Lithium metal electrode for lithium secondary battery and method of manufacturing same

Abstract

The present invention relates to a lithium metal electrode and a method of manufacturing same. The lithium metal electrode of the present invention comprises: a current collector containing Fe and Ni; and a metal layer located on at least one surface of the current collector and containing a lithium alloy.

Description

Lithium metal electrode for lithium secondary battery and method for manufacturing same

[0001] The present invention relates to a lithium secondary battery, and more particularly, to a lithium metal electrode for a lithium secondary battery and a method for manufacturing the same.

[0002] To reduce the cost and increase the energy density of secondary batteries, the use of lithium metal electrodes as cathodes in lithium secondary batteries is essential. Specifically, all-solid-state batteries are attracting attention as next-generation batteries for high-energy densities, such as those required for electric vehicles (EVs).

[0003] All-solid-state batteries offer numerous advantages, including superior stability and high-voltage operation due to the elimination of liquid electrolytes. Furthermore, they reduce the need for cooling and safety-related components, resulting in higher energy density within the battery pack. Furthermore, they operate over a wide temperature range. To achieve truly high energy densities in these all-solid-state batteries, the thick, low-capacity graphite-based anode materials must be replaced with thin, high-capacity lithium. Considering cost-effectiveness and energy density, a thin-film lithium metal electrode with a thickness of 10 to 20 μm is practically required.

[0004] Typically, copper is used as a current collector for lithium metal electrodes. However, its application in sulfide-based all-solid-state batteries is hampered by its corrosion. To address this issue, interest in utilizing nickel or stainless steel (STS) as current collectors is growing. While nickel offers superior corrosion resistance compared to copper, corrosion remains a concern. While STS offers excellent corrosion resistance, it is not economical to manufacture current collectors with thicknesses below 20 ㎛, and surface treatment is difficult.

[0005] Therefore, research is needed on lithium metal electrodes that can replace existing current collectors and have stable and excellent life-cycle characteristics, including corrosion-resistant current collectors.

[0006] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery provides a lithium metal battery that is resistant to corrosion and has excellent battery life characteristics.

[0007] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery provides a method for manufacturing a lithium metal electrode for a lithium secondary battery having the advantages described above.

[0008] According to one embodiment of the present invention, a lithium metal electrode may include a current collector including Fe and Ni and a metal layer positioned on at least one surface of the current collector and including a lithium alloy. In one embodiment, a protective layer positioned on the metal layer may be included.

[0009] In one embodiment, the current collector including Fe and Ni may include 10 to 90 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector. In one embodiment, the current collector including Fe and Ni may include 55 to 70 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector.

[0010] In one embodiment, the metal layer may include at least one lithium-philic metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn). In one embodiment, the metal layer including the lithium-philic metal may have a thickness of 20 to 300 nm.

[0011] In one embodiment, the standard deviation of the thickness of the metal layer including the lithium-friendly metal may be 90 nm or less. In one embodiment, the molar ratio of the lithium-friendly metal in the metal layer including the lithium alloy may increase toward the current collector.

[0012] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode may include a step of preparing a current collector including Fe and Ni, and a step of forming a coating layer on at least one surface of the current collector using a coating composition including a lithium-philic component. In one embodiment, after the step of forming the coating layer, the method may include a step of forming a protective layer on a surface of the coating layer, a step of positioning the current collector on which the coating layer and the protective layer are formed in a plating solution, and then positioning a lithium source at a predetermined distance from the protective layer, and a step of applying a current between the current collector and the lithium source to form a metal layer including a lithium alloy in which the lithium-philic component included in the coating layer and lithium precipitated from the lithium source are alloyed.

[0013] In one embodiment, the step of preparing a current collector including Fe and Ni may include 10 to 90 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector. In one embodiment, the current collector including Fe and Ni may include 55 to 70 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector.

[0014] In one embodiment, the step of forming a coating layer on at least one surface of a current collector using a coating composition including the lithium-philic component may control the thickness of the coating layer to be in the range of 20 to 300 nm. In one embodiment, the step of forming a coating layer on at least one surface of a current collector using a coating composition including the lithium-philic component may control the standard deviation of the thickness of the coating layer to be in the range of 10 to 90 nm.

[0015] In one embodiment, in the step of forming a coating layer on at least one surface of a current collector using a coating composition including the lithium-friendly component, the coating layer may include at least one lithium-friendly metal among gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).

[0016] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery includes an alloy layer containing Fe and Ni within a current collector, thereby providing a lithium metal battery having excellent corrosion resistance and lifespan characteristics.

[0017] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery provides a method for manufacturing a lithium metal electrode for a lithium secondary battery having the advantages described above.

[0018] Figures 1a and 1b illustrate a lithium metal electrode manufactured according to one embodiment.

[0019] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

[0020] FIG. 3 is a scanning electron microscope (SEM) photograph showing the structure and thickness of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.

[0021] Figure 4 shows a cross-sectional structure when lithium is deposited between a protective layer and a current collector by an electrodeposition process according to one embodiment.

[0022] Figures 5a and 5b show the appearance when lithium is deposited according to an embodiment and a comparative example of the present invention.

[0023] Figure 6 is a photograph showing an evaluation of the corrosion resistance of a lithium metal battery according to an embodiment and a comparative example of the present invention.

[0024] Figure 7 shows the cell life evaluation of an all-solid-state battery using an example and a comparative example of the present invention.

[0025] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0027] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0028] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0029] FIG. 1a and FIG. 1b illustrate a lithium metal electrode (100) manufactured according to one embodiment.

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

[0031] The current collector (11) may be a member for electrical connection within a lithium secondary battery. The current collector (11) may have a foil form, but is not limited thereto, and may have, for example, a mesh, foam, rod, wire, or sheet made by weaving wire (fiber).

[0032] The current collector (11) may be made of a material that is electrically conductive and has limited reaction with lithium. Specifically, the material of the current collector (11) may be any one or a combination of, for example, copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, carbon, conductive polymers, and composite fibers coated with a conductive layer on a non-conductive polymer.

[0033] In one embodiment, the thickness of the current collector (11) may be 1 μm to 50 μm. If the thickness of the current collector (11) is excessively thick, there is a problem that the battery weight increases and the energy density of the battery decreases. If the thickness of the current collector (11) is excessively thin, there is a risk of overheating damage during high current operation and damage due to tension during the battery manufacturing process.

[0034] In one embodiment, the current collector (11) may include Fe and Ni. Specifically, the current collector (11) may include an alloy including Fe and Ni. Since the current collector (11) includes Fe and Ni, it has the advantage of having a low coefficient of thermal expansion, which is advantageous for battery application, excellent corrosion resistance, and at the same time, easy surface treatment, which is advantageous for application to all-solid-state batteries.

[0035] In one embodiment, the current collector (11) may include 10 to 90 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector (11). The Fe and Ni in the current collector (11) satisfy the above-described range and have the following advantages.

[0036] Fe: 10 to 90 wt%

[0037] Fe is included in an appropriate amount in the current collector (11), thereby increasing corrosion resistance and providing economic benefits. Fe may be included in an amount of 10 to 90 wt% based on 100 wt% of the current collector (11). Specifically, Fe may be included in an amount of 55 to 70 wt%, and more specifically, 60 to 70 wt%, based on 100 wt% of the current collector (11).

[0038] If the content of the above Fe is outside the upper or lower limit of the above-mentioned range, there is a problem that the reactivity with the electrolyte increases compared to the value within the appropriate range.

[0039] Ni: 10 to 90 wt%

[0040] Ni has the advantage of increased corrosion resistance by being included in the current collector (11). Ni may comprise the remainder, specifically, 90 to 10 wt%, excluding 10 to 90 wt% of Fe, based on 100 wt% of the current collector (11). For example, when Fe is 10 wt%, Ni may be 90 wt%.

[0041] If the content of Ni is excessive, cell instability increases, resulting in poor reproducibility. If the content of Ni is insufficient, the corrosion resistance effect of Ni is minimal.

[0042] The metal layer (12) is positioned on the current collector (11), and may include a lithium alloy layer (21) including a lithium alloy, and a lithium metal layer (41) positioned on the lithium alloy layer (21). The lithium alloy layer (21) may be a layer including a lithium alloy in which a lithium-friendly component included in the metal layer (12) and lithium precipitated from the lithium source (40) are alloyed by applying a current between the current collector (11) and the lithium source (40 in FIG. 2).

[0043] In order to form a metal layer (12), when a high current is applied to perform the electrodeposition process in order to increase the lithium deposition rate, there is a problem that the performance of the lithium secondary battery is reduced. 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 when a high current is applied to perform the electrodeposition process, it is possible to prevent excessive generation of fine lithium particles or destruction of the protective layer (30) during the electrodeposition process.

[0044] Specifically, since the metal layer (12) of one embodiment includes a lithium alloy layer (21) containing a lithium component, when a high current is applied in the electrodeposition process to form a lithium metal layer (41) on the lithium alloy layer (21), the initially generated lithium particles are induced to grow well, thereby forming particles with a coarse structure, and at the same time, the lithium metal layer (41), and consequently the metal layer (12), can have a uniform surface.

[0045] Therefore, the performance, specifically the charge / discharge characteristics, of a secondary battery using the lithium metal electrode according to the present embodiment can be significantly improved. Furthermore, since a high-performance lithium metal electrode for a secondary battery 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.

[0046] In this embodiment, the lithium alloy layer (21) includes a lithium-friendly metal. When the lithium alloy layer (21) includes a lithium-friendly metal, the diffusion of lithium ions becomes smooth due to the decrease in the surface energy of lithium ions on the surface of the lithium-friendly metal. Therefore, there is an advantage in that lithium ion conductivity is improved and the electrodeposition of the lithium metal layer is performed uniformly. The metal layer (12) plays a role in helping lithium to be deposited more effectively under the protective layer (30) during the charging process of the battery.

[0047] In one embodiment, a lithium-friendly metal layer may be further included between the lithium alloy layer (21) and the current collector (11). Specifically, some of the lithium-friendly metal may form an alloy with lithium within the lithium alloy layer (21), and some may remain on the surface of the current collector. Specifically, in one embodiment, the molar ratio of the lithium-friendly metal may increase toward the current collector. This means that some of the lithium-friendly metal applied on the current collector forms an alloy with lithium during the electrolytic plating process to form the lithium alloy layer (21), and the remaining some of the lithium-friendly metal remains on the current collector.

[0048] The lithium alloy layer (21) may be an alloy composed of lithium and a lithium-friendly metal, wherein the lithium-friendly metal may include at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn). Specifically, the lithium-friendly metal may include tin (Sn). Specifically, the lithium-friendly metal includes tin, so that it is advantageously applied to a current collector (11) including Fe and Ni, and can prevent lithium dendrite growth, thereby realizing a stable and long-life lithium metal battery.

[0049] In one embodiment, the thickness of the metal layer including the lithium-friendly metal may be 20 to 300 nm. Specifically, the metal layer including the lithium-friendly metal may be a lithium alloy layer (21). The thickness of the metal layer including the lithium-friendly metal may be 25 to 200 nm, specifically, 50 to 150 nm.

[0050] If the thickness exceeds the upper limit of the aforementioned range, there is a problem of reduced thickness uniformity. If the thickness exceeds the lower limit of the aforementioned range, there is a problem of detrimental effects on cell driving characteristics.

[0051] In one embodiment, the thickness standard deviation of the metal layer including the lithium-friendly metal may be 90 nm or less. Specifically, the thickness standard deviation of the metal layer including the lithium-friendly metal, for example, the lithium alloy layer (21), may be 90 nm or less, specifically, 10 to 90 nm, specifically, 12.5 to 87.1 nm, more specifically, 45 to 65 nm, and even more specifically, 50 to 55 nm.

[0052] The thickness standard deviation of the metal layer including the lithium-friendly metal refers to a value measured by extracting multiple random parts of the sample and using the Cross-section polishing (CP) and Focused ion beam (FIB) methods, and when the thickness standard deviation satisfies the above-mentioned range, the uniformity satisfies a certain range condition, which has the advantage of effectively preventing lithium dendrite growth. When the thickness standard deviation of the metal layer including the lithium-friendly metal exceeds the upper limit of the above-mentioned range, there is a problem that the uniformity of the metal layer differs significantly, which is disadvantageous for inhibiting lithium dendrite growth. In one 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. When the thickness of the metal layer (12) is excessively thick, when the lithium metal electrode of the present embodiment is applied to a secondary battery, there is a problem that the weight and volume of the battery increase, resulting in a decrease in the energy density. 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 ㎛ or less.

[0053] When the thickness of the metal layer (12) is excessively thin, there is a problem that the charge / discharge life of the battery is reduced when the lithium metal electrode of the present embodiment is applied to a secondary battery. Specifically, during charging / discharging of the battery, lithium ions move between the negative electrode and the positive electrode, and a sufficient amount of lithium-philic metal must be distributed on the negative electrode so that the lithium-philic metal maintains the force that attracts lithium ions even when the battery is repeatedly charged / discharged, enabling stable behavior. Therefore, if the lithium-philic metal is present in an insufficient amount, the charge / discharge life of the battery is reduced. The protective layer (30) is located on the metal layer (12) and may include amorphous carbon. When only 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 unevenness in the current density during the charge / discharge process, resulting in a failure due to a short circuit or overvoltage during charge / discharge or a reduction in battery capacity.

[0054] According to one embodiment, a lithium metal electrode can further improve structural safety as well as output characteristics and life characteristics of the lithium metal electrode by including a protective layer including amorphous carbon.

[0055] Specifically, the lithium metal electrode of the present embodiment includes a protective layer (30) containing amorphous carbon, thereby not only improving ion conductivity, but also improving the strength of the protective layer (30), and preventing short circuits between electrodes by physically blocking dendrites when they grow on the lithium electrode, thereby improving the charge / discharge life.

[0056] The above 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.

[0057] In one embodiment, the protective layer (30) may include a binder. The binder may be an aqueous binder, and the aqueous binder may be, but is not limited to, a rubber-based binder selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, and at least one selected from the group consisting of polymer resins such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride.

[0058] Here, the binder may be added in an amount of 1 to 15 parts by weight, specifically 3 to 10 parts by weight, based on the weight of the slurry formed by mixing the amorphous carbon and water. When the content of the binder satisfies the above-mentioned range, the particles constituting the protective layer are efficiently bound to form a protective layer with excellent performance without causing a decrease in battery energy density due to an increase in weight and volume, thereby further improving the life characteristics of the secondary battery.

[0059] If the content of the binder is excessively less than the above-mentioned range, there is a problem that the bonding force between particles is reduced when forming a protective layer, and if the content of the binder is excessively more than the above-mentioned range, there is a problem that not only does it cause a decrease in energy density, but also the resistance of the protective layer is greatly increased, hindering lithium ion conduction.

[0060] In one embodiment, the thickness of the protective layer (30) may be 0.01 μm to 50 μm. Specifically, the thickness of the protective layer (30) may be in the range of 1 μm to 20 μm. When the thickness of the protective layer satisfies the above-described range, lithium dendrites are prevented from forming on the surface of the protective layer, and lithium ions can be well penetrated and conducted inside the protective layer, thereby allowing lithium to be precipitated from the lower surface of the protective layer.

[0061] If the thickness of the protective layer is excessively thin, there is a problem in that it cannot function as a protective layer. If the thickness of the protective layer is excessively thick, the resistance of the protective layer may be excessively large, which may cause an increase in overvoltage during secondary battery operation, and there is a problem in that it causes a decrease in battery energy density due to an increase in weight and volume. However, the thickness of the protective layer can be variably adjusted depending on the design of the secondary battery structure.

[0062] In one embodiment, the lithium metal electrode may further include a film layer disposed within the protective layer (30), between the metal layer (12) and the protective layer (30), and at least a portion of the protective layer (30). Specifically, the film layer may be disposed within at least a portion of the protective layer (30), between the metal layer (12) and the protective layer (30), may be disposed simultaneously within the protective layer (30) and between the metal layer (12) and the protective layer (30), and may be disposed on the protective layer (30).

[0063] The above film layer is formed during the manufacturing process of the metal layer (12) by a reaction between the lithium metal of the electrodeposited lithium source (40) 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.

[0064] In one embodiment, the film layer may include at least a portion of LiF. The LiF may be formed by including at least one solvent having a high dielectric constant among a plurality of solvents used in the electrodeposition process. Specifically, by increasing the salt decomposition dissociation degree of the solvent of the electrodeposition plating solution, the salt decomposition reaction may be suppressed and the solvent decomposition reaction may be promoted during electrodeposition, thereby allowing a sufficient LiF film to be formed within and / or on the surface of the protective layer. By including the film layer including at least a portion of LiF, the battery can have a high ionic conductivity, thereby improving the lifespan and preventing dendrite growth during battery operation.

[0065] The thickness of the film layer may be 2 nm to 2 ㎛. Specifically, the thickness of the film layer may be specifically in the range of 10 nm to 500 nm. If the thickness of the film layer is excessively thick, the lithium ion conductivity decreases and the interfacial resistance increases, which causes a problem in that the charge / discharge characteristics deteriorate when applied to a battery. If the thickness of the film layer is excessively thin, the film layer may be easily lost during the process of applying the lithium metal electrode according to the embodiment to a battery. Therefore, the film layer may have a thin thickness within the range satisfying the above thickness range and may be uniformly and densely formed on the entire surface of the metal layer (12) or the protective layer (30).

[0066] Referring to FIG. 1B, in one embodiment, a lithium metal electrode (100) includes a current collector (11) and a metal layer (12) positioned 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 a current between the current collector (11) and a lithium source (40), thereby alloying a lithium-philic component included in the metal layer (12) formed on the current collector (11) with lithium precipitated from the lithium source (40).

[0067] The above metal layer (12) may include a lithium-friendly metal. Here, the lithium-friendly metal may include tin, and a detailed description thereof may be provided with reference to FIG. 1a.

[0068] In one embodiment, the metal layer (12) is in a form that includes a lithium-philic metal. When the metal layer (12) including a lithium-philic metal is formed in this way, the free energy for nucleation of lithium particles can be lowered in the early stage of nucleation during the electrodeposition process, so that a lithium metal layer having a coarse particle structure can be formed even under high current and overvoltage conditions.

[0069] In one embodiment, the thickness of the metal layer (12) including tin may be 20 to 300 nm. A detailed description thereof is the same as that described in FIG. 1a, as long as it does not contradict the description.

[0070] In one embodiment, the metal layer (12) includes a protective layer (30) positioned on the surface of the metal layer (12), and may further include a film layer on the inside and / or surface of the protective layer (30). For a detailed description of the protective layer (30) and the film layer, reference may be made to the description given above in FIG. 1A.

[0071] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

[0072] Referring to FIG. 2, a method for manufacturing a lithium metal electrode according to one embodiment includes the steps of preparing a current collector (11), forming a coating layer (20) on at least one surface of the current collector (11) using a coating composition including a lithium-philic component, forming a protective layer (30) on the surface of the coating layer (20) using a slurry including amorphous carbon, positioning the current collector (11) on which the coating layer (20) and the protective layer (30) are formed in a plating solution (50), and then positioning a lithium source (40) at a predetermined distance from the protective layer (30), and applying a current between the current collector (11) and the lithium source (40) to form a metal layer including a lithium alloy in which the lithium-philic component included in the coating layer and lithium precipitated from the lithium source (40) are alloyed.

[0073] The step of preparing a current collector (11) may be a step of preparing a current collector including Fe and Ni. The step of preparing the current collector including Fe and Ni may include 10 to 90 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector. Specifically, the current collector including Fe and Ni may include 55 to 70 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector. The detailed description of the Fe and Ni is the same as that described above in FIGS. 1A and 1B, as long as it is not contradictory.

[0074] When the contents of Fe and Ni in the current collector (11) satisfy the above-mentioned range, not only is the corrosion resistance of the current collector increased, but there is an advantage in that most reproducibility problems can be solved. If the content of Fe exceeds the upper or lower limit of the above-mentioned range, there is a problem in that the reactivity between the current collector and the electrolyte increases. If the content of Ni is included excessively, there is a problem in that cell instability increases and reproducibility is poor. If the content of Ni is included insufficiently, there is a problem in that the corrosion resistance effect of Ni is insufficient.

[0075] The step of forming a coating layer (20) on at least one surface of a current collector (11) using a coating composition containing a lithium-friendly component may include coating a lithium-friendly metal, which is an alloy material, on at least one surface of the current collector. As described above with reference to FIGS. 1A and 1B, the lithium-friendly metal may include at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn), and specifically, may include tin (Sn).

[0076] The coating layer (20) may be formed by, after the process described below, forming a lithium alloy layer (21) by forming an alloy between a lithium-friendly metal and lithium, as described above in FIGS. 1A and 1B. In one embodiment, the coating layer (20) may be specifically disposed between a current collector (11) and a protective layer (30), and then forming a lithium alloy layer (21) through electrolytic plating.

[0077] In one embodiment, the step of forming a coating layer (20) on at least one surface of a current collector (11) using a coating composition including a lithium-ion component may control the thickness of the coating layer to a range of 20 to 300 nm. Specifically, the thickness of the coating layer may be 25 to 200 nm, specifically, 50 to 150 nm.

[0078] In one embodiment, the step of forming a coating layer (20) on at least one surface of a current collector (11) using a coating composition including a lithium-philic component can control the thickness standard deviation of the coating layer to 90 nm or less. Specifically, the thickness standard deviation of the coating layer can be 12.5 to 87.1 nm, more specifically, 45 to 65 nm, and even more specifically, 50 to 55 nm.

[0079] In one embodiment, the step of forming the coating layer (20) may be performed using at least one of electrolytic and electroless plating, sputtering, electron beam, and thermal vapor deposition. For example, the step of forming the coating layer may be performed by coating using an electrolytic plating method.

[0080] A protective layer (30) can be formed on the surface of the coating layer (20) using a slurry containing amorphous carbon. The protective layer (30) can be applied by mixing the amorphous carbon and a binder in water using at least one of a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush application method. The protective layer (30) can further include a binder.

[0081] Meanwhile, in the step of forming the protective layer (30), the thickness of the 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.

[0082] If the thickness exceeds the upper limit of the aforementioned range, there is a problem of top-surface electrodeposition where lithium is deposited on the protective layer. If the thickness exceeds the lower limit of the aforementioned range, there is a problem of detrimental effects on cell operating characteristics.

[0083] After the step of forming a protective layer (30), a step of positioning a current collector in which the coating layer (20) and the protective layer (30) are sequentially formed in a plating solution (50), a step of positioning a lithium supply source (40) at a predetermined distance from the current collector (11), and a step of applying current between the current collector (11) and the lithium supply source (40) to form a metal layer (12) are performed.

[0084] Specifically, after positioning a current collector (11) having a coating layer (20) and a protective layer (30) formed within a plating solution, a lithium supply source (40) is positioned at a predetermined distance from the protective layer (30). The lithium supply source (40) may be, for example, lithium metal, a lithium alloy, a foil obtained by pressing the lithium metal or lithium alloy onto a current collector, a plating solution in which a lithium salt is dissolved, etc.

[0085] The plating solution (50) can be prepared by dissolving a lithium salt in a plurality of solvents. Specifically, the lithium salt can 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 can be 1.0 to 3.0 M based on the total electrolyte.

[0086] Specifically, in the present embodiment, the plating solution (50) is characterized in that it includes a nitrogen-based compound as at least one of the lithium salt and a plurality of solvents. 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, e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin.

[0087] Among the above nitrogen compounds, at least one of lithium nitrate, lithium bis fluorosulfonyl imide, and lithium bis trifluoromethane sulfonimide can be used as a lithium salt.

[0088] Among the above nitrogen compounds, at least one of caprolactam (e-caprolactam), methyl caprolactam (N-methyl-e-caprolactam), triethylamine, and tributylamin can be used as a non-aqueous solvent.

[0089] The above plating solution (30) may be manufactured using only the nitrogen-based compound, but may include a general non-aqueous solvent as an auxiliary solvent in consideration of the viscosity of the plating solution (30), etc.

[0090] The auxiliary solvent may include, for example, at least one 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.

[0091] In one embodiment, the auxiliary solvent may be included in an amount of 5 to 70 wt%, preferably 10 to 60 wt%, based on 100 wt% of the total plating solution (50), but is not limited thereto. However, when the auxiliary solvent is included within the above range, the viscosity of the plating solution (50) may be appropriate, thereby shortening the time required for the formation process of the lithium metal layer (12), but is not limited thereto.

[0092] In one embodiment, the plating solution (50) may further include a fluorine-based compound. When the plating solution (50) further includes the fluorine-based compound, there is an advantage in that the properties of the film layer formed on the lithium metal layer (12) can be improved.

[0093] The fluorine-based compounds include, for example, lithium difluoro phosphate, lithium hexafluorophosphate, lithium difluoro bisoxalato phosphate, lithium tetrafluoro oxalato phosphate, lithium difluoro oxalate borate, lithium difluoro oxalato borate, lithium tetrafluoro oxalato borate, fluoroethylene carbonate, difluoroethylene carbonate, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. It may include at least one selected from the group consisting of 2,2,3,3-Tetrafluoropropyl ether.

[0094] The above fluorine-based compound may be included in an amount of 0.1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on 100 wt% of the total plating solution (50). When the fluorine-based compound is included within the above range, the interaction between the nitrogen-based compound and the fluorine-based compound in the plating solution (50) is favorable, so that there is an excellent advantage in improving the properties of the film layer formed on the lithium metal layer (12). In addition, there is an advantage in that the electrochemical properties are excellent because excessive generation of LiF, etc. due to the direct reaction between the fluorine-based compound and lithium is suppressed.

[0095] Next, after positioning an insulating film between the current collector (11) and the lithium supply source (40), the current collector (11), the lithium supply source (40), and the insulating film can be laminated and restrained in both directions using a restraining device. The restraining device can be a non-limiting example, and can be a method commonly used in the art, such as a manual clamping method, a uniaxial pressurization method such as hydraulic or pneumatic.

[0096] In the step of forming a lithium metal layer (12) on at least one surface of the current collector (11) by applying the above current, the current density of the current applied is 0.1 mA / cm 2 100 mA / cm 2 range, more specifically 0.2 mA / cm 2 50 mA / cm 2 Range, 5 mA / cm 2 30 mA / cm 2 range or 7 mA / cm 2 25 mA / cm 2 It could be a range.

[0097] In one embodiment, 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.

[0098] In one embodiment, the step of applying the current to form a lithium metal layer (12) on at least one surface of the current collector (11) may be performed at least once at different current densities. The step of applying the current may be performed in multiple stages. Specifically, the step of applying the current in multiple stages may be performed by increasing the current density from a low current density to a high current density in predetermined time steps. For example, the step of applying the current may be performed at a current density of 0.1 to 0.3 mA / cm. 2 , 0.3 to 0.7 mA / cm 2 , and 0.8 to 1.5 mA / cm 2 It can be applied step by step and increased sequentially.

[0099] In one embodiment, the step of forming a lithium metal layer (12) on at least one surface of the current collector (11) by applying the current is 6 to 12 mA / cm 2 A step of electrodeposition at a maximum current density of the range may be included. Specifically, the maximum current density is 8 to 12 mA / cm 2 It can be performed in the range. The above maximum current density means the limit of the current density at which lithium deposited in the electrodeposition process can precipitate lithium between the protective layer (30) and the current collector (11).

[0100] The step of electrodeposition at the above maximum current density may be a final step performed after the step of depositing in multiple stages, for example, for lithium deposition between the current collector (11) and the protective layer (30). By satisfying the above-described range, lithium is appropriately deposited between the current collector (11) and the protective layer (30), thereby providing advantages such as excellent battery life characteristics and bonding strength between the current collector (11) and the protective layer (30).

[0101] If the maximum current density exceeds the upper limit of the aforementioned range, lithium is deposited on the surface of the protective layer (30), which causes a problem in that the targeted stabilized electrode structure cannot be secured. If the maximum current density exceeds the lower limit of the aforementioned range, the time for lithium to be deposited increases, which causes a problem in that productivity decreases.

[0102] In one embodiment, in the step of forming a lithium metal layer on at least one surface of the current collector (11) by applying the current, the step of electrodepositing the deposited lithium may include a thickness in the range of 3 to 15 μm. Specifically, the thickness of the deposited lithium may be electrodeposited in the range of 5 to 12 μm. The thickness of the deposited lithium may refer to the vertical height of the lithium disposed between the current collector (11) and the protective layer (30).

[0103] If the thickness of the precipitated lithium exceeds the upper limit of the aforementioned thickness, not only will the energy density of the battery decrease, but there will also be problems such as increased process time and metal raw material usage during metal layer formation. If the thickness of the precipitated lithium exceeds the lower limit of the aforementioned thickness, there will be problems such as decreased initial coulombic efficiency due to initial irreversibility and decreased charge / discharge performance due to insufficient excess lithium.

[0104] In one embodiment, in the step of forming a lithium metal layer (12) on at least one surface of the current collector (11) by applying the current, the thickness of the metal layer (12) including a lithium alloy can be controlled to 1 to 100 μm. For a detailed description of the thickness of the metal layer (12), reference may be made to the contents of the aforementioned FIG. 1.

[0105] In this way, in this embodiment, a lithium metal electrode (100) can be manufactured in which a metal layer including a lithium metal layer (12) having a coarse particle structure is formed by preventing excessive generation of fine lithium particles even under high current conditions and inducing the initially generated lithium particles to grow well. In addition, the metal layer manufactured in this way also has excellent surface uniformity.

[0106] According to another embodiment of the present invention, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte positioned between the positive electrode and the negative electrode. Here, the negative electrode may be a lithium metal electrode according to the present invention.

[0107] In one embodiment, a lithium secondary battery may include an electrode assembly including a positive electrode including a positive active material, a negative electrode which is a lithium metal electrode of the present invention, and a separator disposed between the positive electrode and the negative electrode. This electrode assembly may be wound or folded and accommodated in a battery case.

[0108] Thereafter, an electrolyte may be injected into the battery case and sealed to complete the secondary battery. At this time, the battery case may have a cylindrical, square, pouch-shaped, coin-shaped, etc. shape.

[0109] The positive electrode may include a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer may include, for example, a Li compound including 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-metallic element selected from the group consisting of O, F, S, P, and combinations thereof.

[0110] In one embodiment, a conductive material may be further added to the positive electrode active material layer. The conductive material may be, but is not limited to, carbon black, ultrafine graphite particles, fine carbon such as acetylene black, nano metal particle paste, etc.

[0111] The above-described positive electrode current collector serves to support the positive electrode active material layer. Examples of positive electrode current collectors that can be used include, but are not limited to, aluminum foil, nickel foil, or a combination thereof.

[0112] The electrolyte to be filled in the lithium secondary battery may be a non-aqueous electrolyte or a solid electrolyte. Specifically, the electrolyte may be a solid electrolyte. The 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 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, or an inorganic solid electrolyte such as LiI or Li3N.

[0113] The separator may be any membrane commonly used in lithium secondary batteries, as it separates the positive and negative electrodes and provides a passage for lithium ions to move. Specifically, the separator may be one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. 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, when a solid electrolyte is used as the electrolyte, the solid electrolyte may also function as the separator.

[0114] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereby, and the present invention is defined only by the scope of the claims set forth below.

[0115]

[0116] <Experimental Example>

[0117] Manufacturing of cathodes for lithium secondary batteries

[0118] <Example 1>

[0119] <Manufacturing the entire house>

[0120] An Fe-Ni current collector (11) was manufactured by a rolling or electrolytic method. At this time, based on 100 wt% of an alloy of Fe and Ni, the Fe-Ni current collector (11) was manufactured by controlling Fe: 90 wt% and Ni: 10 wt%.

[0121]

[0122] <Coating layer formation>

[0123] Thereafter, a coating layer (20) was formed on both sides of the manufactured collector using an electroplating method. At this time, tin (Sn) was used as the coating layer, and the plating thickness was controlled to approximately 100 nm.

[0124] FIG. 3 is a scanning electron microscope (SEM) photograph showing the structure and thickness of a coating layer (20) plated on a collector (11) according to one embodiment of the present invention.

[0125] Referring to FIG. 3, it can be confirmed that the coating layer (20) plated on the collector (11) of the present invention has a thickness of about 100 nm and a standard deviation of the thickness of 48.5 nm.

[0126]

[0127] <Protective layer formation>

[0128] Thereafter, a protective layer (30) of about 5 μm was formed on the upper surface of the coating layer (20) by slurry coating using a comma coater. Specifically, the protective layer (30) was formed by mixing acetylene black, which is an amorphous carbon, and a binder. At this time, the binder was prepared by adding 3.0 wt% of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR), respectively.

[0129]

[0130] Lithium electrodeposition process

[0131] Thereafter, lithium was removed from the lithium source (40) using an electrodeposition process to form a lithium alloy or pure lithium metal between the protective layer (30) and the current collector (11), and lithium was deposited between the protective layer (30) and the current collector (11). The plating solution (50) used in this type of electrodeposition was prepared by mixing 1,2-dimethoxyethane (DME) as a first solvent and sulfolane (SL) as a second solvent in a molar ratio of 90:10 in a composite solvent, adding lithium bis(fluorosulfonyl)imide, a nitrogen-based compound, and lithium nitrate in amounts of 40 wt% and 5 wt%, respectively, based on 100 wt% of the plating solution, and adding fluoroethylene carbonate, a fluorine-based compound, in an amount of 5 wt% based on 100 wt% of the plating solution. As a lithium supply source (40), a lithium metal plate having a purity of 99.9% or more and a thickness of 500 ㎛ was pressed onto a copper current collector (Cu Plate) and used.

[0132] After electrically insulating the lithium source (40) and the current collector (11) within the plating solution (50), lithium was deposited between the current collector (11) and the protective layer (30) by applying current using a power supply device with the lithium source (40) and the current collector (11) as (+) and (-) electrodes, respectively.

[0133] The current density of the electrodeposition process was 0.2 mA / cm 2 , 0.5 mA / cm 2 , 1 mA / cm 2 Increasing step by step in order, after 5 minutes of deposition, 10 mA / cm 2 The maximum current density was set. The deposition time at the maximum current density was calculated as the time required for a final accumulated lithium thickness of 10 ㎛ to be deposited, and was set variably depending on the size of the maximum current density.

[0134] Figure 4 shows a cross-sectional structure when lithium is deposited between a protective layer (30) and a current collector (11) by an electrodeposition process according to one embodiment.

[0135] Referring to Fig. 4, it can be confirmed that lithium is deposited between the protective layer (30) and the current collector (11) by the aforementioned electrodeposition process. The maximum current density means the limit of the current density at which lithium deposited in the electrodeposition process can deposit lithium between the protective layer (30) and the current collector (11), and at a current density higher than the maximum current density value, lithium is deposited on the surface of the protective layer (30), so the target structure cannot be confirmed.

[0136]

[0137] <Comparative Example 1>

[0138] A lithium metal electrode was manufactured in the same manner as in Example 1, except that it did not contain any Fe at all and contained only 100 wt% of Ni in the step of forming the entire electrode.

[0139]

[0140] Comparative Example 2

[0141] The point that it does not contain any Ni at all in the stage of forming the entire collector and contains only 100 wt% of Fe, and the maximum current that can be deposited is 4 mA / cm 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0142]

[0143] All-solid-state battery manufacturing

[0144] All-solid-state batteries were fabricated using the cathodes manufactured according to the aforementioned examples and comparative examples, and their charge-discharge cycle life was evaluated. To evaluate the all-solid-state battery cells, a pressurized, dedicated evaluation cell from Terraleader, capable of maintaining an inert atmosphere, was used. For the fabrication of the all-solid-state battery cells, a sulfide-based argyrodite (Li6P5Cl) solid electrolyte was used, and the electrolyte was in pellet form with a thickness of approximately 0.7 mm. To ensure a dense electrolyte, the electrolyte was pressurized at a pressure of 370 MPa.

[0145]

[0146] Lithium having a thickness of 0.5 mm was attached to one side of the electrolyte as a reference electrode, and the negative electrode manufactured according to the examples and comparative examples was attached to the opposite side. The reference electrode and the evaluation electrode were pressurized at a pressure of 50 MPa.

[0147] Lithium having a thickness of 0.5 mm was attached as a reference electrode to one side of the electrolyte, and the negative electrode manufactured according to the examples and comparative examples was attached to the opposite side.

[0148]

[0149] <Evaluation Example 1>: Control of Fe-Ni content in the entire collector

[0150] Table 1 below shows the maximum electrodeposition current and the number of charge / discharge cycles when the content ratio of Fe and Ni in the current collector was changed. The standard deviation of the coating layer thickness, the maximum electrodeposition current, and the number of charge / discharge cycles were measured using the following methods.

[0151] Standard deviation of coating layer thickness (nm): Multiple random sections of the sample were extracted and measured using the cross-section polishing (CP) and focused ion beam (FIB) methods.

[0152] Maximum current density (mA / cm 2): The maximum current density refers to the limit of the current density at which lithium deposited according to the above process can precipitate lithium between the protective layer and the current collector, and the maximum current density was measured.

[0153] Charge / discharge performance number (cycles): The reference electrode and evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and the dedicated evaluation cell was pressurized at 16 MPa during the charge / discharge evaluation. The charge / discharge evaluation was performed at 2 mA / cm 2 Charge for 0.5 hours at constant current of 2 mA / cm 2 A 0.5-hour discharge at constant current was defined as one cycle. The charge-discharge life was defined as the end of the life when a short circuit occurred between the reference electrode and the evaluation electrode during the charge-discharge process or when the voltage between the two electrodes exceeded 2 V.

[0154] The maximum deposition current of the alloy content coating layer of the current collector [mA / cm 2 ]Charge-discharge performance number of times [times]Fe [wt%]Ni [wt%]Sn thickness [nm]Sn thickness standard deviation [nm]Example 1901010048.510637Comparative example 1010010061.912122Comparative example 2100010041.34336

[0155] Looking at Table 1 above, it was confirmed that Example 1, which simultaneously includes Fe and Ni as alloy components in the current collector, had a high number of charge / discharge cycles. In contrast, Comparative Examples 1 and 2, which include only Fe or Ni as alloy components in the current collector, had low number of charge / discharge cycles.

[0156]

[0157] <Evaluation Example 2> - Fe:Ni content control

[0158] <Example 2>

[0159] In the step of forming the entire collector, the weight % of Fe:Ni was changed to 64 wt%:36 wt%, and the maximum electrodepositable current was 12 mA / cm 2A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except for this point.

[0160]

[0161] <Example 3>

[0162] In the step of forming the entire collector, the weight % of Fe:Ni was changed to 10 wt%:90 wt%, and the maximum electrodepositable current was 12 mA / cm 2 A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except for this point.

[0163]

[0164] Table 2 below shows the maximum electrodeposition current and the number of charge / discharge cycles when the content ratio of Fe and Ni in the current collector was changed. The standard deviation of the Sn layer thickness, the maximum electrodeposition current, and the number of charge / discharge cycles were measured using the following methods.

[0165] The maximum deposition current of the alloy content coating layer of the current collector [mA / cm 2 ]Charge-discharge performance number [times]Fe [wt%]Ni [wt%]Sn thickness [nm]Sn thickness standard deviation [nm]Example 1901010048.510637Example 2643610052.112712Example 3109010059.412705

[0166] Looking at Table 2 above, it was confirmed that the number of charge / discharge cycles was excellent when both Fe and Ni were included in the current collector, as in Examples 1 to 3. At this time, when Examples 1 and 3 were compared with Example 2, it was confirmed that the number of charge / discharge cycles of Example 2 was more excellent.

[0167] <Evaluation Example 3> - Coating Layer Thickness Control

[0168] <Example 4>

[0169] A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the coating layer was controlled to 25 nm in the step of forming the coating layer.

[0170]

[0171] <Example 5>

[0172] In the step of forming the coating layer, the thickness of the Sn layer is controlled to 200 nm, and the maximum deposition current is 8 mA / cm 2 A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the control was performed by .

[0173]

[0174] <Comparative Example 3>

[0175] In the step of forming the coating layer, the thickness of the Sn layer is controlled to 500 nm, and the maximum deposition current is 6 mA / cm 2 A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the control was performed by .

[0176]

[0177] Comparative Example 4

[0178] In the step of forming the coating layer, the thickness of the Sn layer is controlled to 10 nm, and the maximum deposition current is 6 mA / cm 2 A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the control was performed by .

[0179]

[0180] Comparative Example 5

[0181] A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 0 nm in the step of forming the coating layer.

[0182]

[0183] Figures 5a and 5b show the appearance when lithium is deposited according to an embodiment and a comparative example of the present invention.

[0184] Figures 5a and 5b are 12 mA / cm each 2When electrodeposited, the appearance of the electrodeposition of Example 2 and Comparative Example 4 is shown. Specifically, when electrodeposited at the maximum current density, the appearance is shown when lithium is deposited between the current collector and the protective layer, and when electrodeposited at a current density exceeding the maximum current density. When electrodeposition is performed below the maximum possible electrodepositable current density, the deposited lithium is deposited under the black protective layer, so a black protective layer is observed in appearance. When electrodeposition is performed at a current density exceeding this, it was confirmed that lithium is deposited on the upper surface of the protective layer, and gray-colored lithium is deposited on the upper surface of the protective layer.

[0185]

[0186] Table 3 below shows the maximum electrodeposition current and the number of charge / discharge cycles when the thickness of the coating layer on the current collector was varied. The standard deviation of the coating layer thickness, the maximum electrodeposition current, and the number of charge / discharge cycles were measured using the following methods.

[0187] The maximum deposition current of the alloy content coating layer of the current collector [mA / cm 2 ] Charge / discharge performance number [times] Fe [wt%] Ni [wt%] Sn thickness [nm] Sn layer thickness standard deviation [nm] Example 2 6 4 3 6 1 0 0 5 2.1 1 2 7 1 2 Example 4 6 4 3 6 2 5 5 9.4 1 2 6 9 4 Example 5 6 4 3 6 2 0 0 1 4.7 8 6 8 2 Comparative example 3 6 4 3 6 5 0 0 8 7.1 6 3 1 9 Comparative example 4 6 4 3 6 1 0 6 1.9 4 4 0 1 Comparative example 5 6 4 3 6 0 0--

[0188] Looking at Table 2 above, it was confirmed that when the Sn thickness and the Sn thickness standard deviation satisfied the range of the present invention, as in Examples 2, 4, and 5, the charge / discharge performance number was excellent at 600 or more. However, when the Sn thickness was excessively thick, it was confirmed that the charge / discharge performance number was reduced, as in Comparative Example 3, and when the Sn thickness was excessively thin, it was confirmed that the charge / discharge performance number was good, as in Comparative Example 4.

[0189] In addition, as in Comparative Example 5, when the coating layer is not formed at all on the collector, the maximum deposition current is measured at 0.5 mA / cm under the conditions used in Example 1. 2 Experiments were conducted by lowering the current density to , but even at that current, lithium deposition on the upper surface of the protective layer was observed. As such, it was confirmed that it was difficult to measure the maximum deposition current density because lithium was deposited on the upper surface of the protective layer even at a sufficiently low current density. In addition, when a cell was manufactured without a coating layer as in Comparative Example 5, it was confirmed that about 80% of the cells did not undergo normal cycling and had an internal short circuit problem.

[0190] In addition, looking at Table 3 above, no difference was observed in the standard deviation of the coating layer thickness according to the composition of the current collector, but it was confirmed that the standard deviation tended to increase as the Sn plating thickness increased.

[0191] Figure 6 is a photograph showing an evaluation of the corrosion resistance of a lithium metal battery according to an embodiment and a comparative example of the present invention.

[0192] Referring to FIG. 6, the solid electrolyte surface in contact with the current collector is observed after the cell is disassembled to fabricate an all-solid-state cell using a sulfide-based solid electrolyte according to an embodiment and a comparative example of the present invention. In this case, from the left, the current collectors used are Cu 100 wt%, Fe 100 wt%, Ni 100 wt%, Fe 10 wt% and Ni 90 wt%, Fe 64 wt% and Ni 36 wt%, and Fe 90 wt% and Ni 10 wt%.

[0193] Referring to Fig. 6, it can be confirmed that when Cu, Fe, or Ni is used alone in the current collector, corrosion is severe. In contrast, in the case of a current collector containing both Fe and Ni, it was confirmed that the corrosion resistance is superior compared to when Cu, Fe, or Ni is used alone. In addition, in the current collector containing both Fe and Ni, it was confirmed that the corrosion resistance was the best when Fe was 64% and Ni was 36%.

[0194] Figure 7 shows the cell life evaluation of an all-solid-state battery using an embodiment and a comparative example of the present invention.

[0195] Figure 7 shows the cell life evaluation of an all-solid-state battery using the lithium electrodes of Example 2 of the present invention and Comparative Example 1. Referring to Figure 5, when Fe and Ni as alloy components in the current collector were controlled within the range of the present invention, it was confirmed that the cell life characteristics were excellent at 712 cycles. In contrast, when only Ni was used as the alloy component in the current collector, the cell life characteristics were confirmed to be inferior at 122 cycles.

[0196]

[0197] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A current collector containing Fe and Ni; and A lithium metal electrode comprising a metal layer comprising a lithium alloy and positioned on at least one surface of the above-mentioned collector.

2. In paragraph 1, A lithium metal electrode comprising a protective layer positioned on the above metal layer.

3. In paragraph 1, A current collector including the above Fe and Ni is a lithium metal electrode including 10 to 90 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector.

4. In paragraph 1, A current collector including the above Fe and Ni is a lithium metal electrode including 55 to 70 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector.

5. In paragraph 1, A lithium metal electrode wherein the metal layer includes at least one lithium-philic metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).

6. In paragraph 1, A lithium metal electrode having a thickness of the metal layer including the lithium-friendly metal of 20 to 300 nm.

7. In paragraph 1, A lithium metal electrode having a standard deviation of the thickness of the metal layer including the lithium-friendly metal of 90 nm or less.

8. In paragraph 1, A lithium metal electrode having a higher molar ratio of lithium-friendly metal in the metal layer including the lithium alloy as it moves toward the current collector.

9. Step of preparing a collector containing Fe and Ni; and A method for manufacturing a lithium metal electrode, comprising the step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component.

10. In paragraph 9, After the step of forming the above coating layer, A step of forming a protective layer on the surface of the coating layer; A step of positioning a current collector having the coating layer and protective layer formed in the plating solution and then positioning a lithium supply source at a predetermined distance from the protective layer; and A method for manufacturing a lithium metal electrode, comprising the step of applying a current between the current collector and the lithium source to form a metal layer including a lithium alloy in which a lithium-friendly component included in the coating layer and lithium precipitated from the lithium source are alloyed.

11. In paragraph 9, The step of preparing a current collector including the above Fe and Ni is a method for manufacturing a lithium metal electrode including 10 to 90 wt% of Fe and the remainder of Ni based on 100 wt% of the alloy in the current collector.

12. In paragraph 11, A method for producing a lithium metal electrode, wherein the current collector including the above Fe and Ni comprises 55 to 70 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector.

13. In paragraph 9, A method for manufacturing a lithium metal electrode, wherein the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the lithium-friendly component controls the thickness of the coating layer to a range of 20 to 300 nm.

14. In paragraph 9, A method for manufacturing a lithium metal electrode, wherein the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the lithium-friendly component controls the thickness standard deviation of the coating layer to 10 to 90 nm.

15. In paragraph 9, A method for manufacturing a lithium metal electrode, wherein the coating layer is formed on at least one surface of a current collector using a coating composition including the lithium-friendly component, and the coating layer includes at least one lithium-friendly metal among gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).

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