All-solid-state secondary batteries

Abstract

The all-solid-state secondary battery according to the present aspect includes: a cathode layer including a cathode active material; an anode layer including an anode current collector and an anode active material layer arranged on the anode current collector and including an anode active material and amorphous carbon; and a solid electrolyte layer arranged between the cathode active material layer and the anode active material layer, wherein the weight ratio of the anode active material to the amorphous carbon is 1:3 to 1:1.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an all-solid-state secondary battery. Background Art

[0002] Recently, all-solid-state secondary batteries using solid electrolytes as electrolytes have attracted attention. In order to increase the energy density of such all-solid-state secondary batteries, it has been proposed to use lithium as anode active material. For example, it is known that the capacity density (i.e., capacity per unit mass) of lithium is about 10 times that of graphite, which is commonly used as anode active material. Therefore, when lithium is used as anode active material, all-solid-state secondary batteries can be manufactured to have lighter weight or smaller size, and have increased output power.

[0003] When lithium is used as the anode active material, lithium (metallic lithium) may be precipitated on the anode side during charging. As the all-solid-state secondary battery repeatedly charges and discharges, the lithium precipitated on the anode side may grow in a branched tree-like manner through the gaps (void spaces) of the solid electrolyte. Lithium grown in a branched tree-like manner may be referred to as lithium dendrites, and the growth of dendrites may cause a short circuit in the secondary battery. The growth of lithium dendrites may also cause a reduction in the capacity of the secondary battery. Summary of the Invention

[0004] Technical issues

[0005] According to aspects of the present disclosure, there is provided an all-solid-state secondary battery using lithium as an anode active material.

[0006] Technical Solution

[0007] According to the aspect, the all-solid-state secondary battery may include: a cathode layer including a cathode active material; an anode layer including an anode current collector and an anode active material layer disposed on the anode current collector and including an anode active material and amorphous carbon; and a solid electrolyte layer disposed between the cathode active material layer and the anode active material layer, wherein a weight ratio of the anode active material to the amorphous carbon is 1:3 to 1:1, the anode layer is provided in a panel shape, and the anode layer has a sheet resistance of 0.5 mΩcm or less.

[0008] The anode active material may be included in an amount of 1 weight percent (wt %) to 50 wt % based on the total weight of the anode active material layer.

[0009] The anode active material may include at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), titanium (Ti), and zinc (Zn).

[0010] The amorphous carbon may include at least one of carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), and graphene.

[0011] The anode active material layer may further include a binder.

[0012] The binder may be included in an amount of 0.3 wt % to 15 wt % based on the total weight of the anode active material.

[0013] The anode active material layer may have a thickness ranging from 1 micrometer (μm) to 20 μm.

[0014] The all-solid-state secondary battery may further include a metal layer disposed between the anode current collector and the anode active material layer, wherein the metal layer includes at least one of lithium and a lithium alloy.

[0015] Before the all-solid-state secondary battery is charged, the metal layer may be disposed between the anode current collector and the anode active material layer.

[0016] The metal layer may have a thickness ranging from 1 μm to 200 μm.

[0017] The all-solid-state secondary battery may include a thin film including an element capable of forming an alloy with lithium on the anode current collector, wherein

[0018] The thin film is disposed between the anode current collector and the anode active material layer.

[0019] The thin film may have a thickness ranging from 1 nm to 500 nm.

[0020] In the initial state or after discharge of the all-solid-state secondary battery, the anode current collector, the anode active material layer, and a region between the anode current collector and the anode active material layer may be a region not containing lithium (Li).

[0021] The all-solid-state secondary battery may be a lithium battery.

[0022] Beneficial effects

[0023] In addition, according to the disclosed embodiments, an all-solid-state secondary battery including an anode active material layer including a mixture of an anode active material and amorphous carbon mixed at an appropriate weight ratio may be provided.

[0024] In addition, according to the disclosed embodiments, an all-solid-state secondary battery having enhanced bonding force between an anode active material layer and an anode current collector may be provided.

[0025] In addition, according to the disclosed embodiments, an all-solid-state secondary battery having increased discharge capacity may be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A cross-sectional view illustrating a schematic structure of an all-solid-state secondary battery according to an embodiment;

[0027] Figure 2 is a scanning electron microscope (SEM) image of a cross section of an all-solid-state secondary battery after overcharging the anode active material layer;

[0028] Figure 3 A schematic diagram illustrating an example of measuring the sheet resistance of an anode layer;

[0029] Figure 4 A cross-sectional view illustrating a modified example of the all-solid-state secondary battery according to the embodiment;

[0030] Figure 5 A cross-sectional view illustrating a schematic structure of an all-solid-state secondary battery according to another embodiment;

[0031] Figure 6A is a graph showing the charge and discharge characteristics of the first cycle of each of the all-solid-state secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 2; and

[0032] Figure 6B is a graph showing discharge characteristics of the second cycle of each of the all-solid-state secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0033] The embodiments will now be explained in detail with reference to examples thereof in the accompanying drawings, wherein the same reference numerals refer to the same elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the description set forth herein. Accordingly, the embodiments are described below only with reference to the figures to illustrate various aspects. As used herein, the term "and / or" includes any and all combinations of one or more of the associated enumerated items. Expressions such as "at least one of", when preceding / following a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

[0034] Hereinafter, an all-solid-state secondary battery according to one or more embodiments will be described more fully with reference to the accompanying drawings. For clarity and convenience of explanation, the width and thickness of layers or regions shown in the accompanying drawings may be exaggerated. Throughout the detailed description, the same reference numerals represent the same elements.

[0035] Figure 1 A cross-sectional view illustrating a schematic structure of an all-solid-state secondary battery according to an embodiment. Figure 2 This is a scanning electron microscope (SEM) image of a cross section of an all-solid-state secondary battery after overcharging the anode active material layer. Figure 3 A schematic diagram illustrating an example of measuring the sheet resistance of an anode layer. Figure 4 A cross-sectional view illustrating a modified example of the all-solid-state secondary battery according to the embodiment.

[0036] refer to Figure 1 The all-solid-state secondary battery 10 according to the embodiment may include a cathode 10, an anode 20, and a solid electrolyte layer 30. The cathode layer 100 according to the embodiment may include a cathode current collector 101 and a cathode active material layer 102.

[0037] The cathode current collector 101 may be provided in a panel shape or a film shape. Furthermore, the cathode current collector 101 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 alloys thereof. Depending on the embodiment, the cathode current collector 101 may be omitted as needed.

[0038] The cathode active material layer 102 may include a cathode active material and a solid electrolyte material. The solid electrolyte material included in the cathode active material layer 102 may be substantially the same as the solid electrolyte material included in the solid electrolyte layer 300 (which will be described later). For the sake of clarity, matters related to the solid electrolyte material will be described in detail based on the solid electrolyte layer 300.

[0039] The cathode active material included in the cathode active material layer 102 is capable of reversibly intercalating and deintercalating lithium ions. For example, the cathode active material may include at least one of a lithium salt such as lithium cobalt oxide (hereinafter, referred to as "LCO"), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (hereinafter, referred to as "NCA"), lithium nickel cobalt manganese oxide (hereinafter, referred to as "NCM"), lithium manganate or lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, and vanadium oxide.

[0040] In addition, among the above-mentioned lithium salts, the cathode active material may include a lithium salt of a transition metal oxide having a layered rock salt structure. Here, the term "layered rock salt structure" refers to a structure in which oxygen atomic layers and metal atomic layers are arranged in a cubic rock salt structure. <111> In addition, the term "cubic rock salt structure" as used herein refers to a sodium chloride structure, which is a type of crystal structure. The lithium salt of the transition metal oxide having a layered rock salt structure according to the embodiment may include, for example, a lithium salt of a ternary transition metal oxide, such as LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM), where 0 < x < 1, 0 < y < 1 and 0 < z < 1, where x + y + z = 1. When the cathode active material includes a lithium salt of a transition metal oxide having a layered rock salt structure as described above, the energy density and thermal stability of the all-solid-state secondary battery 10 can be enhanced. In addition, the cathode active material according to an embodiment may be covered with a coating. In an embodiment, the coating according to this embodiment may include Li2O-ZrO2.

[0041] The present disclosure is not limited to the above embodiments, and the cathode active material layer 102 according to an embodiment may include not only the above-described cathode active material and solid electrolyte, but also additives such as a conductive agent, a binder, a filler, a dispersant, and an ion conduction aid. The conductive agent according to an embodiment may include, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and metal powder. In addition, the binder according to an embodiment may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene.

[0042] The anode layer 200 according to an embodiment may include an anode current collector 201 and an anode active material layer 202. The anode current collector 201 may include a material that does not react with lithium, that is, a material that does not form an alloy and a compound. The anode current collector 201 may include, for example, one of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), or an alloy of two or more of them. The anode current collector 201 according to an embodiment may be provided as, for example, a panel or a film.

[0043] As Figure 4 shown, the thin film 204 may be formed on the surface of the anode current collector 201. The thin film 204 may include an element that can form an alloy with lithium. Examples of elements that can form an alloy with lithium may include gold, silver, zinc, tin, indium, silicon, aluminum, and bismuth. The thin film 204 may include one of these metals or various types of alloys thereof. By including the thin film 204, the precipitation form of the metal layer 203 can be further flattened, and the all-solid-state secondary battery 10 can have further enhanced characteristics.

[0044] Here, the thickness of the thin film 204 is not particularly limited, but may be in the range of 1 nm to 500 nm. When the thickness of the thin film 204 is less than 1 nm, the function of the thin film 204 may not be fully exhibited. When the thickness of the thin film 204 is greater than 500 nm, the thin film 204 itself may absorb lithium, and thus the amount of lithium deposited on the anode may be reduced, and the characteristics of the all-solid-state secondary battery 10 may deteriorate. The thin film 204 may be formed on the anode current collector 201 by, for example, vacuum evaporation, sputtering, or electroplating.

[0045] The anode active material layer 202 may include amorphous carbon and an anode active material that forms an alloy or compound with lithium. The anode active material according to the embodiment may include, for example, at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), titanium (Ti), and zinc (Zn). In addition, the amorphous carbon according to the embodiment may include, for example, at least one of carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene (graphene).

[0046] In an embodiment, the anode active material layer 202 may include a mixture of at least one anode active material selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, titanium, and zinc. In an embodiment, the anode active material layer 202 may include: first particles including amorphous carbon and second particles including the anode active material. Here, the mixing ratio (by mass) of the anode active material included in the second particles and the amorphous carbon included in the first particles may be, for example, 1:3 to 1:1. In addition, based on the total weight of the anode active material layer 202, the proportion of the anode active material included may be 1 wt% to 50 wt%.

[0047] As described above, because the anode active material layer 202 includes a mixture of an anode active material and amorphous carbon mixed in an appropriate ratio, the sheet resistance of the anode layer 200 can be reduced. In an embodiment, when the anode active material layer 202 includes only amorphous carbon, such as carbon black, the bonding force between the anode active material layer 202 and the anode current collector 201 can be reduced, and the anode layer 200 can have an increased sheet resistance. In addition, when the anode active material layer 202 includes only an anode active material containing a metal, such as silver (Ag), the amount of lithium (Li) included in the anode active material layer 202 as the anode active material inserted into the silver (Ag) can be increased, thereby reducing the charge / discharge reaction rate. Therefore, when the mixture of the anode active material and amorphous carbon is in an appropriate mixing ratio, as in the above embodiment, the bonding force between the anode active material layer 202 and the anode current collector 201 can be increased, and the sheet resistance of the anode layer 200 can be reduced. In addition, the charge / discharge reaction rate of the all-solid-state secondary battery 10 can be enhanced.

[0048] In an embodiment, when the anode active material layer 202 including a mixture of an anode active material and amorphous carbon is provided on the anode current collector 201 provided in a panel shape or a thin film shape, the sheet resistance of the anode layer 200 can be reduced to 0.5 mΩcm or less. Figure 3 The 4-point probe shown in FIG. 1 measures the sheet resistance of the anode layer 200 .

[0049] Here, when at least one material selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, titanium and zinc is used as the anode active material, the anode active material may have a particle size (e.g., average particle size) of about 4 μm or less. Here, the particle size of the anode active material may be a median diameter (D50) measured by, for example, a laser particle size distribution analyzer. According to an embodiment, the lower limit of the particle size is not particularly limited, but may be about 10 nm.

[0050] In addition, the anode active material layer 202 according to the embodiment may include a binder. In an embodiment, the binder may include at least one of styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The binder may include one of the above materials, or may include a combination of two or more thereof.

[0051] By including a binder in the anode active material layer 202, the anode active material layer 202 can be stabilized on the anode current collector 201. For example, the anode active material layer 202 can be prepared by coating a slurry including the constituent materials of the anode active material layer 202 dispersed therein on the anode current collector 201, followed by drying. By including a binder in the anode active material layer 202, the anode active material can be stabilized in the slurry. As a result, when the slurry is coated on the anode current collector 201 by, for example, screen printing, clogging of the screen (for example, clogging caused by aggregation of the anode active material) can be suppressed.

[0052] In an embodiment, when the anode active material layer 202 includes a binder, the amount of the binder may be in the range of 0.3 wt % to 15 wt % based on the total weight of the anode active material. When the amount of the binder is less than 0.3 wt %, the strength of the anode active material layer 202 may be insufficient, the characteristics of the anode active material layer 202 may deteriorate, and it may be difficult to handle or operate the layer. When the amount of the binder is greater than 20 wt %, the characteristics of the all-solid-state secondary battery 10 may deteriorate. Based on the total weight of the anode active material, the lower limit of the amount of the binder may be about 3 wt %. In addition, the anode active material layer 202 may further include additives used in conventional solid-state secondary batteries, including, for example, fillers, dispersants, and ion conductive agents suitably added thereto.

[0053] In addition, the anode active material layer 202 may have a thickness of, for example, 1 μm to 20 μm. When the thickness of the anode active material layer 202 is less than 1 μm, the characteristics of the all-solid-state secondary battery 10 may not be sufficiently enhanced. When the thickness of the anode active material layer 202 is greater than 20 μm, the anode active material layer 202 has a high resistance value, resulting in insufficient enhancement of the characteristics of the all-solid-state secondary battery 10.

[0054] The solid electrolyte layer 300 according to the embodiment may include a solid electrolyte material provided between the cathode active material layer 102 and the anode active material layer 202. The solid electrolyte material may include, for example, a sulfide-based solid electrolyte material. The sulfide-based solid electrolyte material may include, for example, Li2S-P2S5, Li2S-P2S5-LiX (wherein X is a halogen element), such as iodine (I) or chlorine (Cl), 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 (where m and n are positive numbers, and Z is one of germanium (Ge), zinc (Zn), and gallium (Ga)), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (wherein p and q are positive numbers, and M is one of phosphorus (P), silicon (Si), germanium (Ge), boron (B), aluminum (Al), gallium (Ga) and indium (In)). Here, the sulfide-based solid electrolyte material can be prepared by treating the starting material (e.g., Li2S or P2S5, etc.) by a melt quenching method or a mechanical grinding method. In addition, after the treatment, the sulfide-based solid electrolyte material can be heat-treated. The solid electrolyte according to the embodiment may be amorphous, crystalline or in a mixed form. In an embodiment, when the sulfide-based solid electrolyte material included in the solid electrolyte material includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 may be selected, for example, in the range of about 50:50 to about 90:10.

[0055] In addition, the solid electrolyte layer 300 according to the embodiment may further include a binder. The binder included in the solid electrolyte layer 300 may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The binder of the solid electrolyte layer 300 may be the same as or different from the binder of the cathode active material layer 102 and the anode active material layer 202.

[0056] The all-solid-state secondary battery 10 according to the embodiment can be charged to exceed the charge capacity of the anode active material layer 202. That is, the anode active material layer 202 is overcharged. In the initial stage of charging, lithium is incorporated into the anode active material layer 202. When the all-solid-state secondary battery 10 is charged to exceed the charge capacity of the anode active material layer 202, as shown in FIG. Figure 2As shown in FIG, lithium is deposited on the rear surface of the anode active material layer 202, that is, between the anode current collector 201 and the anode active material layer 202, and a metal layer 203 is formed by the deposited lithium. During discharge, the lithium of the anode active material layer 202 and the metal layer 203 is ionized and transferred to the cathode layer 100. Therefore, in the all-solid-state secondary battery 10, lithium can be used as an anode active material. In addition, since the anode active material layer 202 covers the metal layer 203, the anode active material layer 202 can act as a protective layer for the metal layer 203 and also suppress the deposition and growth of dendrites. This can suppress the short circuit and capacity reduction of the all-solid-state secondary battery 10, and in addition, the characteristics of the all-solid-state secondary battery 10 can be enhanced. In addition, in an embodiment, since the metal layer 203 is not formed in advance, the manufacturing cost of the all-solid-state secondary battery 10 can be reduced. In this case, in the initial state of the all-solid-state secondary battery 10 or after discharge, the anode current collector 201 , the anode active material layer 202 , and the region (interface) therebetween may be a region not containing lithium.

[0057] Figure 5 A cross-sectional view illustrating a schematic structure of an all-solid-state secondary battery according to another embodiment.

[0058] refer to Figure 5 , according to another embodiment, the all-solid-state secondary battery 11 may include a cathode layer 100, an anode layer 210, and a solid electrolyte layer 300. The configuration of the cathode 100 and the solid electrolyte layer 300 is similar to Figure 1 The configuration shown in is basically the same, and a description thereof will be omitted.

[0059] In another embodiment, the anode layer 210 may include an anode current collector 211, an anode active material layer 212, and a metal layer 213. Figure 1 In the embodiment shown in FIG, the metal layer 203 is formed between the anode current collector 201 and the anode active material layer 202 by overcharging the anode active material layer 202. However, in another embodiment, the metal layer 213 may be formed between the anode current collector 211 and the anode active material layer 212 in advance (i.e., before initial charging).

[0060] The configuration of the anode current collector 211 and the anode active material layer 212 is Figure 1The configurations of the anode current collector 201 and the anode active material layer 202 shown in the figure are the same. The metal layer 213 according to another embodiment may include lithium or a lithium alloy. That is, the metal layer 213 may be used as 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 or a Li-Si alloy. The metal layer 213 may be formed of one of these alloys or lithium, or various types of alloys. In another embodiment, since the metal layer 213 acts as a lithium reservoir, the all-solid-state secondary battery 11 may have further enhanced characteristics.

[0061] Here, the thickness of the metal layer 213 is not particularly limited, but may be, for example, in the range of about 1 μm to about 200 μm. When the thickness of the metal layer 213 is less than 1 μm, the function of the metal layer 213 as a reservoir may not be fully demonstrated. When the thickness of the metal layer 213 is greater than 200 μm, the mass and volume of the all-solid-state secondary battery 11 may increase, resulting in significant degradation of characteristics. The metal layer 213 may be, for example, a metal foil having a thickness within the above range.

[0062] Figure 6A is a graph showing the charge and discharge characteristics of the first cycle of each of the all-solid-state secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 2. Figure 6B is a graph showing discharge characteristics of the second cycle of each of the all-solid-state secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 2.

[0063] Examples and comparative examples of the present disclosure will now be described.

[0064] Example 1

[0065] In Example 1, the cathode active material included in the cathode layer 100 may be LiNi 0.9 Co 0.07 Mn 0.03 O2 (NCM). In addition, the solid electrolyte may be LiCl-Li2S-Li3PS4, which is a argyrodite-type crystal structure. In addition, the binder may be polytetrafluoroethylene (Teflon binder available from DuPont). In addition, the conductive agent may be carbon nanofiber (CNF). According to Example 1, the cathode sheet can be manufactured by mixing the cathode active material, the solid electrolyte, the conductive agent and the binder in a weight ratio of 83.8:14.8:0.2:1.2 and molding the resulting mixture into a large-sized sheet form. In addition, the cathode sheet can be extruded on an Al foil with a thickness of 18 μm as the cathode current collector to form a cathode layer.

[0066] The anode layer 200 according to Example 1 may include an anode current collector in the form of a Ni foil having a thickness of 10 μm. In addition, the anode active material layer 202 may include a mixture of silver (Ag) as an anode active material and carbon black as amorphous carbon. Here, the mixing ratio (by mass) of silver (Ag) as an anode active material and carbon black as amorphous carbon may be 1:3. Subsequently, 2 g of FB-A was placed in a container, and an N-methyl-pyrrolidone (NMP) solution including 6.5% by mass of a polyvinylidene fluoride binder (KF-polymer #9300 manufactured by Kureha Corporation) was added thereto. The mixture was then stirred to prepare a slurry. The slurry was applied to the Ni foil using a knife coater and dried in air at 80° C. for 20 minutes. The obtained stacked structure was further dried at 100° C. under vacuum for 12 hours. The anode layer was formed by the above process.

[0067] The solid electrolyte layer 300 according to Example 1 may include LiCl-Li2S-Li3PS4 as a solid electrolyte and an acrylic binder. In Example 1, the solid electrolyte and the acrylic binder may be mixed in a weight ratio of 98.5:1.5. The resulting mixture is stirred while adding xylene and diethylbenzene thereto to prepare a slurry. The slurry is coated on a non-woven fabric using a knife coater and dried in air at 40°C. The resulting stacked structure is dried at 40°C under vacuum for 12 hours. The solid electrolyte layer is formed by the above process.

[0068] The cathode layer 100, the solid electrolyte layer 300, and the anode layer 200 are stacked in this order and encapsulated in a laminate film under a vacuum state to manufacture an all-solid-state secondary battery 10 according to an embodiment. Here, a portion of each of the cathode current collector and the anode current collector is allowed to protrude from the laminate film to the outside so as not to destroy the vacuum state of the battery. These protrusions may be terminals of the cathode layer and the anode layer. In addition, the all-solid-state secondary battery 10 according to the embodiment is subjected to a hydraulic pressure treatment of 500 MPa (MPa) at 85°C for 30 minutes.

[0069] Example 2

[0070] Example 2 is substantially the same as Example 1, except that the mixing ratio (by mass) of silver (Ag) as the anode active material and carbon black as the amorphous carbon included in the anode active material layer 202 is 1:1.

[0071] Comparative Example 1

[0072] Comparative Example 1 is substantially the same as Example 1, except that the anode active material layer 202 includes only carbon black as amorphous carbon, without a separate anode active material.

[0073] Comparative Example 2

[0074] Comparative Example 2 is substantially the same as Example 1, except that the mixing ratio (by mass) of silver (Ag) as the anode active material and carbon black as the amorphous carbon included in the anode active material layer 202 is 25:1.

[0075] Comparative Example 3

[0076] Comparative Example 3 is substantially the same as Example 1, except that the mixing ratio (by mass) of silver (Ag) as the anode active material and carbon black included in the anode active material layer 202 is 1:3.

[0077] Comparison of charging and discharging characteristics

[0078] The charge and discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated in the following charge and discharge test. After each all-solid-state secondary battery was placed in a constant temperature bath at 60°C, the charge and discharge test was performed. In the first cycle, the battery was charged at 0.62 mA / cm 2 The battery was charged at a constant current density of 1000 nm until the voltage reached 4.25 V, and then charged at a constant voltage of 4.25 V until the current reached 0.31 mA / cm 2 After that, the battery was operated at 0.62 mA / cm 2 The battery was discharged at a constant current density of 0.62 mA / cm2 until the voltage reached 2.5 V. 2 The battery was charged at a constant current density of 1000 nm until the battery voltage reached 4.25 V, and then charged at a constant voltage of 4.25 V until the current reached 0.31 mA / cm 2 The discharge process is 6.2mA / cm 2 The current density was continued until the battery voltage reached 2.5V.

[0079] Table 1

[0080]

[0081] The evaluation results of charge and discharge of the batteries manufactured in Examples 1 and 2 and Comparative Examples 1 to 3 are shown in Table 1 below and Figure 6A and Figure 6B With reference to Example 1 and Comparative Examples 1 and 3, it was confirmed that the anode layer of the battery of Example 1, in which silver (Ag) as an anode active material and carbon black as amorphous carbon were mixed, had reduced sheet resistance compared to the anode layer of the battery of Comparative Example 1, in which only carbon black as amorphous carbon was used, or Comparative Example 3, in which silver (Ag) as an anode active material and graphite were mixed.

[0082] In addition, a peel test was performed on each of the batteries of Example 1 and Comparative Example 1 to evaluate the peel strength between the anode active material layer and the anode current collector, and the results thereof are shown in Table 2.

[0083] Table 2

[0084]

[0085] It was confirmed that the bonding strength between the anode active material layer and the anode current collector of the battery of Example 1 was 50 times higher than the bonding strength between the anode active material layer and the anode current collector of the battery of Comparative Example 1.

[0086] Referring again to Table 1, in Examples 1 and 2 and Comparative Example 2 in which the mixing ratios of silver (Ag) as the anode active material and carbon black as the amorphous carbon were different from each other, it was confirmed that when the ratio of silver (Ag) as the anode active material included in the anode active material layer increased, the Q3 / Q1 value was lowered, that is, at 6.2 mA / cm 2 The discharge capacity of the second cycle (Q3) at a constant current density of 6.2 mA / cm 2 The ratio of the charge capacity (Q1) of the first cycle at a constant current density.

[0087] As described above, when only amorphous carbon is included in the anode active material layer, the bonding force between the anode active material layer and the anode current collector is reduced, and the discharge capacity is also reduced. Therefore, the anode active material layer should include a mixture of silver (Ag) as an anode active material and carbon black as amorphous carbon. However, in this case, when the proportion of silver (Ag) as an anode active material is increased to a predetermined level, i.e., 50% or more, the discharge capacity is reduced. Therefore, according to the present disclosure, an appropriate mixing ratio of the anode active material and the amorphous carbon included in the anode active material layer can be determined, thereby providing an all-solid-state secondary battery capable of increasing the discharge capacity while strengthening the peel strength.

[0088] In Examples 1 and 2, silver (Ag) is used as the anode active material included in the anode active material layer, but as described above, the anode active material may include at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), titanium (Ti), and zinc (Zn).

[0089] In the embodiment, Example 3 is substantially the same as Example 1, except that the mixing ratio (by mass) of silicon (Si) as the anode active material and carbon black as the amorphous carbon included in the anode active material layer 202 is 1:3. Example 4 is substantially the same as Example 1, except that the mixing ratio (by mass) of zinc (Zn) as the anode active material and carbon black as the amorphous carbon included in the anode active material layer 202 is 1:3. Example 5 is substantially the same as Example 1, except that the mixing ratio (by mass) of titanium (Ti) as the anode active material and carbon black as the amorphous carbon included in the anode active material layer 202 is 1:3.

[0090] Table 3

[0091]

[0092]

[0093] Table 3 shows the results of charge and discharge tests of batteries of Examples 3 to 5 in which various materials other than silver (Ag) were used. Compared to Example 1 in which silver (Ag) as an anode active material and carbon black as amorphous carbon were mixed at a ratio of 1:3, Examples 3 to 5 showed that the sheet resistance of the anode layer was 0.5 mΩcm or less and the Q3 / Q1 ratio was maintained at 80% or more, confirming that the discharge capacity (Q3) did not decrease.

[0094] Although various embodiments have been described in the foregoing description, the embodiments should be interpreted as illustrations of specific examples rather than as limitations on the scope of the present disclosure. For example, it will be understood by those skilled in the art that all-solid-state secondary batteries and charging methods may vary with reference to the accompanying drawings. It should be understood that, in specific embodiments, the spirit and principles of the present disclosure may be applied to partially solid-state secondary batteries rather than all-solid-state secondary batteries, secondary batteries using partially liquid electrolytes, or batteries other than lithium batteries. Therefore, the scope of the present disclosure is not determined by the above-described embodiments, but by the spirit and scope defined by the appended claims.

Claims

1. An all-solid-state secondary battery, comprising: a cathode layer comprising a cathode active material; an anode layer comprising an anode current collector and an anode active material layer disposed on the anode current collector and comprising an anode active material and amorphous carbon; as well as a solid electrolyte layer disposed between the cathode active material layer and the anode active material layer, wherein the weight ratio of the anode active material to the amorphous carbon is 1:3 to 1:1, The anode layer has a sheet resistance of 0.5 mΩcm or less, and The anode active material includes titanium (Ti). 2 . The all-solid-state secondary battery according to claim 1 , wherein the anode active material is contained in an amount of 1 weight percent (wt %) to 50 wt % based on the total weight of the anode active material layer.

3. The all-solid-state secondary battery according to claim 1, wherein the anode active material further comprises at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn) and zinc (Zn). 4 . The all-solid-state secondary battery according to claim 1 , wherein the amorphous carbon comprises at least one of carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), and graphene. 5 . The all-solid-state secondary battery according to claim 1 , wherein the anode active material layer further comprises a binder. 6 . The all-solid-state secondary battery according to claim 5 , wherein the binder is contained in an amount of 0.3 wt % to 15 wt % based on the total weight of the anode active material. 7 . The all-solid-state secondary battery according to claim 1 , wherein the anode active material layer has a thickness ranging from 1 μm to 20 μm. 8 . The all-solid-state secondary battery according to claim 1 , further comprising a metal layer disposed between the anode current collector and the anode active material layer, wherein the metal layer comprises at least one of lithium and a lithium alloy. 9 . The all-solid-state secondary battery according to claim 8 , wherein the metal layer is provided between the anode current collector and the anode active material layer before the all-solid-state secondary battery is charged. 10 . The all-solid-state secondary battery according to claim 9 , wherein the metal layer has a thickness ranging from 1 μm to 200 μm.

11. The all-solid-state secondary battery according to claim 1, further comprising a thin film comprising an element capable of forming an alloy with the lithium on the anode current collector, The thin film is disposed between the anode current collector and the anode active material layer of the device. 12 . The all-solid-state secondary battery according to claim 11 , wherein the thin film has a thickness ranging from 1 nm to 500 nm.

13. The all-solid-state secondary battery according to claim 1, wherein in an initial state or after discharge of the all-solid-state secondary battery, the anode current collector, the anode active material layer, and the region between the anode current collector and the anode active material layer are regions that do not contain lithium (Li). The all-solid-state secondary battery according to claim 1 , which is a lithium battery.

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