Lithium metal electrode, its manufacturing method and lithium secondary battery including the same

Abstract

The present invention relates to a lithium metal electrode, a manufacturing method thereof, and a lithium secondary battery including the same. According to one embodiment, a lithium metal electrode may be provided that includes a current collector and a metal layer including a lithium component, the metal layer being located on at least one surface of the current collector, and a protective layer including amorphous carbon and lithium ion conduction promoting ceramic particles is formed on the metal side surface.

Description

[Technical Field]

[0001] The present embodiment relates to a lithium metal electrode, a method for manufacturing the same, and a lithium secondary battery including the same. [Background technology]

[0002] BACKGROUND ART In recent years, with the explosive demand for electric vehicles and the demand for increased driving distances, secondary batteries with high capacity and high energy density have been actively developed worldwide to meet this demand.

[0003] In order to reduce the cost of secondary batteries and improve their energy density, it has been proposed to use a lithium metal electrode as the negative electrode of lithium secondary batteries.

[0004] To form such a lithium metal anode, a lithium foil is typically rolled onto the current collector, but rolling it presents a problem in that it is difficult to achieve a lithium metal anode with a thickness of 20 μm or less.

[0005] On the other hand, in order to realize a secondary battery having a high energy density by substantially utilizing a lithium metal negative electrode, a thin-film lithium metal negative electrode having a thickness of 10 to 20 μmm is required.

[0006] However, when lithium metal is used as the anode in an all-solid-state battery, a high-resistance phase is generated due to the reaction between lithium and the all-solid-state electrolyte, and local non-uniformity in current density during charging and discharging can lead to the continuous generation of lithium dendrites or the generation of high-resistance lithium by-products, which can cause failures due to short circuits or overvoltage during charging and discharging, or a decrease in capacity.

[0007] To solve these problems, various methods have been proposed, such as forming a protective coating layer or a lithium alloy layer on the lithium metal to prevent reactions with the all-solid-state battery and the precipitation and growth of lithium dendrites, but they have yet to achieve sufficient lifespan characteristics for use in electric vehicles (EVs).

[0008] To meet these needs, recent publications such as Korean Patent Application No. 10-2018-0136041 (Patent Document 1), Korean Patent Application No. 10-2019-0134804 (Patent Document 2), Korean Patent Application No. 10-2020-7006820 (Patent Document 3), and Nature Energy 5, 299 (2020) (Non-Patent Document 1) have attempted to solve the above problem by using a non-anode coating layer made of a mixture of amorphous carbon and silver (Ag) nanoparticles to precipitate lithium during the charge and discharge process. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent Application No. 10-2018-0136041 [Patent Document 2] Korean Patent Application No. 10-2019-0134804 [Patent Document 3] Korean Patent Application No. 10-2020-7006820 [Non-patent literature]

[0010] [Non-Patent Document 1] Nature Energy 5, 299(2020)

[0011] However, during the charge / discharge process, materials with electronic conductivity, such as lithium-based alloys or lithium-containing compounds, are generated within the anode coating layer or at the interface, which can cause current concentration and lithium dendrites, resulting in a shortened lifespan.

[0012] Furthermore, the initial coulomb efficiency is low due to the irreversible reaction caused by amorphous carbon, which is the main material of the anode coating layer.

[0013] To solve these problems, a sacrificial cathode is used, and a large amount of precious metal nanoparticles is also used, which significantly reduces price competitiveness and makes commercialization difficult.

[0014] Therefore, there is a need to develop a technology that can produce electrodes that have excellent initial efficiency and excellent charge-discharge characteristics. Summary of the Invention [Problem to be solved by the invention]

[0015] As mentioned above, this embodiment aims to solve the problems of lithium dendrite formation and reduced lifespan due to electronically conductive materials in the anode layer, the problem of reduced initial Coulomb efficiency due to initial irreversibility caused by amorphous carbon in the anode coating layer and the need to use a sacrificial cathode to compensate for this, and the problem of using a large amount of noble metal nanoparticles such as silver (Ag) to form an alloy with lithium during charging.

[0016] Another object of the present invention is to provide a lithium metal electrode having excellent charge / discharge characteristics by preventing dendrite formation through a protective layer contained in the electrode layer, a method for manufacturing the same, and a lithium secondary battery including the same. [Means for solving the problem]

[0017] According to an embodiment, a lithium metal electrode includes a current collector, a metal layer including a lithium alloy disposed on at least one surface of the current collector, and a protective layer disposed on the metal layer, the protective layer including amorphous carbon and lithium ion conduction promoting ceramic particles. [Effects of the Invention]

[0018] According to this example, a lithium ion conduction promoting protective layer is formed on a lithium metal electrode, and lithium dendrite formation during the charge and discharge process of a lithium secondary battery to which this is applied can be controlled, thereby mitigating the reduction in the lifespan of the lithium secondary battery.

[0019] Furthermore, it is possible to suppress the decrease in the initial coulomb efficiency of the lithium secondary battery and to significantly improve the charge / discharge characteristics. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram illustrating a lithium metal electrode manufactured according to an embodiment. [Figure 2] FIG. 10 is a schematic diagram of a lithium metal electrode according to another embodiment. [Figure 3] 1A to 1C are diagrams schematically illustrating a process for manufacturing a lithium metal electrode according to an embodiment. [Figure 4] 3 is a SEM photograph showing a cross section of a current collector on which an alloy material coating layer is formed in the process of producing a lithium metal electrode according to Example 1. [Figure 5] 3 is an SEM photograph showing a cross section of a current collector on which an alloy material coating layer and a lithium ion conduction promoting protective layer are formed in the process of producing a lithium metal electrode according to Example 1. [Figure 6a] 1 is a SEM photograph showing a cross section of a lithium metal electrode manufactured in Example 1. [Figure 6b] 1 is an SEM photograph showing a cross section of a lithium metal electrode produced according to Comparative Example 1. [Figure 6c] 1 is an SEM photograph showing a cross section of a lithium metal electrode produced in Comparative Example 2. [Figure 6d] 1 is an SEM photograph showing a cross section of a lithium metal electrode produced in Comparative Example 3. [Figure 7a] 1 is a photograph showing the surface microstructure of the lithium metal electrode prepared in Example 1. [Figure 7b] 1 is a photograph showing the results of component analysis of the lithium metal electrode produced in Example 1. [Figure 8a] 1 is a photograph showing the surface microstructure of a lithium metal electrode prepared according to Comparative Example 1. [Figure 8b] 1 is a photograph showing the results of component analysis of the lithium metal electrode produced in Comparative Example 1. [Figure 9a]1 is a photograph showing the surface microstructure of a lithium metal electrode prepared according to Comparative Example 2. [Figure 9b] 1 is a photograph showing the results of component analysis of the lithium metal electrode produced in Comparative Example 2. [Figure 10a] 1 is a photograph showing the surface microstructure of a lithium metal electrode prepared according to Comparative Example 3. [Figure 10b] 1 is a photograph showing the results of component analysis of the lithium metal electrode produced in Comparative Example 3. [Figure 11] 1 is a diagram showing the results of evaluating the initial effects of secondary batteries manufactured according to Example 1 and Comparative Examples 1 to 3. [Figure 12] 1 is a diagram showing the results of evaluating the charge-discharge life of secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3. [Figure 13] 1 is a diagram showing the results of evaluating the charge-discharge life of secondary batteries manufactured in Examples 1 to 4 and Comparative Example 2. [Figure 14] 1 is a schematic diagram of a secondary battery to which a lithium metal electrode manufactured according to the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0021] Terms such as "first," "second," and "third" are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below can be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0022] The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. As used herein, the term "comprises" refers to the inclusion of specific properties, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other properties, regions, integers, steps, operations, elements, and / or components.

[0023] When a part is described as being "on" or "above" another part, it may be exactly on or above the other part, or it may have other parts between them. In contrast, when a part is referred to as being "directly above" another part, there are no other parts between them.

[0024] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined.

[0025] The following detailed description of the present invention is provided by way of example only, and is not intended to limit the scope of the present invention, which is defined solely by the scope of the claims that follow.

[0026] FIG. 1 is a diagram schematically illustrating a lithium metal electrode manufactured according to one embodiment, FIG. 2 is a diagram schematically illustrating a lithium metal electrode according to another embodiment, and FIG. 3 is a diagram schematically illustrating a method for manufacturing a lithium metal electrode for a secondary battery according to one embodiment.

[0027] Referring to FIG. 1, a lithium metal electrode 100 according to one embodiment includes a current collector 11 and a metal layer 12 disposed on at least one surface of the current collector 11, and a protective layer 30 disposed on the other surface of the metal layer 12 facing the current collector 11.

[0028] The current collector 11 is for electrical connection within the lithium secondary battery.

[0029] The current collector 11 may have the form of a thin film (foil), but is not limited thereto, and may also have the form of, for example, a mesh, a foam, a rod, a wire, or a sheet made of woven wire (fiber).

[0030] A material that is electrically conductive and has limited reactivity with lithium can be used as the material for the current collector 11. For example, the material for the current collector 11 can be any one of copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, carbon, conductive polymers, and composite fibers in which a conductive layer is coated on a non-conductive polymer, or a combination thereof.

[0031] If the thickness of the current collector 11 is too thick, the battery weight increases and the energy density of the battery decreases, whereas if the thickness of the current collector 11 is too thin, there is a risk of overheating and damage during high current operation and the current collector 11 may be damaged by tension during the battery manufacturing process. Therefore, the thickness of the current collector 11 can be in the range of 1 μm to 50 μm.

[0032] The metal layer 12 includes a lithium alloy layer 21 disposed on the current collector 11 and containing a lithium alloy, and a lithium metal layer 41 disposed on the lithium alloy layer 21. The lithium alloy layer 21 may be a layer containing a lithium alloy formed by applying a current between the current collector 11 and a lithium supply source to alloy lithium deposited from the lithium supply source with a lithium parent component contained in the coating layer of the current collector 11. Applying a high current to increase the electrodeposition rate during metal layer formation can result in a decrease in the performance of the lithium secondary battery. However, when the metal layer 12 is formed with a structure including a lithium alloy layer 21 containing a lithium component, applying a high current to perform the electrodeposition process can prevent excessive generation of fine lithium particles and damage to the surface protective film of the lithium metal layer already formed during the electrodeposition process.

[0033] More specifically, since the metal layer 12 of this embodiment includes a lithium alloy layer containing a lithium component, when a lithium metal layer is formed on the lithium alloy layer by applying a high current in an electrodeposition process, the initially generated lithium particles are induced to grow well, resulting in the formation of particles with a coarse structure, and the lithium metal layer, and consequently the metal layer 12, can have a uniform surface.

[0034] Therefore, the performance of the secondary battery using the lithium metal electrode of this embodiment, specifically the charge / discharge characteristics, can be significantly improved. Furthermore, even when a high current is applied to perform a high-speed electrodeposition process, a high-performance lithium metal electrode for a secondary battery can be produced, and the productivity of the lithium metal electrode for a secondary battery can also be significantly improved.

[0035] The lithium alloy layer 21 may be an alloy of lithium and a lithium-loving metal, and the lithium-loving metal may be one or more selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

[0036] In this embodiment, the lithium alloy layer includes a lithium-phile metal, which has high electronic conductivity, and thus has the advantage of facilitating the electrodeposition of the lithium metal layer by smoothly supplying electrons from the current collector and reducing lithium ions.

[0037] Meanwhile, the metal layer serves to facilitate more efficient deposition of lithium beneath the protective layer during the charging process of the battery.

[0038] The thickness of the metal layer 12 can be in the range of 1 μm to 100 μm, more specifically, 5 μm to 30 μm.

[0039] If the thickness of the metal layer 12 is too thick, when the lithium metal electrode of this embodiment is applied to a secondary battery, the weight and volume of the battery increase, resulting in a problem of a low energy density. In addition, when forming the metal layer 12, the time and cost of the electrodeposition process increase in proportion to the thickness, so the thickness of the metal layer 12 is preferably 100 μm or less.

[0040] Furthermore, if the thickness of the metal layer 12 is too thin, when the lithium metal electrode of this embodiment is applied to a secondary battery, the charge / discharge life of the battery may be shortened. Specifically, during charge / discharge of the battery, lithium in the battery is gradually consumed due to side reactions between the lithium contained in the negative electrode active material layer, i.e., the metal layer of the present invention, and the electrolyte, resulting in a decrease in battery capacity. However, if the thickness of the metal layer 12 is too thin, the amount of lithium available to replenish the lithium consumed during charge / discharge is reduced, thereby shortening the charge / discharge life of the battery. Therefore, it is preferable that the thickness of the metal layer 12 be 1 μm or more.

[0041] The protective layer 30 is located on the metal layer 12 and includes amorphous carbon and ceramic particles that promote lithium ion conductivity.

[0042] When lithium metal is used as the anode in an all-solid-state battery, high resistance is generated due to the reaction between the all-solid-state electrolyte and lithium, and localized non-uniformity in current density during charging and discharging can lead to the continuous generation of lithium dendrites or the generation of highly resistive lithium by-products, which can cause failure due to short circuits or overvoltage during charging and discharging, or a decrease in battery capacity.

[0043] However, as in this example, a protective layer containing amorphous carbon and lithium ion conduction promoting ceramic particles can improve not only the output characteristics and life characteristics of the lithium metal electrode, but also the structural safety.

[0044] More specifically, the lithium metal electrode of this embodiment includes a protective layer 30 containing amorphous carbon and lithium ion conductivity-promoting ceramic particles, which can promote the movement of lithium ions on the electrode surface during charge and discharge, suppress the generation of electronically conductive materials at the interface, and reduce the electronic conductivity within the protective layer 30.

[0045] Therefore, the performance of the secondary battery to which the lithium metal electrode according to this embodiment is applied, specifically the output characteristics and life characteristics of the battery, can be significantly improved.

[0046] The amorphous carbon may be at least one selected from the group consisting of acetylene black, super P black, carbon black, denka black, activated carbon, graphite, hard carbon, and soft carbon, but is not limited thereto.

[0047] The lithium ion conductivity promoting ceramic particles are typically Li2TiO3, LiNbO3, LiTaO3, LiZrO3, Li4Ti5O 12The lithium ion conductive ceramic particles may be one or more selected from the group consisting of particles that promote lithium ion conduction and inhibit electron conduction, such as, but not limited to, Li2CO3, Li3BO3, SrTiO3, etc. The lithium ion conductive ceramic particles promote lithium ion conduction and inhibit electron conduction within and at the interface of the protective layer during the charging process of a battery using a lithium negative electrode, thereby allowing lithium to easily move to the bottom of the protective layer.

[0048] In this embodiment, the average particle size D(50) of the lithium ion conductivity promoting ceramic particles may be in the range of 100 nm to 1,000 nm. If the average particle size D(50) of the lithium ion conductivity promoting ceramic particles is less than 100 nm, aggregation between primary particles may result in uneven distribution of the ceramic particles in the coating layer. If the average particle size D(50) of the lithium ion conductivity promoting ceramic particles is greater than 1,000 nm, large particles may act as a resistance layer, resulting in reduced lithium ion conductivity.

[0049] In particular, such a material does not react well with sulfide-based electrolyte materials of all-solid-state batteries and has excellent chemical stability, which is advantageous for improving the interface stability and charge / discharge life of all-solid-state batteries. The ion conduction-promoting protective layer can be formed by preparing the composite in the form of a slurry and applying it. To prepare such a slurry, a binder can be further added.

[0050] The lithium ion conduction promoting protective layer may include amorphous carbon and lithium ion conduction promoting ceramic particles in a weight ratio of 99.5:0.5 to 40:60, specifically 98.5:1.5 to 50:50, and more specifically 97:3 to 70:30.

[0051] If the amount of lithium-ion conduction promoting ceramic particles is too small, the lithium-ion conduction promoting effect of the mixed lithium-ion conduction promoting ceramic particles cannot be sufficiently obtained. If the amount of lithium-ion conduction promoting ceramic particles is too large, the connection between the ceramic particles at room temperature is poor, resulting in a decrease in the density of the protective layer, which may actually hinder lithium-ion conduction. In addition, if an excessive amount of ceramic particles, which have a relatively higher density than amorphous carbon, is included, there is a problem that a decrease in battery energy density occurs.

[0052] On the other hand, the protective layer of this embodiment may contain a binder.

[0053] In this case, the binder may be an aqueous binder, and the aqueous binder may be at least one selected from the group consisting of a rubber-based binder selected from the group consisting of acrylonitrile butadiene rubber, styrene butadiene rubber (SBR), and acrylic rubber, and a polymer resin such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride, but is not limited thereto.

[0054] Here, the binder may be added in an amount of 1 to 15 parts by weight, more specifically 3 to 10 parts by weight, based on the weight of the slurry formed by mixing the lithium ion conductivity promoting ceramic particles, amorphous carbon, and water.

[0055] When the amount of binder added satisfies the above range, the particles constituting the protective layer can be efficiently bound to form a protective layer with excellent performance without inducing a decrease in battery energy density due to an increase in weight and volume, and the life characteristics of the secondary battery can be further improved. If the amount of binder added is too small, the bonding strength between the particles can be reduced when forming the protective layer, while if the amount of binder added is too large, not only does it cause a decrease in energy density but it also causes a significant increase in the resistance of the protective layer, hindering lithium ion conduction.

[0056] The protective layer containing amorphous carbon, lithium ion conduction-promoting ceramic particles, and a binder may have a thickness of 0.01 μm to 50 μm, more specifically, 1 μm to 20 μm. When the protective layer has a thickness within this range, the effects of including amorphous carbon and lithium ion conduction-promoting ceramic particles prevent lithium dendrites from forming on the surface of the protective layer and facilitate lithium ion conduction through the interior of the protective layer, thereby allowing lithium to precipitate from the underside of the protective layer. On the other hand, if the protective layer containing amorphous carbon and lithium ion conduction-promoting ceramic particles is too thin, it may not function as a protective layer. On the other hand, if the protective layer is too thick, its resistance may become too high, potentially causing an overvoltage during secondary battery operation. Furthermore, increased weight and volume may result in a decrease in battery energy density. However, the thickness of the protective layer can be variably adjusted depending on the design of the secondary battery structure.

[0057] Meanwhile, although not shown, the metal layer 12 of this embodiment may further include a coating layer (SEI, Solid-Electrolyte Interphase) located on the surface of the metal layer 12 .

[0058] The coating layer is formed during the manufacturing process of the metal layer 12 by a reaction between the lithium metal of the electrodeposited lithium supply source and the plating solution, and the thickness, composition, and properties of the coating can be controlled by adjusting the composition of the plating solution used and the conditions of the electrodeposition process.

[0059] The thickness of the coating layer can be, for example, in the range of 2 nm to 2 μm, more specifically, 10 nm to 500 nm.

[0060] If the thickness of the coating layer located on the surface of the metal layer 12 is too thick, the lithium ion conductivity may decrease, the interface resistance may increase, and the charge / discharge characteristics when applied to a battery may deteriorate. Also, if the thickness of the coating layer is too thin, the coating layer may easily be washed away during application of the lithium metal electrode according to the embodiment to a battery.

[0061] Therefore, it is preferable that the coating layer be formed uniformly and densely over the entire surface of the metal layer 12 with a small thickness that satisfies the above thickness range.

[0062] In this case, the coating layer may include one or more materials selected from the group consisting of Li-NCHO-based ionic compounds, Li-PCHO-based ionic compounds, LiF, and Li3N.

[0063] FIG. 2 is a schematic diagram of a lithium metal electrode according to another embodiment.

[0064] 2, a lithium metal electrode 100 for a secondary battery according to another embodiment includes a current collector 11 and a metal layer 12 formed by mixing lithium and a lithium alloy and located on at least one surface of the current collector 11. Here, the lithium alloy may be formed by applying a current between the current collector 11 and a lithium supply source, and alloying a lithium-loving component contained in a coating layer formed on the current collector 11 with lithium deposited from the lithium supply source.

[0065] In this case, the metal layer 12 may contain a lithium-loving metal, which may be, but is not limited to, one or more elements selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

[0066] In this example, the metal layer 12 contains a lithium-philic metal. When the metal layer 12 containing the lithium-philic metal is formed in this manner, the nucleation free energy can be reduced at the initial stage of nucleation of lithium particles in the electrodeposition process, and therefore a lithium metal layer having a coarse particle structure can be formed even under high current and overvoltage conditions.

[0067] In this embodiment, the thickness of the metal layer 12 may be in the range of 1 μm to 100 μm, more specifically, 5 μm to 30 μm. In this embodiment, when the metal layer 12 satisfies this thickness range, it is possible to maximize the energy density of the battery while improving the charge / discharge life of the battery, as well as minimize the time and cost of the electrodeposition process when forming the metal layer 12. If the metal layer thickness is too thin, the initial coulomb efficiency decreases due to initial irreversibility, and charge / discharge performance decreases due to a lack of surplus lithium. On the other hand, if the metal layer thickness is too thick, it not only reduces the energy density of the battery, but also increases the process time and the amount of metal raw material used when forming the metal layer.

[0068] Meanwhile, although not shown in FIG. 2, the metal layer of this embodiment may further include a coating layer located on the surface of the metal layer.

[0069] Such a coating layer is the same as that described in the lithium metal electrode for a secondary battery according to the above embodiment, and therefore a description thereof will be omitted here.

[0070] According to one embodiment, a method for manufacturing a lithium metal electrode includes the steps of: forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-loving component; forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and lithium ion conduction promoting particles; positioning the current collector with the coating layer and protective layer formed thereon in a plating solution, and then positioning a lithium supply source at a predetermined distance from the protective layer; and applying a current between the current collector and the lithium supply source to form a metal layer containing a lithium alloy in which the lithium-loving component contained in the coating layer and lithium deposited from the lithium supply source are alloyed.

[0071] In the step of forming a protective layer on the surface of the coating layer using the slurry containing the amorphous carbon and the lithium-ion conduction-promoting ceramic particles, the lithium-ion conduction-promoting protective layer may include amorphous carbon and lithium-ion conduction-promoting ceramic particles in a weight ratio of 99.5:0.5 to 40:60, specifically 98.5:1.5 to 50:50, and more specifically 97:3 to 70:30.

[0072] First, a coating composition containing a lithium-phile metal is used to form an alloy material coating layer on at least one surface of a current collector.

[0073] In this case, the lithium-loving metal may be, for example, one or more selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

[0074] The alloy material coating layer may be formed by at least one of electrolytic and electroless plating, sputtering, electron beam deposition, and thermal vapor deposition.

[0075] Meanwhile, in the step of forming the alloy material coating layer, the thickness of the alloy material coating layer formed on at least one surface of the current collector may be in the range of 0.001 μm to 10 μm, specifically 0.01 μm to 1 μm, more specifically 100 nm to 500 nm.

[0076] If the thickness of the alloy material coating layer is too thin, it is insufficient to form a lithium alloy with lithium, and if the thickness is too thick, it takes a lot of time and money to form the alloy material coating layer, resulting in reduced production efficiency and economic efficiency, increased battery weight, and reduced energy density.

[0077] After the alloy material coating layer forming step, a protective layer is applied to the surface of the formed alloy material coating layer.

[0078] In this case, the protective layer is a lithium ion conduction promoting protective layer and may include amorphous carbon and lithium ion conduction promoting ceramic particles.

[0079] In this case, the amorphous carbon may be at least one selected from the group consisting of acetylene black, super pea black, carbon black, denka black, activated carbon, graphite, hard carbon, and soft carbon, but is not limited thereto.

[0080] The lithium ion conductivity promoting ceramic particles are selected from the group consisting of Li2TiO3, LiNbO3, LiTaO3, LiZrO3, and Li4Ti5O 12 The lithium ion conductive material may be one or more selected from the group consisting of particles having low electronic conductivity and high lithium ion conductivity, such as Li2CO3, Li3BO3, and SrTiO3, but is not limited thereto.

[0081] Meanwhile, the lithium ion conduction promoting protective layer may contain a binder.

[0082] The binder may be an aqueous binder, and the aqueous binder may be at least one selected from the group consisting of a rubber-based binder selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, and a polymer resin such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride, but is not limited thereto.

[0083] The lithium ion conduction promoting protective layer may be formed by applying a slurry prepared by mixing the amorphous carbon, the lithium ion conduction promoting ceramic particles, and a binder in water using at least one of a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.

[0084] Here, the lithium ion conduction promoting protective layer may include amorphous carbon and lithium ion conduction promoting ceramic particles in a weight ratio of 99.5:0.5, specifically 98.5:1.5 to 50:50, and more specifically 97:3 to 70:30.

[0085] The binder may be added in an amount of 0.5 to 10 parts by weight, more specifically 1 to 3 parts by weight, based on the weight of the lithium ion conductivity promoting ceramic particles, amorphous carbon, and water mixed together.

[0086] Meanwhile, in the step of forming the lithium ion conduction promoting protective layer, the thickness of the lithium ion conduction promoting protective layer formed on the surface of the alloy material coating layer may be in the range of 0.01 μm to 50 μm, more specifically, 1 μm to 20 μm.

[0087] When the thicknesses of the alloy material coating layer and the lithium ion conduction promoting protective layer satisfy the above ranges, the lithium metal electrode for a secondary battery according to an embodiment can be manufactured to have the lithium metal electrode structure shown in FIG. 1 or FIG. 2.

[0088] After the lithium ion conduction promoting protective layer forming step, the steps of positioning the current collector on which the alloy material coating layer and the lithium ion conduction promoting protective layer are sequentially formed in a plating solution, positioning a lithium supply source at a predetermined distance from the current collector, and applying a current between the current collector and the lithium supply source to form a metal layer are performed.

[0089] The step of forming the metal layer will be described in more detail with reference to FIG.

[0090] First, the current collector 11 having the alloy material coating layer 20 and the lithium ion conduction promoting protective layer 30 formed thereon is placed in the plating solution 50, and then the lithium supply source 40 is placed at a predetermined distance from the lithium ion conduction promoting protective layer 30.

[0091] The lithium supply source 40 may be, for example, lithium metal, a lithium alloy, a foil of the lithium metal or lithium alloy pressed onto a current collector, or a plating solution in which a lithium salt is dissolved.

[0092] The current collector 11 is the same as that described above, and a description thereof will be omitted here.

[0093] The plating solution 50 can be prepared by dissolving a lithium salt in a non-aqueous solvent.

[0094] More specifically, the lithium salt may be LiCl, LiBr, LiI, LiCO3, LiNO3, LiFSI, LiTFSI, LiBF4, LiPF6, LiAsF6, LiClO4, LiN(SO2CF3)2, LiBOB, or a combination thereof. The concentration of the lithium salt may be 0.1 to 3.0 M based on the total electrolyte solution.

[0095] More specifically, in this embodiment, the plating solution contains a nitrogen-based compound in at least one of the lithium salt and the non-aqueous solvent.

[0096] The nitrogen-based compound may include, for example, one or more selected from the group consisting of lithium nitrate, lithium bis fluorosulfonyl imide, lithium bis trifluoromethane sulfonimide, caprolactam (e-caprolactam), methyl caprolactam (N-methyl-e-caprolactam), triethylamine, and tributylamine.

[0097] Among the nitrogen-based compounds, at least one of lithium nitrate, lithium bisfluorosulfonyl imide, and lithium bistrifluoromethane sulfonimide can be used as the lithium salt.

[0098] Among the nitrogen-based compounds, at least one of caprolactam (e-caprolactam), methylcaprolactam (N-methyl-e-caprolactam), triethylamine, and tributylamine can be used as the non-aqueous solvent.

[0099] Meanwhile, the plating solution may contain a general non-aqueous solvent as a solvent, taking into consideration the viscosity of the plating solution, etc. If the viscosity of the plating solution is too high, the mobility of lithium ions decreases, reducing the ionic conductivity of the plating solution, thereby increasing the time required for the electrodeposition process and reducing productivity.

[0100] The solvent can include, for example, one or more selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, and 1,3,5-trioxane.

[0101] The current density of the current applied in the step of applying a current to form a lithium metal layer on at least one surface of the current collector is 0.1 mA / cm 2 ~100mA / cm 2 in the range of 0.2mA / cm 2 ~50mA / cm 2 range, 5mA / cm 2 ~30mA / cm 2 range or 7mA / cm 2 ~25mA / cm 2 may be in the range of

[0102] The duration of application of the current may be in the range of 0.05 hours to 50 hours, more specifically, in the range of 0.25 hours to 25 hours.

[0103] As described above, this embodiment prevents excessive production of fine lithium particles even under high current conditions and encourages the initial production of lithium particles to grow, thereby fabricating a lithium metal electrode having a metal layer including a lithium metal layer with a coarse particle structure. Furthermore, the metal layer fabricated in this manner also has excellent surface uniformity. Specifically, as shown in FIG. 1, a lithium alloy layer 21 containing a lithium component and a lithium metal layer 41 located on the lithium alloy layer 21 can be fabricated to have a lithium metal electrode structure including a metal layer 12, or a lithium metal electrode structure including a metal layer 12 composed of a mixture of lithium and a lithium alloy, as shown in FIG. 2. The thickness of the metal layer 12 can be in the range of 1 μm to 100 μm, more specifically, 5 μm to 30 μm.

[0104] When the lithium metal electrode manufactured according to this embodiment is applied, the charge / discharge characteristics of the secondary battery can be significantly improved.

[0105] A secondary battery according to one embodiment includes a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode, where the negative electrode may be the lithium metal electrode according to the present invention.

[0106] FIG. 14 is a diagram schematically illustrating the structure of a secondary battery according to an embodiment.

[0107] Referring to FIG. 14, the secondary battery 200 of this embodiment may include an electrode assembly including a positive electrode 70, a negative electrode 100, and a separator 90 disposed between the positive electrode 70 and the negative electrode 100.

[0108] Such an electrode assembly is wound or folded and housed in a battery case 95 .

[0109] Then, the electrolyte 80 is injected into the battery case 95 and sealed to complete the secondary battery 200. The battery case 95 may have a cylindrical, square, pouch, coin, or other shape.

[0110] For convenience, FIG. 14 shows the negative electrode according to one embodiment as the negative electrode 100, but any of the lithium metal electrodes for secondary batteries according to the above-described embodiments can be applied to the negative electrode.

[0111] The positive electrode 70 may include a positive electrode active material layer and a positive electrode current collector.

[0112] The positive electrode active material layer may contain, for example, at least one metal selected from the group consisting of Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, and Ce, and a Li compound containing at least one nonmetallic element selected from the group consisting of O, F, S, P, and combinations thereof. The positive electrode active material layer may contain active material particles having an average particle size of approximately 0.01 μm to 200 μm, which may be appropriately selected depending on the required characteristics of the battery.

[0113] In some cases, a conductive agent may be added to the positive electrode active material layer.

[0114] The conductive agent may be, for example, fine carbon such as carbon black and ultrafine graphite particles, acetylene black, nano metal particle paste, etc., but is not limited thereto.

[0115] The positive electrode current collector serves to support the positive electrode active material layer, and may be, for example, an aluminum foil, a nickel foil, or a combination thereof, but is not limited thereto.

[0116] The electrolyte 80 filled in the lithium secondary battery 200 may be a non-aqueous electrolyte solution or a solid electrolyte.

[0117] The non-aqueous electrolyte solution may contain, for example, a lithium salt such as lithium hexafluorophosphate or lithium perchlorate and a solvent such as ethylene carbonate, propylene carbonate, or butylene carbonate. The solid electrolyte may be, for example, a gel polymer electrolyte obtained by impregnating a polymer electrolyte such as polyethylene oxide or polyacrylonitrile with an electrolyte solution, or an inorganic solid electrolyte such as LiI or LiN.

[0118] The separator 90 separates the positive and negative electrodes and provides a path for lithium ions to move. Any material commonly used in lithium secondary batteries can be used. That is, materials with low resistance to ion movement and excellent electrolyte impregnation ability can be used. The separator can be made of, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and may be in the form of a nonwoven or woven fabric. Meanwhile, when a solid electrolyte is used as the electrolyte 80, the solid electrolyte can also serve as the separator 90. [Example]

[0119] Hereinafter, embodiments of the present invention will be described in detail, but these are presented as examples and are not intended to limit the present invention, which is defined only by the scope of the claims that follow.

[0120] [Example 1] A lithium metal electrode for a secondary battery according to Example 1 was manufactured using the same process as in FIG.

[0121] First, a coating layer 20 containing silver (Ag) was formed to a thickness of about 300 nm on one surface of a copper current collector 11 using an electroless plating method (see FIG. 4).

[0122] Thereafter, a protective layer 30 was formed on the surface of the coating layer 20 by slurry coating using a comma coater to a thickness of about 5 μm, specifically, a lithium ion conduction promoting protective layer (see FIG. 5).

[0123] Here, the protective layer 30 was made by mixing amorphous carbon using acetylene black and lithium ion conductivity promoting ceramic particles using lithium titanium oxide (Li2TiO3) in a weight ratio of 7:3 with a water-based solvent. At this time, 1.5 wt% each of carboxymethyl cellulose and styrene-butadiene rubber binders were added to the mixture of acetylene black, lithium titanium oxide (Li2TiO3), and water to prepare a slurry.

[0124] The current collector 11 having the coating layer 20 and the protective layer 30 formed thereon is placed in the plating solution 50, and then the lithium supply source 40 is placed at a predetermined distance from the protective layer 30.

[0125] The plating solution 50 was prepared by adding 40 wt % and 10 wt % of nitrogen-based compounds, lithium bis(fluorosulfonyl)imide and lithium nitrate, respectively, based on 100 wt % of the plating solution, to a 1,2-dimethoxyethane solvent, and adding 10 wt % of fluoroethylene carbonate, a fluorine-based compound, based on 100 wt % of the plating solution.

[0126] As the lithium supply source 40, a lithium metal plate with a purity of 99.9% or more and a thickness of 500 μm was used by being pressed onto a copper current collector (Cu plate).

[0127] After laminating the lithium supply source 40 and the current collector 11 in an electrically insulated state in the plating solution 50, a current was applied using a power supply device with the lithium supply source 40 and the current collector 11 as the (+) and (-) electrodes, respectively, to deposit lithium between the current collector 11 and the lithium ion conduction promoting protective layer 30, thereby forming a metal layer.

[0128] At this time, the average current density of the process is 4mA / cm 2 The process time was about 15 minutes, and a lithium metal electrode, i.e., a negative electrode, was produced on which a metal layer having a thickness of about 5 μm was formed.

[0129] [Examples 2, 3, 4 and Reference Example 1] A negative electrode was prepared in the same manner as in Example 1, except that the weight ratio of amorphous carbon and lithium ion conduction promoting ceramic particles was adjusted as shown in Table 3 below when preparing the protective layer.

[0130] [Comparative Example 1] A negative electrode was prepared in the same manner as in Example 1, except that no coating layer was formed on one side of the current collector, and a protective layer was formed using 100% amorphous carbon, and no metal layer was formed between the current collector and the protective layer.

[0131] Comparative Example 2 A negative electrode was prepared in the same manner as in Example 1, except that the protective layer was formed using 100% amorphous carbon.

[0132] Comparative Example 3 A negative electrode was prepared in the same manner as in Example 1, except that no coating layer was formed on one surface of the current collector and no metal layer was formed between the current collector and the protective layer.

[0133] (Experimental Example 1) The cross-sectional structures of the negative electrodes prepared in Example 1 and Comparative Examples 1, 2, and 3 were analyzed and are shown in FIGS. 6a, 6b, 6c, and 6d, respectively.

[0134] 6a, 6b, 6c, and 6d are photographs showing cross sections of the negative electrodes prepared in Example 1 and Comparative Examples 1, 2, and 3 analyzed using a scanning electron microscope (SEM).

[0135] 6b and 6d, it can be seen that the negative electrodes prepared in Example 1 and Comparative Example 2 had a uniform metal layer formed between the protective layer and the current collector.

[0136] (Experimental Example 2) The surface microstructures of the negative electrodes prepared in Example 1 and Comparative Examples 1, 2, and 3 are shown in Figures 7a, 8a, 9a, and 10a, respectively. The surface components of the negative electrodes prepared in Example 1 and Comparative Examples 1, 2, and 3 were analyzed and are shown in Figures 7b, 8b, 9b, and 10b.

[0137] The surface microstructure of the negative electrode was analyzed using a scanning electron microscope (SEM), and the components of the negative electrode surface were analyzed using energy dispersive X-ray spectroscopy.

[0138] Comparing Figures 7a, 7b, 10a, and 10b with Figures 8a, 8b, 9a, and 9b, titanium (Ti) element was observed on the surface of the anodes fabricated in Example 1 and Comparative Example 3, which contained lithium ion conduction-promoting ceramic particles. This is believed to be due to the use of lithium titanium oxide (Li2TiO3) as the lithium ion conduction-promoting ceramic particles. On the other hand, fluorine (F) and sulfur (S) were additionally observed on the surface of the anodes fabricated in Example 1 and Comparative Example 2, which used an electrodeposition plating process. This is believed to be due to a surface insulating layer (SEI) formed by the decomposition reaction of the plating solution during the electrodeposition process. This confirms that the surface of the anode contains a layer containing a Li-NCHO-based ionic compound and an ion-conducting material, such as LiF, formed by the fluorine-based compound in the plating solution.

[0139] (Experimental Example 3) All-solid-state batteries were fabricated using the negative electrodes, i.e., lithium metal electrodes, fabricated in Example 1 and Comparative Examples 1, 2, and 3, as shown in FIG. 14, and the initial coulombic efficiency was evaluated.

[0140] To evaluate the initial coulombic efficiency of the all-solid-state battery cell, a pressurized dedicated evaluation cell capable of maintaining an inert atmosphere was used.

[0141] Specifically, the solid electrolyte used was sulfide-based ajirodite (Li6PS5Cl). The solid electrolyte was fabricated into a pellet with a thickness of approximately 0.7 mm and compressed at a pressure of 370 MPa to increase its density.

[0142] A 0.5 mm thick lithium layer was placed on one side of the solid electrolyte, and the negative electrodes prepared in Example 1 and Comparative Examples 1, 2, and 3 were placed on the other side. A pressure of 50 MPa was applied to attach the positive electrode and the negative electrode according to the present invention to the solid electrolyte.

[0143] During the initial coulombic efficiency evaluation, the dedicated evaluation cell was pressurized to a pressure of 16 MPa.

[0144] Here, the initial coulombic efficiency is 1 mA / cm during the first charging process. 2 Charge for 3 hours at a constant current of 3mAh / cm 2 After charging, 1mA / cm 2 The battery was discharged at a constant current of 1 V, and when the discharge voltage exceeded 1 V, the discharge was stopped and the discharge capacity was measured and calculated.

[0145] The results of evaluating the initial coulombic efficiency of the secondary battery are shown in FIG. 11 and Table 1 below.

[0146] [Table 1]

[0147] 8a, 8b, 10a, 10b and Table 1, the solid-state batteries using the anodes manufactured according to Comparative Examples 1 and 3, in which no metal layer was formed between the current collector and the protective layer, exhibited low initial Coulombic efficiencies of 81.3% and 92.3%, respectively. This indicates that a considerable amount of lithium is consumed in an initial irreversible reaction during the charging process, which is believed to be mainly due to the irreversible reaction caused by amorphous carbon in the protective layer.

[0148] Meanwhile, the secondary batteries using the anodes manufactured in Example 1 and Comparative Example 2, in which a metal layer was formed between the current collector and the protective layer through an electrodeposition process, exhibited high initial Coulombic efficiency of 131.0% and 138.2%, respectively. This is thought to be due to the lithium contained in the metal layer and the excess lithium in the lithium alloy, which resulted in the initial discharge capacity being larger than the charge capacity.

[0149] Therefore, it can be confirmed that when a negative electrode having a metal layer formed thereon is manufactured by the same method as in this example, the problem of a decrease in discharge capacity due to initial irreversibility does not occur.

[0150] (Experimental Example 4) (Experimental Example 4-1) All-solid-state batteries were fabricated using the negative electrodes, i.e., lithium metal electrodes, fabricated in Example 1 and Comparative Examples 1, 2, and 3, as shown in FIG. 14, and then the charge-discharge characteristics were evaluated.

[0151] The all-solid-state battery cell used in the charge / discharge evaluation was the pressurized dedicated evaluation cell used in Experimental Example 3.

[0152] The charge / discharge performance was evaluated as follows.

[0153] 1mA / cm 2 Charge for 1 hour at a constant current of 1mA / cm 2 One cycle was defined as one hour of discharge at a constant current.

[0154] In addition, the charge / discharge life was defined as the end of the life when a short circuit occurs between the positive electrode and the negative electrode manufactured according to the present invention during the charge / discharge process or when the voltage between the two electrodes exceeds 2V.

[0155] The results of evaluating the charge / discharge performance are shown in FIG. 12 and Table 2 below.

[0156] [Table 2]

[0157] 12 and Table 2, the charge-discharge lifespans of all-solid-state batteries employing anodes manufactured according to Comparative Example 1 and Comparative Example 3, in which no metal layer was formed between the current collector and the protective layer, were 68 and 220 cycles, respectively, and the charge-discharge lifespans of all-solid-state batteries employing anodes manufactured according to Comparative Example 2 and Example 1, in which a metal layer was formed between the current collector and the protective layer, were 292 and 921 cycles, respectively. In other words, it was confirmed that the charge-discharge lifespans of all-solid-state batteries employing anodes in which a metal layer was formed between the current collector and the protective layer were significantly superior to those of all-solid-state batteries employing anodes in which no metal layer was formed between the current collector and the protective layer.

[0158] Therefore, it can be confirmed that when a negative electrode having a metal layer formed between a current collector and a protective layer is used, the charge / discharge life of the secondary battery is significantly improved.

[0159] Furthermore, when a comparison was made between Comparative Example 2 in which a metal layer was formed between the current collector and the protective layer and Example 1, it was found that the charge-discharge life of the all-solid-state battery employing the anode manufactured according to Example 1, which contained ceramic particles in the protective layer, was 921 cycles, which was significantly superior to the charge-discharge life of the all-solid-state battery employing the anode manufactured according to Comparative Example 2, which did not contain ceramic particles in the protective layer, which was 292 cycles.

[0160] Similarly, when Comparative Example 1 and Comparative Example 3, in which no metal layer was formed between the current collector and the protective layer, were compared, the charge-discharge life of the all-solid-state battery using the anode manufactured according to Comparative Example 3, in which the protective layer contained ceramic particles, was 220 cycles, which was significantly superior to the charge-discharge life of the all-solid-state battery using the anode manufactured according to Comparative Example 1, in which the protective layer did not contain ceramic particles, which was 68 cycles.

[0161] Therefore, it can be confirmed that the charge / discharge life of a secondary battery containing ceramic particles in the protective layer is significantly improved.

[0162] In particular, the charge-discharge life of the all-solid-state battery using the anode manufactured according to Example 1, in which a metal layer was formed between the current collector and the protective layer and the protective layer contained ceramic particles, was 921 cycles, which was found to be significantly superior to the charge-discharge life of the all-solid-state batteries using the anodes manufactured according to Comparative Examples 1, 2, and 3.

[0163] Therefore, it can be seen that when a negative electrode in which a metal layer is formed between a protective layer containing ceramic particles and a current collector according to the present invention is applied, the charge / discharge life of the secondary battery can be significantly improved.

[0164] (Experimental Example 4-2) The charge-discharge characteristics of all-solid-state batteries using anodes prepared according to Examples 2, 3, and 4 and Reference Example 1, in which the weight ratio of amorphous carbon to lithium ion conduction promoting ceramic particles was changed when preparing the lithium ion conduction promoting protective layer, were evaluated. The results are shown in FIG. 13 and Table 3 below.

[0165] [Table 3]

[0166] Referring to FIG. 13 and Table 3, as the amount of lithium ion conduction promoting ceramic particles in the lithium ion conduction promoting protective layer increases, the charge / discharge life of the all-solid-state battery tends to increase and then decrease again.

[0167] When the weight ratio of lithium ion conduction-promoting ceramic particles to amorphous carbon in the lithium ion conduction-promoting protective layer was 70:30, the charge / discharge life was found to be shorter than that of an all-solid-state battery containing a protective layer made of 100% amorphous carbon.

[0168] The present invention is not limited to the above-described examples, and can be manufactured in various different forms. Those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, the above-described examples should be understood to be illustrative in all respects and not restrictive.

Claims

1. current collector; a metal layer including a lithium alloy and located on at least one surface of the current collector; and a protective layer overlying the metal layer; The lithium metal electrode, wherein the protective layer comprises amorphous carbon and lithium ion conduction facilitating ceramic particles.

2. The lithium ion conductivity promoting ceramic particles include Li ２ TiO ３ , LiNbO ３ , LiTaO ３ , LiZrO ３ , Li ４ Ti ５ O １２ , Li ２ CO ３ , Li ３ BO ３ , SrTiO ３ 2. The lithium metal electrode of claim 1, wherein the lithium metal electrode comprises one or more of the following:

3. 2. The lithium metal electrode of claim 1, wherein the protective layer comprises amorphous carbon and lithium ion conductivity promoting ceramic particles in a weight ratio of 99.5:0.5 to 40:

60.

4. The metal layer containing a lithium alloy is 10. The lithium metal electrode of claim 1, comprising a lithium alloy layer disposed on the current collector and a lithium metal layer disposed on the lithium alloy layer.

5. 2. The lithium metal electrode according to claim 1, wherein the metal layer containing the lithium alloy is a composite layer containing one or more of In, Ag, Sn, Zn, Si, Al, and Bi.

6. 2. The lithium metal electrode of claim 1, wherein the average thickness of the metal layer is 1 μm to 100 μm.

7. 2. The lithium metal electrode of claim 1, wherein the protective layer has an average thickness of 1 μm to 20 μm.

8. The protective layer is Further comprising a coating layer located on the surface of the protective layer, The coating layer is made of an ionic compound such as Li-N-C-H-O, Li-P-C-H-O, LiF, and Li ３ 10. The lithium metal electrode of claim 1, wherein the lithium metal electrode comprises one or more materials selected from the group consisting of N.

9. forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-phile metal; forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and lithium ion conductivity-promoting ceramic particles; a step of placing the current collector having the coating layer and the protective layer formed thereon in a plating solution, and then placing a lithium supply source at a predetermined distance from the protective layer; applying a current between the current collector and the lithium source to form a metal layer containing a lithium alloy in which the parent lithium metal contained in the coating layer is alloyed with lithium deposited from the lithium source; The lithium-loving metal comprises at least one selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

10. In the step of forming the coating layer, 10. The method of claim 9, wherein the coating layer formed on at least one surface of the current collector has a thickness ranging from 0.001 μm to 10 μm.

11. forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and lithium ion conductivity promoting ceramic particles; 10. The method of claim 9, wherein the weight ratio of the amorphous carbon to the lithium ion conductivity promoting ceramic particles is 99.5:0.5 to 40:

60.

12. In the step of forming the metal layer, The metal layer is a lithium alloy layer containing the lithium alloy; The method for producing a lithium metal electrode according to claim 9, wherein the lithium metal electrode has a multilayer structure including a lithium metal layer formed on the lithium alloy layer.

13. In the step of forming a metal layer containing a lithium alloy, The method for producing a lithium metal electrode according to claim 9, wherein the thickness of the metal layer is 1 μm to 100 μm.

14. Negative electrode; a positive electrode; and Contains electrolytes, A lithium secondary battery, wherein the negative electrode is the lithium metal electrode according to any one of claims 1 to 8.

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