Lithium metal anode, method of preparing the same and lithium secondary battery using the same

Abstract

The present embodiments relate to a lithium metal electrode, a method for manufacturing the same, and a lithium secondary battery including the same. According to one embodiment, a lithium metal electrode may be provided, comprising a current collector and a metal layer located on at least one surface of the current collector and containing a lithium component, wherein a protective layer comprising amorphous carbon and lithium ion conduction-promoting ceramic particles is formed on the metal-side surface.

Description

Technology Field

[0001] The present embodiments relate to a lithium metal electrode, a method for manufacturing the same, and a lithium secondary battery including the same. Background Technology

[0003] Driven by the recent explosive demand for electric vehicles and the need for increased driving range, the development of high-capacity, high-energy-density secondary batteries to meet these demands is actively underway worldwide.

[0004] To lower the cost of secondary batteries and improve their energy density, it is proposed to use a lithium metal electrode as the negative electrode of a lithium secondary battery.

[0005] To form such a lithium metal anode, a method of rolling lithium foil onto a current collector is generally used. However, in the case of rolling, there is a problem in that it is difficult to realize a lithium metal anode with a thickness of 20 μm or less.

[0006] Meanwhile, in order to practically realize a secondary battery with high energy density using a lithium metal anode, a thin film lithium metal anode with a thickness of 10 to 20 μm is required.

[0007] However, when lithium metal is used as the negative electrode in an all-solid-state battery, a high-resistance phase is formed due to the reaction between lithium and the all-solid-state electrolyte, and lithium dendrites are continuously formed or high-resistance lithium byproducts are formed due to local non-uniformity of current density during the charging and discharging process, resulting in failure or capacity degradation due to short circuits or overvoltage during charging and discharging.

[0008] To solve these problems, various methods have been proposed, such as forming a protective coating layer on lithium metal or forming a lithium alloy layer to prevent reaction with solid-state batteries and prevent the precipitation growth of lithium dendrites, but sufficient lifespan characteristics suitable for use in electric vehicles (EVs) have not yet been achieved.

[0009] To satisfy these requirements, the above problem was addressed in recent studies, such as 10-2018-0136041, 10-2019-0134804, 10-2020-7006820, Nature Energy 5, 299 (2020), by using a non-cathode coating layer mixed with amorphous carbon and silver (Ag) nanoparticles to precipitate lithium during the charging and discharging process.

[0010] However, during the charging and discharging process, electronically conductive materials such as lithium-based alloys or lithium-containing compounds are formed within the non-cathode coating layer or at the interface, causing current concentration and lithium dendrites, which leads to a shortened lifespan.

[0011] In addition, there is a problem of low initial Coulomb efficiency due to the irreversible reaction caused by amorphous carbon, which is the main material of the non-cathode coating layer.

[0012] To solve these problems, not only is a sacrificial anode used, but the use of large amounts of precious metal nanoparticles also significantly reduces price competitiveness, making commercialization difficult.

[0013] Therefore, the development of technology capable of manufacturing electrodes with excellent initial efficiency and charge / discharge characteristics is required. The problem to be solved

[0015] In this embodiment, as discussed above, we aim to solve the problems of lithium dendrite formation and lifespan degradation caused by the electronically conductive material in the cathode layer, the problem of reduced initial Coulomb efficiency due to initial irreversibility caused by amorphous carbon in the non-cathode coating layer, the problem of having to use a sacrificial cathode to compensate for this, and the problem of having to use a large amount of precious metal nanoparticles such as silver (Ag) to form an alloy with lithium during the charging process.

[0016] In addition, we aim to provide a lithium metal electrode having excellent charge / discharge characteristics and preventing dendrite formation by means of a protective layer included in the electrode layer, a method for manufacturing the same, and a lithium secondary battery including the same. means of solving the problem

[0018] A lithium metal electrode according to one embodiment comprises a current collector, a metal layer comprising a lithium alloy located on at least one surface of the current collector, and a protective layer located on the metal layer, wherein the protective layer may include amorphous carbon and lithium ion conduction-promoting ceramic particles. Effects of the invention

[0020] According to the present embodiment, a lithium ion conduction-promoting protective layer is formed on a lithium metal electrode to control the formation of lithium dendrites during the charging and discharging process of a lithium secondary battery to which the same is applied, and to mitigate the degradation of the lifespan of the lithium secondary battery.

[0021] In addition, it is possible to control the degradation of the initial Coulomb efficiency of lithium secondary batteries and significantly improve charge and discharge characteristics. Brief explanation of the drawing

[0023] FIG. 1 schematically shows a lithium metal electrode manufactured according to one embodiment. FIG. 2 schematically shows a lithium metal electrode according to another embodiment. FIG. 3 schematically illustrates the process of manufacturing a lithium metal electrode according to one embodiment. Figure 4 is an SEM image showing a cross-section of a current collector in which an alloy material coating layer is formed during the process of manufacturing a lithium metal electrode according to Example 1. Figure 5 is an SEM image showing a cross-section of a current collector in which an alloy material coating layer and a lithium ion conduction-promoting protective layer are formed during the process of manufacturing a lithium metal electrode according to Example 1. Figures 6a, 6b, 6c, and 6d are SEM images showing cross-sections of lithium metal electrodes prepared according to Example 1 and Comparative Examples 1 to 3. Figures 7a, 7b, 8a, 8b, 9a, 9b, 10a and 10b are photographs showing the surface microstructure and compositional analysis results of lithium metal electrodes prepared according to Example 1 and Comparative Examples 1 to 3. FIG. 11 is a figure showing the results of evaluating the initial effects of secondary batteries manufactured according to Example 1 and Comparative Examples 1 to 3. FIG. 12 is a figure showing the results of evaluating the charge-discharge life of secondary batteries manufactured according to Example 1 and Comparative Examples 1 to 3. FIG. 13 is a figure showing the results of evaluating the charge-discharge life of secondary batteries manufactured according to Examples 1 to 4 and Comparative Example 2. FIG. 14 is a schematic diagram of a secondary battery with a lithium metal electrode manufactured according to the present invention. Specific details for implementing the invention

[0024] 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 solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0025] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0026] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0027] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0028] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0029] FIG. 1 schematically shows a lithium metal electrode manufactured according to one embodiment, FIG. 2 schematically shows a lithium metal electrode according to another embodiment, and FIG. 3 schematically shows a method for manufacturing a lithium metal electrode for a secondary battery according to one embodiment.

[0030] Referring to FIG. 1, a lithium metal electrode (100) according to one embodiment comprises a current collector (11) and a metal layer (12) located on at least one surface of the current collector (11), and also comprises a protective layer (30) located on the other surface of the metal layer (12) facing the current collector (11).

[0031] The current collector (11) is for electrical connection within the lithium secondary battery.

[0032] The current collector (11) may have the form of a foil, but is not limited thereto, and may have the form of a mesh, foam, rod, wire, or a sheet woven from wire or fiber.

[0033] As the material of the current collector (11), a material having electrical conductivity and limited reaction with lithium can be used. As the material of the current collector (11), for example, copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, carbon, conductive polymer, or composite fiber with a conductive layer coated on a non-conductive polymer, or any one or a combination thereof can be used.

[0034] If the thickness of the current collector (11) is thick, the weight of the battery increases and the energy density of the battery decreases; if the thickness of the current collector (11) is thin, there is a risk of overheating damage during high-current operation and damage due to tension during the battery manufacturing process. Therefore, the thickness of the current collector (11) may be in the range of 1 μm to 50 μm.

[0035] The metal layer (12) is located on the current collector (11) and includes a lithium alloy layer (21) containing a lithium alloy and a lithium metal layer (41) located on the lithium alloy layer (21). Here, the lithium alloy layer (21) may be a layer comprising a lithium alloy in which lithium precipitated from the lithium source and a lithium component included in the coating layer of the current collector (11) are alloyed by applying a current between the current collector (11) and the lithium source. When performing the electrodeposition process by applying a high current to increase the speed of electrodeposition when forming the metal layer, there is a problem in that the performance of the lithium secondary battery is degraded. However, when the metal layer (12) is formed with a structure including a lithium alloy layer (21) containing a lithium component as in the present embodiment, even if the electrodeposition process is performed by applying a high current, it is possible to prevent the excessive generation of fine lithium particles or the destruction of the film, which is the surface protection layer of the lithium metal layer already formed during the electrodeposition process.

[0036] More specifically, since the metal layer (12) of the present embodiment includes a lithium alloy layer containing a lithium component, when a high current is applied in the electrodeposition process to form a lithium metal layer on the lithium alloy layer, the lithium particles initially generated are induced to grow well so that particles with a coarse structure are formed, and at the same time, the lithium metal layer, and consequently the metal layer (12), can have a uniform surface.

[0037] Accordingly, the performance of a secondary battery using a lithium metal electrode according to the present embodiment, specifically the charge / discharge characteristics, can be significantly improved. In addition, since a lithium metal electrode for a secondary battery with high performance can be manufactured even when a high current is applied and the electrodeposition process is performed at a high speed, the productivity of the lithium metal electrode for a secondary battery can also be significantly improved.

[0038] The lithium alloy layer (21) may be an alloy composed of lithium and a lithium-friendly metal, wherein the lithium-friendly 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.

[0039] In this embodiment, the lithium alloy layer includes a lithium-friendly metal. When the lithium alloy layer includes a lithium-friendly metal in this manner, electrons are smoothly supplied from the current collector because the lithium-friendly metal has high electron conductivity, thereby reducing lithium ions and facilitating the electrodeposition of the lithium metal layer.

[0040] Meanwhile, the above-mentioned metal layer plays a role in helping lithium to precipitate more effectively beneath the protective layer during the battery charging process.

[0041] 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.

[0042] 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, there is a problem in that the weight and volume of the battery increase, and the energy density decreases. In addition, since the time and cost of the electrodeposition process increase in proportion to the thickness when forming the metal layer (12), it is preferable that the thickness of the metal layer (12) be 100 μm or less.

[0043] In addition, if the thickness of the metal layer (12) is too thin, there is a problem that the charge / discharge life of the battery is reduced when the lithium metal electrode of this embodiment is applied to a secondary battery. Specifically, during the charge / discharge of the battery, the 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, thereby reducing the battery capacity. However, if the thickness of the metal layer (12) is thin, the amount of lithium available to replenish the lithium consumed during charge / discharge decreases, thus reducing the charge / discharge life of the battery. Therefore, it is preferable that the thickness of the metal layer (12) be 1 μm or more.

[0044] The above protective layer (30) is located on the metal layer (12) and includes amorphous carbon and lithium ion conductivity-promoting ceramic particles.

[0045] When lithium metal is used as the negative electrode in an all-solid-state battery, high resistance is generated by the reaction between the all-solid-state electrolyte and lithium, and lithium dendrites are continuously generated or high-resistance lithium byproducts are generated due to local non-uniformity of current density during the charging and discharging process, resulting in failure due to short circuits or overvoltage during charging and discharging or a decrease in battery capacity.

[0046] However, as in the present embodiment, a protective layer comprising amorphous carbon and lithium ion conductivity-promoting ceramic particles can improve not only the output characteristics and lifespan characteristics of the lithium metal electrode but also additionally the structural safety.

[0047] More specifically, since the lithium metal electrode of the present embodiment includes a protective layer (30) comprising amorphous carbon and lithium ion conductivity-promoting ceramic particles, it can promote the movement of lithium ions on the electrode surface during charging and discharging and suppress the formation of an electron-conducting material at the interface. In addition, it can serve to reduce the electron conductivity within the protective layer (30).

[0048] Therefore, the performance of a secondary battery using a lithium metal electrode according to the present embodiment, specifically the output characteristics and lifespan characteristics of the battery, can be significantly improved.

[0049] The above amorphous carbon may be one or more 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.

[0050] In addition, the above lithium ion conductivity-promoting ceramic particles are, representatively, Li2TiO3, LiNbO3, LiTaO3, LiZrO3, and Li4Ti5O. 12 It may be one or more selected from a group of particles that promote lithium ion conduction and inhibit electron conduction, such as Li2CO3, Li3BO3, SrTiO3, etc., but is not limited thereto. The above lithium ion-conducting ceramic particles play a role in enabling lithium to move well to the bottom of the protective layer by promoting lithium ion conduction and inhibiting electron conduction within the protective layer and at the interface during the charging process of a battery using a lithium anode.

[0052] 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, there may be a problem with the distribution of ceramic particles in the coating layer being uneven due to aggregation between primary particles, and if it is larger than 1,000 nm, the large particles may act as a resistance layer, thereby reducing lithium ion conductivity.

[0053] In addition, in particular, the above-mentioned material does not react well with the sulfide-based electrolyte material of the all-solid-state battery and has excellent chemical stability, which is advantageous for improving interfacial stability and extending charge / discharge life of the all-solid-state battery. The ion conduction-promoting protective layer can be applied by preparing the above-mentioned composite in the form of a slurry, and a binder may be additionally included to prepare such a slurry.

[0054] The above lithium ion conduction-promoting protective layer may contain a weight ratio of amorphous carbon to lithium ion conduction-promoting ceramic particles of 99.5:0.5 to 40:60. Specifically, it may contain 98.5:1.5 to 50:50, and more specifically, 97:3 to 70:30.

[0055] If too little lithium-ion conductive ceramic particles are mixed, the effect of lithium-ion conductive promotion due to the mixing of lithium-ion conductive ceramic particles cannot be sufficiently obtained, and if too much lithium-ion conductive ceramic particles are mixed, the connection between ceramic particles at room temperature is poor, which reduces the density of the protective layer and consequently hinders lithium-ion conduction, and if an excessive amount of ceramic particles with a relatively high density compared to amorphous carbon is contained, there is a problem of causing a decrease in battery energy density.

[0056] Meanwhile, the protective layer of the present embodiment may include a binder.

[0057] At this time, the binder may be a water-based binder, and the water-based binder may be one or more 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 polymer resins such as hydroxyethyl cellulose, carboxymethyl cellulose and polyvinyleden fluoride, but is not limited thereto.

[0058] Here, the binder can be added in an amount of 1 to 15 parts by weight based on the weight of the slurry formed by mixing the lithium ion conductivity-promoting ceramic particles, amorphous carbon, and water, and more specifically, in an amount of 3 to 10 parts by weight.

[0059] When the amount of binder added satisfies the above range, the particles constituting the protective layer are efficiently bound together to form a high-performance protective layer without causing a decrease in battery energy density due to an increase in weight and volume, thereby further improving the lifespan characteristics of the secondary battery. If too little binder is mixed, there is a problem of reduced inter-particle bonding strength when forming the protective layer; conversely, if too much binder is mixed, not only does it cause a decrease in energy density, but the resistance of the protective layer also increases significantly, hindering lithium ion conduction.

[0060] The thickness of the protective layer comprising the amorphous carbon, lithium ion conductivity-promoting ceramic particles, and binder may be in the range of 0.01 μm to 50 μm, more specifically 1 μm to 20 μm. When the thickness of the protective layer satisfies the above range, the effect obtained by including the amorphous carbon and lithium ion conductivity-promoting ceramic particles described above prevents the formation of lithium dendrites on the surface of the protective layer and allows lithium to penetrate well into the interior of the protective layer and conduct, thereby enabling lithium to precipitate from the lower surface of the protective layer. On the other hand, if the thickness of the protective layer comprising the amorphous carbon and lithium ion conductivity-promoting ceramic particles is too thin, there is a disadvantage that it cannot perform the function of a protective layer. Meanwhile, if the thickness of the protective layer is too thick, the resistance of the protective layer becomes excessively high, which can cause an increase in overvoltage during the operation of the secondary battery, and there is also a problem of causing a decrease in battery energy density due to an increase in weight and volume. However, the thickness of this protective layer can be variably adjusted according to the design of the secondary battery structure.

[0061] Meanwhile, although not illustrated, the metal layer (12) of the present embodiment may further include a film layer (SEI, Solid-Electrolyte Interphase) located on the surface of the metal layer (12).

[0062] The above film layer is formed during the manufacturing process of the metal layer (12) through a reaction between the lithium metal of the electrodeposited lithium source and the plating solution, and the thickness, composition, and characteristics of the film can be controlled by adjusting the composition of the plating solution used and the conditions of the electrodeposition process.

[0063] The thickness of the above film layer may be, for example, in the range of 2 nm to 2 µm, more specifically in the range of 10 nm to 500 nm.

[0064] If the thickness of the film layer located on the surface of the metal layer (12) is too thick, the lithium ion conductivity is lowered and the interfacial resistance increases, which may degrade the charge / discharge characteristics when applied to a battery. In addition, if the thickness of the film layer is too thin, the film layer may be easily lost during the process of applying the lithium metal electrode according to the embodiment to the battery.

[0065] Accordingly, it is preferable that the film layer be formed uniformly and densely over the entire surface of the metal layer (12) with a thin thickness within the thickness range satisfying the above thickness range.

[0066] At this time, the film 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.

[0067] FIG. 2 schematically shows a lithium metal electrode according to another embodiment.

[0068] Referring to FIG. 2, a lithium metal electrode (100) for a secondary battery according to another embodiment comprises a current collector (11) and a metal layer (12) located on at least one surface of the current collector (11) and composed of a mixture of lithium and a lithium alloy. Here, the lithium alloy may be formed by applying an electric current between the current collector (11) and a lithium source, thereby alloying the lithium-friendly component contained in the coating layer formed on the current collector (11) with the lithium precipitated from the lithium source.

[0069] At this time, the metal layer (12) may include a lithium-friendly metal. Here, the lithium-friendly metal may be one or more selected from the group consisting of, for example, In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

[0070] In this embodiment, the metal layer (12) is in the form of containing a lithium-friendly metal. When forming a metal layer (12) containing a lithium-friendly metal in this way, the nucleation free energy can be lowered during the initial nucleation of lithium particles in the electrodeposition process, so a lithium metal layer having a coarse particle structure can be formed even under high current and overvoltage conditions.

[0071] 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 the thickness range, there is an advantage in that the energy density of the battery can be maximized while improving the charge / discharge life of the battery, as well as the time and cost of the electrodeposition process when forming the metal layer (12). If the thickness of the metal layer is too thin, the initial Coulomb efficiency is reduced due to initial irreversibility, and the charge / discharge performance is degraded because there is a shortage of excess lithium. On the other hand, if the thickness of the metal layer is too thick, there is a problem in that the energy density of the battery decreases, and the process time and the amount of metal raw material used increase when forming the metal layer.

[0072] Meanwhile, although not illustrated in FIG. 2, the metal layer of the present embodiment may further include a film layer located on the surface of the metal layer.

[0073] As such a film layer is the same as that described in the lithium metal electrode for a secondary battery according to the aforementioned embodiment, it will be omitted here.

[0075] A method for manufacturing a lithium metal electrode according to one embodiment comprises: a step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component; a step of forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and lithium ion conduction-promoting particles; a step of positioning the current collector having the coating layer and the protective layer formed thereon in a plating solution and then positioning a lithium source at a predetermined distance from the protective layer; and a step of applying an electric current between the current collector and the lithium source to form a metal layer comprising a lithium alloy in which the lithium-friendly component contained in the coating layer and the lithium precipitated from the lithium source are alloyed.

[0076] In the step of forming a protective layer on the surface of the coating layer using a slurry comprising the above-mentioned amorphous carbon and lithium ion conductivity-promoting ceramic particles, the lithium ion conductivity-promoting protective layer may comprise a weight ratio of amorphous carbon to lithium ion conductivity-promoting ceramic particles of 99.5:0.5 to 40:60. Specifically, it may comprise 98.5:1.5 to 50:50, and more specifically, 97:3 to 70:30.

[0077] First, a step is performed to form an alloy material coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly metal.

[0078] At this time, the above lithium-ion metal may be one or more selected from the group consisting of, for example, In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

[0079] In addition, the alloy material coating layer can be formed using at least one method among, for example, electrolytic and electroless plating, sputtering, electron beam, and thermal vapor deposition.

[0080] 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㎛ to 10㎛, specifically 0.01㎛ to 1㎛, more specifically 100nm to 500nm.

[0081] If the thickness of the alloy material coating layer is too thin, it is insufficient to perform the role of forming lithium and lithium alloy, and if the thickness is too thick, a large amount of cost and time is consumed to form the alloy material coating layer, which reduces production efficiency and economic feasibility, and increases the weight of the battery, resulting in a problem of lower energy density.

[0082] After the step of forming the alloy material coating layer, a step of applying a protective layer to the surface of the formed alloy material coating layer is performed.

[0083] At this time, the protective layer may be a lithium ion conduction-promoting protective layer and may include amorphous carbon and lithium ion conduction-promoting ceramic particles.

[0084] At this time, the amorphous carbon may be one or more 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.

[0085] In addition, the lithium ion conductivity-promoting ceramic particles are Li2TiO3, LiNbO3, LiTaO3, LiZrO3, Li4Ti5O 12It may be one or more selected from a group of particles having low electron conductivity and high lithium ion conductivity, such as Li2CO3, Li3BO3, SrTiO3, etc., but is not limited thereto.

[0086] Meanwhile, at this time, a binder may be added to the lithium ion conduction-promoting protective layer.

[0087] The above binder may be a water-based binder, and the water-based binder may be one or more selected from the group consisting of a rubber-based binder selected from acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, and polymer resins such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyleden fluoride, but is not limited thereto.

[0088] The above lithium ion conductivity-promoting protective layer can be applied by using at least one method among the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, and brush coating method, by applying a slurry formed by mixing the amorphous carbon, lithium ion conductivity-promoting ceramic particles, and binder in water.

[0089] Here, the lithium ion conduction-promoting protective layer may contain a weight ratio of amorphous carbon to lithium ion conduction-promoting ceramic particles of 99.5:0.5, specifically 98.5:1.5 to 50:50, and more specifically 97:3 to 70:30.

[0090] In addition, the binder can be added in an amount of 0.5 to 10 parts by weight based on the weight of the mixture of the lithium ion conductivity-promoting ceramic particles, amorphous carbon, and water, and more specifically, in an amount of 1 to 3 parts by weight.

[0091] 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㎛ to 50㎛, more specifically 1㎛ to 20㎛.

[0092] When the thickness of the alloy material coating layer and the lithium ion conduction-promoting protective layer satisfies the above range, a lithium metal electrode for a secondary battery according to one embodiment, more specifically, can be manufactured to have a lithium metal electrode structure such as that shown in FIG. 1 or FIG. 2.

[0093] After the step of forming the lithium ion conduction-promoting protective layer, a current collector having the alloy material coating layer and the lithium ion conduction-promoting protective layer formed sequentially is positioned in a plating solution, a lithium source is positioned at a predetermined distance from the current collector, and a metal layer is formed by applying current between the current collector and the lithium source.

[0094] Referring to Fig. 3, the step of forming a metal layer will be explained in more detail.

[0095] First, a current collector (11) having an alloy material coating layer (20) and a lithium ion conduction-promoting protective layer (30) formed thereon is placed in a plating solution (50), and then a lithium source (40) is placed at a predetermined distance from the lithium ion conduction-promoting protective layer (30).

[0096] The above lithium source (40) may use, for example, lithium metal, lithium alloy, a foil in which the lithium metal or lithium alloy is pressed onto a current collector, a plating solution in which a lithium salt is dissolved, etc.

[0097] The entire house (11) is the same as the one described above, so it will be omitted here.

[0098] The above plating solution (50) can be prepared by dissolving a lithium salt in a non-aqueous solvent.

[0099] 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.

[0100] More specifically, in this embodiment, the plating solution is characterized by including a nitrogen-based compound as at least one of the lithium salt and the non-aqueous solvent.

[0101] The above 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, e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin.

[0102] Among the above nitrogen-based compounds, at least one of lithium nitrate, lithium bis fluorosulfonyl imide, and lithium bis trifluoromethane sulfonimide can be used as a lithium salt.

[0103] Among the above nitrogen compounds, at least one of caprolactam (e-caprolactam), methyl caprolactam (N-methyl-e-caprolactam), triethylamine (triethylamine) and tributylamin (tributylamin) can be used as a non-aqueous solvent.

[0104] Meanwhile, a general non-aqueous solvent may be added to the plating solution, taking into account the viscosity of the plating solution. This is because if the viscosity of the plating solution is too high, the mobility of lithium ions decreases, which in turn lowers the ionic conductivity of the plating solution; consequently, the time required for the electrodeposition process increases, leading to a decrease in productivity.

[0105] The above solvent may 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.

[0106] The current density of the current applied in the step of forming a lithium metal layer on at least one surface of the current collector by applying the above current is 0.1 mA / cm² 2 Up to 100 mA / cm 2 Range, more specifically 0.2 mA / cm 2 Up to 50 mA / cm 2 Range, 5 mA / cm 2 Up to 30 mA / cm 2 Range or 7 mA / cm 2 Up to 25 mA / cm 2 It can be a range.

[0107] In addition, the time for applying 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.

[0108] In this embodiment, it is possible to manufacture a lithium metal electrode having a metal layer formed thereon, which includes a lithium metal layer having a coarse particle structure, by preventing the excessive generation of fine lithium particles even under high current conditions and inducing the initial lithium particles to grow well. In addition, the metal layer manufactured in this way has excellent surface uniformity. Accordingly, 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 manufactured to have a lithium metal electrode structure having a metal layer (12), or as shown in FIG. 2, a lithium metal electrode structure having a metal layer (12) composed of a mixture of lithium and a lithium alloy. 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.

[0109] When a lithium metal electrode manufactured according to the present embodiment is applied, the charge and discharge characteristics of a secondary battery can be significantly improved.

[0110] A secondary battery according to one embodiment comprises a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode. Herein, the negative electrode may be a lithium metal electrode according to the present invention.

[0111] FIG. 14 schematically shows the structure of a secondary battery according to one embodiment.

[0112] Referring to FIG. 14, the secondary battery (200) of the present embodiment may include an electrode assembly comprising a positive electrode (70), a negative electrode (100), and a separator (90) disposed between the positive electrode (70) and the negative electrode (100).

[0113] These electrode assemblies are wound or folded and accommodated in a battery case (95).

[0114] Afterwards, the electrolyte (80) is injected into the battery case (95) and sealed to complete the secondary battery (200). At this time, the battery case (95) may have a shape such as a cylindrical, prismatic, pouch, or coin.

[0115] In FIG. 14, for convenience, a cathode according to one embodiment is shown as the cathode (100), but any lithium metal electrode for a secondary battery according to the aforementioned embodiments can be applied as the cathode.

[0116] The above anode (70) may include an anode active material layer and an anode current collector.

[0117] The positive active material layer may include, for example, a Li compound comprising at least one metal selected from the group consisting of Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, and Ce, and at least one non-metal element selected from O, F, S, P, and combinations thereof. The positive active material layer may include active material particles having an average particle size of approximately 0.01 μm to 200 μm, and may be appropriately selected according to the required characteristics of the battery.

[0118] In some cases, a conductive material may be added to the positive active material layer.

[0119] The above conductive material may be, for example, carbon black and ultrafine graphite particles, fine carbon such as acetylene black, nano metal particle paste, etc., but is not limited thereto.

[0120] The above positive current collector serves to support the positive active material layer. As the positive current collector, for example, an aluminum foil, a nickel foil, or a combination thereof may be used, but is not limited thereto.

[0121] The electrolyte (80) filled in the above lithium secondary battery (200) may be a non-aqueous electrolyte or a solid electrolyte.

[0122] The above-mentioned non-aqueous electrolyte may include, for example, a lithium salt such as lithium hexafluorophosphate or lithium perchlorate, and a solvent such as ethylene carbonate, propylene carbonate, or butylene carbonate. In addition, the above-mentioned solid electrolyte may be, for example, a gel-type polymer electrolyte in which the electrolyte is impregnated into a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li3N.

[0123] The above separator (90) separates the positive and negative electrodes and provides a pathway for the movement of lithium ions; any separator commonly used in lithium secondary batteries can be used. That is, a separator with low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity can be used. Here, the separator may be selected from, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and may be in the form of a non-woven fabric or a woven fabric. Meanwhile, if a solid electrolyte is used as the above electrolyte (80), the solid electrolyte may also serve as the separator (90).

[0124] Embodiments of the present invention will be described in detail below. However, these are presented as examples and do not limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0126] Example 1

[0127] A lithium metal electrode for a secondary battery according to Example 1 was manufactured using a process as shown in Fig. 1.

[0128] First, a coating layer (20) containing silver (Ag) was formed on one side of a copper current collector (11) using an electroless plating method to a thickness of about 300 nm (see FIG. 4).

[0129] Next, a protective layer (30) was formed on the surface of the coating layer (20) with a thickness of about 5 μm by slurry coating using a comma coater, specifically forming a lithium ion conductivity-promoting protective layer (see FIG. 5).

[0130] Here, the protective layer (30) was prepared by mixing amorphous carbon using acetylene black and lithium ion conduction-promoting ceramic particles using lithium titanium oxide (Li2TiO3) in a solvent using water with a weight ratio of 7:3. At this time, a slurry was prepared by adding 1.5% by weight each of carboxymethyl cellulose and styrene-butadiene rubber binder based on the weight of the mixture composed of acetylene black, lithium titanium oxide (Li2TiO3), and water.

[0131] After placing the current collector (11), having the coating layer (20) and protective layer (30) formed as described above, in the plating solution (50), a lithium source (40) is placed at a predetermined distance from the protective layer (30).

[0132] The above plating solution (50) was prepared by adding 40% by weight and 10% by weight of lithium bis(fluorosulfonyl)imide, a nitrogen-based compound, and lithium nitrate, respectively, based on 100% by weight of the plating solution, to a 1,2-dimethoxyethane solvent, and adding 10% by weight of fluoroethylene carbonate, a fluorine-based compound, based on 100% by weight of the plating solution.

[0133] In addition, as a lithium source (40), a lithium metal plate with a thickness of 500 μm and a purity of 99.9% or higher was pressed onto a copper current collector plate (Cu plate) and used.

[0134] After stacking the lithium source (40) and the current collector (11) in an electrically insulated state within the plating solution (50), a current is applied using a power supply device with the lithium source (40) and the current collector (11) as (+) and (-) electrodes, respectively, thereby depositing lithium between the current collector (11) and the lithium ion conduction-promoting protective layer (30) to form a metal layer.

[0135] At this time, the average current density of the process is 4 mA / cm² 2 A lithium metal electrode, i.e., a negative electrode, was manufactured by forming a metal layer approximately 5㎛ thick with a process time of about 15 minutes.

[0137] Examples 2, 3, 4 and Reference Example 1

[0138] A cathode 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.

[0140] Comparative Example 1

[0141] A cathode was manufactured in the same manner as in Example 1, except that a coating layer was not formed on one side of the current collector, a protective layer was formed using 100% amorphous carbon, and a metal layer was not formed between the current collector and the protective layer.

[0143] Comparative Example 2

[0144] A cathode was prepared in the same manner as in Example 1, except that a protective layer was formed using 100% amorphous carbon.

[0146] Comparative Example 3

[0147] A cathode was manufactured in the same manner as in Example 1, except that a coating layer was not formed on one side of the current collector and a metal layer was not formed between the current collector and the protective layer.

[0149] (Experimental Example 1)

[0150] The cross-sectional structures of the cathodes prepared according to Example 1 and Comparative Examples 1, 2, and 3 were analyzed and are shown in FIGS. 6a, 6b, 6c, and 6d, respectively.

[0151] That is, Figures 6a, 6b, 6c, and 6d show cross-sections of cathodes prepared according to Example 1 and Comparative Examples 1, 2, and 3, analyzed using a Scanning Electron Microscope (SEM).

[0152] Referring to FIGS. 6b and FIGS. 6d, it can be seen that the cathode prepared according to Example 1 and Comparative Example 2 has a metal layer uniformly formed between the protective layer and the current collector.

[0154] (Experimental Example 2)

[0155] The surface microstructures of the cathodes prepared according to Example 1 and Comparative Examples 1, 2, and 3 are shown in FIGS. 7a, 8a, 9a, and 10a, respectively, and the composition of the surface of the cathodes prepared according to Example 1 and Comparative Examples 1, 2, and 3 was analyzed and is shown in FIGS. 7b, 8b, 9b, and 10b.

[0156] The microstructure of the cathode surface was analyzed using a scanning electron microscope (SEM), and the compositional analysis of the cathode surface was performed using energy dispersive X-ray spectroscopy.

[0157] Comparing FIGS. 7a, 7b, 10a, and 10b with FIGS. 8a, 8b, 9a, and 9b, it can be confirmed that titanium (Ti) elements are observed on the surface of the cathode prepared according to Example 1 and Comparative Example 3, which contains lithium ion conduction-promoting ceramic particles. This is believed to be because lithium titanium oxide (Li2TiO3) was used as the lithium ion conduction-promoting ceramic particles. Meanwhile, fluorine (F) and sulfur (S) are additionally observed on the surface of the cathode prepared according to Example 1 and Comparative Example 2, which applied an electrodeposition plating process. This is believed to be due to the surface film layer (SEI) generated by the decomposition reaction of the plating solution during the electrodeposition process. From this, it can be confirmed that the surface of the cathode contains a film layer containing Li-NCHO-based ionic compounds and an ion-conducting material such as LiF formed by fluorine-based compounds contained in the plating solution.

[0159] (Experimental Example 3)

[0160] After manufacturing an all-solid-state battery as shown in FIG. 14 using the negative electrode, i.e., the lithium metal electrode, prepared according to Example 1 and Comparative Examples 1, 2, and 3, the initial Coulomb efficiency was evaluated.

[0161] To evaluate the initial Coulomb efficiency of the all-solid-state battery cell, a pressurized dedicated evaluation cell capable of maintaining an inert atmosphere was used.

[0162] Specifically, sulfide-based azirodite (Li6PS5Cl) was used as the solid electrolyte. The solid electrolyte was prepared in the form of pellets with a thickness of about 0.7 mm and pressurized to a pressure of 370 MPa to improve density.

[0163] Lithium having a thickness of 0.5 mm was placed on one side of the solid electrolyte, and a cathode prepared according to Example 1 and Comparative Examples 1, 2, and 3 was placed on the other side. Here, the anode and the cathode according to the present invention were attached to the solid electrolyte by applying a pressure of 50 MPa.

[0164] During the initial Coulomb efficiency evaluation, the dedicated evaluation cell was pressurized to a pressure of 16 MPa.

[0165] Here, the initial Coulomb efficiency was calculated by charging with a constant current of 1 mA / ㎠ for 3 hours during the first charging process to charge a total of 3 mAh / ㎠, then discharging with a constant current of 1 mA / ㎠ and stopping the discharge at the point where the discharge voltage exceeded 1V to measure the discharge capacity.

[0166] The results of evaluating the initial Coulomb efficiency of the secondary battery are shown in Fig. 11 and Table 1 below.

[0167] [Table 1]

[0168]

[0170] Referring to Figures 8a, 8b, 10a, 10b and Table 1, all-solid-state batteries using cathodes prepared according to Comparative Example 1 and Comparative Example 3, in which no metal layer is formed between the current collector and the protective layer, exhibited low initial Coulomb efficiencies of 81.3% and 92.3%, respectively. From this, it can be confirmed that a significant amount of lithium is consumed in the initial irreversible reaction during the charging process, which is believed to be mainly due to the irreversible reaction caused by amorphous carbon within the protective layer.

[0171] On the other hand, secondary batteries using negative electrodes prepared according to Example 1 and Comparative Example 2, in which a metal layer was formed between the current collector and the protective layer through an electrodeposition plating process, exhibited high initial Coulomb effects of 131.0% and 138.2%, respectively. It is believed that this is because the initial discharge capacity is greater than the charge capacity due to the lithium contained in the metal layer and the excess lithium within the lithium alloy.

[0172] Therefore, when manufacturing a cathode in which a metal layer is formed by the same method as in the present embodiment, it can be confirmed that the problem of reduced discharge capacity due to initial irreversibility does not occur.

[0174] (Experimental Example 4)

[0175] (Experimental Example 4-1)

[0176] After manufacturing an all-solid-state battery as shown in FIG. 14 using the negative electrode, i.e., the lithium metal electrode, prepared according to Example 1 and Comparative Examples 1, 2, and 3, the charge and discharge characteristics were evaluated.

[0177] The all-solid-state battery cell used for the charge / discharge evaluation was the pressurized dedicated evaluation cell used in Experimental Example 3 above.

[0178] The charge / discharge performance evaluation was performed as follows.

[0179] One cycle was defined as charging with a constant current of 1 mA / ㎠ for 1 hour and discharging with a constant current of 1 mA / ㎠ for 1 hour.

[0180] In addition, the charge / discharge life is defined as ending 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.

[0181] The results of evaluating the above charge / discharge performance are shown in Fig. 12 and Table 2 below.

[0182] [Table 2]

[0183]

[0184] Referring to Figure 12 and Table 2, the charge-discharge lifespan of all-solid-state batteries using cathodes prepared according to Comparative Example 1 and Comparative Example 3, in which no metal layer is formed between the current collector and the protective layer, was found to be 68 and 220 cycles, respectively, while the charge-discharge lifespan of all-solid-state batteries using cathodes prepared according to Comparative Example 2 and Example 1, in which a metal layer is formed between the current collector and the protective layer, was found to be 292 and 921 cycles, respectively. In other words, it can be confirmed that all-solid-state batteries using cathodes in which a metal layer is formed between the current collector and the protective layer have a significantly superior charge-discharge lifespan compared to all-solid-state batteries using cathodes in which no metal layer is formed between the current collector and the protective layer.

[0185] Therefore, it can be confirmed that the charge / discharge life of the secondary battery is significantly improved when a negative electrode with a metal layer formed between the current collector and the protective layer is applied.

[0186] In addition, when comparing Comparison 2, in which a metal layer is formed between the current collector and the protective layer, with Example 1, the charge-discharge life of the all-solid-state battery using the negative electrode manufactured according to Example 1, which contains ceramic particles in the protective layer, was 921 cycles, which was significantly superior to the charge-discharge life of the all-solid-state battery using the negative electrode manufactured according to Comparative Example 2, which does not contain ceramic particles in the protective layer, which was 292 cycles.

[0187] Likewise, when comparing Comparison 1 and Comparative Example 3, in which no metal layer is formed between the current collector and the protective layer, the charge-discharge life of the all-solid-state battery using the negative electrode manufactured according to Comparative Example 3, which contains ceramic particles in the protective layer, was 220 cycles, which was found to be significantly superior to the charge-discharge life of the all-solid-state battery using the negative electrode manufactured according to Comparative Example 1, which does not contain ceramic particles in the protective layer, which was 68 cycles.

[0188] Therefore, it can be confirmed that the charge / discharge life of a secondary battery containing ceramic particles in the protective layer is significantly improved.

[0189] In particular, the charge-discharge life of an all-solid-state battery using a cathode prepared according to Example 1, in which a metal layer is formed between the current collector and the protective layer and ceramic particles are included in the protective layer, was found to be 921 cycles, which is significantly superior to the charge-discharge life of an all-solid-state battery using a cathode prepared according to Comparative Examples 1, 2, and 3.

[0190] Therefore, it can be confirmed that the charge / discharge life of a secondary battery can be significantly improved by applying a negative electrode that forms a metal layer between a protective layer containing ceramic particles and a current collector according to the present invention.

[0192] (Experimental Example 4-2)

[0193] The charge and discharge characteristics of an all-solid-state battery using a negative electrode prepared according to Examples 2, 3, 4 and Reference Example 1, in which the weight ratio of amorphous carbon to lithium ion-conducting ceramic particles was varied when preparing the lithium ion-conducting protective layer, were evaluated and are shown in FIG. 13 and Table 3 below.

[0194] [Table 3]

[0195]

[0196] Referring to Figure 13 and Table 3 above, as the amount of lithium ion conduction-promoting ceramic particles in the lithium ion conduction-promoting protective layer increased, the charge-discharge life of the all-solid-state battery showed a trend of increasing and then decreasing again.

[0197] When the weight ratio of lithium ion conduction-promoting ceramic particles and amorphous carbon included in the lithium ion conduction-promoting protective layer is 70:30, it was found that the charge / discharge life is shorter than that of an all-solid-state battery containing a protective layer composed of 100% amorphous carbon.

[0199] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A lithium metal electrode comprising: a current collector; a metal layer comprising a lithium alloy located on at least one surface of the current collector; and a protective layer located on the metal layer; wherein the protective layer comprises amorphous carbon and lithium ion conduction-promoting ceramic particles, and the metal layer comprising a lithium alloy comprises a lithium alloy layer located on the current collector and a lithium metal layer located on the lithium alloy layer. Claim 2 In claim 1, the lithium ion conduction-promoting ceramic particles are Li2TiO3, LiNbO3, LiTaO3, LiZrO3, Li4Ti5O 12 A lithium metal electrode comprising one or more of Li2CO3, Li3BO3, and SrTiO3. Claim 3 A lithium metal electrode according to 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. Claim 4 delete Claim 5 A lithium metal electrode according to claim 1, wherein the metal layer comprising the lithium alloy is composed of a mixture of lithium and a lithium alloy. Claim 6 A lithium metal electrode according to claim 1, wherein the metal layer comprising the lithium alloy comprises one or more of In, Ag, Sn, Zn, Si, Al, and Bi. Claim 7 A lithium metal electrode according to claim 1, wherein the average thickness of the metal layer is 1 μm to 100 μm. Claim 8 A lithium metal electrode according to claim 1, wherein the average thickness of the protective layer is 1 μm to 20 μm. Claim 9 A lithium metal electrode according to claim 1, wherein the protective layer further comprises a film layer located on the surface of the protective layer, and the film layer comprises one or more materials selected from the group consisting of Li-NCHO-based ionic compounds, Li-PCHO-based ionic compounds, LiF, and Li3N. Claim 10 A method for manufacturing a lithium metal electrode, comprising: a step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component; a step of forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and lithium ion-conducting ceramic particles; a step of positioning the current collector having the coating layer and the protective layer formed thereon in a plating solution, and then positioning a lithium source at a predetermined distance from the protective layer; and a step of applying an electric current between the current collector and the lithium source to form a metal layer comprising a lithium alloy in which the lithium-friendly component contained in the coating layer and the lithium precipitated from the lithium source are alloyed. Claim 11 A method for manufacturing a lithium metal electrode according to claim 10, wherein, in the step of forming the coating layer, the thickness of the coating layer formed on at least one surface of the current collector is in the range of 0.001 μm to 10 μm. Claim 12 A method for manufacturing a lithium metal electrode according to claim 10, wherein, in the step of forming a protective layer on the surface of the coating layer using a slurry comprising amorphous carbon and lithium ion conductivity-promoting ceramic particles, the weight ratio of the amorphous carbon and the lithium ion conductivity-promoting ceramic particles is 99.5:0.5 to 40:

60. Claim 13 A method for manufacturing a lithium metal electrode according to claim 10, wherein, in the step of forming the metal layer, the metal layer is formed in a multilayer structure comprising a lithium alloy layer including the lithium alloy; and a lithium metal layer formed on the lithium alloy layer. Claim 14 A method for manufacturing a lithium metal electrode according to claim 10, wherein, in the step of forming the metal layer, the metal layer is formed as a single layer structure comprising the lithium alloy and the lithium metal precipitated from the lithium source. Claim 15 A method for manufacturing a lithium metal electrode according to claim 10, wherein, in the step of forming a metal layer comprising the lithium alloy, the thickness of the metal layer is 1 μm to 100 μm. Claim 16 A lithium secondary battery comprising a negative electrode; a positive electrode; and an electrolyte, wherein the negative electrode is a lithium metal electrode according to any one of claims 1 to 3 and claims 5 to 9.

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