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; a coating layer located on at least one surface of the current collector and containing a lithium-philic alloy material; and a protective layer located on the coating layer, wherein the coating layer is disposed in an area of 25.0 to 80.0% of the total area of the current collector.

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, lithium metal electrodes face challenges in manufacturing thin layers of lithium metal through commercial processes. Furthermore, uneven current density and dendrite growth caused by electrochemical reactions during the charging and discharging of secondary batteries pose challenges. This can lead to persistent side reactions with the electrolyte and even internal short circuits where the cathode and anode come into contact.

[0005] The growth of the above dendrites can cause significant problems in terms of low life characteristics and stability, and thus, it is difficult to practically utilize ultra-thin lithium metal anodes.

[0006] Various methods have been proposed to suppress the above-mentioned dendrites and increase the lifespan, but it is difficult to simultaneously achieve high energy density through ultra-thin lithium and sufficient lifespan characteristics. To solve this problem, a nano-scale metal layer made of a lithium-philic layer material is coated on the current collector to maximize the surface area of ​​the lithium-philic material that can react with lithium to form an alloy, and to prevent a decrease in current density due to an increase in the surface area of ​​the current collector.

[0007] However, forming a metal layer made of lithium-friendly material on the entire body has the problem of making it difficult to commercialize due to the increased cost of raw materials.

[0008] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery reduces raw material costs and at the same time provides a lithium secondary battery with improved charge / discharge life characteristics when applied to the battery.

[0009] 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.

[0010] According to one embodiment of the present invention, a lithium metal electrode includes a current collector, a coating layer positioned on at least one surface of the current collector and including a lithium-philic alloy material, and a protective layer positioned on the coating layer, wherein the coating layer may be disposed on an area of ​​25.0 to 80.0% of the total area of ​​the current collector. In one embodiment, the coating layer may include a metal material having a plurality of island shapes.

[0011] In one embodiment, the area of ​​the island shape may be 0.01 to 0.50 μm. In one embodiment, the current collector may include at least one of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof.

[0012] In one embodiment, the lithium-friendly alloy material of the coating layer may include at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi. In one embodiment, the protective layer may include amorphous carbon.

[0013] In one embodiment, the coating layer may include a metal layer comprising a lithium alloy layer forming a lithium alloy. In one embodiment, the metal layer may be disposed on the lithium alloy layer and may include lithium.

[0014] According to another embodiment of the present invention, a lithium metal electrode includes a current collector, a metal layer including a coating layer positioned on at least one surface of the current collector and including a lithium-philic alloy material and a lithium alloy layer forming a lithium alloy, and a protective layer disposed on the metal layer, wherein the coating layer may be disposed on an area of ​​25.0 to 80.0% of the total area of ​​the current collector. In one embodiment, the metal layer may be disposed on the lithium alloy layer and may include lithium.

[0015] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode comprises the steps of: preparing a current collector;

[0016] A method for forming a coating layer comprising a lithium-friendly alloy material on at least one surface of a current collector using a coating composition comprising a lithium-friendly component, and a method for forming a protective layer on the surface of the coating layer comprising the lithium-friendly alloy material, may include a step of forming a coating layer comprising the lithium-friendly alloy material.

[0017] <Formula 1>

[0018] 3.40 ≤ plating time (h) × coating layer coverage (%) × 100 ≤ 75.0

[0019] (In the above formula 1, the plating time is the electroplating time in the step of forming a coating layer containing a lithium-friendly alloy material, and the coating layer coverage means the area on which the coating layer containing a lithium-friendly alloy material is disposed based on 100% of the current collector area)

[0020] In one embodiment, the step of forming a coating layer including the lithium-friendly alloy material may include a step of controlling the coating layer coverage to 25.0 to 80.0%. In one embodiment, after the step of forming the protective layer, the step of positioning a current collector having the coating layer including the lithium-friendly alloy material 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 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.

[0021] In one embodiment, the step of forming a coating layer including the lithium alloy material has a cumulative current of 0.10 to 1.30 mAh / dm 2 In one embodiment, the step of forming a coating layer including the lithium alloy material may be performed at a plating time of 45 seconds or less.

[0022] In one embodiment, the step of forming a coating layer including the lithium alloy material is performed at a plating current of 0.5 to 2.0 mA / cm 2 It can be performed in the range. In one embodiment, in 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 a coating layer including the lithium-friendly alloy material and lithium precipitated from the lithium source are alloyed, 6 to 12 mA / cm 2 A step of electrodeposition at a maximum current density of the range may be included.

[0023] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery includes a metal layer having a predetermined range of coverage on a current collector, thereby providing an economical lithium secondary battery having improved charge / discharge cycle life characteristics.

[0024] 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.

[0025] Figures 1a to 1c illustrate lithium metal electrodes manufactured according to one embodiment.

[0026] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

[0027] 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.

[0028] Figures 4a and 4b show the microstructure of the surface and cross-section when a protective layer is placed on a current collector coated with an alloy material.

[0029] Figures 5a and 5b show the appearance of electrodeposition according to the maximum current density in the electrodeposition process according to the examples and comparative examples.

[0030] FIGS. 6a and 6b are drawings showing the results of mapping the surface microstructure and plating layer image of an embodiment of the present invention, FIGS. 6c and 6d are drawings showing the results of mapping the surface microstructure and plating layer image of a comparative example of the present invention, and FIGS. 6e and 6f are drawings showing the results of mapping the surface microstructure and plating layer image of a comparative example of the present invention.

[0031] Figure 7 shows the results of charge / discharge life evaluation of examples and comparative examples of the present invention.

[0032] 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 solely 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] FIGS. 1A to 1C illustrate a lithium metal electrode (100) manufactured according to one embodiment.

[0037] Referring to FIG. 1a, a lithium metal electrode (100) according to one embodiment includes a current collector (11) and a coating layer (20) including a lithium-friendly alloy material located on at least one surface of the current collector (11), and further includes a protective layer (30) located on the other surface of the coating layer (20) including a lithium-friendly alloy material facing the current collector (11).

[0038] 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).

[0039] 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, for example, one or a combination of copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium, and alloys thereof.

[0040] 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.

[0041] The coating layer (20) including the lithium-friendly alloy material is positioned on the current collector (11) and may be arranged in an area of ​​25.0 to 80.0% of the total area of ​​the current collector. Specifically, the coating layer (20) including the lithium-friendly alloy material may include the lithium-friendly alloy material. Specifically, the coating layer (20) including the lithium-friendly alloy material may be 30 to 70% of the total area of ​​the current collector, more specifically, 35 to 65%, more specifically, 35.2 to 62.5%, and even more specifically, 38 to 62.5%. The area of ​​the coating layer (20) including the lithium-friendly alloy material may mean the area occupied by the lithium-friendly alloy material in the total area when the coating layer (20) including the lithium-friendly alloy material is coated on the current collector (11) by plating.

[0042] The coating layer (20) of the present invention is not disposed on the entire surface of the current collector (11), but is disposed on the current collector (11) within the aforementioned range, which has the advantage of allowing lithium to be easily precipitated between the protective layer (30) and the current collector (11).

[0043] If the area ratio of the coating layer (20) to the entire current collector (11) is outside the upper limit of the aforementioned range, there is a problem that lithium is not deposited between the current collector (11) and the protective layer (30) but on the opposite surface of the protective layer (30) during the process of growing lithium by a precipitation method or charging the battery. If the area ratio of the coating layer (20) to the entire current collector (11) is outside the lower limit of the aforementioned range, the amount of the lithium-affinity alloy material is insufficient to smoothly form an alloy with lithium, so the movement of lithium is inhibited, and likewise, there is a problem that lithium is deposited on the opposite surface of the protective layer (30).

[0044] In one embodiment, the coating layer (20) may include a metal material having a plurality of island shapes. Specifically, the coating layer (20) may have an amorphous island shape, for example, in which at least one particle is aggregated. The island shape may be a case in which the particles of the metal material constituting the coating layer (20) are amorphous, and the particles of the metal material are connected to form a lump.

[0045] In one embodiment, the area of ​​the island shape is 0.01 to 0.50 μm. 2 It can be. The area of ​​the above island shape is 5 ㎛ in width, 5 ㎛ in length, and 25 ㎛ in area as observed using a scanning electron microscope. 2 It can be a value measured as a range from the minimum area to the maximum area when the image of the range is divided into individual islands using the ImageJ program and the area of ​​each island is calculated. Specifically, the area of ​​the island shape is 0.01 to 0.20㎛. 2 , more specifically 0.01 to 0.15 ㎛ 2 It could be.

[0046] If the area of ​​the above-mentioned island shape is outside the upper limit of the above-mentioned range, the size of the particles of the coating layer (200) including the individual lithium-philic alloy is too large and the coverage is excessive, so there is a problem that lithium is precipitated on the outer surface of the protective layer. If the area of ​​the above-mentioned island shape is outside the lower limit of the above-mentioned range, the amount of the lithium-philic alloy material is too insufficient to smoothly form an alloy with lithium, so that the movement of lithium is inhibited during the charging process, etc., so that lithium is not precipitated between the current collector and the protective layer, but there is a problem that lithium is precipitated on the opposite surface of the protective layer.

[0047] In one embodiment, the coating layer (20) may include a lithium-friendly metal. Specifically, the lithium-friendly metal may include at least one metal selected from the group consisting of, for example, In, Ag, Sn, Zn, Si, Al, and Bi.

[0048] The protective layer (30) is positioned on the coating layer (20) including a lithium-philic alloy material and may include amorphous carbon. When lithium metal is used as an anode 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 or a decrease in battery capacity due to a short circuit or overvoltage during charge / discharge.

[0049] 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 (30) including amorphous carbon.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 first amorphous carbon and / or the second amorphous carbon and water. When the content of the binder satisfies the above-described 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.

[0054] 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.

[0055] 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-mentioned range, not only does the protective layer function as a protective layer by having an appropriate thickness of the protective layer, but also has an effect of having an appropriate resistance for the movement of lithium ions, thereby preventing the formation of lithium dendrites on the surface of the protective layer and allowing lithium ions to penetrate well into the protective layer and conduct, thereby allowing lithium to be precipitated from the lower surface of the protective layer.

[0056] 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 high, 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.

[0057] In one embodiment, the lithium metal electrode may 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).

[0058] 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.

[0059] 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.

[0060] 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) and the protective layer (30).

[0061] Referring to FIG. 1b and FIG. 1c, unlike FIG. 1a, a layer including a lithium alloy is formed by forming an alloy between a coating layer (20) including a lithium-friendly alloy material and lithium through a lithium electrodeposition process.

[0062] Referring back to FIG. 1B, in one embodiment, the metal layer (12) 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 on the current collector (11) by applying a current between the current collector (11) and the lithium source (40 of FIG. 2). Specifically, the metal layer (12) may include a lithium alloy layer (21) formed by alloying lithium deposited with a coating layer (20) including a lithium-friendly alloy material, and a lithium metal layer (41) positioned on the lithium alloy layer (21).

[0063] 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. Specifically, the thickness of the metal layer (12) may mean a thickness including a lithium alloy layer (21) formed by alloying a coating layer (20) including a lithium-friendly alloy material arranged in a plurality of island shapes, and a lithium metal layer (41) positioned on the lithium alloy layer (21).

[0064] If 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 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), the thickness of the metal layer (12) is preferably 100 μm or less.

[0065] When the thickness of the metal layer (12) is excessively thin, when the lithium metal electrode of the present embodiment is applied to a secondary battery, there is a problem that the charge / discharge life of the battery is reduced. Specifically, during charge / discharge of the battery, lithium in the battery is gradually consumed due to side reactions between the lithium contained in the negative active material layer, i.e., the metal layer of the present invention, and the electrolyte, so that the battery capacity is reduced, and the amount of lithium that can replenish the lithium consumed during charge / discharge is reduced, so that the charge / discharge life of the battery is reduced. Therefore, the thickness of the metal layer (12) is preferably 1 ㎛ or more.

[0066] When the electrodeposition process is performed by applying a high current to increase the speed of electrodeposition during the formation of the metal layer (12), 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 if the electrodeposition process is performed by applying a high current, it is possible to prevent excessive generation of fine lithium particles or destruction of the protective layer (30) located on the surface of the lithium metal layer (41) already formed in the electrodeposition process.

[0067] 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.

[0068] 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.

[0069] In one embodiment, the lithium alloy layer (21) includes a lithium-philic metal. In this case, when the lithium alloy layer (21) includes a lithium-philic metal, since it includes a lithium-philic metal with high electronic conductivity, there is an advantage in that electrons are smoothly supplied from the current collector, and lithium ions are reduced, thereby facilitating electrodeposition of the lithium metal layer. The metal layer (12) plays a role in helping lithium to be more effectively deposited under the protective layer (30) during the charging process of the battery.

[0070] In one embodiment, the protective layer (30) may be positioned on the metal layer (12). Specifically, when a lithium electrodeposition process is performed, the protective layer (30) may be positioned on the metal layer (12). When a lithium electrodeposition process is performed, lithium may be electrodeposited between the current collector (11) and the protective layer (30), and a metal layer (12) including a coating layer (20) including a lithium-philic alloy material, a lithium alloy layer (21) in which lithium forms an alloy, and a lithium metal layer (41) disposed on the lithium alloy layer (21) and including lithium may be disposed.

[0071] In one embodiment, the protective layer (30) may include amorphous carbon. When lithium metal is used as an anode 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 and discharge process, resulting in failure or a decrease in battery capacity due to a short circuit or overvoltage during charge and discharge.

[0072] Referring back to FIG. 1C, 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 lithium precipitated from the lithium source (40) with a lithium-friendly alloy material in a coating layer (20) including the lithium-friendly alloy material formed on the current collector (11).

[0073] The above metal layer (12) may include a lithium-friendly metal. For a detailed description thereof, refer to Fig. 1a.

[0074] 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.

[0075] In one embodiment, the metal layer (12) includes a protective layer (30) positioned on the surface of the metal layer (12), and may include a film layer on the interior 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.

[0076] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

[0077] 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) including a lithium-philic alloy material 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) including the lithium-philic alloy material using a slurry including amorphous carbon, positioning the current collector (11) on which the coating layer (20) including the lithium-philic alloy material 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 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.

[0078] In the step of preparing the current collector (11), 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, for example, one or a combination of copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, carbon, conductive polymers, and composite fibers coated with a conductive layer on a non-conductive polymer.

[0079] The step of forming a coating layer (20) including a lithium-friendly alloy material on at least one surface of a current collector (11) using a coating composition including a lithium-friendly component may coat the lithium-friendly alloy material on at least one surface of the current collector. The lithium-friendly alloy material may include, for example, at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

[0080] In one embodiment, the step of forming a coating layer (20) including a lithium-friendly alloy material may be performed using at least one of electrolytic or electroless plating, sputtering, electron beam, and thermal vapor deposition. For example, the step of forming the coating layer may be coated using an electroless plating method.

[0081] In one embodiment, the step of forming the coating layer coverage may satisfy the following equation 1.

[0082] <Formula 1>

[0083] 3.40 ≤ plating time (h) × coating layer coverage (%) × 100 ≤ 75.0

[0084] (In the above formula 1, the plating time is the electroplating time in the step of forming a coating layer containing a lithium-friendly alloy material, and the coating layer coverage means the area on which the coating layer containing a lithium-friendly alloy material is disposed based on 100% of the current collector area)

[0085] The above formula 1 can additionally be an indicator that lithium can be deposited between the current collector (11) and the protective layer (30) during the process of growing lithium by a precipitation method or charging the battery. Specifically, the above formula 1 can satisfy 3.53 to 75.0, specifically, 3.53 to 73.0, more specifically, 40.0 to 72.5, and even more specifically, 45.0 to 60.0. By satisfying the above formula 1, there is an advantage of easy lithium electrodeposition characteristics and excellent charge / discharge performance when applied to a battery.

[0086] If the above equation 1 is outside the upper limit of the aforementioned range, there is a problem that lithium is not deposited between the current collector and the protective layer but on the opposite surface of the protective layer during the process of growing lithium by a precipitation method or charging the battery. If the above equation 1 is outside the lower limit of the aforementioned range, there is a problem that lithium is deposited on the opposite surface of the protective layer because the amount of the lithium-affinity alloy material is insufficient to smoothly form an alloy with lithium, thereby hindering the movement of lithium.

[0087] In one embodiment, the step of forming the coating layer may be a step of controlling the coating layer coverage to 25.0 to 80.0%. Specifically, the coating layer coverage refers to an area where the coating layer is disposed on the current collector based on 100% of the current collector area, and may satisfy 30.0 to 70.0%, more specifically, 35.0 to 65.0%, more specifically, 35.2 to 62.5%, and even more specifically, 38.0 to 62.5%.

[0088] By controlling the coverage of the coating layer within the above-mentioned range, there is an advantage of excellent characteristics during lithium electrodeposition and excellent charge / discharge performance when applied to a battery. If the coverage of the coating layer exceeds the upper limit of the above-mentioned range, there is a problem that lithium is precipitated on the surface opposite to the protective layer because the particle size of the individual lithium-friendly alloy material is too large and the coverage is excessive. If the above-mentioned Equation 1 exceeds the lower limit of the above-mentioned range, the particles of the lithium-friendly alloy material are excessively small and do not smoothly form an alloy with lithium, so the movement of lithium is inhibited, and there is a problem that lithium is precipitated on the surface opposite to the protective layer (30) likewise.

[0089] In one embodiment, the step of forming the coating layer comprises a cumulative current of 0.10 to 1.30 mAh / dm 2can be performed. The above cumulative current means the product of the current density and the plating time. The above cumulative current is 0.14 to 1.25 mAh / dm 2 , more specifically, 0.40 to 1.00 mAh / dm 2 , more specifically, 0.42 to 0.83 mAh / dm 2 It can be performed in. Since the above-mentioned accumulated current satisfies the above-mentioned range, lithium electrodeposition is advantageous, and there is an advantage of excellent charge / discharge performance number when applied to a battery.

[0090] Specifically, the accumulated current can be controlled differently depending on the components of the current collector and the components of the coating layer. In one embodiment, when the component of the current collector is Ni, the accumulated current is 0.20 to 1.25 mAh / dm 2 , more specifically, 0.80 to 1.25 mAh / dm 2 , more specifically, 0.83 to 1.25 mAh / dm 2 can be performed in .

[0091] In one embodiment, when the component of the collector is Fe-Ni, the cumulative current is 0.14 to 1.25 mAh / dm 2 , more specifically, 0.15 to 0.50 mAh / dm 2 , more specifically, 0.20 to 0.30 mAh / dm 2 can be performed in .

[0092] In one embodiment, when the component of the entire collector is STS, the cumulative current is 0.08 to 0.40 mAh / dm 2 , more specifically, 0.10 to 0.25 mAh / dm 2 , more specifically, 0.11 to 0.20 mAh / dm 2 can be performed in .

[0093] If the above-mentioned accumulated current exceeds the upper limit of the above-mentioned range, there is a problem that the plating amount of the lithium-friendly alloy material is excessively large, resulting in excessive coverage, and lithium is deposited on the surface opposite to the protective layer. If the above-mentioned accumulated current exceeds the lower limit of the above-mentioned range, there is a problem that the plating amount is excessively small, resulting in an insufficient amount of the lithium-friendly alloy material, and thus a failure to smoothly form an alloy with lithium.

[0094] In one embodiment, the step of forming the coating layer may be performed at a plating time of 45 seconds or less. Specifically, the plating time may be performed at 30 seconds or less, specifically, 2.5 to 30 seconds, and more specifically, 30 to 40 seconds.

[0095] In one embodiment, the step of forming the coating layer comprises a plating current of 0.5 to 2.0 mA / cm 2 It can be performed in the range. Specifically, the plating current is 0.5 to 1.5 mA / cm 2 Range, more specifically, 0.5 to 1.0 mA / cm 2 It can be performed in a range.

[0096] Since the plating current and the plating time satisfy the above-mentioned ranges, there is an advantage in that lithium electrodeposition is easy and a battery with excellent life characteristics can be implemented when applied to the battery. If the plating current and the plating time exceed the upper limit of the above-mentioned ranges, there is a problem in that the plating amount of the lithium-friendly alloy material is too large and the coverage is excessive, causing lithium to precipitate on the surface opposite to the protective layer. If the plating current and the plating time exceed the lower limit of the above-mentioned ranges, there is a problem in that the plating amount is too small and the amount of the lithium-friendly alloy material is insufficient, preventing a smooth alloy formation with lithium.

[0097] A protective layer (30) can be formed on the surface of a coating layer (20) including a lithium-philic alloy material using a slurry containing amorphous carbon. The protective layer (30) can be formed by mixing the amorphous carbon and a binder in water and applying the slurry 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.

[0098] Meanwhile, in the step of forming the protective layer (30), the thickness of the lithium ion conduction promoting protective layer formed on the surface of the alloy material coating layer may be in the range of 0.01 µm to 50 µm, more specifically, 1 µm to 20 µm.

[0099] After the step of forming a protective layer (30), a current collector in which a coating layer (20) including the lithium-friendly alloy material and a protective layer (30) are sequentially formed is positioned in a plating solution (50), and then 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.

[0100] Specifically, after positioning a current collector (11) having a coating layer (20) and a protective layer (30) including a lithium-friendly alloy material formed within a plating solution, a lithium supply source (40) is positioned at a predetermined distance from the protective layer (30). For example, the lithium supply source (40) may be 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] The above plating solution (50) 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 (50), etc.

[0106] 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.

[0107] 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 (41), but is not limited thereto.

[0108] 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 (41) can be improved.

[0109] 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.

[0110] 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 (41). 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.

[0111] 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.

[0112] In the step of forming a lithium metal layer on at least one surface of the current collector 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.

[0113] 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.

[0114] In one embodiment, the step of applying the current to form a lithium metal layer on at least one surface of the current collector 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.

[0115] 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).

[0116] 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).

[0117] 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.

[0118] In one embodiment, the step of forming a lithium metal layer on at least one surface of the current collector by applying the current may include a step of electrodepositing the deposited lithium to a thickness in the range of 5 to 15 μm. Specifically, the thickness of the deposited lithium may be electrodeposited to a thickness in the range of 8 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).

[0119] 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.

[0120] In one embodiment, in the step of forming a 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 the lithium alloy layer (21) can be controlled to 1 to 100 μm. For a detailed description of the thickness of the metal layer (12) including the lithium alloy layer (21), reference may be made to the contents of the aforementioned FIGS. 1b and 1c.

[0121] In this way, in this embodiment, a lithium metal electrode (100) can be manufactured in which a metal layer (12) including a lithium alloy layer (21) having a coarse particle structure is formed by preventing excessive generation of fine lithium particles even under high current conditions and inducing initially generated lithium particles to grow well. In addition, the metal layer manufactured in this way also has excellent surface uniformity.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131]

[0132] <Experimental Example>

[0133] Manufacturing of cathodes for lithium secondary batteries

[0134] <Example 1>

[0135] <Manufacturing the entire house>

[0136] A nickel (Ni) current collector was prepared for use in the negative electrode of the lithium secondary battery of the present invention.

[0137]

[0138] <Formation of alloy material coating layer>

[0139] Afterwards, an alloy material was coated on both sides of the nickel collector using an electrolytic plating method. Silver (Ag) was used as the alloy material, and the current density for plating the lithium-affinity layer was 1 mA / cm. 2 , the plating time was controlled to 30 seconds, and the accumulated current was 0.83 mAh / dm 2 It was.

[0140] FIGS. 3a and 3b are scanning electron microscope (SEM) photographs showing the microstructure of the surface and cross-section of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.

[0141] Referring to FIGS. 3a and 3b, it can be confirmed that the lithium-friendly layer on the collector has an island shape over the entire area and has an appropriate level of coverage on the collector surface.

[0142]

[0143] <Protective layer formation>

[0144] Afterwards, a protective layer of about 5 ㎛ was formed on the upper surface of the coating layer by slurry coating using a comma coater. Specifically, the protective layer was formed by mixing amorphous carbon, a binder, and a solvent. At this time, the binder was prepared by adding 3.0 parts by weight and 6.0 parts by weight of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR), respectively, to 100 parts by weight of the amorphous carbon, for a total of 9.0 parts by weight. In addition, the solvent was used so that water and ethylene glycol (EG) were in a weight ratio of 80:20. The total amount of the solvent was about 25 wt% of the sum of the amorphous carbon and the binder to maintain an appropriate viscosity for the coating. At this time, the amorphous carbon used was acetylene black.

[0145] Figures 4a and 4b show the microstructure of the surface and cross-section when a protective layer is placed on a current collector coated with an alloy material.

[0146] Referring to FIGS. 4a and 4b, it was confirmed that an alloy material coating layer, which is a lithium-friendly metal plating layer, was plated on the current collector and a protective layer was formed on the coating layer.

[0147]

[0148] Lithium electrodeposition process

[0149] Afterwards, lithium was removed from the lithium source using an electrodeposition process to form a lithium alloy or pure lithium metal between the protective layer and the current collector, and lithium was deposited between the protective layer and the current collector. The plating solution used for this electrodeposition was a composite solvent in which 1,2-dimethoxyethane (DME) as the first solvent and sulfolane (SL) as the second solvent were mixed in a molar ratio of 90:10, and lithium bis(fluorosulfonyl)imide, a nitrogen-based compound, and lithium nitrate were added in amounts of 40 wt% and 5 wt%, respectively, based on 100 wt% of the plating solution, and fluoroethylene carbonate, a fluorine-based compound, was added in an amount of 5 wt% based on 100 wt% of the plating solution. A lithium metal plate with a purity of 99.9% or higher and a thickness of 500 μm was used by pressing it onto a copper current collector plate (Cu Plate) as a lithium supply source (40).

[0150] After electrically insulating the lithium source and the current collector in the plating solution, lithium was deposited between the current collector and the protective layer by applying current using a power supply device with the lithium source and the current collector as (+) and (-) electrodes, respectively.

[0151] 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.

[0152] Figures 5a and 5b show the appearance of electrodeposition according to the maximum current density in the electrodeposition process according to the examples and comparative examples.

[0153] Fig. 5a shows the appearance of the electrodeposition when electrodeposition is performed below the maximum current density, and Fig. 5b shows the appearance of the electrodeposition when electrodeposition is performed above the maximum current density. Referring to Figs. 5a and 5b, when electrodeposition is performed below the maximum possible current density, the precipitated lithium is deposited under the black protective layer, so that a black protective layer is visible in appearance. When electrodeposition is performed above the maximum possible current density, lithium is deposited on the upper surface of the protective layer, so that gray-colored lithium is deposited on the upper surface of the protective layer. Through this, the maximum current density is defined as the maximum possible current density for electrodeposition, which is the maximum current density at which lithium is deposited between the current collector and the protective layer in the electrodeposition process.

[0154]

[0155] All-solid-state battery manufacturing

[0156] 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.

[0157] Lithium having a thickness of 0.5 mm was attached as a reference electrode on one side of the electrolyte, and the negative electrode manufactured according to the examples and comparative examples was attached on the opposite side. The reference electrode and the evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and during the charge and discharge evaluation, the pressure was applied to 16 MPa in a dedicated evaluation cell.

[0158]

[0159] <Example 2>

[0160] In the above alloy material coating layer plating step, the plating time is 45 seconds, and the cumulative current is 1.25 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0161]

[0162] <Example 3>

[0163] In the above alloy material coating layer plating step, the plating time is 10 seconds, and the cumulative current is 0.28 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0164]

[0165] <Comparative Example 1>

[0166] In the above alloy material coating layer plating step, the plating time is 50 seconds, and the accumulated current is 1.39 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0167]

[0168] <Comparative Example 2>

[0169] In the above alloy material coating layer plating step, the plating time is 5 seconds, and the accumulated current is 0.14 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0170]

[0171] <Evaluation Example 1> - Evaluation based on the same plating current

[0172] Table 1 below shows the lithium-friendly layer coverage, island area range, maximum electrodeposition current, and charge / discharge performance number when Ag was used as a lithium-friendly metal on a Ni collector, and the plating current, plating time, and cumulative current were controlled.

[0173] Lithium-rich layer coverage, island area range, maximum electrodeposition current, and charge / discharge cycle performance were measured by the following methods.

[0174] Lithium-affinity layer coverage and island area range: To measure the surface coverage and island area of ​​the lithium-affinity plating layer, the microstructure was observed using a GEMINI-500 scanning electron microscope from ZEISS. The coverage of the lithium-affinity plating layer was measured as the area on a two-dimensional plane of the lithium-affinity plating layer relative to the total area using the ImageJ image program developed by the National Institute of Health (NIH) using the photograph observed with the scanning electron microscope. The islands were defined as particles with independent perimeters, each measuring 5 ㎛ in width, 5 ㎛ in height, and 25 ㎛ in area. 2 The range of minimum to maximum areas for each island contained within the image was measured.

[0175] 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.

[0176] 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.

[0177] Separation Lithium layer plating conditions Product effect formula 1 * Total Lithium-friendly metal plating current, Plating time, Cumulative current, Lithium-friendly layer coverage, Island area range, Maximum possible electrodeposition current, Charge / discharge performance, Number of cycles, Unit--[mA / cm 2][Sec][mAh / dm 2 ][%][㎛ 2 ][mA / cm 2 ][Time]-Example 1 NiAg 1 30 0.8 3 5 1.5 0.01~0.10 10 8 7 2 4 2.75 Example 2 NiAg 1 45 1.2 5 6.3 0.01~0.15 8 8 15 7 0.38 Example 3 NiAg 1 10 0.2 8 3 5.2 0.01~0.10 10 7 2 8 9.86 Comparative Example 1 NiAg 1 5 0 1.3 9 8 3.8> 1 4 4 4 2 1 1 5 79 Comparative Example 2 NiAg 1 5 0.1 4 1 7 6 0.01~0.20 2 3 5 9 2.46 Formula 1* = Plating time (h) × Lithium-affinity alloy material coating layer coverage (%) × 100

[0178] Looking at Table 1 above, the current collector material is Ni, the lithium-friendly metal is Ag, and the plating current is 1 mA / cm 2 When the plating time and the accumulated current are controlled to control the lithium-friendly layer coverage within the range of the present invention, the maximum electrodeposition current and the number of charge / discharge cycles are each 8 mA / cm. 2 And it was confirmed that it was excellent for more than 700 times. In contrast, Comparative Example 1 had excessively high plating time and cumulative current, so that the lithium-friendly layer coverage was 83.8%, covering an excessively large area of ​​the current collector with the lithium-friendly layer, and accordingly, the island was not implemented, and 1 ㎛ 2 It was confirmed that the lithium-friendly layer material formed above had a low maximum electrodeposition current and poor charge / discharge performance. In addition, Comparative Example 2 had excessively low plating time and cumulative current, indicating that the lithium-friendly layer material was 0.01 to 0.20 ㎛. 2 It appears as an island shape with an area of ​​the range, but it was confirmed that the lithium-friendly layer coverage was excessively low, so the maximum possible electrodeposition current was low and the number of charge / discharge cycles was inferior.

[0179] In addition, it was confirmed that the embodiments of the present invention satisfy the value of Equation 1, while the comparative examples do not satisfy the value of Equation 1, and accordingly, the maximum electrodeposition current and the number of charge / discharge cycles are low.

[0180] FIGS. 6a and 6b are drawings showing the results of mapping the surface microstructure and plating layer image of an embodiment of the present invention, FIGS. 6c and 6d are drawings showing the results of mapping the surface microstructure and plating layer image of a comparative example of the present invention, and FIGS. 6e and 6f are drawings showing the results of mapping the surface microstructure and plating layer image of a comparative example of the present invention.

[0181] FIG. 6a and FIG. 6b are drawings showing the results of mapping the surface microstructure and plating layer image of Example 1 of the present invention, FIG. 6c and FIG. 6d are drawings showing the results of mapping the surface microstructure and plating layer image of Comparative Example 1 of the present invention, and FIG. 6e and FIG. 6f are drawings showing the results of mapping the surface microstructure and plating layer image of Comparative Example 2 of the present invention. Referring to FIG. 6a and FIG. 6b, it can be confirmed that the coverage fraction of the lithium-philic layer material on the surface of the current collector is 51.5%, and the island area is 0.01 to 0.10 ㎛. 2 It was confirmed that the range was satisfied. Referring to Figures 6c and 6d, it can be confirmed that the coverage fraction of the lithium-philic layer material on the surface of the collector is 83.3%, and the island area is 1 ㎛. 2 It can be confirmed that the larger size is larger. Specifically, the island shape is not developed, and the grains are clumped together. Referring to Figures 6e and 6f, it can be confirmed that the coverage fraction of the lithium-philic layer material on the surface of the collector is 17.6%, and the island area is 0.01 to 0.20 ㎛. 2 You can see that the range is satisfied.

[0182] Figure 7 shows the results of charge / discharge life evaluation of examples and comparative examples of the present invention.

[0183] Figure 7 shows the results of charge / discharge life evaluations of all-solid-state batteries manufactured according to Example 1 and Comparative Example 1. Referring to Figure 7, it can be confirmed that the charge / discharge life evaluation of Example 1 is superior to that of Comparative Example 1.

[0184]

[0185] <Evaluation Example 2> - Lithium-affinity layer plating conditions according to current collector material and lithium-affinity layer metal

[0186] <Example 4>

[0187] In the above alloy material coating layer plating step, the plating current is 1.5 mA / cm 2 Plating time is 20 seconds, cumulative current is 0.83 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0188]

[0189] <Example 5>

[0190] In the above alloy material coating layer plating step, Sn is used instead of Ag as a lithium-friendly metal, and the plating current is 0.5 mA / cm 2 Plating time 30 seconds, cumulative current 0.42 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0191]

[0192] <Example 6>

[0193] In the above alloy material coating layer plating step, Fe-Ni is used as the current collector, and the plating current is 2 mA / cm 2 Plating time is 5 seconds, cumulative current is 0.28 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0194]

[0195] <Example 7>

[0196] In the above alloy material coating layer plating step, STS (stainless steel) is used as the current collector, and the plating current is 0.5 mA / cm 2 Plating time 10 seconds, cumulative current 0.14 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0197]

[0198] <Example 8>

[0199] In the above alloy material coating layer plating step, STS (stainless steel) is used as the current collector, and the plating current is 1.0 mA / cm 2 Plating time is 5 seconds, cumulative current is 0.14 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0200]

[0201] <Example 9>

[0202] In the above alloy material coating layer plating step, STS (stainless steel) is used as the current collector, and the plating current is 2.0 mA / cm 2 Plating time is 2.5 seconds, cumulative current is 0.14 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0203]

[0204] <Comparative Example 3>

[0205] In the above alloy material coating layer plating step, the plating current is 0.5 mA / cm 2 Plating time is 60 seconds, cumulative current is 0.83 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0206]

[0207] <Comparative Example 4>

[0208] In the above alloy material coating layer plating step, STS (stainless steel) is used as the current collector, and the plating current is 0.5 mA / cm 2 Plating time 30 seconds, cumulative current 0.42 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0209]

[0210] Comparative Example 5

[0211] In the above alloy material coating layer plating step, STS (stainless steel) is used as the current collector, and the plating current is 0.5 mA / cm 2 Plating time 30 seconds, cumulative current 0.07 mAh / dm 2 The same procedure as Example 1 was followed, except that the following was performed in .

[0212] Separation Lithium layer plating conditions Product effect formula 1 * Total Lithium-friendly metal plating current, Plating time, Cumulative current, Lithium-friendly layer coverage, Island area range, Maximum possible electrodeposition current, Charge / discharge performance, Number of cycles, Unit--[mA / cm 2 ][Sec][mAh / dm 2 ][%][㎛ 2 ][mA / cm 2 ][Time]-Example 4NiAg1.5200.8358.50.01~0.201071732.37Example 5NiSn0.5300.4262.50.01~0.151290252.50Example 6Fe-NiAg2.050.2853.50.01~0.15127597.49Example 7STSAg0.5100.1438.50.01~0.25880110.78Example 8STSAg 1.050.1443.20.01~0.20107306.05Example 9STSAg2.02.50.1450.40.01~0.20108243.53Comparative Example 3NiAg0.5600.8390.5>14566150.23Comparative Example 4STSAg0.5300.4292.5>1247677.70Comparative Example 5STSAg0.550.0723.20.01~0.2044163.25Formula 1* = Plating time (h) × Lithium-affinity alloy material Coating layer coverage (%) × 100

[0213] Looking at Table 2 above, it was confirmed that there was a clear difference between the examples and the comparative examples in terms of maximum electrodeposition current and number of charge / discharge cycles when the coverage of the lithium-loving layer was controlled within the scope of the present invention even though the types of current collectors and lithium-loving metals were different. In addition, it was confirmed that the examples satisfying Equation 1 had a higher maximum electrodeposition current and superior number of charge / discharge cycles compared to the comparative examples that did not satisfy Equation 1.

[0214] 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. Whole house; A coating layer located on at least one surface of the above-mentioned collector and including a lithium-friendly alloy material; and A protective layer positioned on the above coating layer is included, A lithium metal electrode in which the coating layer is disposed over an area of ​​25.0 to 80.0% of the total area of ​​the entire collector.

2. In paragraph 1, A lithium metal electrode wherein the coating layer comprises a metal material having a plurality of island shapes.

3. In paragraph 2, A lithium metal electrode having an area of ​​the above island shape of 0.01 to 0.50 ㎛.

4. In paragraph 1, The above-mentioned collector is a lithium metal electrode comprising at least one of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof.

5. In paragraph 1, A lithium metal electrode wherein the lithium-friendly alloy material of the coating layer includes at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

6. In paragraph 1, The above protective layer is a lithium metal electrode containing amorphous carbon.

7. In paragraph 1, A lithium metal electrode comprising a metal layer including a lithium alloy layer forming a lithium alloy with the above coating layer.

8. In paragraph 7, A lithium metal electrode comprising a lithium metal layer including lithium, wherein the metal layer is disposed on a lithium alloy layer.

9. Whole house; A metal layer including a coating layer comprising a lithium-friendly alloy material and a lithium alloy layer forming a lithium alloy, the coating layer being located on at least one surface of the above-mentioned collector; A protective layer is included that is disposed on the metal layer, A lithium metal electrode in which the coating layer is disposed over an area of ​​25.0 to 80.0% of the total area of ​​the entire collector.

10. In paragraph 9, A lithium metal electrode comprising a lithium metal layer including lithium, wherein the metal layer is disposed on the lithium alloy layer.

11. Step to prepare the entire house; A step of forming a coating layer including a lithium-friendly alloy material on at least one surface of a current collector using a coating composition including a lithium-friendly component; and Comprising a step of forming a protective layer on the surface of a coating layer including the lithium alloy material, A method for manufacturing a lithium metal electrode, wherein the step of forming a coating layer including the lithium-friendly alloy material satisfies the following formula 1. <Formula 1> 3.40 ≤ Plating time (h) × Coating layer coverage (%) × 100 ≤ 75.0 (In the above formula 1, the plating time is the electroplating time in the step of forming a coating layer including a lithium-friendly alloy material, and the coating layer coverage means the area on which the coating layer including a lithium-friendly alloy material is disposed based on 100% of the current collector area.) 12. In paragraph 11, A method for manufacturing a lithium metal electrode, wherein the step of forming a coating layer including the lithium-friendly alloy material includes a step of controlling the coating layer coverage to 25.0 to 80.0%.

13. In paragraph 11, After the step of forming the above protective layer, A step of positioning a current collector having a coating layer including the lithium-friendly alloy material and the protective layer formed thereon within a 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.

14. In paragraph 11, The step of forming a coating layer including the above lithium alloy material has a cumulative current of 0.10 to 1.30 mAh / dm 2 A method for manufacturing a lithium metal electrode performed in .

15. In paragraph 14, A method for manufacturing a lithium metal electrode, wherein the step of forming a coating layer including the lithium-friendly alloy material is performed at a plating time of 45 seconds or less.

16. In paragraph 12, The step of forming a coating layer including the lithium alloy material is performed at a plating current of 0.5 to 2.0 mA / cm. 2 A method for manufacturing a lithium metal electrode performed in a range.

17. In paragraph 11, In 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 a coating layer including the lithium-friendly alloy material and lithium precipitated from the lithium source are alloyed, 6 to 12 mA / cm 2 A method for manufacturing a lithium metal electrode, comprising the step of electrodepositing at a maximum current density in the range.

Images