A negative electrode layer for all-solid-state secondary batteries and all-solid-state secondary batteries containing the same

Abstract

Provided is an anode layer for an all-solid-state secondary battery, the anode layer including an anode current collector and a first anode active material layer including a carbon-based material, the carbon-based material including a mixture of amorphous carbon black and crystalline carbon black, the amorphous carbon black having a D peak / G peak intensity ratio of 1.5 or more as determined by Raman analysis, and the crystalline carbon black having a D peak / G peak intensity ratio of more than 0.5 and less than 1.5 as determined by Raman analysis. Also provided is an anode layer for an all-solid-state secondary battery, and an all-solid-state secondary battery including the same.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state secondary battery and a method for manufacturing the same. [Background technology]

[0002] Recently, industrial demands have led to active development of batteries with high energy density and safety. For example, lithium-ion batteries are being put into practical use not only in the fields of information-related equipment and communication equipment, but also in the automotive sector. In the automotive sector, safety is of particular importance because it concerns human life.

[0003] Currently available lithium-ion batteries use an electrolyte that includes flammable organic solvents, so a short circuit could cause overheating and fire. In response to this, all-solid-state batteries that use a solid electrolyte instead of a liquid electrolyte have been proposed.

[0004] Solid-state batteries, by not using flammable organic solvents, significantly reduce the likelihood of fire or explosion even in the event of a short circuit. Therefore, such solid-state batteries offer significantly greater safety compared to lithium-ion batteries that use electrolytes.

[0005] When manufacturing the negative electrode layer of an all-solid-state battery, carbon-based materials such as Ketjenblack or Denkablack can be used. However, when such carbon-based materials are used, localized dendrite growth occurs due to the non-uniformity of the electrode plate, leading to frequent short circuits and a decrease in output characteristics, and improvements to address this are required. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The problem that this invention aims to solve is to provide a negative electrode layer for an all-solid-state secondary battery that solves the above-mentioned problems, exhibits excellent uniformity of the electrode plates, and reduces the occurrence of short circuits.

[0007] Furthermore, the problem that the present invention aims to solve is to provide an all-solid-state secondary battery that has the above-described negative electrode layer and improved energy density and output characteristics. [Means for solving the problem]

[0008] In one aspect, a negative electrode layer for an all-solid-state secondary battery is provided, which includes a negative electrode current collector and a first negative electrode active material layer containing a carbon-based material, wherein the carbon-based material contains a mixture of amorphous carbon black and crystalline carbon black, the D-peak / G-peak intensity ratio (intensity ratio) determined by Raman analysis of the amorphous carbon black is 1.5 or greater, and the D-peak / G-peak intensity ratio (intensity ratio) determined by Raman analysis of the crystalline carbon black satisfies the condition of being greater than 0.5 and less than 1.5.

[0009] The weight ratio of the mixture of amorphous carbon black and crystalline carbon black is 1:0.05 to 1:2.5.

[0010] In other aspects, it is an all-solid-state secondary battery comprising a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive and negative electrode layers. The negative electrode layer is provided as described above in the all-solid-state secondary battery. [Effects of the Invention]

[0011] All-solid-state secondary batteries with a single-sided design employ a negative electrode layer containing carbon-based materials to suppress short circuits, improve output characteristics, and achieve high energy density. [Brief explanation of the drawing]

[0012] [Figure 1A] This diagram shows the Raman analysis results of carbon A and carbon D, amorphous carbon blacks used in the manufacturing of the negative electrode layer in one example. [Figure 1B]This diagram shows the Raman analysis results of carbon A and carbon D, amorphous carbon blacks used in the manufacturing of the negative electrode layer in one example. [Figure 1C] This diagram shows the Raman analysis results of carbon K and carbon J, which are crystalline carbon blacks used in the manufacturing of the negative electrode layer in one example. [Figure 1D] This diagram shows the Raman analysis results of carbon K and carbon J, which are crystalline carbon blacks used in the manufacturing of the negative electrode layer in one example. [Figure 2] This is a schematic diagram illustrating the structure of an all-solid-state secondary battery based on one actual example. [Figure 3] This is a schematic diagram showing the structure of another example of an all-solid-state secondary battery. [Figure 4] Furthermore, this is a diagram illustrating the structure of another example of an all-solid-state secondary battery. [Modes for carrying out the invention]

[0013] The following provides a more detailed description of a negative electrode layer for an all-solid-state secondary battery based on one example, an all-solid-state secondary battery containing the same, and a method for manufacturing the same.

[0014] When manufacturing the negative electrode layer of an all-solid-state battery, amorphous carbon such as Ketjenblack is used. Amorphous carbon facilitates the movement of lithium ions and acts as a buffer, but the non-uniformity of the electrode plate can cause localized dendrite growth, increasing the probability of short circuits. When crystalline carbon such as Denkablack is used in the manufacturing of the negative electrode layer, its crystallinity is high, resulting in excellent uniformity and physical properties of the electrode plate, but lithium ion movement is difficult, which can lead to a significant decrease in output characteristics.

[0015] In order to solve the above-mentioned problems and manufacture an all-solid-state secondary battery with improved output characteristics while reducing the probability of short circuits, the inventors use a mixture of amorphous carbon black and crystalline carbon black when manufacturing the negative electrode layer and when forming the negative electrode active material layer.

[0016] An example of a negative electrode layer for an all-solid-state secondary battery includes a negative electrode current collector and a first negative electrode active material layer containing a carbon-based material, wherein the carbon-based material includes a mixture of amorphous carbon black and crystalline carbon black. The D-peak / G-peak intensity ratio (D / G peak intensity ratio) determined by Raman analysis of the amorphous carbon black is 1.5 or greater, and the D-peak / G-peak intensity ratio (D / G peak intensity ratio) determined by Raman analysis of the crystalline carbon black is greater than 0.5 and less than 1.5. The mixed weight ratio of amorphous carbon black and crystalline carbon black is 1:0.05 to 1:2.5.

[0017] The D / G intensity ratios of amorphous carbon black are, for example, 1.6–4.0, 1.61–3.5, 1.62–3.0, or 1.65–2.82.

[0018] The D / G intensity ratio of crystalline carbon black is 0.8-1.5, 0.9-1.3, 1.0-1.2, or 1.07-1.13. If the D / G intensity ratio falls outside this range, it exhibits high crystallinity, irreversibly charges / discharges, and is unable to perform its role as a deposition-type anode.

[0019] Carbon black is detected at wavenumber 1350 cm⁻¹ in the Raman spectroscopy spectrum. -1 , 1580cm -1 , 2700cm -1 A peak is observed at wavenumber 1580 cm⁻¹. Such peaks provide information related to the thickness, crystallinity, and charge doping state of the carbon black. -1 The peak indicated is the G-mode, which is caused by an vibrational mode corresponding to the stretching of the carbon-carbon bond, and the energy of the G-mode is determined by the density of excess charge doped into the graphene. And the wavenumber is 2700 cm⁻¹. -1 The peak indicated is a 2D mode peak, which is useful when evaluating the thickness of carbon black. -1 The peak that comes out is a peak called D-mode, SP 2It is a peak shown when there are defects in the crystal structure. And the D / G intensity ratio gives information related to the degree of disorder of the carbon black crystals.

[0020] The mixing weight ratio of the amorphous carbon black and the crystalline carbon black is 1:0.05 to 1:2.5. When the content of the amorphous carbon black is within the above range, an all-solid-state secondary battery with reduced occurrence of short circuits and improved output characteristics can be manufactured.

[0021] The primary particle size of the amorphous carbon black is 15 nm to 60 nm, for example, 30 to 50 nm, and the specific surface area is 15 to 1500 m 2 / g, 20 to 500 m 2 / g or 30 to 200 m 2 / g, and the crystallite size Lc in the c-axis direction is 3.0 nm or less or 1.0 to 2.5 nm, and the interlayer spacing (d-spacing) (d [[ID=第十五]] 002 ) is 0.350 nm to 0.370 nm. In this specification, the crystallite size Lc in the c-axis direction and the interlayer spacing of carbon can be measured using Cu-Kα characteristic X-ray diffraction (wavelength: about 1.54 Å) analysis.

[0022] The primary particle size of the crystalline carbon black is 15 nm to 60 nm, or 35 to 55 nm, and the specific surface area is 15 to 500 m 2 / g, 20 to 500 m 2 / g or 30 to 200 m 2 / g, and Lc is 2.0 nm to 10.00 nm or 1.0 to 5.0 nm, and the interlayer spacing (d 002 ) is 0.335 nm to 0.357 nm.

[0023] In this specification, when the particles are spherical, "size" indicates the average particle diameter, and when they are non-spherical, it indicates the major axis length. The particle size can be measured using an electron scanning microscope or a particle size analyzer. Examples of the particle size analyzer include, for example, HORIBA, LA-950 laser particle size analyzer.

[0024] When measuring particle size using a particle size analyzer, the average particle size is referred to as D50. D50 represents the average diameter of particles that account for 50% of the cumulative volume in the particle size distribution. In a distribution curve where particle sizes are accumulated from the smallest to the largest particles, D50 represents the particle size value that accounts for 50% of the total number of particles, with the total number of particles being 100%.

[0025] The D / G intensity ratio and BET for amorphous and crystalline carbon black in one example are shown in Table 1 below.

[0026] [Table 1]

[0027] In one embodiment of an all-solid-state secondary battery, the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer, and the negative electrode current collector, the negative electrode active material layer, and the region between them are lithium (Li)-free regions that do not contain lithium (Li) in the initial state or post-discharge state of the all-solid-state secondary battery. In one embodiment of an all-solid-state secondary battery, a lithium deposition layer may be included between the negative electrode current collector and the negative electrode active material during or after charging.

[0028] Other aspects provide an all-solid-state secondary battery having the negative electrode layer described above.

[0029] Referring to Figure 2, the all-solid-state secondary battery 1 includes a positive electrode layer 10; a negative electrode layer 20; and a solid electrolyte layer 30 containing a solid electrolyte disposed between the positive electrode layer 10 and the negative electrode layer 20.

[0030] The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on the positive electrode current collector 11, and the negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on the negative electrode current collector according to one embodiment.

[0031] The first negative electrode active material layer 22 may further include a metal, a metalloid, or a combination thereof. The metal, metalloid, or combination thereof includes, for example, silver, platinum, zinc, silicon, tin, iron, copper, aluminum, indium, vizmus, or a combination thereof.

[0032] The content of the metal, metalloid, or combination thereof is 1 to 40 parts by weight based on 100 parts by weight of the total weight of the first negative electrode active material layer, and the content of the carbon-based material is 60 to 99 parts by weight. The content of the metal, metalloid, or combination thereof is, for example, 1 to 30 parts by weight, 2 to 20 parts by weight, or 3 to 15 parts by weight. When the content of the metal, metalloid, or combination thereof in the first negative electrode active material layer is within the above range, it is possible to manufacture an all-solid-state secondary battery with improved cycle characteristics and output characteristics and high energy density.

[0033] The thickness of the first negative electrode active material layer 22 is 1 to 20 μm, for example, 1 to 10 μm, for example, 2 to 8 μm, for example, 4 to 6 μm.

[0034] The negative electrode current collector 21 and the first negative electrode active material layer 22 further include a lithium metal or lithium alloy thin film. Furthermore, the negative electrode current collector 21 and the first negative electrode active material layer 22 further include a metal or metalloid thin film. The metal or metalloid thin film includes gold (Au), silver (Ag), magnesium (Mg), zinc (Zn), silicon (Si), tin (Sn), platinum (Pt), palladium (Pd), aluminum (Al), vizmus (Bi), or a combination thereof, and the thickness of the metal or metalloid thin film is 1 to 800 nm, 2 to 500 nm, 5 to 100 nm, or 10 to 30 nm.

[0035] The first negative electrode active material layer 22 has a porous structure. The porosity of the first negative electrode active material layer 22 is 30% or less, for example, 5 to 25%. When the porosity of the first negative electrode active material layer 22 is within the above range, the growth of dendrites to the positive electrode active material layer is effectively suppressed, thereby suppressing the occurrence of short circuits due to dendrites, and an all-solid-state secondary battery with excellent high voltage, high capacity, and life characteristics can be manufactured.

[0036] At the interface between the solid electrolyte layer 30 and the negative electrode current collector 21, metallic lithium can be deposited, as this interface becomes a deposition point for metallic lithium. The deposited lithium can then form dendrites that grow towards the positive electrode active material layer 12 through the voids in the solid electrolyte layer 30, potentially causing a short circuit in the all-solid-state secondary battery 1.

[0037] However, when the porosity of the first negative electrode active material layer is within the aforementioned range, the growth of dendrites into the positive electrode active material layer is effectively suppressed, thereby preventing short circuits caused by dendrites and enabling the manufacture of an all-solid-state secondary battery with excellent high voltage, high capacity, and lifespan characteristics.

[0038] In this specification, porosity can be determined by mercury porosity measurement or by an electron scanning microscope (SEM). The method of measurement using a mercury porosity analyzer involves adding mercury to a sample and measuring the amount of mercury added to calculate the pore size and pore distribution.

[0039] The negative electrode layer in one embodiment may further include a second negative electrode active material layer. The second negative electrode active material layer may be located above the first negative electrode active material layer, or one or more layers of the negative electrode current collector and the first negative electrode active material layer. The second negative electrode active material layer may include a metal, metalloid element, or combination thereof that forms an alloy with lithium.

[0040] The metal and metalloid elements that form alloys with lithium include one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), vizmus (Bi), tin (Sn), and zinc (Zn).

[0041] The second negative electrode active material layer is, for example, a metal layer containing lithium or a lithium alloy.

[0042] According to one example, the surface of the second negative electrode active material layer may contain lithium fluoride (LiF).

[0043] The second negative electrode active material layer is also a lithium-free region that does not contain lithium metal or lithium alloy in the initial state or after discharge of an all-solid-state secondary battery. Before charging, the negative electrode layer has a structure comprising a negative electrode current collector, a metal or semimetallic film, and a first negative electrode active material layer. After charging such a negative electrode layer, a second negative electrode active material layer may be formed on top of the first negative electrode active material layer. The second negative electrode active material layer is also non-porous.

[0044] A carbon layer is further included between the first negative electrode active material layer and the solid electrolyte layer. The carbon layer is formed using, for example, carbon black, carbon fibers, graphite, carbon nanotubes, graphene, or a combination thereof. By forming a carbon layer in this way, the resistance between the first negative electrode active material layer and the solid electrolyte layer can be reduced, thereby suppressing lithium dendrite formation. Therefore, an all-solid-state secondary battery having a negative electrode layer with an additional carbon layer can have further improved lifespan characteristics compared to an all-solid-state secondary battery having a negative electrode layer without a carbon layer.

[0045] This document describes a method for manufacturing an all-solid-state secondary battery based on one example.

[0046] First, a negative electrode layer is provided, which includes a negative electrode current collector and a first negative electrode active material layer.

[0047] A positive electrode layer is provided separately from this.

[0048] The process includes preparing a laminate by providing a solid electrolyte layer between the negative electrode layer and the positive electrode layer, and then pressing the laminate.

[0049] The solid electrolyte layer is manufactured by drying a composition containing a solid electrolyte, a binder, and a solvent at 25°C to 80°C. The viscosity of the composition is controlled to approximately 200 cP to 10,000 cP. By forming a solid electrolyte layer using a composition with such viscosity, a solid electrolyte layer with excellent interfacial bonding to the negative electrode layer can be manufactured.

[0050] According to one example, drying can be carried out in a convection oven controlled to 25-75°C.

[0051] In another embodiment, drying can be carried out in multiple stages, for example, in two stages. Primary drying is performed at 25-70°C, followed by secondary drying at 30-75°C. When primary drying is performed at a higher temperature than secondary drying, the interfacial properties between the negative electrode layer and the solid electrolyte layer are improved.

[0052] The aforementioned drying time is 30 minutes to 24 hours, 1 hour to 20 hours, or 1 hour to 15 hours.

[0053] The pressurization of the laminate is carried out by methods such as roll press, flat press, hot press, and warm isostatic press (WIP), with warm isostatic press being used as an example.

[0054] Pressurization is carried out at room temperature (20-25°C) or 90°C. Pressurization can also be carried out at high temperatures of 100°C or higher. The duration of pressurization is, for example, 30 minutes or less, 20 minutes or less, 15 minutes or less, or 10 minutes or less. The duration of pressurization is 1 ms to 30 minutes, 1 ms to 20 minutes, 1 ms to 15 minutes, or 1 ms to 10 minutes. Pressurization methods include, for example, isotactic press, roll press, and flat press, but are not necessarily limited to these methods; any pressurization method used in the relevant technical field can be used. Through such pressurization, for example, solid electrolyte powder is sintered to form a solid electrolyte layer.

[0055] The pressurization time varies depending on the temperature and pressure, but is typically less than 30 minutes or less than 20 minutes.

[0056] After pressurization, the thickness of the positive electrode active material layer is approximately 100-150 μm, the thickness of the negative electrode active material layer is 10-15 μm, and the thickness of the solid electrolyte layer is 100-150 μm.

[0057] According to one example, pressurization is carried out by WIP, and the pressure is 200-600 MPa, 300-550 MPa, 350-520 MPa, 380-500 MPa, or 400-500 MPa.

[0058] During pressurization, the temperature is set to 60°C-90°C, 65°C-88°C, 70°C-85°C, or 75°C-85°C. The pressurization time varies depending on the temperature and pressure during pressurization, ranging from 10 minutes to 6 hours, 15 minutes to 5 hours, 20 minutes to 3 hours, 20 minutes to 2 hours, or 30 minutes to 1 hour.

[0059] The above-described method for manufacturing all-solid-state secondary batteries is suitable for mass production, and when the layers are easily stacked and then pressurized, a tight interface can be formed between the electrode layer and the solid electrolyte layer. Furthermore, this method for manufacturing all-solid-state secondary batteries can reduce the interfacial resistance between the positive electrode layer and the solid electrolyte layer while simultaneously improving battery performance such as rate characteristics and lifespan characteristics.

[0060] In all-solid-state secondary batteries, the negative electrode layer is manufactured by coating and drying a composition containing a first negative electrode active material, a binder, and a solvent.

[0061] As a binder, an aqueous binder, an organic binder, or a combination thereof can be used. Examples of binders that can be used include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or a combination thereof.

[0062] As an aqueous binder, styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), or a combination thereof can be used. When using an aqueous binder, water is used as the solvent.

[0063] As organic binders, polytetrafluoroethylene, polyvinylidene fluoride, or mixtures thereof are used, and when such organic binders are used, N-methylpyrrolidone (NMP) or the like is used as the solvent.

[0064] In one embodiment of an all-solid-state secondary battery, the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer, and a second negative electrode active material layer is arranged above the first negative electrode active material layer, on one or more of the negative electrode current collector and the first negative electrode active material layer, and the second negative electrode active material layer may contain lithium or a lithium alloy.

[0065] The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer, and the negative electrode current collector, the first negative electrode active material layer, and the region between them are lithium (Li)-free regions that do not contain lithium in the initial state or after discharge state of the all-solid-state secondary battery. Furthermore, the all-solid-state secondary battery includes a lithium deposition layer between the negative electrode current collector and the first negative electrode active material layer during or after charging.

[0066] The following provides a more detailed explanation of all-solid-state rechargeable batteries using illustrative examples.

[0067] [All-solid-state secondary battery] Referring to Figure 2, the all-solid-state secondary battery 1 includes a positive electrode layer 10; a negative electrode layer 20; and a solid electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20. The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on the positive electrode current collector 11, and the negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on the negative electrode current collector according to one embodiment.

[0068] [Positive electrode layer: Positive electrode current collector] The positive electrode current collector 11 may be a plate or foil made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector 11 is optional.

[0069] [Cathode layer: Cathode active material] The positive electrode active material layer 12 includes, for example, a positive electrode active material and a solid electrolyte. The solid electrolyte contained in the positive electrode layer 10 is similar to or different from the solid electrolyte contained in the solid electrolyte layer 30. For detailed information regarding the solid electrolyte, please refer to the description of the solid electrolyte layer 30.

[0070] The positive electrode active material is a positive electrode active material that can reversibly absorb and desorb lithium ions. Examples of positive electrode active materials include lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide, and lithium iron phosphate, as well as nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. However, the material is not necessarily limited to these, and any material that can be used as a positive electrode active material in the relevant art can be used. The positive electrode active material can be a single material or a mixture of two or more materials.

[0071] Lithium transition metal oxides include, for example, Lithium a A 1-b B b D2 (In the above formula, 0.90 ≤ a ≤ 1 and 0 ≤ b ≤ 0.5); Li a E 1-b Bb 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 formula, 0≦b≦0.5 and 0≦c≦0.05); Li a Ni 1-b-c Co b B c D α (In the above formula, 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 formula, 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 F2(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 formula, 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 formula, 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 F2(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 dO2(In the above formula, 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1);Li a Ni b Co c Mn d GeO2 (In the above formula, 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1); Li a NiG b O2 (In the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (In the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (In the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (In the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0≦f≦ 2);Li (3-f)A compound represented by one of the following chemical formulas: Fe2(PO4)3 (0≦f≦2);LiFePO4. In such a compound, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, 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 is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use compounds with a coating layer attached to their surface, and mixtures of the above-mentioned compounds and compounds with a coating layer attached are also possible. The coating layer attached to the surface of such compounds includes, for example, coating element compounds of oxides, hydroxides, oxyhydroxys, oxycarbonates, or hydroxycarbonates of the coating element. The compounds forming such a coating layer are amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method is, for example, spray coating or immersion method. Specific coating methods are well understood by those skilled in the art, so a detailed explanation is omitted.

[0072] The positive electrode active material includes, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the above-described lithium transition metal oxides. The "layered rock salt type structure" is, for example, a structure in which oxygen atom layers and metal atom layers are regularly arranged alternately in the <111> direction of a cubic rock salt type structure, whereby each atom layer forms a two-dimensional plane. The "cubic rock salt type structure" indicates a sodium chloride type (NaCl type) structure which is a kind of crystal structure. Specifically, it indicates a structure in which face-centered cubic lattices (fcc) formed by cations and anions are displaced from each other by 1 / 2 of the ridge of the unit lattice. Such a lithium transition metal oxide having a layered rock salt type structure is, for example, LiNi x Co y Al z O2 (NCA) or LiNi x Co y Mn z O2 (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1), etc., which are ternary lithium transition metal oxides. When the positive electrode active material includes a ternary lithium transition metal oxide having a layered rock salt type structure, the energy density and thermal stability of the all-solid-state secondary battery 1 are further improved.

[0073] The positive electrode active material is also covered by a coating layer as described above. Any coating layer can be used as long as it is known as a coating layer for the positive electrode active material of an all-solid-state secondary battery. The coating layer is, for example, Li2O-ZrO2 (LZO), etc.

[0074] When the positive electrode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), it is possible to increase the capacity density of the all-solid-state secondary battery 1 and reduce the metal elution of the positive electrode active material in the charged state. As a result, the cycle characteristics of the all-solid-state secondary battery 1 in the charged state are improved.

[0075] The shape of the positive electrode active material is, for example, a particle shape such as a perfect sphere or an ellipsoid. The particle size of the positive electrode active material is not particularly limited and is within the range applicable to the positive electrode active material of conventional all-solid-state secondary batteries. The content of the positive electrode active material in positive electrode 10 is also not particularly limited and is within the range applicable to the positive electrode of conventional all-solid-state secondary batteries.

[0076] [Positive electrode layer: solid electrolyte] The positive electrode active material layer 12 may, for example, contain a solid electrolyte. The solid electrolyte contained in the positive electrode layer 10 may be the same as or different from the solid electrolyte contained in the solid electrolyte layer 30. For detailed information regarding the solid electrolyte, please refer to the section on the solid electrolyte layer 30.

[0077] The solid electrolyte contained in the positive electrode active material layer 12 has a smaller average D50 particle size compared to the solid electrolyte contained in the solid electrolyte layer 30. For example, the average D50 particle size of the solid electrolyte contained in the positive electrode active material layer 12 is 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 compared to the average D50 particle size of the solid electrolyte contained in the solid electrolyte layer 30.

[0078] [Positive electrode layer: Binder] The positive electrode active material layer 12 may contain a binder. Examples of binders include styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene.

[0079] [Positive electrode layer: conductive material] The positive electrode active material layer 12 may contain a conductive material. Examples of conductive materials include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and metal powder.

[0080] [Positive electrode layer: Other additives] In addition to the positive electrode active material, solid electrolyte, binder, and conductive material described above, the positive electrode layer 10 may further contain additives such as fillers, coating agents, dispersants, and ion conductivity enhancers.

[0081] As fillers, coating agents, dispersants, ion conductivity assisting agents, etc. contained in the positive electrode layer 10, known materials generally used for electrodes of all-solid-state secondary batteries can be used.

[0082] [Solid electrolyte layer] The solid electrolyte is also a sulfide-based solid electrolyte.

[0083] [Solid electrolyte layer: Sulfide-based solid electrolyte] Referring to FIGS. 2 to 4, the solid electrolyte layer 30 includes a sulfide-based solid electrolyte disposed between the positive electrode 10 and the negative electrode layer 20.

[0084] The sulfide-based solid electrolyte is, for example, Li2S-P2S5, Li2S-P2S5-LiX (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 and 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 xOne or more are selected from the range (0 ≦ x ≦ 2). The sulfide-based solid electrolyte is produced, for example, by processing starting materials such as Li2S and P2S5 using a melt quenching method or a mechanical milling method. Further, heat treatment can be performed after such processing. The solid electrolyte can be in an amorphous state, a crystalline state, or a state in which they are mixed. Further, the solid electrolyte may contain, for example, sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using Li2S-P2S5 as the sulfide-based solid electrolyte material, the mixing molar ratio of Li2S and P2S5 is, for example, 50:50 to 90:10.

[0085] The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x (0 ≦ x ≦ 2), Li 7-x PS 6-x Br x (0 ≦ x ≦ 2), and Li 7-x PS 6-x I x It is also an Argyrodite-type compound containing one or more selected from the range (0 ≦ x ≦ 2). In particular, the sulfide-based solid electrolyte is also an Argyrodite-type compound containing one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0086] The density of the Argyrodite-type solid electrolyte is also 1.5 to 2.0 g / cc. When the Argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state secondary battery decreases, and penetration of the solid electrolyte by Li can be effectively suppressed.

[0087] The elastic modulus of the solid electrolyte is, for example, 15 to 35 GPa.

[0088] [Solid electrolyte layer: Binder] The solid electrolyte layer 30 may, for example, contain a binder. The binder contained in the solid electrolyte layer 30 may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these, and any material used as a binder in the art may be used. The binder of the solid electrolyte layer 30 is the same as or similar to the binder contained in the positive electrode active material layer 12 and the first negative electrode active material layer 22.

[0089] [Negative electrode layer] [Structure of the negative electrode layer] The thickness of the first negative electrode active material layer 22 is, 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. The thickness of the first negative electrode active material layer is, for example, 1 μm to 20 μm, 2 μm to 10 μm, or 3 μm to 7 μm. If the thickness of the first negative electrode active material layer is excessively thin, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 will cause the first negative electrode active material layer to collapse, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the thickness of the negative electrode active material layer is excessively increased, the energy density of the all-solid-state secondary battery 1 will decrease, the internal resistance of the all-solid-state secondary battery 1 due to the first negative electrode active material layer will increase, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0090] If the thickness of the first negative electrode active material layer decreases, for example, the charging capacity of the first negative electrode active material layer also decreases. The charging capacity of the first negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less compared to the charging capacity of the positive electrode active material layer 12. The charging capacity of the first negative electrode active material layer 22 is, for example, 0.1% to 50%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% to 10%, 0.1% to 5%, or 0.1% to 2% compared to the charging capacity of the positive electrode active material layer 12. If the charging capacity of the first negative electrode active material layer 22 is excessively small, the thickness of the first negative electrode active material layer 22 becomes very thin, causing lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 during repeated charge-discharge processes to disintegrate the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the charging capacity of the first negative electrode active material layer 22 increases excessively, the energy density of the all-solid-state secondary battery 1 decreases, increasing the internal resistance of the all-solid-state secondary battery 1 due to the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0091] The charging capacity of the positive electrode active material layer 12 is obtained by multiplying the charging capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer 12. When various positive electrode active materials are used, the charging capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the charging capacity of the positive electrode active material layer 12. The charging capacity of the first negative electrode active material layer 22 is calculated in the same way. That is, the charging capacity of the first negative electrode active material layer 22 is obtained by multiplying the charging capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer 22. When various negative electrode active materials are used, the charging capacity density × mass value is calculated for each negative electrode active material, and the sum of these values ​​is the capacity of the first negative electrode active material layer 22. Here, the charging capacity densities of the positive electrode active material and the negative electrode active material are capacities estimated using an all-solid-state half-cell with lithium metal as the relative electrode. The charging capacity of the positive electrode active material layer 12 and the first negative electrode active material layer 22 is directly measured using an all-solid-state half-cell. By dividing the measured charging capacity by the mass of the active material, the charging capacity density can be obtained. Furthermore, the charging capacity of the positive electrode active material layer 12 and the first negative electrode active material layer 22 is also the initial charging capacity measured during the first charging cycle.

[0092] [Negative electrode layer: negative electrode current collector] The negative electrode current collector 21 is made of a material that does not react with lithium, i.e., does not form any alloys or compounds. The materials constituting the negative electrode current collector 21 include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but are not necessarily limited to these; any material that can be used as an electrode current collector in the art can be used. The thickness of the negative electrode current collector is 1 to 20 μm, for example, 5 to 15 μm, for example, 7 to 10 μm.

[0093] The negative electrode current collector 21 is composed of one of the metals mentioned above, or an alloy or coating material of two or more metals. The negative electrode current collector 21 is, for example, in the form of a plate or foil.

[0094] Referring to Figure 3, the all-solid-state secondary battery 1 further includes, for example, a thin film 24 containing an element that forms an alloy with lithium on the negative electrode current collector 21. The thin film 24 is positioned between the negative electrode current collector 21 and the first negative electrode active material layer 22.

[0095] The thin film 24 contains, for example, an element that forms an alloy with lithium. Elements that form alloys with lithium include, for example, gold, silver, zinc, tin, indium, silicon, aluminum, and vizmus, but are not necessarily limited to these; any element that forms an alloy with lithium in the relevant art can be used. The thin film 24 is composed of one of these metals or an alloy of various metals. By placing the thin film 24 on the negative electrode current collector 21, for example, the deposition morphology of the second negative electrode active material layer (not shown) deposited between the thin film 24 and the first negative electrode active material layer 22 can be further flattened, potentially improving the cycle characteristics of the all-solid-state secondary battery 1.

[0096] The thickness of the thin film 24 is, 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 is less than 1 nm, the function of the thin film 24 is difficult to achieve. If the thickness of the thin film is excessively thick, the thin film 24 itself will absorb lithium, reducing the amount of lithium deposited in the negative electrode layer, which can lower the energy density of the all-solid-state battery and degrade the cycle characteristics of the all-solid-state secondary battery 1. The thin film 24 is disposed on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, or plating, but is not necessarily limited to such methods; any method that can form the thin film 24 in the relevant art can be used.

[0097] [Negative electrode layer: negative electrode active material] The negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on the negative electrode current collector. The first negative electrode active material layer 22 includes, for example, a negative electrode active material and a binder. If the negative electrode active material in the first negative electrode active material layer 22 includes a metal, a metalloid, or a combination thereof, the negative electrode active material has, for example, a particle form. The average particle size of the negative electrode active material having a particle form is, for example, 4 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less. The average particle size of the negative electrode active material having a particle form is, for example, 10 nm to 4 μm, 10 nm to 2 μm, or 10 nm to 900 nm. Having the negative electrode active material have an average particle size in such a range makes reversible absorption and / or desorbing of lithium during charging and discharging even easier. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size analyzer.

[0098] First negative electrode [Negative electrode layer: Binder] The binder included in the first negative electrode active material layer 22 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these, and any material used as a binder in the art can be used. The binder may consist of one or more different binders.

[0099] The inclusion of a binder in the first negative electrode active material layer 22 stabilizes the first negative electrode active material layer 22 on the negative electrode current collector 21. Furthermore, cracking of the first negative electrode active material layer 22 is suppressed despite volume changes and / or relative positional changes of the first negative electrode active material layer 22 during the charge-discharge process. For example, if the first negative electrode active material layer 22 does not contain a binder, the first negative electrode active material layer 22 can be easily separated from the negative electrode current collector 21. When the negative electrode active material layer 22 detaches from the negative electrode current collector 21, the exposed portion of the negative electrode current collector 21 comes into contact with the second solid electrolyte layer 23, increasing the likelihood of a short circuit. The first negative electrode active material layer 22 is manufactured, for example, by coating the negative electrode current collector 21 with a slurry containing the materials constituting the first negative electrode active material layer 22 and drying it. By including the binder in the first negative electrode active material layer 22, stable dispersion of the negative electrode active material in the slurry is possible. For example, when the slurry is applied onto the negative electrode current collector 21 by screen printing, screen clogging (e.g., clogging due to aggregates of the negative electrode active material) can be suppressed.

[0100] [Negative electrode layer: Other additives] The first negative electrode active material layer 22 may further contain additives used in conventional all-solid-state secondary batteries 1, such as fillers, coating agents, dispersants, and ion conductivity enhancers.

[0101] [Negative electrode layer: first negative electrode active material layer] The thickness of the first negative electrode active material layer 22a is, 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 12. The thickness of the first negative electrode active material layer 22a is, for example, 1 μm to 20 μm, 2 μm to 10 μm, or 3 μm to 7 μm. When the thickness of the first negative electrode active material layer 22a is within the above range, the cycle characteristics of the all-solid-state secondary battery 1 are excellent, and the charging capacity of the first negative electrode active material layer 22a is excellent. The charging capacity of the first negative electrode active material layer 22a is, for example, 50% or less, 30% or less, 10% or less, 5% or less, or 2% or less compared to the charging capacity of the positive electrode active material layer 12. The charging capacity of the first negative electrode active material layer 22a is, for example, 0.1% to 50%, 0.1% to 30%, 0.1% to 10%, 0.1% to 5%, or 0.1% to 2% compared to the charging capacity of the positive electrode active material layer 12. When the charging capacity of the first negative electrode active material layer 22a is within the above range, the cycle characteristics and energy density of the all-solid-state secondary battery 1 are excellent in repeated charge-discharge processes when the thickness of the first negative electrode active material layer 22a is controlled within an appropriate range.

[0102] The charging capacity of the positive electrode active material layer 12 is obtained by multiplying the charging capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer 12. When various positive electrode active materials are used, the charging capacity density x mass value is calculated for each positive electrode active material, and the sum of these values ​​is the charging capacity of the positive electrode active material layer 12. The charging capacity of the first negative electrode active material layer 22a is calculated in the same way. That is, the charging capacity of the first negative electrode active material layer 22a is obtained by multiplying the charging capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer 22a. When various negative electrode active materials are used, the charging capacity x mass value is calculated for each negative electrode active material, and the sum of these values ​​is the capacity of the first negative electrode active material layer 22a. Here, the charging capacity densities of the positive electrode active material and the negative electrode active material are capacities estimated using an all-solid-state half-cell with lithium metal as the relative electrode. The charging capacity of the positive electrode active material layer 12 and the first negative electrode active material layer 22a is directly measured using an all-solid-state half-cell. By dividing the measured charging capacity by the mass of the active material, the charging capacity density can be obtained. Furthermore, the charging capacity of the positive electrode active material layer 12 and the first negative electrode active material layer 22a is also the initial charging capacity measured during the first charging cycle.

[0103] [Negative electrode layer: precipitated layer] Referring to Figure 4, the all-solid-state secondary battery 1 further includes a second negative electrode active material layer 23 which is positioned between the negative electrode current collector 21 and the first negative electrode active material layer 22 upon charging. Although not shown, the all-solid-state secondary battery 1 may further include the second negative electrode active material layer 23 which is positioned between the solid electrolyte layer 30 and the first negative electrode active material layer 22 upon charging, or it may be configured to include the second negative electrode active material layer 23 alone.

[0104] The second negative electrode active material layer 23 is a metallic layer containing lithium or a lithium alloy. The metallic layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer 23 is a metallic layer containing lithium, it acts, for example, as a lithium reservoir. Examples of lithium alloys include, but are not limited to, Li-Al alloys, Li-Sn alloys, Li-In alloys, Li-Ag alloys, Li-Au alloys, Li-Zn alloys, Li-Ge alloys, and Li-Si alloys; any alloy used as a lithium alloy in the art can be used. The second negative electrode active material layer 23 consists of one or more of these alloys or of lithium, or of a variety of alloys.

[0105] The thickness of the second negative electrode active material layer is not particularly limited, but for example, it can be 1 μm to 1000 μm, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the second negative electrode active material layer is excessively thin, it will be difficult for the second negative electrode active material layer 23 to perform its role as a lithium reservoir. If the thickness of the second negative electrode active material layer is excessively thick, the mass and volume of the all-solid-state secondary battery 1 will increase, which may degrade the cycle characteristics. The second negative electrode active material layer 23 can also be, for example, a metal foil having a thickness within such a range.

[0106] In the all-solid-state secondary battery 1, the second negative electrode active material layer 23 is either placed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before the assembly of the all-solid-state secondary battery 1, or deposited between the negative electrode current collector 21 and the first negative electrode active material layer 22 by charging after the assembly of the all-solid-state secondary battery 1.

[0107] If a second negative electrode active material layer 23 is placed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before the assembly of the all-solid-state secondary battery 1, the second negative electrode active material layer 23, being a lithium-containing metal layer, acts as a lithium reservoir. The cycle characteristics of the all-solid-state secondary battery 1 including the second negative electrode active material layer 23 are further improved. For example, lithium foil is placed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before the assembly of the all-solid-state secondary battery 1.

[0108] If the second negative electrode active material layer 23 is positioned by charging after the assembly of the all-solid-state secondary battery 1, the energy density of the all-solid-state secondary battery 1 increases because the second negative electrode active material layer 23 is not included at the time of assembly. For example, when charging the all-solid-state secondary battery 1, the charging is performed beyond the charging capacity of the first negative electrode active material layer 22. That is, the first negative electrode active material layer 22 is overcharged. In the initial stages of charging, lithium is absorbed into the first negative electrode active material layer 22. That is, the negative electrode active material contained in the first negative electrode active material layer 22 forms an alloy or compound with lithium ions that have moved from the positive electrode layer 10. If the charging is performed beyond the capacity of the first negative electrode active material layer 22, for example, lithium is deposited on the back surface of the first negative electrode active material layer 22, i.e., between the negative electrode current collector 21 and the first negative electrode active material layer 22, and the deposited lithium forms a metal layer corresponding to the second negative electrode active material layer 23. The second negative electrode active material layer 23 is a metal layer mainly composed of lithium (i.e., metallic lithium). Such a result is obtained, for example, by having the negative electrode active material contained in the first negative electrode active material layer 22 be composed of a material that forms an alloy or compound with lithium. During discharge, the lithium in the first negative electrode active material layer 22 and the second negative electrode active material layer 23, i.e., the metal layer, is ionized and moves toward the positive electrode layer 10. Therefore, lithium can be used as the negative electrode active material in the all-solid-state secondary battery 1. Furthermore, since the first negative electrode active material layer 22 covers the second negative electrode active material layer 23, it acts as a protective layer for the second negative electrode active material layer 23, i.e., the metal layer, and also plays a role in suppressing the deposition and growth of lithium dendrites. Therefore, short circuits and capacity degradation of the all-solid-state secondary battery 1 are suppressed, and as a result, the cycle characteristics of the all-solid-state secondary battery 1 are improved. Furthermore, when the second negative electrode active material layer 23 is positioned by charging after the assembly of the all-solid-state secondary battery 1, the negative electrode current collector 21, the first negative electrode active material layer 22, and the region between them are, for example, lithium (Li)-free regions that do not contain lithium (Li) in the initial state or after discharge of the all-solid-state secondary battery.

[0109] One example of an all-solid-state secondary battery is applicable to medium- and large-sized batteries or energy storage systems (ESS).

[0110] The present invention will be explained in more detail through the following examples and comparative examples. However, the examples are provided to illustrate the present invention, and the scope of the present invention is not limited to them alone.

[0111] Manufacturing Example 1 The positive electrode active material having an aLi2O-ZrO2 coating film was manufactured by the method disclosed in Korean Published Patent No. 10-2016-0064942, but the one used was manufactured by the method described below.

[0112] Cathode active material LiNi 0.9 Co 0.05 Mn 0.05 A mixture of O2(NCM), lithium methoxide, zirconium propoxide, ethyl alcohol, and ethyl acetoethyl was stirred and mixed for 30 minutes to prepare an alcoholic solution of aLi2O-ZrO2(a=1) (aLi2O-ZrO2 coating solution). Here, the content of lithium methoxide and zirconium propoxide was adjusted so that the content of aLi2O-ZrO2(a=1) coated on the surface of the positive electrode active material was 0.5 mol%.

[0113] Next, the aLi2O-ZrO2 coating solution was mixed with the fine powder of the positive electrode active material described above, and the mixed solution was heated to approximately 40°C while stirring to evaporate and dry the solvent such as alcohol. During this process, the mixed solution was irradiated with ultrasound.

[0114] By carrying out the above process, we were able to support aLi2O-ZrO2 precursor on the particle surface of the positive electrode active material fine powder.

[0115] Furthermore, the aLi2O-ZrO2(a=1) precursor supported on the particle surface of the positive electrode active material was heat-treated at approximately 350°C for 1 hour in an oxygen atmosphere. During this heat treatment process, the aLi2O-ZrO2(a=1) precursor present on the upper part of the positive electrode active material was converted to aLi2O-ZrO2(a=1). The Li2O-ZrO2(LZO) content is approximately 0.4 parts by weight based on 100 parts by weight of NCM.

[0116] According to the manufacturing process described above, LiNi having an aLi2O-ZrO2 coating film 0.9 Co 0.05 Mn 0.05 O2(NCM) was obtained. In aLi2O-ZrO2, a is 1.

[0117] Example 1 (Negative electrode layer manufacturing) A 10 μm thick SUS foil was prepared as the negative electrode current collector.

[0118] Also, amorphous carbon black (primary particle size (average particle size): 38 nm, BET specific surface area: 55 m²) 2 ( / g, Lc: 1.6, D / G intensity ratio: 2.81), crystalline carbon black (primary particle size (average particle size): 48 nm, BET specific surface area: 39 m²) 2 A mixture was prepared by mixing Ag nanoparticles (average particle size: approximately 60 nm), which are the negative electrode active material, with a water-based binder consisting of styrene butadiene rubber and CMC (sodium carboxymethyl cellulose) in a 2:1 weight ratio, in a ratio of 25:62.5:5:6:3. In the mixture, the weight ratio of amorphous carbon black to crystalline carbon black was controlled to 30:70, as shown in Table 1 below. Binder solutions were prepared using water as the solvent for the SBR and CMC.

[0119] The mixture was stirred in a Synkey mixer to adjust it to an appropriate viscosity. Next, 2 mm zirconia balls were added and stirred in the Synkey mixer to produce a slurry. The stirred slurry was coated onto a SUS foil and then vacuum-dried at 100°C to produce a 10 μm thick negative electrode layer.

[0120] (Manufacturing of solid electrolyte layer) An argyrodite-type solid electrolyte, Li6PS5Cl, was mixed with isobutylyl isobutyrate (IBIB) as a binder solution. The mixture was then stirred in a Thinky mixer to adjust it to an appropriate viscosity. The weight ratio of the solid electrolyte to the binder was 98.5:1.5. After adjusting the viscosity of the mixture to 2,000 cP, zirconia balls with an average diameter of 2 mm were added, and the mixture was stirred again in the Thinky mixer to produce a slurry. The slurry was cast onto a release polyethylene terephthalate (PET) film and dried at room temperature (25°C) to produce a solid electrolyte layer.

[0121] (Positive electrode layer manufacturing) Li2O-ZrO2(LZO) coated LiNi obtained by Manufacturing Example 1 was used as the positive electrode active material. 0.9 Co 0.05 Mn 0.05 O2(NCM) was prepared. As the solid electrolyte, an argyrodite-type crystalline Li6PS5Cl solid electrolyte (D50 = 1 μm or less, crystalline) was used. Then, a polytetrafluoroethylene (PTFE) binder (DuPont's Teflon® binder) was prepared as the binder, and carbon nanofibers (CNF) were prepared as the conductive material. These materials were mixed with xylene in a weight ratio of positive electrode active material:solid electrolyte:conductive material:binder = 85:15:3:1.5 to form a positive electrode active material composition. This composition was then formed into a sheet and vacuum-dried at 45°C for 2 hours to produce a positive electrode layer with a thickness of approximately 150 μm.

[0122] (Manufacturing of all-solid-state rechargeable batteries) A laminate was prepared by placing a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The prepared laminate was pressurized at 80°C and 500 MPa for 60 minutes using a WIP (Wipe-In Press) method to manufacture an all-solid-state secondary battery. Such pressurization treatment sinters the solid electrolyte layer, improving the battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 μm. The thickness of the pressurized positive electrode active material layer was approximately 120 μm, the thickness of the negative electrode active material layer was 12 μm, the thickness of the solid electrolyte layer was 120 μm, and the thickness of the mixed layer was 2 μm.

[0123] Examples 2-6 and Comparative Examples 1-2 The manufacturing of the negative electrode layer of the all-solid-state secondary battery was carried out in the same manner as in Example 1, except that the composition of the negative electrode material was controlled to change as shown in Table 2 below.

[0124] Comparative Example 3 An all-solid-state secondary battery was manufactured using the same method as in Example 1, except that graphite (TGS (BTR Corporation), D / G intensity ratio of 0.18, BET specific surface area: less than 15 m / g) was used during the manufacturing of the negative electrode layer.

[0125] [Table 2]

[0126] Evaluation Example 1: Raman Analysis Raman analysis was performed on the amorphous carbon black and crystalline carbon black used in the manufacturing of the first negative electrode active material layer of the negative electrode layer in Example 1.

[0127] Raman analysis was performed using Raman 2010 Spectra (NT-MDT Development Co.) (Laser system: 473, 633, 785 nm, Lowest Raman shift: ~50 cm⁻¹). -1 The experiment was conducted using a spatial resolution of approximately 500 nm.

[0128] Carbon-based materials showed a Raman spectrum of 1350 cm⁻¹. -1 , 1580cm -1 , 2700cm -1 A peak is observed, and this peak provides information related to the thickness, crystallinity, and charge doping state of the carbon black. 1580cm -1 The peak indicated is the G-mode, which is a vibrational mode corresponding to the stretching of carbon-carbon bonds, and the energy of the G-mode is determined by the density of excess charge doped into the carbon black. -1 The peak indicated is a 2D mode peak, which is useful when evaluating the thickness of carbon black. -1 The peak indicated by is the D-mode peak, SP 2 This peak is shown when there are defects in the crystal structure. The D / G intensity ratio provides information related to the degree of disorder in the carbon black crystal.

[0129] Figures 1A and 1B show the Raman analysis results for amorphous carbon blacks, carbon A and carbon D, respectively, while Figures 1C and 1D show the Raman analysis results for crystalline carbon blacks, carbon K and carbon J, respectively.

[0130] Referring to Figures 1A and 1B, the D / G intensity ratios of amorphous carbon blacks, carbon A and carbon D, are 2.81 and 1.65, respectively. Then, referring to Figures 1C and 1D, the D / G intensity ratios of crystalline carbon blacks, carbon K and carbon J, are 1.10 and 1.13, respectively.

[0131] Evaluation Example 2: 1C Discharge Capacity The initial discharge capacity was evaluated by performing charge and discharge on the all-solid-state secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1 to 3. During battery life evaluation, the initial discharge capacity was evaluated by the following method under 1C 2.5V CC discharge conditions after charging at 45°C at 0.1C 4.25V CC / CV (0.05C cutoff).

[0132] The charge-discharge test was performed by placing the all-solid-state secondary battery in a constant temperature bath at 45°C.

[0133] The battery was charged at a constant current of 0.1C for approximately 10 hours until the battery voltage reached 4.25V. After charging at a constant voltage until the current was reduced to 0.05C at 4.25V, there was a 10-minute rest period. Subsequently, the battery was discharged at a constant current of 1C for approximately 1 hour until the battery voltage reached 2.5V. After this process, the initial discharge capacity at 1C was evaluated and is shown in Table 2 below.

[0134] Evaluation Example 3: Lifespan The capacity retention rate was evaluated for the all-solid-state secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1 to 3. During the capacity retention rate evaluation, charging and discharging were performed at 45°C under the conditions of 0.33C 4.25V CC / CV (0.1C cutoff) charging and 0.33C 2.5V CC discharging. The ratio of remaining capacity to initial capacity after 100 life cycle evaluations is shown in Table 1 below. The evaluation method is described in detail as follows.

[0135] The charge-discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated by the following charge-discharge tests. The charge-discharge tests were performed by placing the all-solid-state secondary batteries in a constant temperature bath at 45°C.

[0136] The battery was charged at a constant current of 0.1C for 10 hours until the battery voltage reached 4.25V, and then discharged at a constant current of 0.1C for 10 hours until the battery voltage reached 2.5V (first cycle).

[0137] Next, the battery was charged at a constant current of 0.1C for 10 hours until the battery voltage reached 4.25V, and then discharged at a constant current of 0.33C for 3 hours until the battery voltage reached 2.5V (second cycle).

[0138] Subsequently, the battery was charged at a constant current of 0.1C for 10 hours until the battery voltage reached 4.25V. Following this, it was discharged at a constant current of 0.5C for 2 hours until the battery voltage reached 2.5V (third cycle).

[0139] Subsequently, the battery was charged at a constant current of 0.1C for 10 hours until the battery voltage reached 4.25V. Following this, it was discharged at a constant current of 1C for 1 hour until the battery voltage reached 2.5V (fourth cycle).

[0140] Subsequently, the battery was charged at a constant current of 0.33C for 3 hours until the battery voltage reached 4.25V. Following this, it was discharged at a constant current of 0.33C for 3 hours until the battery voltage reached 2.5V (5th cycle).

[0141] The aforementioned cycle was repeated a total of 110 times, and the change in capacity and the capacity retention rate with respect to the number of cycles were evaluated. The number of cycles at which the capacity decreased by 25% according to the USAC (United States Advanced Battery Consortium) regulations was determined.

[0142] Evaluation Example 4: Initial Irreversible Measurement In Table 3 below, the initial irreversible capacity was determined by discharging a solid-state battery manufactured as a half-cell at 0.05C for 20 hours, and measuring the capacity up to the inflection point that occurs when the voltage drop begins at OCV (approximately 2.5V) and reaches ~0mV. The initial irreversible capacity was determined by Equation 1 below.

[0143] [Formula 1] Initial irreversible capacitance (%) = (Capacity up to the 0mV inflection point / Total cell capacitance) x 100

[0144] [Table 3]

[0145] From Table 3, NG for 1C-rate capacity means less than 100mAh / g, and ○ means 100mAh / g or more. For lifespan, ○ indicates that the capacity retention rate drops to less than 25% up to >100 cycles, and NG otherwise. For initial irreversible capacity %, NG indicates 10% or more, and ○ indicates 10% or less. When the irreversible capacity is 10%, the energy density decreases. Referring to Table 3, it can be seen that the all-solid-state secondary batteries of Examples 1 to 6 not only have improved 1C discharge capacity compared to the all-solid-state secondary batteries of Comparative Examples 1 and 2, but also have improved capacity retention rate and initial irreversible capacity characteristics.

[0146] The all-solid-state secondary battery of Comparative Example 1 showed superior 1C and 0.33C discharge capacities compared to the all-solid-state secondary battery of Example 1, but exhibited reduced capacity retention and initial irreversible capacity. Similarly, the all-solid-state secondary battery of Comparative Example 2 showed good capacity retention and initial irreversible capacity compared to the all-solid-state secondary battery of Example 1, but exhibited reduced 1C and 0.33C discharge capacities. This indicates that when amorphous carbon black or crystalline carbon black alone was used during the manufacturing of the negative electrode layer, the aforementioned characteristics deteriorated compared to when a mixture of amorphous and crystalline carbon black was used.

[0147] In Comparative Example 3, the all-solid-state secondary battery used only graphite in the manufacturing of the negative electrode layer, and compared to Example 1, the remaining characteristics, excluding the initial irreversible capacity, were poor. From these results, it can be seen that the negative electrode layer materials of Examples 1 to 6 exhibit superior characteristics during the manufacturing of the negative electrode layer.

[0148] Although an exemplary embodiment has been described in detail above with reference to the attached drawings, this original idea is not limited to such an example. It is self-evident that any person with ordinary skill in the art to which this original idea belongs can derive various modifications or alterations within the scope of the technical idea described in the claims, and it goes without saying that these also fall within the technical scope of this original idea. [Explanation of Symbols]

[0149] 1. All-solid-state secondary battery 10 Positive electrode layer 11 Positive current collector 12 Positive active material layer 20 Negative Electrode Layer 21 Negative current collector 22 First Negative Active Material Layer 23 Second Negative Polarity Active Material Layer 24 films 30 Solid electrolyte layer

Claims

1. This is a negative electrode layer for an all-solid-state secondary battery, comprising a negative electrode current collector and a first negative electrode active material layer containing a carbon-based material. The carbon-based material includes a mixture of amorphous carbon black and crystalline carbon black. The D-peak / G-peak intensity ratio determined by Raman analysis of the amorphous carbon black is 1.5 or greater, and the D-peak / G-peak intensity ratio determined by Raman analysis of crystalline carbon black satisfies the condition of being greater than 0.5 and less than 1.

5. The negative electrode layer for an all-solid-state secondary battery has a mixed weight ratio of amorphous carbon black to crystalline carbon black of 1:0.05 to 1:2.

5.

2. The first negative electrode active material layer further comprises a metal, a metalloid, or a combination thereof. The negative electrode layer for an all-solid-state secondary battery according to claim 1, wherein the metal, metalloid or combination thereof includes silver, platinum, zinc, silicon, tin, iron, copper, aluminum, indium, vizmus or combination thereof.

3. The content of the aforementioned metal, metalloid, or combination thereof is 1 to 40% by weight based on 100 parts by weight of the total weight of the first negative electrode active material layer. The negative electrode layer for an all-solid-state secondary battery according to claim 2, wherein the content of the carbon-based material is 60 to 99% by weight.

4. The primary particle size of the amorphous carbon black is 15 nm to 60 nm, and the specific surface area is 15 to 1500 m². ２ The coefficient is / g, the crystallite size Lc in the c-axis direction is 3.0 nm or less, and the carbon interlayer spacing (d ００２ ) is 0.350 nm to 0.370 nm, The primary particle size of the crystalline carbon black is 15 nm to 60 nm, and the specific surface area is 15 to 500 m². ２ The coefficient of energy is / g, the crystallite size Lc in the c-axis direction is 2.0 nm to 10.0 nm, and the intercalation spacing of carbon atoms is (d ００２ ) is 0.335 nm to 0.357 nm, The negative electrode layer for an all-solid-state secondary battery according to claim 1, wherein the primary particle size is the average particle size.

5. The negative electrode layer for an all-solid-state secondary battery according to claim 1, wherein the D-peak / G-peak intensity ratio of the amorphous carbon black is 1.6 to 4.0, and the D-peak / G-peak intensity ratio of the crystalline carbon black is 0.8 to 1.

5.

6. The negative electrode layer for an all-solid-state secondary battery according to claim 1, further comprising a lithium metal or lithium alloy thin film between the negative electrode current collector and the first negative electrode active material layer.

7. The negative electrode layer for an all-solid-state secondary battery according to claim 1, further comprising a thin metal or semimetallic film between the negative electrode current collector and the first negative electrode active material layer.

8. The aforementioned metal or metalloid thin film includes gold (Au), silver (Ag), magnesium (Mg), zinc (Zn), silicon (Si), tin (Sn), platinum (Pt), palladium (Pd), aluminum (Al), vizmus (Bi), or a combination thereof. The negative electrode layer for an all-solid-state secondary battery according to claim 7, wherein the thickness of the metal or semimetallic thin film is 1 to 800 nm.

9. The aforementioned negative electrode layer further comprises a second negative electrode active material layer, The negative electrode layer for an all-solid-state secondary battery according to claim 1, wherein the second negative electrode active material layer comprises a metal, a metalloid element or combination thereof that forms an alloy with lithium, and the second negative electrode active material layer is a metal layer containing lithium or a lithium alloy.

10. The first negative electrode active material layer includes a binder, The negative electrode layer for an all-solid-state secondary battery according to claim 1, wherein the binder is styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, carboxymethylcellulose, or a combination thereof.

11. A solid-state secondary battery comprising a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, All-solid-state secondary battery, wherein the negative electrode layer is the negative electrode layer described in any one of claims 1 to 10.

12. The all-solid-state secondary battery according to claim 11, wherein the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer, and a second negative electrode active material layer is disposed above the first negative electrode active material layer, on one or more of the negative electrode current collector and the first negative electrode active material layer, and the second negative electrode active material layer includes lithium or a lithium alloy.

13. The all-solid-state secondary battery according to claim 11, wherein the negative electrode layer comprises a negative electrode current collector and a first negative electrode active material layer, and the negative electrode current collector, the negative electrode active material layer, and the region between them are Li-free regions that do not contain lithium (Li) in the initial state or after discharge state of the all-solid-state secondary battery.

14. The all-solid-state secondary battery according to claim 11, wherein the all-solid-state secondary battery includes a lithium deposition layer between the negative electrode current collector and the negative electrode active material during or after charging.

15. The all-solid-state secondary battery according to claim 11, wherein the solid electrolyte layer includes a sulfide-based solid electrolyte.

16. The sulfide-based solid electrolyte is Li ２ S - P ２ S ５ 、Li ２ S - P ２ S ５ - LiX (X is a halogen element), Li ２ S - P ２ S ５ - Li ２ O, Li ２ S - P ２ S ５ - Li ２ O - LiI, Li ２ S - SiS[[ID=三十一]] ２ 、Li ２ S - SiS ２ - LiI, Li ２ S - SiS ２ - LiBr, Li ２ S - SiS ２ - LiCl, Li ２ S - SiS ２ - B ２ S ３ - LiI, Li ２ S - SiS ２ - P ２ S ５ - LiI, Li ２ S - B ２ S ３ 、Li ２ S - P<000003-nine]] ２ S ５ - Z ｍ S ｎ (m, n are positive numbers, Z is one of Ge, Zn or Ga), Li ２ S - GeS ２ 、Li ２ S - SiS ２ - Li ３ PO<( ４ 、Li ２ S - SiS ２ - Li ｐ MO ｑ (p, q are positive numbers, M is one of P, Si, Ge, B, Al, GaIn), Li ７－ｘ PS ６－ｘ ( ｘ Cl ｘ 、0 ≦ x ≦ 2, Li ７－ｘ PS ６－ｘ Br ｘ 、0 ≦ x ≦ 2、and Li It should be noted that there may be some tags that need to be further checked for accuracy in the context, especially the numbering tags like ２ etc. which seem to be in a rather specific format that might require more domain knowledge to ensure proper handling. Also, some parts of the chemical formula translation might need to be double - checked according to the standard chemical naming conventions. ７－ｘ PS ６－ｘ I ｘ The all-solid-state secondary battery according to claim 15, wherein one or more of the following are selected: 0 ≤ x ≤ 2.

17. The sulfide-based solid electrolyte is Li ６ PS ５ Cl, Li ６ PS ５ Br and Li ６ PS ５ The all-solid-state secondary battery according to claim 15, wherein the solid electrolyte is an algyrodite type containing one or more selected from among I.

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