Composite cathode material.

12. In Paragraph 10, The above metal halide is AlI3, Composite cathode material.

13. Composite cathode material according to paragraph 1; and containing sulfide-based solid electrolytes, Cathode for all-solid-state batteries.

14. In Paragraph 13, The content of the lithium ion-conducting sulfide in the anode is 1 to 15 weight%, Cathode for all-solid-state batteries.

15. In Paragraph 13, The content of the composite cathode material in the anode is 80 to 99 weight%, Cathode for all-solid-state batteries.

16. In Paragraph 13, The content of the sulfide-based solid electrolyte in the anode is 1 to 20 weight%, Cathode for all-solid-state batteries.

17. In Paragraph 13, The above sulfide-based solid electrolyte is Li 7-a PS 6-a (X) a Includes (0≤a≤2), X is F, Cl, Br, I, or a combination thereof, Cathode for all-solid-state batteries.

18. Anode pursuant to Paragraph 13; A solid electrolyte layer comprising a sulfide-based solid electrolyte; and including a cathode, All-solid-state battery.

19. In Paragraph 18, The above cathode comprises a cathode current collector and a cathode coating layer on the cathode current collector, and The above cathode coating layer includes a first particle and a second particle, and The first particle above is amorphous carbon, crystalline carbon, porous carbon, or a combination thereof, and The second particle comprises gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof. All-solid-state battery.

20. In Paragraph 19, It further includes a lithium metal layer between the above-mentioned negative current collector and the negative coating layer, and The above lithium metal layer comprises lithium or a lithium alloy, All-solid-state battery.

Images